Re: [Qgis-user] QGIS 3.36.1 Installation

[Nyall Dawson via QGIS-User]

On Tue, 16 Apr 2024 at 03:56, Pham, Ty via QGIS-User
 wrote:
>
> Hello Team,
>
>
>
> I am trying to onboard 3.36.1 here at JPMorgan and our internal packaging 
> team receives the below error when launching shortcut.
>
>
>
>
>
> Is it possible to disable this so that it does NOT prompt install of Open 
> Sans font?

There's a fix queued for the next round of patch releases -- you'll
need to wait for these.

Nyall
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Re: [Qgis-user] adding offset to QgsSvgMarkerSymbolLayer using pyqgis

[Nyall Dawson via QGIS-User]

On Thu, 25 Jan 2024, 7:04 pm Bernhard Seckinger via QGIS-User, <
qgis-user@lists.osgeo.org> wrote:

> Hi,
>
> I wrote a plugin which changes the symbology of a layer using SVG-images.
> Almost everything works but I need to add an offset to the SVG-image and
> did
> not find a way to set it from pyqgis.
>
> That's what I'm doing currently (rule is a rule from a
> QgsRuleBasedRenderer):
>
> icon = os.path.dirname(__file__) + 'a.svg';
> marker = QgsSvgMarkerSymbolLayer(icon)
> marker.setAngle(100) # setting the angle works
> # marker.setOffset(5,5) # this doesn't work (there is no setOffset method)
>

setOffset exists, but requires a QPointF argument. See
https://qgis.org/pyqgis/master/core/QgsMarkerSymbolLayer.html#qgis.core.QgsMarkerSymbolLayer.setOffset

Nyall


rule.symbol().changeSymbolLayer(0,marker)
>
> Any ideas?
>
> Thanks, Bernhard
>
> --
> Bernhard Seckinger 
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Re: [Qgis-user] QGIS Qt6 Wayland ongoing status

[Nyall Dawson via QGIS-User]

> Thanks very much for this detailed authoritative explanation, Nyall.  I
have a couple of specific comments below...

>  It's disappointing to read this as there's clearly a disconnect between
what e.g. QGIS developers are experiencing and what Fedora, Gentoo and
maybe others are saying about Qt5 and Wayland.  For example, this on the
Gentoo Wiki here https://wiki.gentoo.org/wiki/Wayland

That gentoo page is fairly optimistic in that it's considering wayland
support "complete" just because it works for common use cases.

>> For Qt an additional package called dev-qt/qtwayland is required. In the
Qt Wiki it says: "QtWayland is a Qt 5 module that wraps the functionality
of Wayland. QtWayland is separated into a client and server side. The
client side is the wayland platform plugin, and provides a way to run Qt
applications as Wayland clients. The server side is the QtCompositor API,
and allows users to write their own Wayland compositors."

This is definitely incorrect. Qt5 on wayland, regardless of whether or not
QtWayland is in play, will still be broken. It will "kind of" work in some
circumstances, but eg docks/toolbars are broken and will NEVER work
correctly under this setup.

> And this on Fedora here
https://fedoraproject.org/wiki/Changes/Qt_Wayland_By_Default_On_Gnome
>
>> Qt Wayland plugin has been available for a long time, but it hasn't been
in condition where it could be enabled by default. With Qt 5.12 the state
of the Wayland plugin is much better and it's becoming more and more
reliable.

"becoming more reliable" does not equate to "reliable" 藍

>  It now supports all the needed protocols and has been enabled by default
for non-Gnome Wayland sessions. With Qt Wayland on Gnome Wayland session we
need to support CSD, it's actually the only way how decorations are going
to work in Qt apps right now. Qt Wayland implements basic decorations,
which really doesn't match Gnome Adwaita theme, therefore there are new CSD
being implemented as part of QGnomePlatform.
>>
>> To make Qt applications run natively on Wayland we need to modify Qt 5,
specifically qt5-qtbase module, where we allow the Wayland plugin to be
used also for Gnome sessions. The new decorations from QGnomePlatform will
be used automatically once they are fully implemented and updated in Fedora.
>
> (the above dated 2019!!!)

Right, but that's all focusing on a very narrow topic -- getting client
side decorations working under wayland and allowing Qt applications to
open. Once again, trying to use anything but a very simple single window /
"hello world" type application will quickly run into breakage. That
particular page is written from a "running Qt apps on Wayland under gnome"
viewpoint, and isn't trying to consider the lower lying topics about
getting full functionality for any qt app (on any platform) working under
Wayland.

>>
>> Read about the sorry state of it here:
https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/247
>
>
> An exceptionally informative pull request.  I was particularly struck by
this comment:
>
>>  Of course you could argue that all of these applications should be
rewritten from the ground up, but especially in science this is not
feasible - people will use X11 indefinitely rather than going to Wayland
with a much degraded user experience.
>
>
> Maybe it's just me, but I have to think that the lack of a placement
protocol (when X, Windows and OSX all support this) is a design mis-feature
in Wayland, rather than a decision taken to guide the architecture of
future desktop applications...

I should have linked to the original posting relating to this (couldn't
find it yesterday). Here's the full gory details:
https://blog.tenstral.net/2024/01/wayland-really-breaks-things-just-for-now.html


Nyall



>
>>
>> So yeah, not a happy situation. At least on the QGIS side we're making
progress toward Qt 6 compatibility, and that's all we can really do from
our end.
>
>
> Well as always, extreme thank-yous to all QGIS developers.  And again the
information you provide here is very valuable at least to me, so thanks
again for taking the time to write this!
>>
>>
>> Nyall
>
>
> [previous stuff deleted]
>
>
> --
> Chris Hermansen · clhermansen "at" gmail "dot" com
>
> C'est ma façon de parler.
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Re: [Qgis-user] QGIS Qt6 Wayland ongoing status

[Nyall Dawson via QGIS-User]

On Thu, 18 Jan 2024 at 13:56, chris hermansen via QGIS-User <
qgis-user@lists.osgeo.org> wrote:
>
> Adam and list,
>
> On Wed, Jan 17, 2024 at 5:34 PM Adam Nielsen 
wrote:
>>
>> > I have been trying to find a mostly definitive and mostly up-to-date
>> > conversation about the status of QGIS, Qt6 and Wayland and I'm not
having
>> > any luck.
>>
>> What's the underlying need for this information?

... gather round folks, for a truly sorry tale! Here's the definitive(*)
situation regarding QGIS and wayland.

- Qt 5 based applications do NOT work well under any wayland environment.
There's fundamental broken functionality, and its functionality which QGIS
requires. A good example is trying to drag a toolbar or dock panel --
you'll instantly "break" the application with non functional empty windows.
- This particular issue HAS been fixed in very recent Qt versions. Read all
about it here:
https://blog.david-redondo.de/kde/wayland/qt/2023/08/08/xdg-toplevel-drag.html
. BUT... this fix ONLY works if the desktop environment supports the fix.
So you'll also need a very recent KDE release for this to work. Gnome, in
typical Gnome fashion, have shown no interest in helping out other toolkits
and implementing this new Wayland protocol and so Qt applications (even
those built with Qt 6.6+) will still be broken. There's little hope on the
horizon that Gnome will change their ways, so you'll also need to move to
KDE and put Gnome in the past. 路
- So let's say you're running KDE, on a distro with a very recent Qt
version. You'll still need a QGIS build based on Qt 6. That's a heavy work
in progress at the moment. We're all ACTIVELY working toward that, but it's
still some time away. You CAN build master versions and get a mostly
working QGIS Qt6 build, so long as you don't require any Python support,
that is!
- Ok, now lets assume you're on KDE, have recent Qt 6 library, have built
QGIS master with Qt6 support and don't need python/plugins. Yay! Will
everything work on Wayland? Well, not quite!.. There's still going to be
broken functionality (such as the color picker not working outside of the
QGIS application). There's also STILL fundamental missing bits in Wayland
itself, such as proper restoring of Window locations. Every time QGIS opens
a new dialog it'll just be thrown on some random screen at some random
location. There's still no real progress toward that being fixed. Read
about the sorry state of it here:
https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/247

So yeah, not a happy situation. At least on the QGIS side we're making
progress toward Qt 6 compatibility, and that's all we can really do from
our end.

Nyall




>
>
> I don't know if you have recently run QGIS on a Wayland desktop, but
there is a stern message strongly suggesting reverting to X.
>
> So as we seem to be marching away from X and ever forward to Wayland, I
would like to start planning ahead a bit, and I would especially like to
find some real information, as opposed to "I think this (but I really don't
know)", or even worse, the people who can see a bright future for (let's
say) Wayland-only desktops and aren't worried about the bumps on the road
getting there.
>
> Fortunately it seems Ubuntu 24.04 will continue to support X
https://discourse.ubuntu.com/t/ubuntu-desktop-24-04-lts-roadmap-highlights/41032
so in my case at least I know I can drop back to X if / as necessary for
the immediate future.
>>
>>
>> > There is some stuff on GitHub but it seems to be at least a year or two
>> > old, talking about Qt6.0 and I gather we are at Qt6.6 by now.  Plus
endless
>> > short conversations in places like Reddit that throw off more heat than
>> > light.
>>
>> Updating to a new Qt version is likely going to be a lot of work, so I
>> imagine nobody is that keen on starting until there's really no choice.
>
>
> As it happens, a search for qt6 in the QGIS repo on GitHub shows work
being done on qt6, apparently for QGIS 4.  So maybe someone has started
already?  I wonder how that's going?
>>
>>
>> > Does anyone have any suggestions as to where to keep informed on this
>> > topic?  Because it seems like Wayland is coming whether we want it or
not...
>>
>> Wayland has been around for many years at this point, and is already the
>> default on some Linux distributions, which have no problem running
>> QGIS.  There is so much legacy code that they are always going to have
>> compatibility modules to keep non-Wayland programs usable.  I wouldn't
>> worry about any programs suddenly breaking due to Wayland.
>
>
> While I appreciate your attempts to reassure me, this isn't helping.
>
> I'm aware from firsthand experience that Wayland has been around for many
years at this point.  I have even used it on and off.  In fact it's my
daily driver on my laptop.
>
> My concern is learning how QGIS development might converge - or not -
with a Wayland-only future, since it seems several important Linux distros
are leaning away from supporting X to 

Re: [Qgis-user] Canvas larger than viewport is rendered/drawn for vector layers, but not for raster layers

[Nyall Dawson via QGIS-User]

On Thu, 16 Nov 2023, 2:40 am Thomas Larsen Wessel via QGIS-User, <
qgis-user@lists.osgeo.org> wrote:

> This screen capture demonstrates much better than words:
> https://imgur.com/5LSEsiY.
>
> Is there any way I can make it prerender the raster data as well?
>
> What I have already tried:
> * setting almost infinite cache size
> * all the relevant QGIS options/settings I could find
> * both local (gpkg) and remote WMS raster data
> * both Windows and Linux
> * QGIS 3.22 and 3.30
> * different CRS for layer
>
> Some of my tests did make the rendering speed up, but no matter what it
> always renders the raster data only for the canvas inside the view port,
> and does not render anything outside of the view port, whereas vector data
> is always rendered for an area that extends outside the view port.
>

There's a few parts to the logic defining whether a layer will be included
in the outside-visible-extent preview:

- WMS layers are **never** included. This is by design, to reduce
unnecessary server load
- when a layer is drawn the time taken to render it is recorded. If this
time exceeds a certain threshold, then the layer is marked as too expensive
to render in these optional out-of-canvas areas.

(You can check the new renderer profile option available in the F12
debugging tools panel in 3.34 for more detailed information about layer
render times)

Nyall



> Sincerely, Thomas
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Re: [Qgis-user] Accessing iface from jupyter to create map from QGIS

[Nyall Dawson via QGIS-User]

On Thu, 7 Dec 2023 at 13:13, noshin prachi via QGIS-User <
qgis-user@lists.osgeo.org> wrote:

> Thank you Adam for your response. I have imported iface from from
> qgis.utils import iface. I am working in qgis environment.   It is my
> first work with qgis and I am finding it difficult to understand. Can you
> please share where I am going wrong? Is there any other way to activate a
> layer from multiple layers and create a map?  I have google street map ,
> shape file and dfsu file in these layers which are required to be added in
> the map.
>

iface is ONLY available when you're running the QGIS desktop application.
It contains methods for interacting with the parts of the desktop
application, which have no meaning when run from elsewhere (such as in a
notebook). In this situation you should avoid iface and use only the
classes from qgis.core instead.

Hope that helps!
Nyall



>
> On Wed, 6 Dec 2023 at 18:10, Adam Nielsen via QGIS-User <
> qgis-user@lists.osgeo.org> wrote:
>
>> > While trying to activate with iface.setactivelayer I am facing an error.
>>
>> The error is complaining that iface is None.  Your code doesn't show
>> what value you assigned to this variable - where did you set iface and
>> what value did you set it to?  I think you forgot to set it and that is
>> why you are getting this error.
>>
>> Cheers,
>> Adam.
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Re: [Qgis-user] Reselect Features

[Nyall Dawson via QGIS-User]

On Fri, 17 Nov 2023 at 12:48, Michael Edward McNeil via QGIS-User <
qgis-user@lists.osgeo.org> wrote:

>
> This is the moment when it would be exceedingly nice if one could just
> pull down Edit > Select > Reselect Features and thereby get back to the
> last previous selected set of features as they existed just prior to the
> last keystroke/click entered.
>
> But that command appears to do nothing.
>

Reselect only works if you've previously "cleared" a selection. If you're
*changing* the selection, then reselect won't do anything.

I think what you're ultimately asking for is a undo/redo history for
selections Which is a GOOD idea! 

Nyall


>
> (Thanks again for your response!)
>
> Best,
> Michael McNeil
>
>
> > On Nov 16, 2023, at 16:33, Andrea Giudiceandrea via QGIS-User <
> qgis-user@lists.osgeo.org> wrote:
> >
> > 
> >>
> >> Michael Edward McNeil memcneil02 at gmail.com
> >> Thu Nov 16 16:04:37 PST 2023
> >
> >> Why doesn't the Edit > Select > Reselect Features command work?
> >
> > Hi Michael,
> > it seems to me the command works as expected [1], at least using QGIS
> 3.28 on Windows.
> >
> > May you provide a detailed list of steps that lead to such command to
> not work properly?
> >
> > Best regards.
> >
> > Andrea
> >
> > [1]
> https://docs.qgis.org/3.28/en/docs/user_manual/introduction/general_tools.html#selecting-manually-on-the-map-canvas
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[Qgis-user] QEP: Authentication system updates

[Nyall Dawson via QGIS-User]

Hi lists,

I've created a new QGIS enhancement proposal at
https://github.com/qgis/QGIS-Enhancement-Proposals/issues/278
concerning changes to the inbuilt authentication system / secure storage
support in QGIS.

By its nature, the authentication framework needs to be secure and any
changes to the authentication logic need careful consideration.

Comments and discussion on the github ticket linked above are encouraged!

Kind regards,
Nyall
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Re: [Qgis-user] Removal of overlap geometries within the same layer - merge to largest neighbor polygon

[Nyall Dawson via QGIS-User]

On Tue, 25 July 2023, 8:02 pm Andreas Neumann via QGIS-User, <
qgis-user@lists.osgeo.org> wrote:

> Hi,
>
> A friend of mine has a dirty input data set with lots of overlapping
> geometries (within the same layer) and asked me if there is a tool within
> QGIS to automatically remove the overlaps and assign the overlapping area
> to the neighbor polygon with the largest area.
>
> The solution was surprisingly hard to find, although I am pretty sure
> there are multiple combinations of algorithms that would solve the problem.
> Here is the solution I came up with: 
> https://github.com/qgis-ch/overlap_removal/tree/main
> - perhaps you have better ideas - more elegant solutions?
>
> Wouldn't it be great if QGIS had a processing tool to solve this overlap
> cleaning within the same layer "out of the box" without having to use a
> graphical model or a more or less complicated sequence of algorithms in the
> processing toolbox? Apparently, ArcGIS has such a tool ...
>
> Saga and GRASS also might have such tools - but I couldn't get the SAGA
> based QGIS plugin "Dissect and dissolve overlaps" (
> https://plugins.qgis.org/plugins/dissect_dissolve_overlaps).
>
> The same problem exists for automatically filling small gaps in the
> polygon data set ...
>

The recently introduced geos tools for coverage layer cleaning and
simplification seem like a good fit here! See eg
https://lin-ear-th-inking.blogspot.com/2022/08/validating-polygonal-coverages-in-jts.html?m=1

These tools would ideally be exposed through the qgis processing toolbox.

Nyall

Andreas
>
>
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Re: [Qgis-user] Possible bug?

[Nyall Dawson via QGIS-User]

On Sun, 23 July 2023, 5:39 pm Richard Duivenvoorde via QGIS-User, <
qgis-user@lists.osgeo.org> wrote:

> Hi Roxo,
>
> You are right, I can confirm this with a very recent build of QGIS:
>
> - with extension we ask for confirmation of overwriting
> - without extension we silently overwrite an old file
>

It's actually an operating system (well, gtk library) issue. The same thing
happens in other apps too on that same platform.

Nyall


> Please file an issue (https://github.com/qgis/QGIS/issues), this seems
> easily fixable.
> See
> https://qgis.org/en/site/getinvolved/development/bugreporting.html#bugs-features-and-issues
>
> Regards,
>
> Richard Duivenvoorde
>
> On 7/22/23 20:21, Fernando M. Roxo da Motta via QGIS-User wrote:
> >
> >
> >Hi all,
> >
> >Today I was exporting some QGis projects as PNG images
> > (project>import/export>export map to image).   At certain point I made
> > a mistake and repeated the name of the previous map, and QGis happily
> > overwrote the previous image, without asking before.  I tried to repeat
> > the action giving the full name of the file (map10.png) and QGis asked
> > for confirmation.The difference was that the first time I gave jjust
> > a name, without the "extension" .png.
> >
> >It seems that even if QGis will give the default "extension" to the
> > filename, it does not verify the prior existence of the file after it
> > attach the "extension".
> >
> >This was in a QGis 3.26.0 on Linux Xubuntu 20.04.   I know that both
> > the QGis and system are kind of old, but if this "feature" is present
> > in current versions it can be cumbersome.
> >
> >
> >
> >Roxo
> >
>
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Re: [Qgis-user] Color Picker Only Partially Opens

[Nyall Dawson via QGIS-User]

On Wed, 12 July 2023, 6:24 pm Alexandru Munteanu via QGIS-User, <
qgis-user@lists.osgeo.org> wrote:

> Hi,
> I can confirm the issue. It's the same with me. I have to click two times
> for the color selector to show entirely. I'm using 3.28 version. I have two
> monitors of the same resolution and make. On my laptop is the same.
>

Is this reproducible on versions 3.30 or later? A fix was added in 3.30
which should address this.

Nyall


> Alexandru
>
>
> On Wed, Jul 12, 2023, 10:45 Frank Broniewski via QGIS-User <
> qgis-user@lists.osgeo.org> wrote:
>
>> Hi Tim,
>>
>>
>>
>> I cannot replicate the issue on my Windows 11 machine (OSGeo4W Installer
>> w QGIS 3.28), but I have all kinds of scaling / UI issues when using mixed
>> DPI screens. I.e. when using my Laptops HiRes Screen and attach a normal
>> FullHD-Monitor, things can get all wonky … do you have by any chance this
>> kind of setup?
>>
>>
>>
>> *Von:* QGIS-User  *Im Auftrag von *Tim
>> Malloy via QGIS-User
>> *Gesendet:* Dienstag, 11. Juli 2023 21:06
>> *An:* qgis-user@lists.osgeo.org
>> *Betreff:* [Qgis-user] FW: Color Picker Only Partially Opens
>>
>>
>>
>> Greetings QGIS Users,
>>
>>
>>
>> I have a long-standing issue with the color picker dialog box in QGIS –
>> all versions (running on Windows 11, but issue has been encountered on
>> various Windows versions) and I’m wondering if there is a setting or some
>> other fix to resolve this.  The issue is that when I click on the down
>> arrow on the color settings dialog in the Layer Styling panel the color
>> picker dialog box only partially opens (image on the left).  I have to
>> click twice more to close and then reopen the color picker dialog box to
>> get it to fully open (image on the right).  This happens the first time I
>> attempt to open the dialog box after performing another function.  If I
>> remain in the same layer and test other colors the dialog will open fully
>> with one click.   This seems minor but when I’m setting up colors for lots
>> of new layers or matching colors to those of other features within a
>> project, where the “Pick Color” function is really handy, it gets pretty
>> tedious.  I suspect this is a Windows issue but any thoughts about the
>> issue and how to resolve it would be appreciated.
>>
>>
>>
>> Tim
>>
>>
>>
>> [image: A screenshot of a computer Description automatically generated]
>> [image: A screenshot of a computer Description automatically generated]
>>
>>
>>
>> Tim Malloy
>>
>> 402 Park Drive
>>
>> t...@tgmalloy.com
>>
>>
>>
>>
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Re: [Qgis-user] [QGIS-Developer] Call of testing of nightlies on hi-dpi displays

[Nyall Dawson via QGIS-User]

On Mon, 29 May 2023 at 19:23, Richard Duivenvoorde  wrote:
>
> Hi Nyall,
>
> Happy to do some testing, I do have a (dual boot) laptop/tablet with 
> 3000x2000 screen (that's high-dpi, yes?), but in Gnome I set the Display 
> 'Scale' on 200% to have proper applications (an to me readable text :-) ).
>
> Is there some test plan/idea's?

There's a few things in particular we need to identify:

- Widgets which are now showing as pixelated. Basically just hunt
through the UI looking for things which look pixelated! This might be
icons, graphics, or even just the drawing of the widget itself. You'll
spot them immediately, as they clearly stand out. But there's a LOT of
different dialogs/tabs/widgets/pages/... in QGIS and it will take some
time to hunt through them all.
- Icons/images which look the wrong size. Eg the marker symbols shown
in the layer tree right now are incorrectly sized and will be half the
size of the actual symbol shown on the map. That's a known regression,
but there's likely others like this hiding around the place.
- Text which is the wrong size. If something has a hard-coded sizing
it's possible that we'll get fonts scaled badly, so if you spot any
text which noticably looks incorrectly sized vs other UI elements then
that's also something we need to fix.

> Is my setup something you want to test (200%), or is is preferred to use the 
> 100% scale?

This is EXACTLY the kind of setup we need testing on! If the display
scaling is set to 100% (in Windows, or Linux), then you'll see no
difference between the old approach vs new. The new logic only kicks
in when display scaling is present.

> I'm not sure what is supposed to be the 'normal' way of scaling (like what 
> does a mac do)?

Things should just look perfect, regardless of whether or not display
scaling is active :)

Nyall

> Or is it more to try to see if the icons/widgets scale up/down when fidling 
> with scale (or what it is called in Windows)?
>
> Regards,
>
> Richard Duivenvoorde
>
> On 5/29/23 06:01, Nyall Dawson via QGIS-Developer wrote:
> > Hi lists,
> >
> > For the upcoming QGIS 3.32 release a change has been made in how QGIS
> > handles high dpi (and retina) displays. This should ultimately make
> > QGIS behave MUCH better on these displays, but there's likely some
> > short-term fallout and regressions caused by the change.
> >
> > If you've access to a high-dpi display, please test out the nightly
> > releases and file bug reports on github for any regressions you spot
> > -- in particular we are looking for widgets and places where the QGIS
> > interface is now looking pixelated or where the scale / sizes of
> > objects are incorrect.
> >
> > (Currently there's known regressions for the icons shown in the layer
> > tree panel, and for pixelated icons in the style manager dialog.)
> >
> > Thanks in advance!
> > Nyall
> > ___
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> > qgis-develo...@lists.osgeo.org
> > List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer
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[Qgis-user] Call of testing of nightlies on hi-dpi displays

[Nyall Dawson via QGIS-User]

Hi lists,

For the upcoming QGIS 3.32 release a change has been made in how QGIS
handles high dpi (and retina) displays. This should ultimately make
QGIS behave MUCH better on these displays, but there's likely some
short-term fallout and regressions caused by the change.

If you've access to a high-dpi display, please test out the nightly
releases and file bug reports on github for any regressions you spot
-- in particular we are looking for widgets and places where the QGIS
interface is now looking pixelated or where the scale / sizes of
objects are incorrect.

(Currently there's known regressions for the icons shown in the layer
tree panel, and for pixelated icons in the style manager dialog.)

Thanks in advance!
Nyall
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[Qgis-user] PSA: Don't update to Gnome 44!

[Nyall Dawson via QGIS-User]

Hi lists,

Just a quick PSA: If you're using QGIS (or any Qt based app), I recommend
avoiding an upgrade to any gnome 44 based distribution for now.

You'll get hit with this nasty bug:
https://gitlab.gnome.org/GNOME/mutter/-/issues/2715 which breaks drag and
drop functionality in all Qt applications. And in the process, basically
makes QGIS unusable... 

You've been warned!

Nyall
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Re: [Qgis-user] Placing random points

[Nyall Dawson via QGIS-User]

On Thu, 23 Mar 2023 at 19:20, Thomas Sebastien via QGIS-User
 wrote:
>
> Dear QGIS users,
>
> I’m trying to place a small number of points, n, randomly in a large number 
> of polygons, N. But, the Vector>Research Tools> Random points in polygons 
> tool only lets me place a minimum of 1 random point in each of the N 
> polygons, i.e N points when I only need n. Do you know a way I can go about 
> this?

How about dissolving the polygons into a single feature and then
placing the desired random number of points inside this dissolved
feature?

Nyall

>
> Thanks,
>
> Sebastien
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Re: [Qgis-user] Problems with transformation including height values

[Nyall Dawson via QGIS-User]

On Tue, 21 Mar 2023, 8:21 pm Richard McDonnell, 
wrote:

> Hi,
>
> Just to add to what Nyall said.
>
> See link below, which suggests a way using OGR to carry out the process
> you require.
>
>
>
>
> https://gis.stackexchange.com/questions/324848/transform-datum-csv-csv-using-ogr2ogr
>
>
>
> It suggests you preform your horizontal transformation first, this can be
> done in QGIS, then carry out the Vertical Transformation. This can be done
> in command line, if you are on windows, the best option is to use the *OSGeo4w
> Shell*, as all the needed environmental settings are applied.
>
> I hope the above helps.
>
>
>
> Maybe there is an opportunity to have QGIS preform Vertical translations,
> even if these are a separate step? It’s something that would be useful for
> both Raster and Vector Data.
>

It's definitely on the radar -- especially for transformation of point
clouds. It's just a very involved task with a high degree of complexity,
and will need funding to happen.

Nyall

Regards,
>
>
> Richard
>
>
>
>
>
>
>
> ——
> Richard McDonnell MSc GIS, FME Certified Professional
> *FRM Data Management*
>
> ——
> Oifig na nOibreacha Poiblí
> Office of Public Works
>
> Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36
> Jonathan Swift Street, Trim, Co Meath, C15 NX36
> ——
> M +353 87 688 5964 T +353 46 942 2409
> https://gov.ie/opw
>
> ——
> To send me files larger than 30MB, please use the link below
> https://filetransfer.opw.ie/filedrop/richard.mcdonn...@opw.ie
>
> Email Disclaimer:
> https://www.gov.ie/en/organisation-information/439daf-email-disclaimer/
>
> ——
> MSc GIS, FME Certified Professional
>
> ——
> Oifig na nOibreacha Poiblí
> Office of Public Works
>
> Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36
> Jonathan Swift Street, Trim, Co Meath, C15 NX36
> ——
> M +353 87 688 5964 T +353 46 942 2409
> https://https://gov.ie/opw <https://www.opw.ie>
>
> ——
> Email Disclaimer:
> https://www.gov.ie/en/organisation-information/439daf-email-disclaimer/
> <https://www.opw.ie/en/disclaimer/>
>
> *From:* QGIS-User  *On Behalf Of *Nyall
> Dawson via QGIS-User
> *Sent:* 21 March 2023 10:14
> *To:* Bo Victor Thomsen 
> *Cc:* qgis-user 
> *Subject:* Re: [Qgis-user] Problems with transformation including height
> values
>
>
>
>
>
> On Tue, 21 Mar 2023, 8:06 pm Bo Victor Thomsen via QGIS-User, <
> qgis-user@lists.osgeo.org> wrote:
>
> Hi list -
>
> I have a problem with transforming a csv file containing x,y *and *z
> values from EPSG:4326 to EPSG:7416, i.e I want to transform the height
> value from LongLat/ WGS84 ellipsoid height to UTM32/Etrs89 with vertical
> reference DVR90.
>
> The file look like this:
>
>
> *== data.csv, EPSG:4326 id: col1, x: col3, y: col2, z: col4 == *
> a;55.0;12.0;42.0
> b;55.05;12.0;43.0
> c;55.10;12.0;44.0
> d;55.15;12.0;45.0
> e;55.20;12.0;46.0
> *===*
>
> *Step 1*: I import the file into QGIS using the Data Source Manager -->
> "Delimited Text" and define the projection to be EPSG:4326 *and* to
> include z values. This works and the points are shown on my map where I
> expect them to be (Somewhere in the middle of Zealand, Denmark)
>
> *Step 2*: I export the layer as a geojson file using "Export" --> "Save
> features as.." from the layer manager and choose EPSG:7416 (UTM32/ETRS89
> with DVR90 as vertical reference. And to include z-values
>
> The resulting file looks like this:
>
>
> *== data.geojson, EPSG:7416 == *{
> "type": "FeatureCollection",
> "name": "data",
> "crs": { "type": "name", "properties": { "name":
> "urn:ogc:def:crs:EPSG::4979" } },
> "features": [
> { "type": "Feature", "properties": { "field_1": "a", "field_2": 55.0,
> "field_3": 12.0, "field_4": 42.0 }, "geometry": { "type": "Point",
> "coordinates": [ 12.0, 55.0, 42.0 ] } },
> { "type": "Feature", "properties": { "field_1": "b", "field_2": 55.05,
> "field_3": 12.0, "field_4": 43.0 }, "geometry": { "type": "Point",
> "coordinates": [ 12.0, 55.05, 43.0 ] } },
> { "type": "Feature", "properties": { "field_1": "c", "field_2": 55.1,
> "field_3": 12.0, "field_4": 44.0 }, "geometry": { "ty

Re: [Qgis-user] Problems with transformation including height values

[Nyall Dawson via QGIS-User]

On Tue, 21 Mar 2023, 8:06 pm Bo Victor Thomsen via QGIS-User, <
qgis-user@lists.osgeo.org> wrote:

> Hi list -
>
> I have a problem with transforming a csv file containing x,y *and *z
> values from EPSG:4326 to EPSG:7416, i.e I want to transform the height
> value from LongLat/ WGS84 ellipsoid height to UTM32/Etrs89 with vertical
> reference DVR90.
>
> The file look like this:
>
> *== data.csv, EPSG:4326 id: col1, x: col3, y: col2, z: col4 ==*
> a;55.0;12.0;42.0
> b;55.05;12.0;43.0
> c;55.10;12.0;44.0
> d;55.15;12.0;45.0
> e;55.20;12.0;46.0
> *===*
>
> *Step 1*: I import the file into QGIS using the Data Source Manager -->
> "Delimited Text" and define the projection to be EPSG:4326 *and* to
> include z values. This works and the points are shown on my map where I
> expect them to be (Somewhere in the middle of Zealand, Denmark)
>
> *Step 2*: I export the layer as a geojson file using "Export" --> "Save
> features as.." from the layer manager and choose EPSG:7416 (UTM32/ETRS89
> with DVR90 as vertical reference. And to include z-values
>
> The resulting file looks like this:
>
> *== data.geojson, EPSG:7416 ==*
> {
> "type": "FeatureCollection",
> "name": "data",
> "crs": { "type": "name", "properties": { "name":
> "urn:ogc:def:crs:EPSG::4979" } },
> "features": [
> { "type": "Feature", "properties": { "field_1": "a", "field_2": 55.0,
> "field_3": 12.0, "field_4": 42.0 }, "geometry": { "type": "Point",
> "coordinates": [ 12.0, 55.0, 42.0 ] } },
> { "type": "Feature", "properties": { "field_1": "b", "field_2": 55.05,
> "field_3": 12.0, "field_4": 43.0 }, "geometry": { "type": "Point",
> "coordinates": [ 12.0, 55.05, 43.0 ] } },
> { "type": "Feature", "properties": { "field_1": "c", "field_2": 55.1,
> "field_3": 12.0, "field_4": 44.0 }, "geometry": { "type": "Point",
> "coordinates": [ 12.0, 55.1, 44.0 ] } },
> { "type": "Feature", "properties": { "field_1": "d", "field_2": 55.15,
> "field_3": 12.0, "field_4": 45.0 }, "geometry": { "type": "Point",
> "coordinates": [ 12.0, 55.15, 45.0 ] } },
> { "type": "Feature", "properties": { "field_1": "e", "field_2": 55.2,
> "field_3": 12.0, "field_4": 46.0 }, "geometry": { "type": "Point",
> "coordinates": [ 12.0, 55.2, 46.0 ] } }
> ]
> }
> *===*
>
> The new file is shown in my map exactly on top of the original point
> layer, meaning the horizontal projection is accurate. However, my z
> coordinates are not reprojected to the new vertical reference. All the
> z-values are exactly the same as the values in the .csv - file.
>
> After some digging through Google and other places, I discover that
> EPSG:4326 *doesn't* have a z component. Surprise ! You have to use
> EPSG:4979, which is the same as EPSG:4326 with ellipsoid height.
>
> But, *after *repeating *step 1*, *but* using EPSG:4979 as CRS during
> import, and subsequently repeating *step 2*, I get the exact same result:
> No transformation of height values.
>
> So, what is not working ? Am I doing something wrong ?? Or is QGIS
> incapable of transforming z values ???
>

The second -- qgis currently doesn't handle vertical crs at all. My
recommendation is to use gdal utilities to do a transform respecting
vertical datums.

Nyall

>
> --
> Med venlig hilsen / Best regards
>
> Bo Victor Thomsen
>
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Re: [Qgis-user] Export to ESRI File Geodatabase

[Nyall Dawson via QGIS-User]

On Wed, 18 Jan 2023 at 07:04, Even Rouault via QGIS-User
 wrote:
>
> Randal,
>
> Support for the OpenFileGDB driver in the Save As dialog only dates back
> to a few days ago per https://github.com/qgis/QGIS/pull/51397 , so
> you'll have to wait for 3.28.3

Just to clarify -- the missing bit in 3.28 was that FileGeodatabase
wasn't showing in the layer right-click menus.
It should still be possible to export to GDB in 3.28 without that fix.
From the browser panel, you can create a new empty Geodatabase by
right-clicking on a folder, and then drag and drop layers directly
into that GDB to import them!

Nyall


>
> What you must see with the driver being interminently available is that
> some of your installations might have the FileGDB driver (not
> OpenFileGDB) that relies on the ESRI closed source SDK.
>
> Even
>
> Le 17/01/2023 à 21:56, Randal Hale via QGIS-User a écrit :
> > I don't think this is just me - BUT - I wanted to check before filing
> > a bug report. This is all with QGIS 3.28.2 On Windows 10 and using
> > GDAL 3.6.1
> >
> > I was checking on a problem and had used Network Installer to install
> > QGIS - I had File Geodatabase as a choice for Export (Right Click on
> > Layer -> Export As ->pick  ESRI File Geodatabase).
> >
> > I installed QGIS using the Stand Alone installer (after removing QGIS
> > Network Install) and didn't have ESRI File Geodatabase as a choice on
> > export Features. This is confirmed by another user using the
> > standalone installer.
> >
> > I removed QGIS and Reinstalled using the Network Installer and didn't
> > have ESRI File Geodatabase as a choice (but I did before).
> >
> > So it seems like I'm missing something - I've been digging through
> > options and creating new profiles but I can't make the ERI File
> > Geodatabase consistently appear or disappear. Is there something else
> > I should try?
> >
> > Randy
> >
> >
> --
> http://www.spatialys.com
> My software is free, but my time generally not.
>
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Re: [Qgis-user] Unable to open some LISTdata open data ESRI File Geodatabases

[Nyall Dawson via QGIS-User]

On Fri, 16 Dec 2022 at 09:18, Even Rouault via QGIS-User
 wrote:
>
> Hi Peter,
>
> yes I confirm this dataset is a raster gdb. I can sort-of open it with
> my QGIS + GDAL master build using the OpenFileGDB driver, but you'll see
> the raster tables in a raw unusable way. For example layers like
> fras_blk_NCH_ES_WATER_LOGGING_HAZARD which contains the tiles as
> compressed data in a BLOB column.
>
> You could try the https://github.com/r-barnes/ArcRasterRescue utility to
> convert into GeoTIFF

FWIW, I've had more luck with the fork at
https://github.com/justinfisk/ArcRasterRescue

Nyall

>
> You could also kindly or not kindly suggest your administration to not
> use proprietary formats for open data whereas thereare so many open
> alternatives, like GeoTIFF...
>
> Small "advertizing": for those interesting, there's a funding
> opportunity to develop a GDAL open source raster driver to be able to
> read filegdb rasters that QGIS could use to open directly such files.
> Contact me off-list if interested.
>
> Even
>
> Le 15/12/2022 à 23:49, JOLLY, Peter via QGIS-User a écrit :
> > Hello
> >
> > I've downloaded some  datasets from the LISTdata open data repository 
> > (https://listdata.thelist.tas.gov.au/opendata/index.html) -  which is a 
> > great service.
> > However, I can't open any datasets that are solely an ESRI File 
> > Geodatabase, e.g. 
> > https://listdata.thelist.tas.gov.au/opendata/data/NCH_ES_WATER_LOGGING_HAZARD_STATEWIDE.zip
> >  (279 MB)
> > Maybe these are raster gdb datasets? How can I tell if that is the case?
> > Is there any way the open a raster gdb other than with ESRI software?
> >
> > I can open gdb files in QGIS from LISTdata that are included as part of a 
> > set with shapefile and MapInfo tab files (e.g. in the "Tasmanian Irrigation 
> > Irrigation District" dataset). I'm guessing that is because these are 
> > vector gdb files?
> >
> > I'm running QGIS 3.10.6 ltr on Windows 10 64-bit (yes I know it's not the 
> > latest ltr, but it was the most recent "portable" build I have been able to 
> > find and run successfully).
> >
> > Thanks
> > Peter
> > Tasmania, Australia
> >
> > ___
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>
> --
> http://www.spatialys.com
> My software is free, but my time generally not.
>
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Re: [Qgis-user] Georeferencer Problem

[Nyall Dawson via QGIS-User]

On Thu, 8 Dec 2022 at 09:53, Grant Boxer via QGIS-User
 wrote:
>
> I am having issues with the georeferencer. When I register an image the 
> process does not recognise the CRS entered into the settings window. It 
> returns the layer with an invalid projection. When I try to change the 
> projection in the new layer it creates this error.
>
>
>
> Has anyone else had this problem? See output below, Any thoughts?


That error is coming from the "enmapboxplugin" plugin. Try removing
that plugin and re-testing.

Nyall

>
>
>
> Regards Grant Boxer, Perth WA
>
>
>
> An error has occurred while executing Python code:
>
> RuntimeError: The JPEG driver does not support update access to existing 
> datasets.
>
> Traceback (most recent call last):
>   File 
> "C:\Users/boxer/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\enmapboxplugin\enmapbox\qgispluginsupport\qps\layerconfigwidgets\gdalmetadata.py",
>  line 1218, in apply
> ds = gdalDataset(self.mapLayer(), gdal.GA_Update)
>   File 
> "C:\Users/boxer/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\enmapboxplugin\enmapbox\qgispluginsupport\qps\utils.py",
>  line 829, in gdalDataset
> return gdalDataset(dataset.source(), eAccess=eAccess)
>   File 
> "C:\Users/boxer/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\enmapboxplugin\enmapbox\qgispluginsupport\qps\utils.py",
>  line 833, in gdalDataset
> ds = gdal.Open(dataset, eAccess)
>   File "C:\OSGeo4W\apps\Python39\lib\site-packages\osgeo\gdal.py", line 4708, 
> in Open
> return _gdal.Open(*args)
> RuntimeError: The JPEG driver does not support update access to existing 
> datasets.
>
>
> Python version: 3.9.5 (tags/v3.9.5:0a7dcbd, May  3 2021, 17:27:52) [MSC 
> v.1928 64 bit (AMD64)]
> QGIS version: 3.28.1-Firenze Firenze, fde3b8fbb8
>
> Python Path:
>
> · C:/OSGeo4W/apps/qgis/./python
>
> · 
> C:/Users/boxer/AppData/Roaming/QGIS/QGIS3\profiles\default/python
>
> · 
> C:/Users/boxer/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins
>
> · C:/OSGeo4W/apps/qgis/./python/plugins
>
> · C:\OSGeo4W\bin\python39.zip
>
> · C:\OSGeo4W\apps\Python39\DLLs
>
> · C:\OSGeo4W\apps\Python39\lib
>
> · C:\OSGeo4W\bin
>
> · 
> C:\Users\boxer\AppData\Roaming\Python\Python39\site-packages
>
> · C:\OSGeo4W\apps\Python39
>
> · C:\OSGeo4W\apps\Python39\lib\site-packages
>
> · C:\OSGeo4W\apps\Python39\lib\site-packages\win32
>
> · C:\OSGeo4W\apps\Python39\lib\site-packages\win32\lib
>
> · C:\OSGeo4W\apps\Python39\lib\site-packages\Pythonwin
>
> · 
> C:/Users/boxer/AppData/Roaming/QGIS/QGIS3\profiles\default/python
>
> · 
> C:\Users/boxer/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\enmapboxplugin\site-packages
>
> · 
> C:\Users/boxer/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\enmapboxplugin
>
> · 
> C:\Users\boxer\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\enmapboxplugin\enmapbox\site-packages
>
> · 
> C:\Users\boxer\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\enmapboxplugin\enmapbox\apps
>
> · 
> C:\Users\boxer\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\enmapboxplugin\enmapbox\coreapps
>
> · 
> C:\Users\boxer\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\enmapboxplugin\enmapbox\eo4qapps
>
> .
>
>
>
>
>
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Re: [Qgis-user] New crowdfunding campaign: point clouds and 3D improvements in QGIS

[Nyall Dawson via Qgis-user]

On Tue, 27 Sept 2022 at 16:40, Saber Razmjooei
 wrote:
>
> Hi Andreas,
>
> Many thanks for your email.
> @Nyall Dawson can comment on that, but I think it should be possible to add 
> SVG format too as an option to export elevation profiles to.

The issue with including SVG export is the time-old limitation in Qt
regarding SVG exports when clipping paths are present. We use clipping
paths heavily in the elevation plots, so if we exported these to SVG
then the clipping would be ignored and the results would be an
unusable mess.

(I'll revisit this when the issue is resolved in Qt, as the actual
QGIS part of SVG exports is trivial)

Nyall




>
> Kind regards
> Saber
>
>
> On Tue, 27 Sept 2022 at 08:25, Andreas Neumann  wrote:
>>
>> Hi Saber,
>>
>> Very good. Hopefully it will be another successful campaign.
>>
>> A question on the export of the profile: CSV and DXF is mentioned. Wouldn't 
>> it also make sense to add SVG export, so the profile could be exported to 
>> Inkscape/Illustrator? I know, it is already possible to export a layout to 
>> SVG (and with the new enhancement, the profile can then be part of a 
>> layout), but it would be convenient, being able to export to SVG without 
>> having to create a layout first. Not sure, how much effort this would mean?
>>
>> I will help to spread the word!
>>
>> Andreas
>>
>> On Mon, 26 Sept 2022 at 17:43, Saber Razmjooei via Qgis-user 
>>  wrote:
>>>
>>> Dear all,
>>>
>>> As you know, in the past couple of years, we (Lutra, North Road and 
>>> https://hobu.co/) added support point clouds and developed several new 3D 
>>> features to QGIS (e.g. Profile tool).
>>>
>>> For the next round of crowdfunding, after feedback by several user groups 
>>> and organizations, we decided to bring processing of point clouds to QGIS. 
>>> In addition, there will be several enhancements to the profile tool and 3D 
>>> maps. For more information, see:
>>> https://www.lutraconsulting.co.uk/crowdfunding/pointcloud-processing-qgis/
>>>
>>> Your help is needed to make this happen. Please support our crowdfunding 
>>> campaign by filling out the pledge form. If you are from a larger 
>>> organisation and require extra information to contribute to the campaign, 
>>> please contact me.
>>>
>>> Kind regards
>>> Saber
>>>
>>> --
>>> Saber Razmjooei
>>> www.lutraconsulting.co.uk
>>>
>>> ___
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>>> Qgis-user@lists.osgeo.org
>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>
>>
>>
>> --
>>
>> --
>> Andreas Neumann
>> QGIS.ORG board member (treasurer)
>
>
>
> --
> Saber Razmjooei
> www.lutraconsulting.co.uk
>
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Re: [Qgis-user] Event loop in QGIS3

[Nyall Dawson via Qgis-user]

On Wed, 17 Aug 2022 at 06:54, Tudorache, Marian via Qgis-user
 wrote:
>
> Hi Chris,
>
>
>
> I read that article and based on it I found out that I need to put 
> processEvents() and I understand the logic in this.
>
>
>
> Someone said:
>
> In more recent QGIS versions the Python console no longer triggers this event 
> loop, as it's often quite dangerous to execute the loop in the middle of 
> other running code.
>
>
>
> It seems somehow QGIS 2.18 was designed to send automatically updates to the 
> GUIs when a loop is running and this capability was eliminated in QGIS 3

That's correct -- there was a forced processEvents in QGIS 2 after
printing anything, but that directly lead to crashes in some
circumstances. processEvents is a potentially very dangerous call, so
now the responsibility is on end users/developers to make sure it's
safe to call after a print.

Nyall



>
> Anyway, thank you for your answer.
>
>
>
> Marian
>
>
>
> From: chris hermansen 
> Sent: August 16, 2022 4:40 PM
> To: Tudorache, Marian 
> Cc: qgis-user@lists.osgeo.org
> Subject: [EXT] Re: [Qgis-user] Event loop in QGIS3
>
>
>
> Marian and list, On Tue, Aug 16, 2022 at 12: 02 PM Tudorache, Marian via 
> Qgis-user  wrote: Hello community,   A while 
> ago I sent a question about a problem with QMessageBox and message bar does 
> not get updated
>
> Marian and list,
>
>
>
> On Tue, Aug 16, 2022 at 12:02 PM Tudorache, Marian via Qgis-user 
>  wrote:
>
> Hello community,
>
>
>
> A while ago I sent a question about a problem with QMessageBox and message 
> bar does not get updated during a long process.
>
> In my example I create a script like this.
>
>
>
> from qgis.PyQt import QtWidgets
>
> message = "Wait to open the airspace project..."
>
> msg = QtWidgets.QMessageBox()
>
> msg.setText(message)
>
> msg.show()
>
> qgis.utils.iface.messageBar().pushMessage("Wait", message)
>
>
>
>
>
> for i in range(1000):
>
> print(i)
>
> qgis.utils.iface.messageBar().pushMessage("Done", "The process is done")
>
> msg.setText("The process is done")
>
> msg.show()
>
> qgis.utils.iface.messageBar().pushMessage("Done", "The process is done"))
>
>
>
>
>
> When I run the scrip in QGIS 2.18 the QMessageBox displays first the message 
> "Wait to open the airspace project...". The same message is pushed to 
> messageBar.
>
> Then during the loop it displays the variable i.
>
> At the end of the loop the QMessageBox displays the message "The process is 
> done" which is also pushed to the messageBar.
>
>
>
> When I run the same scrip on QGIS 3 the QMessageBox is empty. The message 
> "Wait to open the airspace project..." is not displayed by QMessageBox nor by 
> messageBar.
>
> The print inside the loop displays the I and when the loop is done the 
> QMessageBox displays the message "The process is done".
>
> The messageBar displays also the message "The process is done". And after a 
> while it displays the initial message "Wait to open the airspace project..."
>
>
>
> I modified the scrip by adding QApplication.processEvents() inside the loop 
> and now everything is fine.
>
> It seems QGIS3 no longer triggers this event loop and I have to do this 
> explicitly by calling processEvents from QApplication.
>
>
>
> Why QGIS 3 needs to call QApplication.processEvents() and QGIS 2 does not 
> need?
>
>
>
>
>
> Marian, did you read this article?
>
>
>
> https://doc.qt.io/qt-5/qcoreapplication.html#details
>
>
>
> There you will see this:
>
>
>
> The event loop is started with a call to exec(). Long-running operations can 
> call processEvents() to keep the application responsive.
>
>
>
> In your case, your "long-running operation" is your for loop.  And it is not 
> QGIS3 that has the responsibility to trigger processEvents() but your own 
> long-running operation, at least the way I'm reading this.
>
>
>
> As to why QGIS 2 did not need this, I don't know.
>
>
> --
>
> Chris Hermansen · clhermansen "at" gmail "dot" com
>
> C'est ma façon de parler.
>
>
> 
>
> This electronic message, as well as any transmitted files included in the 
> electronic message, may contain privileged or confidential information and is 
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> addressed. If you have received this electronic message in error please 
> notify the sender immediately and delete the electronic message. Any 
> unauthorized copying, disclosure or distribution of the electronic message is 
> strictly forbidden. NAV CANADA accepts no liability for any damage caused by 
> any virus and/or other malicious code transmitted by this electronic 
> communication.
>
> Le présent message électronique et tout fichier qui peut y être joint peuvent 
> contenir des renseignements privilégiés ou confidentiels destinés à l’usage 
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> immédiatement et supprimez le. Toute 

Re: [Qgis-user] Convert huge shapefile to small size

[Nyall Dawson via Qgis-user]

On Fri, 29 Jul 2022 at 06:22, Madry, Scott via Qgis-user
 wrote:
>
> Thanks Chris, but I do think that this is a topic is worth considering by the 
> QGIS community, beyond the limitations of the archaeic shapefile format. We 
> are moving into an era of very big data, both raster and vector, and QGIS 
> should be able to meet this challenge. This will require some foresight and 
> planning, thus my raising the issue. Or not...

In truth QGIS is already well prepared for handling massive datasets.
(E.g. you'll see in recent versions how well it handles mammoth point
cloud formats!). Sure, there's further improvements which can be made,
but they're evolutionary rather than revolutionary!

Nyall


>
> Best,
>
> Scott
>
> On Jul 28, 2022, at 4:05 PM, chris hermansen  wrote:
>
> Scott and list,
>
> With respect I think this conversation is moving off the point, which was 
> related to a 5gb shapefile
>
> https://en.m.wikipedia.org/wiki/Shapefile
>
> Which is beyond the design limits of the Shapefile standards and perhaps 
> therefore the source of the problem that the OP has.
>
> Notably not a limitation of QGIS
>
> On Thu, Jul 28, 2022, 10:45 Madry, Scott via Qgis-user 
>  wrote:
>>
>> Dear colleagues,
>>
>> As we move more into the world of big data, IOE, data mining, and data 
>> analytics, dealing with larger and larger data sets will become required, 
>> and, eventually, the norm.
>>
>> GRASS GIS has made very good progress in this regard, optimizing the code to 
>> run on massively parallel computer architectures, with very good effect:
>>
>> https://grasswiki.osgeo.org/wiki/Supercomputing
>>
>> Perhaps it is time for QGIS to consider this in its future development 
>> plans? We will certainly be needing this in the future.
>>
>> And thanks to all the team who keep the QGIS train running, I am constantly 
>> amazed at the energy, effort, and availability of people to the broader 
>> community.
>>
>> Scott
>>
>> Scott Madry, Ph.D.
>> Research Associate Professor of Archaeology
>> The University of North Carolina at Chapel Hill
>>
>> Tel 1-919-448-4493
>> Email:mad...@email.unc.edu
>> https://scottmadry.web.unc.edu
>> Skype:   scott madry
>>
>>
>>
>> On Jul 28, 2022, at 10:14 AM, jhubbslist--- via Qgis-user 
>>  wrote:
>>
>> Past a point, trying to run a GIS app with very large data structures just 
>> doesn't work well. If you really need all the information you're carrying 
>> around for your analysis or whatever, you may need to reach for different 
>> tools or use the tools you have differently.
>>
>> I assume it's not so much the >5GiB of disk space that's the issue and that 
>> you've maxxed out the CPU, graphics, and disk I/O rate as much as is 
>> practical so mostly it's a matter of how long it takes maps etc. to paint 
>> onscreen. It may help you to move the heavy-lift onto PostgreSQL/PostGIS 
>> where you can make use of spatial indexing. Or, you can craft your 
>> operations the way you want them in QGIS but do the actual work with e.g. 
>> GDAL calls in Python. I spoke with someone a couple weeks ago whose 
>> particular GIS process worked better in GRASS than in QGIS, so that's 
>> something you might look into as well.
>>
>> On 7/28/22 7:52 AM, krishna Ayyala via Qgis-user wrote:
>>
>> dbf file itself is 5.1GB. Rest all other files are less than 500MB. It is 
>> the number of records which is huge. It has about 117,2100 points.
>>
>> On Thu, Jul 28, 2022 at 12:02 AM Bernd Vogelgesang via Qgis-user 
>>  wrote:
>>>
>>> how big is the dbf file of that shape? Maybe you can also drop some
>>> attributes.
>>>
>>> Am 28.07.22 um 03:46 schrieb krishna Ayyala via Qgis-user:
>>> > Hello,
>>> > I have a shapefile of 5GB in size. Is it possible to convert this
>>> > shapefile to a smaller size file? It can be any format, not
>>> > necessarily a shapefile. But, preferably a vector format. I tried to
>>> > convert it into tiles, but that didn't work as it was losing the
>>> > resolution. I am looking to convert this 5GB size file to about 500MB.
>>> >
>>> > Regards.
>>> >
>>> > ___
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>>> > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
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>>
>>
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Re: [Qgis-user] [QGIS-Developer] A good task for someone wanting to get involved -- update CPT ramps

[Nyall Dawson via Qgis-user]

On Wed, 20 Jul 2022 at 09:50,  wrote:
>
> Here is a pull request for the requested changes:
> https://github.com/qgis/QGIS/pull/49423

Wow -- that was fast!! :D

Nyall

>
> --
> James
>
> -Original Message-
> From: QGIS-Developer  On Behalf Of
> Nyall Dawson via QGIS-Developer
> Sent: Tuesday, July 19, 2022 4:36 PM
> To: qgis-developer ; qgis-user
> 
> Subject: [QGIS-Developer] A good task for someone wanting to get involved --
> update CPT ramps
>
> Hi all,
>
> Here's an idea for a good task for someone wanting to get involved in QGIS
> contributions which doesn't require any c++/python.
>
> Currently we package a subset of the CPT ramps archive in QGIS, which you
> can see here
> https://github.com/qgis/QGIS/tree/master/resources/cpt-city-qgis-min
>
> It's missing a lot of the ramps present in the current version of the CPT
> archive from http://soliton.vm.bytemark.co.uk/pub/cpt-city/ . Some of these
> are because the licenses won't permit bundling with QGIS (e.g. the ESRI
> sets), but others are just missing because we haven't updated our subset in
> a loong time. (E.g. compare the subset present in QGIS
> https://github.com/qgis/QGIS/tree/master/resources/cpt-city-qgis-min/gmt
> from the GMT set vs
> http://soliton.vm.bytemark.co.uk/pub/cpt-city/gmt/index.html )
>
> It would be great to update our subset and re-sync it with the upstream
> collection. We're missing a lot of nice ramps we could be bundling by
> default :)
>
> I'm happy to mentor this task if someone wants to give it a shot...
>
> Nyall
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[Qgis-user] A good task for someone wanting to get involved -- update CPT ramps

[Nyall Dawson via Qgis-user]

Hi all,

Here's an idea for a good task for someone wanting to get involved in
QGIS contributions which doesn't require any c++/python.

Currently we package a subset of the CPT ramps archive in QGIS, which
you can see here
https://github.com/qgis/QGIS/tree/master/resources/cpt-city-qgis-min

It's missing a lot of the ramps present in the current version of the
CPT archive from http://soliton.vm.bytemark.co.uk/pub/cpt-city/ . Some
of these are because the licenses won't permit bundling with QGIS
(e.g. the ESRI sets), but others are just missing because we haven't
updated our subset in a loong time. (E.g. compare the subset
present in QGIS
https://github.com/qgis/QGIS/tree/master/resources/cpt-city-qgis-min/gmt
from the GMT set vs
http://soliton.vm.bytemark.co.uk/pub/cpt-city/gmt/index.html )

It would be great to update our subset and re-sync it with the
upstream collection. We're missing a lot of nice ramps we could be
bundling by default :)

I'm happy to mentor this task if someone wants to give it a shot...

Nyall
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Re: [Qgis-user] Qgis 3.22.8 Error messages displayed in the GUI

[Nyall Dawson via Qgis-user]

On Mon, 11 Jul 2022 at 21:40, Piet via Qgis-user
 wrote:
>
> Dear List,
>
> I used a selfcompiled Qgis, build with 'Debug-Option' set in ccmake.
>
> Now there's a small red window in the main window which displayed 
> errors/warning.
>
> In my case "Qt: QXcbConnection: XCB error: 3 (BadWindow), sequence: 65154, 
> resource id: 11286601, major code: 40 (TranslateCoords), minor code: 0",
>
> which seems to be a known QT-Bug.
>
> Can I turn of this error window?

This particular one is now filtered out for 3.26+, as it's not
reflective of a bug in QGIS.

The others still remain, as they likely ARE indicative of something
which needs fixing in QGIS. If you encounter them, you should open
tickets for each so that the underlying cause can be identified.

Nyall

>
> Because it's upset me a bit and I can see the warnings in a console as well.
>
> Thank you for any hint!
>
> Kind regards
>
> Piet
>
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[Qgis-user] QEP: Layout Legends - Rework handling of initial layer set and synchronization

[Nyall Dawson via Qgis-user]

Hi all,

Please see https://github.com/qgis/QGIS-Enhancement-Proposals/issues/253
for a newly submitted QGIS enhancement proposal regarding the initial
content and layer synchronization of legends in print layouts.

Comments/suggestions/feedback is welcome (and encouraged!) on the page
linked above!

Nyall
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[Qgis-user] QGIS 3.26 Elevation profile/cross section tool deep dive - live today

[Nyall Dawson via Qgis-user]

Hi all,

Later today (May 13), at 19:30 AEST (GMT+10) / 11:30 CEST I'll be
doing an in-depth live exploration of all the new elevation
profile/cross section functionality coming in QGIS 3.26. Tim Sutton
will be joining me, so it's guaranteed to be an educational &
entertaining session!

You can tune in live here https://youtu.be/AknJjNPystU (a recording
will also be made available after the event).

Regards,
Nyall
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Re: [Qgis-user] QGIS 3.24 Ubuntu

[Nyall Dawson via Qgis-user]

On Fri, 22 Apr 2022 at 06:03, Angeles Raphaël Saul via Qgis-user
 wrote:
>
> Dear QGIS community,
>
> I have two questions : Do you know how to install easily pcraster on ubuntu ? 
> How can I uninstall the latest version of QGIS 3.24 and get an older version 
> of QGIS on ubuntu ?
>
>
> Situation : I am a recent ubuntu user and I need to install pcraster for 
> advanced watershed calculations. Apparently it is possible to install it 
> using anaconda-navigator, so I first needed to install anaconda using this 
> tutorial : 
> https://gisunchained.wordpress.com/2019/05/29/using-qgis-from-conda/. But 
> once QGIS 3.18.3 installed and opened, any plugin utilization do not work at 
> all. For example, applying strahler order tool from SAGA on a DEM does not 
> work. Every time, the python error is :
>
>
> WARNINGTraceback (most recent call last):
>
> File 
> "/home/raphael/anaconda3/envs/demonstration/share/qgis/python/plugins/processing/gui/AlgorithmDialog.py",
>  line 194, in runAlgorithm
>
> self.cancelButton().setEnabled(self.algorithm().flags() & 
> QgsProcessingAlgorithm.FlagCanCancel)
>
> TypeError: setEnabled(self, bool): argument 1 has unexpected type 'Flags'

This is (unfortunately) expected -- Python 3.9 broke some API
compatibility, so the older QGIS 3.18 release ISN'T compatible with
the newer Python version. As you've concluded, the solution is
updating to a newer, supported QGIS version.

Nyall


>
>
> Thus I tried to install QGIS 3.24 via this link 
> https://www.qgis.org/en/site/forusers/alldownloads.html#debian-ubuntu to see 
> if the problem can be resolved with a more recent version. The problem is 
> that this tutorial is not for a conda environment, so now I want to uninstall 
> 3.24 to go to an older and more stable version and I don't know how to do it. 
> If I install and uninstall QGIS, the version 3.24 still appears. Moreover, I 
> still don't have pcraster installed and operational which I need the most.
>
> Thank you in advance for your precious answer and have a good night!
>
> Raphaël
>
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Re: [Qgis-user] Help with scales in print layouts for geographic CRS

[Nyall Dawson via Qgis-user]

On Thu, 7 Apr 2022 at 10:26, Greg Troxel  wrote:
>
>
> Nyall Dawson  writes:
>
> > In all cases (projected OR geographic) the scalebar logic is:
> >
> > 1. Create a horizontal line across the width of the layout map
> > 2. Calculate the length of that line using great circle/ellipsoidal
> > calculations, based on the project's ellipsoid settings.
> > 3. Compare the length of the ellipsoidal line vs the map width to
> > calculate the corresponding scale
>
> That is a very straightforward approach with easy-to-understand
> semantics.
>
> > So qgis scalebar calculations are ALWAYS based on great
> > circle/ellipsoidal lengths*.
>
> And more precisely, a true geodesic between two points varying in x and
> with constant y in the layout CRS.  For north-up (at least ish)
> projections, that means a line of constant latitude.
>
> For a lat/lon CRS in the layout, at mid latitudes, it's going to mean
> that the scale in the y axis is smaller by about 110km/70km; a square in
> lat/lon is taller than it is wide (and plus it's not a square, but
> that's less obvious).  Equivalently, a square on the ground has a larger
> difference in longitude than it does in latitude.  Or maybe I have that
> backward, but using lat/lon in a layout does not preserve shapes.
>
> This is what I was trying to get at: a single concept of scale is really
> only valid for a projection that has the same scale in x and y.  Which I
> think is true iff the projection is conformal.  And it's only truly
> valid if the scale doesn't change over the layout, which is probably
> ~never exactly true, but many projections aim to have it remain close
> enough to be treated as constant (e.g. UTM).
>
> Which is a long way of getting around to "if you are using lat/lon as
> the axes in your layout, either you are doing something odd on purpose
> or you probably should rethink your approach."  If you really do mean
> it, I would find the explanation of why interesting.

All correct, indeed!

I've been thinking about introducing a new warning when exporting
layouts, which would look something like this:

1. For each scale bar, look at the referenced map
2. Measure the scale using multiple lines, each across the
top/middle/bottom horizontally and left/center/right vertically
3. Compare these scale values, and if any differ by more than XXX %
then show a warning to the user. Something like "The scale for map 1
varies from 1: to 1:y across different parts of the map.
Consider using an alternative form of representing the map scale (such
as a grid overlay), as the scale bar may be misleading for this map."

What do you think?

Nyall


>
> > * Unless the project itself is set to not use ellipsoidal calculations
> > and only use planar calculations, in the project properties dialog
>
> Presumably those calculations are in the project CRS's xy space, and
> would typically (when used sensibly) be grid distance in UTM, some State
> Plane Coordinate System, or similar.
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Re: [Qgis-user] Help with scales in print layouts for geographic CRS

[Nyall Dawson via Qgis-user]

On Wed, 6 Apr 2022 at 09:34, Greg Troxel via Qgis-user
 wrote:
>
> Jorge Gustavo Rocha via Qgis-user  writes:
>
> > I need you help to understand how scale works with geographic
> > coordinate systems.


In all cases (projected OR geographic) the scalebar logic is:

1. Create a horizontal line across the width of the layout map
2. Calculate the length of that line using great circle/ellipsoidal
calculations, based on the project's ellipsoid settings.
3. Compare the length of the ellipsoidal line vs the map width to
calculate the corresponding scale

So qgis scalebar calculations are ALWAYS based on great
circle/ellipsoidal lengths*.

Nyall

* Unless the project itself is set to not use ellipsoidal calculations
and only use planar calculations, in the project properties dialog
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Re: [Qgis-user] Is it possible to import Arcgis Pro map to QGIS?

[Nyall Dawson]

On Wed, 2 Mar 2022 at 08:13, Alexandre Neto  wrote:
>
> ArcGIS pro map is a binary (non-human-readable) proprietary format. Which 
> means that, apart from ESRI, no one knows how to read and write those files.
>
>  So, no. You can't.

Actually -- just to clarify. SLYR (https://north-road.com/slyr/)
currently has support for reading ArcMap documents (including
lyr/mxd/etc) and converting to QGIS, and is shortly to receive support
for conversion of ArcGIS Pro lyrx/aprx documents too!

Nyall

>
> A terça, 1/03/2022, 21:49, krishna Ayyala  escreveu:
>>
>> Hello,
>> I have a Arcgis pro map saved with (.mapx ) extension.Is it possible to 
>> bring this map into QGIS without losing the symbology?
>>
>> Regards.
>> ___
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Re: [Qgis-user] Index attribute no longer updated automatically

[Nyall Dawson]

On Mon, 21 Feb 2022 at 15:08, Johanna Botman  wrote:
>
> Hi,
>
>
>
> Another QGIS 3.22.3 question.
>
>
>
> I have layers that come from a MSSQL database. Those tables were loaded into 
> SQL using Easy Loader (I know, shh!) so they have the MI_PRINX attribute.
>
> In past versions of QGIS, this MI_PRINX attribute was updated automatically 
> when a new feature is saved in a layer. That has stopped in 3.22.
>
>
>
> In my settings when a new feature is created, the default behaviour of 
> Suppress attribute from pop-up after feature creation is not ticked, so a new 
> feature created does open a pop-up box. The attribute for MI_PRINX is Orange 
> and there is a small orange x on the right hand side.

Sounds like your database table has a not-null constraint on this
MI_PRINX attribute, which QGIS is detecting. That's what the orange x
represents -- the attribute value isn't valid for the layer.

Nyall
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Re: [Qgis-user] Print layout raster misalignment when label masked symbol layers are enabled

[Nyall Dawson]

On Mon, 21 Feb 2022 at 11:38, Tony Shepherd (FarmMaps NZ)
 wrote:
>
> Hi All
>
>
>
> This has been a long-standing issue for me, and likely others for the last 
> three or four versions.


What is the most recent QGIS version you've tested this with?

Nyall
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Re: [Qgis-user] Raster calculation: if Layer1 is > 1, then Layer2 should be 0

[Nyall Dawson]

On Fri, 18 Feb 2022 at 09:22, Nyall Dawson  wrote:

> By
> not setting a "maximum" value in the row we indicate that the range is
> from 100 < input value < +infinity.

Gah, that should be "1 < input value < +infinity"!
Nyall
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Re: [Qgis-user] Raster calculation: if Layer1 is > 1, then Layer2 should be 0

[Nyall Dawson]

On Fri, 18 Feb 2022 at 08:56, Bernd Vogelgesang
 wrote:
>
> Hi Nyall,
>
> sorry, mixed things up. The native raster calculator only threw errors,
> while the GDAL worked.

Thanks for the clarification! Indeed there are some open tickets
regarding the native raster calculator.

FWIW, I'd actually suggest going with the native "reclassify by table"
to perform this task. It's a very efficient tool and will handle
massive rasters without issue. The table parameter would be set to a
single row with "minimum" = 1, "maximum" = blank/not set, and "value"
= 0. Leave everything else at their default values.

To explain: If you don't check the advanced parameter "use no data
when no range matches value" (the default is that it's unchecked!)
then any input pixel value which doesn't fall into one of the ranges
defined in the table will be copied unchanged to the output. So only
pixel values > 1 will match a rule, and will output a "0" value. By
not setting a "maximum" value in the row we indicate that the range is
from 100 < input value < +infinity. It's a bit clearer when you run
the algorithm, as the log will show a descriptive explanation of the
classes. Something like this:

"Using classes:
1) 1 < x ≤ ∞ → 0"

ie. values > 1 and <= infinity will map to 0, others will be unchanged.

Hope that helps!

Nyall











>
> Now that I tried again, everything is fine. Strange hickup.
>
> Anyway, everything ist fine now and things start getting sorted.
>
> Happy again :)
>
> Cheers,
>
> Bernd
>
>
>
> Am 17.02.22 um 23:22 schrieb Nyall Dawson:
> > On Fri, 18 Feb 2022 at 08:08, Bernd Vogelgesang
> >  wrote:
> >> Hi Sebastian,
> >>
> >> thanx, that worked.
> >>
> >> But somehow, the hole process feels a bit clumsy.
> >>
> >> Having to fumble together a classification with "thru" (juck!), then the 
> >> toolbox reclassify just seems to be broken,
> > Which reclassify tool are you referring to exactly? The native QGIS
> > ones are 100% NOT broken. (The SAGA one may be, but that's a 3rd party
> > tool.)
> >
> > Nyall
> >
> >
> > gladly gdal calculator does ...
> >> Why isn't there some "raster SQL" that saves one from all these stupid 
> >> single steps?
> >>
> >> Ok, will then try to build a model and hope it will work for the tests to 
> >> come…
> >>
> >> Thanks a lot,
> >>
> >> Bernd
> >>
> >>
> >> Am 17.02.22 um 22:19 schrieb Sebastian Gutwein:
> >>
> >> Reclassify your Layer 1 to be anything greater than 1 = 0 everything else 
> >> equals 1. This will give you a binary 1 and 0 raster (Layer 3)  that you 
> >> can use in the raster calculator: Layer 2 * Layer 3.  Anywhere where layer 
> >> 3 is 1 your layer 2 values will stay the same and anywhere where layer 3 
> >> is 0 your layer 2 values will become 0.
> >>
> >> On Thu, Feb 17, 2022 at 3:19 PM Bernd Vogelgesang 
> >>  wrote:
> >>> Hi folk,
> >>>
> >>> I hardly never work with raster calculations, and unfortunately there is 
> >>> nowhere a collection of syntax examples for different use cases to be 
> >>> found (documentation :( ).
> >>>
> >>> Anything apart from +-*/ is beyond my scope.
> >>>
> >>> So,
> >>>
> >>> I made a viewshed analysis over a digital surface model (try the awesome 
> >>> Visibility Analysis plugin form Zoran Čučković and buy him a beer!)
> >>>
> >>> A lot of "views" are caught by tree canopy, but I am only interest in the 
> >>> flat grounds.
> >>>
> >>> So I substracted the surface model layer from the ground model layer, and 
> >>> this is Layer 1.
> >>>
> >>> Giving a threshold of 1 meters difference for inaccuracities, all pixels 
> >>> in this layer above 1 should result in 0 (zero) in my viewshed raster 
> >>> (Layer 2)
> >>>
> >>> Please give me some hints,
> >>>
> >>> Cheers,
> >>>
> >>> Bernd
> >>>
> >>>
> >>> ___
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> >>> Qgis-user@lists.osgeo.org
> >>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
> >>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
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Re: [Qgis-user] Raster calculation: if Layer1 is > 1, then Layer2 should be 0

[Nyall Dawson]

On Fri, 18 Feb 2022 at 08:08, Bernd Vogelgesang
 wrote:
>
> Hi Sebastian,
>
> thanx, that worked.
>
> But somehow, the hole process feels a bit clumsy.
>
> Having to fumble together a classification with "thru" (juck!), then the 
> toolbox reclassify just seems to be broken,

Which reclassify tool are you referring to exactly? The native QGIS
ones are 100% NOT broken. (The SAGA one may be, but that's a 3rd party
tool.)

Nyall


gladly gdal calculator does ...
>
> Why isn't there some "raster SQL" that saves one from all these stupid single 
> steps?
>
> Ok, will then try to build a model and hope it will work for the tests to 
> come…
>
> Thanks a lot,
>
> Bernd
>
>
> Am 17.02.22 um 22:19 schrieb Sebastian Gutwein:
>
> Reclassify your Layer 1 to be anything greater than 1 = 0 everything else 
> equals 1. This will give you a binary 1 and 0 raster (Layer 3)  that you can 
> use in the raster calculator: Layer 2 * Layer 3.  Anywhere where layer 3 is 1 
> your layer 2 values will stay the same and anywhere where layer 3 is 0 your 
> layer 2 values will become 0.
>
> On Thu, Feb 17, 2022 at 3:19 PM Bernd Vogelgesang  
> wrote:
>>
>> Hi folk,
>>
>> I hardly never work with raster calculations, and unfortunately there is 
>> nowhere a collection of syntax examples for different use cases to be found 
>> (documentation :( ).
>>
>> Anything apart from +-*/ is beyond my scope.
>>
>> So,
>>
>> I made a viewshed analysis over a digital surface model (try the awesome 
>> Visibility Analysis plugin form Zoran Čučković and buy him a beer!)
>>
>> A lot of "views" are caught by tree canopy, but I am only interest in the 
>> flat grounds.
>>
>> So I substracted the surface model layer from the ground model layer, and 
>> this is Layer 1.
>>
>> Giving a threshold of 1 meters difference for inaccuracities, all pixels in 
>> this layer above 1 should result in 0 (zero) in my viewshed raster (Layer 2)
>>
>> Please give me some hints,
>>
>> Cheers,
>>
>> Bernd
>>
>>
>> ___
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Re: [Qgis-user] Drop the points and show only clusters

[Nyall Dawson]

On Fri, 28 Jan 2022 at 06:26, krishna Ayyala  wrote:
>
> Hello,
> I have a point shape with about 10,000 points. On the map, I wish to show 
> only those points that are within 1000ft of each other and drop the rest of 
> the points. All I am trying to see is only the clusters. Can anyone help 
> please?

Try exploring the "DB SCAN" tool available in the Processing toolbox!

Nyall
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Re: [Qgis-user] Accessing temporal controller stuff via the python console

[Nyall Dawson]

On Wed, 26 Jan 2022 at 07:30, Cory Albrecht  wrote:
>
> Thanks.
>
> While I no longer got a whole bunch of similar images, instead I got a series 
> of partially rendered canvases in triplets. First the static, 
> non-temporal-data layers and a few features of one of the temporal layers. 
> Second is all the layers but no labels. Third is with the labels (including 
> the date of the frame). Each triplet appears to be from the same time frame 
> selected with setCurrentFrameNumber(), but the third image of the triplet 
> shows a date that is is three items in the list after the previous one.

As you've found, saving the canvas is a fragile approach. Calling
canvas.saveAsImage() will save **whatever** is currently shown in the
canvas to an image, even if it's only a half-rendered map!

The better approach is using the QgsMapRenderer classes directly,
which allow you to render maps as images without going through the
canvas at all. This has many benefits:

- The extent, scale, and image size can all be precisely controlled,
and you aren't bound to the canvas size itself. (Of course, you could
take those extent/scale/sizes direct from the canvas if this is
behaviour you do wany)
- The map rendering can be done in a "blocking" way, so that you can
be sure that the render is completely finished before saving the image
out.
- You aren't messing with the canvas's temporal range, so after
exporting images the previous time range will still be visible and the
user's QGIS state won't be magically changed after running your
script.

Something like this should work (will need some adapting!)

   # now create an set of images so you can create an animated gif or so
   def render_time_range(map_settings, time_range):
 img = QImage(map_settings.outputSize(), map_settings.outputImageFormat())
 img.fill(map_settings.backgroundColor().rgb())

 p = QPainter()
 p.begin(img)
 map_settings.setTemporalRange(time_range)
 render = QgsMapRendererCustomPainterJob(map_settings, p)
 render.start()
 render.waitForFinished()
 p.end()
 return img

   map_settings = QgsMapSettings()
   # setup all your default map settings stuff here, e.g. scale,
extent, image size, etc
   map_settings.setLayers(iface.mapCanvas().layers())
   map_settings.setOutputSize(QSize(300, 150)) # width, height
   rect = QgsRectangle(iface.mapCanvas().fullExtent())
   map_settings.setExtent(rect)
   map_settings.setIsTemporal(True)

  for time_range in :
  img = render_time_range(map_settings, time_range)
  img.save( ... )



> Longer waits in processEvents() or time.sleep() after setting the frame 
> didn't seem to matter, the key was sleeping and processing events multiple 
> times and 5 seems to be the minimum. I also had to do the set frame to the 
> first date before the loop, as for some reason inside the loop it required 
> more than 5 times when jumping backwards from the final date to the beginning 
> and would thus result in a bunch of incompletely drawn images and a few 
> skipped dates.
>
> Next I need to find if there is a way to change the size of the output image 
> to different than the map canvas, but I suspect that will require playing 
> with the pyqgis stuff that controlls the Print Layout stuff, and that is 
> probably beyond my nonexistent python skills.
>
> On Mon, Jan 24, 2022 at 6:27 PM Nyall Dawson  wrote:
>>
>> On Tue, 25 Jan 2022 at 04:39, Cory Albrecht  wrote:
>> >
>> > But the `navigator.setCurrentFrameNumber(f)` doesn't change the canvas' 
>> > temporal frame.
>> >
>> > If I do `f=54003` manually in the console and then 
>> > `navigator.setCurrentFrameNumber(f)` manually as well, the frame changes. 
>> > I've used time.sleep() with values up to 5 seconds to see if setting the 
>> > frame was just a background task that returns early before actually 
>> > completed, but that didn;t make any difference.
>> >
>>
>> Try QCoreApplication.processEvents() instead of time.sleep
>>
>> > Why does it not change the frame in the middle of the for loop?
>>
>> it's a bit technical, but you need to let the Qt "event loop" process
>> in order for any GUI widgets to update. time.sleep doesn't do this --
>> it just blocks the caller for the requested time, and doesn't let Qt
>> do it's thing and update the screen.
>>
>> But a huge warning is needed here: processEvents() is very dangerous
>> to call in certain circumstances. Here it's ok to do, but definitely
>> use with caution!! (You'll know you're using it wrong if you get
>> crashes...)
>>
>> Nyall
>>
>>
>>
>> >
>> > On Tue, Jan 18, 2022 at 2:32 PM Cory Albrecht  wrote:
>> >>
>> >>

Re: [Qgis-user] Accessing temporal controller stuff via the python console

[Nyall Dawson]

On Tue, 25 Jan 2022 at 04:39, Cory Albrecht  wrote:
>
> But the `navigator.setCurrentFrameNumber(f)` doesn't change the canvas' 
> temporal frame.
>
> If I do `f=54003` manually in the console and then 
> `navigator.setCurrentFrameNumber(f)` manually as well, the frame changes. 
> I've used time.sleep() with values up to 5 seconds to see if setting the 
> frame was just a background task that returns early before actually 
> completed, but that didn;t make any difference.
>

Try QCoreApplication.processEvents() instead of time.sleep

> Why does it not change the frame in the middle of the for loop?

it's a bit technical, but you need to let the Qt "event loop" process
in order for any GUI widgets to update. time.sleep doesn't do this --
it just blocks the caller for the requested time, and doesn't let Qt
do it's thing and update the screen.

But a huge warning is needed here: processEvents() is very dangerous
to call in certain circumstances. Here it's ok to do, but definitely
use with caution!! (You'll know you're using it wrong if you get
crashes...)

Nyall



>
> On Tue, Jan 18, 2022 at 2:32 PM Cory Albrecht  wrote:
>>
>> Thanks, I'll check it out.
>>
>> On Sun, Jan 16, 2022 at 8:04 PM Nyall Dawson  wrote:
>>>
>>> On Mon, 17 Jan 2022 at 10:46, Cory Albrecht  wrote:
>>> >
>>> > Thanks for the pointer, but unfortunately it is incomplete. It tells me 
>>> > this:
>>> >
>>> > # get the current  responsible for the mapCanvas behaviour and 
>>> > Temporal Controller gui
>>> > navigator = iface.mapCanvas().temporalController()
>>> >
>>> > And a few other methods for that object, but it's all about mimicking the 
>>> > "Save Animation" button with no explanation how to choose a specific 
>>> > frame or even anything as simple as going forward or backward by a single 
>>> > frame. Is there no list anywhere of all that temporal controller object's 
>>> > methods?
>>>
>>> Yes, in the usual place (the PyQGIS API reference):
>>>
>>>  https://qgis.org/pyqgis/master/core/QgsTemporalNavigationObject.html
>>>
>>> Nyall
>>>
>>> >
>>> >
>>> >
>>> > On Sun, Jan 16, 2022 at 3:40 PM Delaz J  wrote:
>>> >>
>>> >> Hi Cory,
>>> >>
>>> >> I don't know if it's still compatible with API and of any help, but 
>>> >> there's that stale pull request in the docs by Richard 
>>> >> (https://github.com/qgis/QGIS-Documentation/pull/5521) you might want to 
>>> >> look at.
>>> >>
>>> >> Regards,
>>> >>
>>> >> Harrissou
>>> >>
>>> >> Le 16/01/2022 à 18:34, Cory Albrecht a écrit :
>>> >>
>>> >> Hello,
>>> >>
>>> >> Is there a way I can access and change/set stuff for the dynamic 
>>> >> temporal controller programmatically in python? I'm looking to make a 
>>> >> simple script that I can just cut and paste into the python console that 
>>> >> will change the current frame of the DTC to a given timestamp, export 
>>> >> the canvas to a PNG, and repeat for all the timestamps in an array.
>>> >>
>>> >> ___
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>>> >
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Re: [Qgis-user] QGIS 3.22 breaks CRS Transform Files?

[Nyall Dawson]

On Thu, 20 Jan 2022 at 05:25, John Layt  wrote:

> 2) If you create a new Project and it defaults to WGS84, and then you change 
> the CRS to OSGB36, you get the "Ballpark Transform" warning even though there 
> is no data to be transformed, and may never be. Also, the warning gets 
> displayed as an inline alert on the canvas as soon as you select the new CRS, 
> so if you don't Apply and close the Properties you still see the warning. 
> This may be a regression of https://github.com/qgis/QGIS/issues/34983, but 
> the message probably shouldn't be displayed in these circumstances.

Fixed here: https://github.com/qgis/QGIS/pull/46957

Nyall
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Re: [Qgis-user] Accessing temporal controller stuff via the python console

[Nyall Dawson]

On Mon, 17 Jan 2022 at 10:46, Cory Albrecht  wrote:
>
> Thanks for the pointer, but unfortunately it is incomplete. It tells me this:
>
> # get the current  responsible for the mapCanvas behaviour and Temporal 
> Controller gui
> navigator = iface.mapCanvas().temporalController()
>
> And a few other methods for that object, but it's all about mimicking the 
> "Save Animation" button with no explanation how to choose a specific frame or 
> even anything as simple as going forward or backward by a single frame. Is 
> there no list anywhere of all that temporal controller object's methods?

Yes, in the usual place (the PyQGIS API reference):

 https://qgis.org/pyqgis/master/core/QgsTemporalNavigationObject.html

Nyall

>
>
>
> On Sun, Jan 16, 2022 at 3:40 PM Delaz J  wrote:
>>
>> Hi Cory,
>>
>> I don't know if it's still compatible with API and of any help, but there's 
>> that stale pull request in the docs by Richard 
>> (https://github.com/qgis/QGIS-Documentation/pull/5521) you might want to 
>> look at.
>>
>> Regards,
>>
>> Harrissou
>>
>> Le 16/01/2022 à 18:34, Cory Albrecht a écrit :
>>
>> Hello,
>>
>> Is there a way I can access and change/set stuff for the dynamic temporal 
>> controller programmatically in python? I'm looking to make a simple script 
>> that I can just cut and paste into the python console that will change the 
>> current frame of the DTC to a given timestamp, export the canvas to a PNG, 
>> and repeat for all the timestamps in an array.
>>
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Re: [Qgis-user] Readonly gpkg

[Nyall Dawson]

On Wed, 12 Jan 2022 at 11:40, Greg Troxel  wrote:
>
>
> Nyall Dawson  writes:
>
> > On Wed, 12 Jan 2022 at 11:00, Greg Troxel  wrote:
> >>
> >>
> >>  writes:
> >>
> >> > A. Ideally WAL/DELETE would be a connection (in the sense of the
> >> > Browser connections list) level decision changeable by the user, not a
> >> > layer-level decision and not (as now) an application setting used for
> >> > all gpkg connections.
> >>
> >> Fundamentally WAL/DELETE is a (changeable) property of an sqlite3 file,
> >> and thus of a geopackage container.  So exposing it as a db browser
> >> property and allowing it to be changed, with a warning that it is a DB
> >> Admin operation, not a connection operation, seems ok.
> >
> > Instead of exposing this as a per-workstation, QGIS only property, I'd
> > propose instead that the property be set somewhere in the gpkg
> > metadata itself, so that regardless of which user opens it in a
> > multi-user environment, they'll always get the property set by the db
> > administrator. (Maybe this could even become a future formal gpkg
> > extension...?)
>
> Right now, I think WAL/DELETE is a property of the sqlite3 file which
> contains the geopackage data.  But it's a sqlite3 property, not a
> geopackage property.  (And qgis whacks it on every open.)
>
> If I am following, you are suggesting a geopackage-level property (in
> some table?), and a rule that when a reader or write opens the file, if
> the sqlite3 setting does not match, the sqlite3 setting is forced and an
> error is logged?

That's correct, but without the error logging.

Nyall
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Re: [Qgis-user] Readonly gpkg

[Nyall Dawson]

On Wed, 12 Jan 2022 at 11:00, Greg Troxel  wrote:
>
>
>  writes:
>
> > A. Ideally WAL/DELETE would be a connection (in the sense of the
> > Browser connections list) level decision changeable by the user, not a
> > layer-level decision and not (as now) an application setting used for
> > all gpkg connections.
>
> Fundamentally WAL/DELETE is a (changeable) property of an sqlite3 file,
> and thus of a geopackage container.  So exposing it as a db browser
> property and allowing it to be changed, with a warning that it is a DB
> Admin operation, not a connection operation, seems ok.

Instead of exposing this as a per-workstation, QGIS only property, I'd
propose instead that the property be set somewhere in the gpkg
metadata itself, so that regardless of which user opens it in a
multi-user environment, they'll always get the property set by the db
administrator. (Maybe this could even become a future formal gpkg
extension...?)

Nyall



>
> > In the distant future, I could see the Browser providing a UI wrapper
> > to send the right pragma JOURNAL_MODE if user requests.
>
> Yes, that makes sense.
>
>
>
> > B. Currently, one option would be for me/others to set
> > qgis/walForSqlite to false, which would solve the problem for readonly
> > gpkgs and only slightly downgrade performance for (modest-sized)
> > writeable gpkg primarily edited via the canvas.
>
> I think so.  It would also fix the bug that reading a geopackage layer
> causes a write operation to the filesystem.
>
> However, it would have a bug that if someone had set a geopackage to
> WAL, then this would reset it back to DELETE.
>
> > C. Alternately, continuing to let QGIS use WAL, but setting the
> > specific .gpkg file to be read-only in the file system is a harmless
> > if crude solution (as long as I have no intention of actually editing
> > the layers in that gpkg).
>
> Probably, but I do want to edit.  I just don't want a fs write unless I
> actually do so.
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Re: [Qgis-user] is there a way to clip a shapefile without changing it from point to multipoints?

[Nyall Dawson]

On Wed, 8 Dec 2021 at 01:03, Katrin Schneider  wrote:

>
> 1.   I had to clip my layer A(points) with shapefile B (polygon). The 
> resulting layer C is multipoint despite consisting only of points.

This is indeed a bug -- I'll submit a fix shortly.


> b)  Multipoint to point -> umlauts/mutated vowels are not readable anymore

Can you explain this issue? Is it using the "multipart to singleparts"
tool from the processing toolbox, or some other tool?

Nyall


>
>
>
> Kind regards,
>
> Katrin
>
>
>
> Katrin Schneider
>
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>
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>
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>
> KORINA-Newsletter
>
>
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>
>
>
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[Qgis-user] Minimal docker image for qgis_process/processing

[Nyall Dawson]

Hi lists,

Is anyone aware of any minimal QGIS dockers which are designed just
for using the processing tools (either via Python or qgis_process)?

(Ideally I'm hoping to find one which has no
GUI/server/application/etc components, but does have all the desirable
libraries for a full-featured processing experience!)

Nyall
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Re: [Qgis-user] QGIS server in professional use?

[Nyall Dawson]

On Mon, 18 Oct 2021 at 17:23, Mats Elfström  wrote:
>
> I am not too happy if I have to start over on a new machine.

With all due respect, what do you expect as the outcome of this
discussion?  You're complaining about software you obtained for free!
If you're looking for commercial SUPPORT for QGIS then you need to
contract a QGIS support provider (see
https://qgis.org/en/site/forusers/commercial_support.html). If you're
not experienced enough to setup the server yourself, I strongly
caution you NOT to expose it to the internet and instead pay someone
with the experience to do this for you, and ensure it's done
correctly.

If it's a volunteer task and you don't want to pay for support, then
you NEED to moderate your language and avoid the inflammatory wording.
That's never an effective way to get a good response from the
volunteer side of the community.

Nyall




>
> Regards, Mats.E
>
>
> Den mån 18 okt. 2021 kl 04:31 skrev Richard Greenwood 
> :
>>
>> Posting again without screenshot, which apparently caused my previous email 
>> to await moderator approval.
>>
>> Mats,
>>
>> I fired up a new Ubuntu 20.04 instance on AWS and did the following 5 steps 
>> which got me an XML capabilities document.
>>
>> # standard practice when starting a new instance
>> sudo apt update && sudo apt upgrade -y
>> # reboot if a new kernel was installed by apt upgrade
>> sudo reboot
>> # install qgis-server and apache web server
>> sudo apt install qgis-server apache2 libapache2-mod-fcgid
>> # enable apache fcgi and cgi
>> sudo a2enmod fcgi cgi
>> sudo systemctl restart apache2
>> # in a web browser you should now get an XML document from the following 
>> request
>> http://IP-ADDRESS-OR-HOST-NAME/cgi-bin/qgis_mapserv.fcgi?SERVICE=WMS=1.3.0=GetCapabilities
>>
>> And 3 more steps got me a map
>>
>> # load some test data
>> wget https://github.com/qgis/QGIS-Training-Data/archive/v2.0.zip
>> sudo apt install unzip
>> unzip v2.0.zip
>> # in a web browser you should get a map from the following request
>> http://IP-ADDRESS-OR-HOST-NAME/cgi-bin/qgis_mapserv.fcgi?SERVICE=WMS=1.3.0=GetCapabilities=/home/ubuntu/QGIS-Training-Data-2.0/exercise_data/qgis-server-tutorial-data/world.qgs=countries=WMS=1.3.0=GetMap=EPSG:4326=400=200=-90,-180,90,180
>>
>> The tutorial tries to cover a lot of ground, maybe too much. And the 8 steps 
>> above certainly don't cover enough for a production server. But it's quite 
>> unfair to say that "QGIS Server is not ready for production". As Donovan 
>> pointed out, there are a lot of moving parts and you have to have some 
>> proficiency with all of them if you are doing it on your own.
>>
>> The basic principle is that QGIS Server is serving WMS, WFS, WCS requests 
>> via CGI (or Fast-CGI). Apache, Ngix, IIS, Tomcat all can serve CGI and 
>> Fast-CGI. Pick whatever operating system and web server you're the most 
>> proficient with. Install QGIS Server, start with the simplest configuration 
>> that you can, as I did above. Then start tuning it to your needs. If you run 
>> into problems ask for help on the list or https://gis.stackexchange.com/ 
>> with specific details as to what the problem is.
>>
>> --
>> Richard W. Greenwood
>> www.greenwoodmap.com
>
>
>
> --
>
>
> GisKraft, Geodatakonsult
>
> Mats Elfström, Marsvinsholms stationsväg 80, 271 93 Ystad, Sweden
> tel: +46 70 595 39 35 / www.giskraft.se
>
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Re: [Qgis-user] Normalised data

[Nyall Dawson]

On Mon, 11 Oct 2021 at 06:09, Dario  wrote:
>
> Hi,
> In my Organization, unfortunately, I receive data which are often not 
> normalised, specially, for example, for addresses.
> Is there any tool (even not in qgis) that can start from a list searching 
> from a official catalogue, adjusting (in this case) name of address by 
> similarity?

Possibly libpostal is what you're after: https://github.com/openvenues/libpostal

Nyall

>
> I usually use excel but using very complicated formulas, each time different. 
> At the end, however,  they never work finding similarity, but only same 
> correspondence.
>
> I hope I’ve been quite clear in what I’m looking for.
>
> Thanks
>
> _
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[Qgis-user] QEP: Render layers as groups

[Nyall Dawson]

Hi lists,

Please see the following QEP for a proposal concerning rendering
layers as groups, as a means to achieve symbology and cartography
effects which are currently not possible in QGIS:

https://github.com/qgis/QGIS-Enhancement-Proposals/issues/235

Comments/discussion/questions are welcome, but please keep these on
the QEP page in order to keep discussion centralised.

Regards,
Nyall
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Re: [Qgis-user] PDF output of QGIS: features disappear

[Nyall Dawson]

On Mon, 4 Oct 2021 at 17:16, Uwe Fischer  wrote:
>
> Hello List,
>
>
>
> I have to create a PDF map which contains air photos and vectors. With QGIS 
> 2.14.2 (which I still run for certain reasons) it works fine, the output PDF 
> is about 96 MByte and contains all the features. But the PDF is not 
> georeferenced (which is important for use in Avenza).
>
>
>
> So I opened the exact same project file in QGIS 3.18 and saved it to a new 
> qgz file. Then repeated the print composer PDF export. Now, the output is 
> geolocated, but there are vector features missing in an unpredictable way 
> (please see attachment, blue arrows).

Can you open a bug ticket with a reproducible test case demonstrating this?

Nyall
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Re: [Qgis-user] Transform vectordata using affine transformation

[Nyall Dawson]

On Sun, 26 Sept 2021 at 02:49, Bo Victor Thomsen
 wrote:
>
> Hi list -
>
> One of my customers just received a data file, where the coordinates is not 
> in any projection: Center of map data is (0,0), units in mm. not meter, maybe 
> some rotation too. However, at least it's a planar coordinate system (I hope).
>
> Instead of sending the #¤%&! data file back to the "GIS no-good" architect 
> who send it , I've decided to - once and for all - to find a method to  
> transform this kind of data to a reasonable CRS using an affine 
> transformation.
>
> I'm aware of the Processing algorithm "Affine transform" that can do the 
> actual transformation once I know the translation, rotation and scale 
> coefficients of the transformation.
> And I know how to find the affine transformation matrix using a set of points 
> from the data that corresponds with a set of points in the destination CRS.
>
> However, Is there any plug-in that can:
>
> Digitize a set of positions from the original data.
> Digitize or manually set the corresponding positions in the destination CRS
> Create the translation, scale and rotation parameters using data from (2)
> Run the "Affine transformation" algorithm to transform the data to the right 
> position in the chosen CRS
>
> In short - a Georeferencer for vector data

The good news is that this is close...ish. A lot of the groundwork API
has been done, and there's an open PR at
https://github.com/qgis/QGIS/pull/41386 which adds vector support to
the georeferencer. This PR needs some work though, so I'm hoping
someone steps up and funds a couple of days development so that I can
clean it up and get it merged...

Nyall


>
> A name of a functioning plug-in would be lovely
>
> A set QGIS classes/methods that could help with establishing the 
> transformation matrix and other stuff would be really nice
>
> A "No" to all my wishes would suck. However, In that case, I can start 
> developing without have the nagging feeling that someone has done this before
>
> --
> Med venlig hilsen / Kind regards
>
> Bo Victor Thomsen
>
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Re: [Qgis-user] Convert LYR 2 SHP

[Nyall Dawson]

On Wed, 8 Sept 2021 at 05:58, Charles Dixon-Paver  wrote:
>
> To my knowledge, lyr files are definitions for data sources, styles, and 
> other layer configuration information.

Correct. They are a direct equivalent of QLYR/QML files in QGIS land.

> If you have a layer package you want to convert or extract data from, I'm not 
> actually sure of what FOSS tooling supports it at all.

A lpk is actually just a 7zip file renamed with a different extension.
If you open the lpk in 7zip you'll see a .lyr file with the styling
information together with a .gdb dataset containing the actual layer
data. The .gdb will open fine in QGIS, but you'd need the licensed
SLYR plugin in order to get the original .lyr styling to apply.

Nyall
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Re: [Qgis-user] .qpj files

[Nyall Dawson]

On Wed, 8 Sept 2021 at 09:52, Pat Brown  wrote:
>
> I have a number of these files, associated with .cpg, .prj, .shp, .shx, .csv 
> and .dbf files. These date back to 2019. I cannot seem to get them to open in 
> QGIS version 3.18. Do I need to first open them with an older version of QGIS?

They aren't needed anymore. They were an old workaround around getting
QGIS to correctly identify the projection of the shapefiles, but all
that logic is moved to the PROJ library and these files are no longer
required.

Nyall
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Re: [Qgis-user] Problem using Model Inputs variable in an Select by expression in the model Designer

[Nyall Dawson]

On Tue, 24 Aug 2021 at 03:53, Charles Dixon-Paver  wrote:
>
> Honestly I have no idea 
>
> I mean, of course what is happening is QGIS is needing to identify a field 
> from a text string, and it's even possible that with some convoluted chain of 
> escape characters or funky regex the process could correct itself and "just 
> work".
>
> In all likelihood you could have just stumbled onto some obscure bug in the 
> underlying processing API where the context of that field object get's 
> dropped or orphaned when  trying to access it.

There's no bug here -- the variable value is just a pure text string,
and the expression engine can't automatically guess that you actually
want the value of the field with that name, and not just the name
string itself. Hence the need for the attribute function, which allows
you to retrieve a feature's fields via a text string containing the
field name.

Nyall


>
> My assumption is that using attribute() just compensates for whatever is 
> going on under the hood by reinstantiating the context behind the field 
> object, or at the very least provides a robust interface for referencing it 
> ¯\_(ツ)_/¯
>
> I would definitely call it a work around though
>
> On Mon, 23 Aug 2021 at 18:52, Nicolas Cadieux  
> wrote:
>>
>> Hi,
>>
>> if(attribute(to_string( @NamelengthField )) != "LENGTH2", TRUE, FALSE )
>>
>> ("LENGHT2" is an existing field and @NamelengthField was a model input 
>> string.)
>>
>> This worked  for me!   If you have the time, please explain why I needed the 
>> attribute() function for this to work.  I looked in the documentation and 
>> did not find it very clear.
>>
>> Thanks a million you saved my butt!
>>
>> Nicolas
>>
>>
>> On 2021-07-20 5:53 a.m., Charles Dixon-Paver wrote:
>>
>> Hi Nicholas,
>>
>> I haven't had time to dig into this extensively or encountered this 
>> particular issue, but I would suggest trying to "force" the expression to 
>> retrieve the correct info regardless of context using something like this:
>>
>> with_variable('Length2',  to_string(@NamelengthField) || '2', 
>> if(attribute(to_string(@NamelengthField)) != attribute(@Length2), TRUE, 
>> FALSE))
>>
>> That's probably an extreme example but hopefully it illustrates my point. If 
>> you want to share a sample dataset/ model I can try to have a look at how to 
>> resolve it.
>>
>> Regards
>>
>> On Tue, 20 Jul 2021 at 10:46, Richard McDonnell  
>> wrote:
>>>
>>> Nicolas,
>>>
>>> I have not looked at this in too much detail, but at a quick glance, could 
>>> it not be the fact that you should be using the newly created fields? As in 
>>> instead of @NamelengthField != @NamelengthField || '2', should it not be 
>>> more like your previous example Length != Length2
>>>
>>>
>>>
>>> Regards,
>>>
>>>
>>>
>>> Richard
>>>
>>>
>>>
>>>
>>>
>>>
>>> ——
>>> Richard McDonnell MSc GIS, FME Certified Professional
>>> FRM Data Management
>>>
>>> ——
>>> Oifig na nOibreacha Poiblí
>>> Office of Public Works
>>>
>>> Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36
>>> Jonathan Swift Street, Trim, Co Meath, C15 NX36
>>> ——
>>> M +353 87 688 5964 T +353 46 942 2409
>>> https://gov.ie/opw
>>>
>>> ——
>>> To send me files larger than 30MB, please use the link below 
>>> https://filetransfer.opw.ie/filedrop/richard.mcdonn...@opw.ie
>>>
>>> Email Disclaimer: 
>>> https://www.gov.ie/en/organisation-information/439daf-email-disclaimer/
>>>
>>> From: Qgis-user  On Behalf Of Nicolas 
>>> Cadieux
>>> Sent: 20 July 2021 09:27
>>> To: Qgis Users List 
>>> Subject: Re: [Qgis-user] Problem using Model Inputs variable in an Select 
>>> by expression in the model Designer
>>>
>>>
>>>
>>> Hi,
>>>
>>> Does anyone have an idea?
>>>
>>> Nicolas Cadieux
>>>
>>> https://gitlab.com/njacadieux
>>>
>>>
>>>
>>> Le 8 juill. 2021 à 01:17, Nicolas Cadieux  a 
>>> écrit :
>>>
>>> 
>>>
>>> Hi,
>>>
>>> I am creating a model that fixes Network files before they are used in the 
>>> QGIS Network analysis (Shortest path) tools.
>>>
>>> This is my work flow:
>>>
>>> Create a "Length" field (value) and calculate $length in the field 
>>> calculator
>>> Split the Multipart lines into Singlepart lines
>>> Create a "Length2" field (value) and calculate $length in the field 
>>> calculator
>>> Select by expression Length != Length2.  This basically gives me a 
>>> selection of line that have been modified by the Multipart to Singlepart 
>>> algorithm. (I get 8 results)
>>>
>>> This works well
>>>
>>> The problem is when I create and Input String to let the user create a 
>>> "Length" field.  This become a variable called @NamelengthField. My work 
>>> flow become:
>>>
>>> User input "Length" in the Model input. (@NamelengthField)
>>> Create a "Length" field using  @NamelengthField (as pre-calculated value) 
>>> and calculate $length in the field calculator: This is OK
>>> Split the Multipart lines into Singlepart lines: This is OK
>>> Create a "Length2" field using  @NamelengthField ||'2'  (as pre-calculated 
>>> value) and calculate 

[Qgis-user] QEP Proposal #230: Officially drop support for the SAGA provider (without removing it), show warning to all users when running SAGA tools

[Nyall Dawson]

Hi all,

Please see https://github.com/qgis/QGIS-Enhancement-Proposals/issues/230
for a newly filed QEP for discussion regarding officially marking the
SAGA Processing provider as unsupported by QGIS. Note that this
proposal does NOT include removal of the tools, rather just seeks to
add a user-facing warning that the tools are not supported. It also
seeks to formalise a policy where no bug reports will be accepted by
QGIS regarding this provider.

Discussion and comments on the github page are welcome!

Nyall
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Re: [Qgis-user] Single lines for road network

[Nyall Dawson]

On Sat, 31 Jul 2021 at 10:58, krishna Ayyala  wrote:
>
> Hello,
> I have a huge road network that has double lines such as below. We see such 
> roads mostly for express highways.
>
> In the same road network, there are also some streets with single lines such 
> as below.
>
>
>
> Is it possible to convert the entire road network such that we have only 
> single lines and not double lines such as above. Since the road network is 
> huge, it may not be possible to select manually each segment and run the 
> tools. Is there an automated tool that can do this for the entire network?

The "Cartography Tools" plugin has some (beta quality!) processing
tools which may help in this situation.

Nyall

>
> Regards.
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Re: [Qgis-user] [QGIS-Developer] Bug with GeoPackage and Expressions?

[Nyall Dawson]

On Thu, 29 Jul 2021 at 15:31, Matthias Kuhn  wrote:
>
> Can you fill a bug for this? The expression compiler in QGIS should not 
> forward it to ogr/gpkg/sqlite in this case.

My interpretation is that Calvin is setting a layer filter, so QGIS
expressions aren't involved (i.e. no bug).

Nyall

>
> Matthias
>
> On Wed, Jul 28, 2021 at 10:08 PM C Hamilton  wrote:
>>
>> Thanks everyone for that explanation. This does complicate the ability to 
>> set an expression filter in a plugin when it depends on the data source 
>> type. I'm not sure what to do about that.
>>
>> Regards,
>> Calvin
>>
>> On Wed, Jul 28, 2021 at 8:00 PM Anita Graser  wrote:
>>>
>>> Hi Calvin,
>>>
>>> 28 Jul 2021 21:43:40 C Hamilton :
>>> > If I use LIKE instead of ILIKE then it works. It is like ILIKE was not 
>>> > implemented for GeoPackage. Can anyone verify this?
>>>
>>> Yes, there seems to be no iLike in sqlite:
>>>
>>> https://stackoverflow.com/questions/15480319/case-sensitive-and-insensitive-like-in-sqlite
>>>
>>> And therefore neither in geopackage.
>>>
>>> Regards
>>> Anita
>>
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Re: [Qgis-user] Rasters in print layout are not aligned 3.20

[Nyall Dawson]

On Fri, 9 Jul 2021 at 08:24, Drew French  wrote:
>
> Thanks, I gave that I try, but it didn't work for me. It is possible I missed 
> a mask, I'm working on a complicated project. I will try a simpler project 
> and see if it works.

If you can't track it down can you please open a bug report with a
sample project which demonstrates this?

Nyall

>
> On Thu, Jul 8, 2021, 5:05 PM Tony Shepherd (FarmMaps NZ)  
> wrote:
>>
>> Hi
>>
>>
>>
>> See my post from Wed 7th July.
>>
>>
>>
>> I have exactly the same problem since loading 3.20.  By chance do you have 
>> label masking enabled on any layers?  I discovered that if I disable the 
>> layer masking, then the rasters and vector data will then align correctly.  
>> Re apply masking and then the error pops up again.
>>
>>
>>
>> It’s a bit of a pain as I have a template that I start new jobs with that 
>> has label masking enabled on several layers, so I have resorted to using 
>> 3.18 again, but 3.20 does have some cool features.
>>
>>
>>
>> Cheers
>>
>> Tony
>>
>>
>>
>> Tony Shepherd  |  GeoSpatial / Mapping Manager
>>
>> Ph 027 435 6193  |  E t...@farmmaps.nz
>>
>> FarmMaps NZ, 3 Kerwood Place, Gore 9740
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> From: Qgis-user  On Behalf Of Drew French
>> Sent: Friday, 9 July 2021 6:10 am
>> To: QGIS List 
>> Subject: [Qgis-user] Rasters in print layout are not aligned 3.20
>>
>>
>>
>> I have noticed that all my rasters, as well as WMS layers, are not aligned 
>> in print layout. This tells me that there is a setting somewhere that is 
>> wrong. I am using 3.20 on Linux Mint. All the layers CRS are the same. If I 
>> could get help with this I would really appreciate it!
>>
>>
>> --
>>
>> Drew French
>>
>> (715) 986-8088
>>
>> www.ecologicaldesign.land
>
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Re: [Qgis-user] using georferenced PDF map files as layers

[Nyall Dawson]

On Thu, 8 Jul 2021 at 08:00,  wrote:
>
> Hi,  I have the latest ver. of QGIS, I have imported two georeferenced PDF 
> maps but need to delete the boarders and legends to stitch the two into one 
> map while retaining the georef. Data for use in Avenza.  Cannot find in the 
> excellent docs and tutorials. Can anyone advise please.

Make a temporary polygon layer and draw a polygon over the area of the
PDF layer you want to retain. Then from the Processing Toolbox run the
"Clip Raster by Mask Layer" algorithm to clip the pdf layer out to the
polygon's area only.

Nyall

>
> Keep up the good work folks.
>
>
>
> Kind regards,
>
> Robert M. Dare  OAM
>
> robertd...@tpg.com.au  Mob. 0428503385
>
>
>
>
> Virus-free. www.avg.com
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Re: [Qgis-user] getting area and centroid from vector tile

[Nyall Dawson]

On Sun, 30 May 2021 at 22:11, Ryan Peel  wrote:
>
> I have this xyz tile server added into qgis.  It is the microsoft building 
> footprints.
>
> https://tiles.arcgis.com/tiles/P3ePLMYs2RVChkJx/arcgis/rest/services/Microsoft_Building_Footprints/VectorTileServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D.pbf
>
> Is there a way to get the centroid as well as area of the features shown?  I 
> would like to create my own table from this xyz tile layer.

No, but you can get the original (non-vector tiles) datasets from a
number of sources (eg
https://github.com/Microsoft/USBuildingFootprints). You can then do
any kind of normal processing with these, including centroids/area/
etc.

Nyall
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Re: [Qgis-user] Geocoding with MMQGIS - Web service geocode

[Nyall Dawson]

On Fri, 28 May 2021 at 09:31, krishna Ayyala  wrote:
>
> Nyall,
> Thanks for the reply. I have qgis3.16 version. I tried install this plugin 
> via install from zip. I am getting the following error .
>
> https://plugins.qgis.org/plugins/google_maps_geocoder/

Yes, you need 3.18 for the plugin -- it relies on newer functionality
introduced in that version.

Nyall

>
>
>
> On Thu, May 27, 2021 at 4:13 PM Nyall Dawson  wrote:
>>
>> On Fri, 28 May 2021 at 06:08, krishna Ayyala  wrote:
>> >
>> > Hello,
>> > I have a csv file with the columns "Address", "City", "State" and 
>> > "Country". I have 40 rows each row representing one address. All the 
>> > addresses are from the United States. I have the API key which I purchased 
>> > through subscription. For the web service option, I have chosen Google.
>> >
>> > When I try to geocode, I am getting an empty shape file? Can anyone help 
>> > me fix this problem?
>>
>> There's some great solutions available these days! Here's what I suggest.
>>
>> 1. Since you already have a Google Maps API key, you can use this
>> plugin (so long as you are on QGIS 3.18!)
>> https://plugins.qgis.org/plugins/google_maps_geocoder/ . It adds a new
>> processing batch geocoder using Google maps, and since it's a
>> Processing algorithm it's very flexible to run (and can be used in
>> models, from the command line, etc). It also adds a new locator bar
>> shortcut for directly navigating to places on the map using Google
>> maps locations.
>>
>> 2. If you download a nightly pre-release of QGIS 3.20, then there's an
>> out-of-the-box "Batch Nominatim geocoder" tool in the Processing
>> toolbox which geocodes using OpenStreetMap data. This is super
>> convenient, because you don't need ANY api keys or plugins... it's
>> just ready to go! The one catch is that it's rate-limited, so will be
>> slow if you need to geocode a lot of results.
>>
>> All in all, the QGIS geocoding situation is MUCH improved since previous 
>> years!
>>
>> Hope that helps!
>>
>> Nyall
>>
>>
>>
>> >
>> > Regards.
>> > ___
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>> > Qgis-user@lists.osgeo.org
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Re: [Qgis-user] Geocoding with MMQGIS - Web service geocode

[Nyall Dawson]

On Fri, 28 May 2021 at 06:08, krishna Ayyala  wrote:
>
> Hello,
> I have a csv file with the columns "Address", "City", "State" and "Country". 
> I have 40 rows each row representing one address. All the addresses are from 
> the United States. I have the API key which I purchased through subscription. 
> For the web service option, I have chosen Google.
>
> When I try to geocode, I am getting an empty shape file? Can anyone help me 
> fix this problem?

There's some great solutions available these days! Here's what I suggest.

1. Since you already have a Google Maps API key, you can use this
plugin (so long as you are on QGIS 3.18!)
https://plugins.qgis.org/plugins/google_maps_geocoder/ . It adds a new
processing batch geocoder using Google maps, and since it's a
Processing algorithm it's very flexible to run (and can be used in
models, from the command line, etc). It also adds a new locator bar
shortcut for directly navigating to places on the map using Google
maps locations.

2. If you download a nightly pre-release of QGIS 3.20, then there's an
out-of-the-box "Batch Nominatim geocoder" tool in the Processing
toolbox which geocodes using OpenStreetMap data. This is super
convenient, because you don't need ANY api keys or plugins... it's
just ready to go! The one catch is that it's rate-limited, so will be
slow if you need to geocode a lot of results.

All in all, the QGIS geocoding situation is MUCH improved since previous years!

Hope that helps!

Nyall



>
> Regards.
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Re: [Qgis-user] Geocoding with MMQGIS - Web service geocode

[Nyall Dawson]

On Fri, 28 May 2021 at 06:22, Erich Purpur  wrote:
>
> For what it's worth, Geocoding is one thing I have not found a good solution 
> for in QGIS (including trying the MMQGIS plugin tool). In my experience, none 
> of the geocoding plugins in QGIS work very well. I am lucky to have access to 
> an ESRI license as well and do geocoding in ArcPro.
>
> I know that is not a solution for you, but if anyone else has a good 
> geocoding solution in QGIS I'd love to hear it!
>
> -Erich Purpur
>
> On Thu, May 27, 2021 at 4:05 PM krishna Ayyala  
> wrote:
>>
>> Hello,
>> I have a csv file with the columns "Address", "City", "State" and "Country". 
>> I have 40 rows each row representing one address. All the addresses are from 
>> the United States. I have the API key which I purchased through 
>> subscription. For the web service option, I have chosen Google.
>>
>> When I try to geocode, I am getting an empty shape file? Can anyone help me 
>> fix this problem?
>>
>> Regards.
>> ___
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[Qgis-user] QEP 227: Add helper hooks to common Python geo libraries (shapely, numpy, pyproj)

[Nyall Dawson]

Hi all,

Please see https://github.com/qgis/QGIS-Enhancement-Proposals/issues/227
for a newly filed QEP concerning adding convenient helper methods to
interface PyQGIS with common external spatial libraries, including
shapely, pyproj and numpy.

Discussions and comments are welcome on the QEP page!

Nyall
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Re: [Qgis-user] Multi-core use

[Nyall Dawson]

On Wed, 19 May 2021 at 08:26, Grant Boxer  wrote:
>
> I have had a query from a user - does QGIS uses multi cores during
> processing?

It depends on the particular algorithm you're running, but generally
they will only use a single core.

Nyall
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Re: [Qgis-user] Slooooow spatial joins

[Nyall Dawson]

On Tue, 18 May 2021 at 11:59, Ryan Peel  wrote:
>
> I have tried using MMQGIS plugin, refFunctions geomwith function and the 
> aggregate function.  I am using 3.18 QGIS
>
> Despite having spatial indexes on both tables, when I try to use any of these 
> operations to assign the value of a field in the polygon layer to one in the 
> point layer, it goes very slow.  Like, ridiculously slow and of no value.  
> And, I only have 600 records in the points layer and just a few thousand 
> records in the polygon layer.
>
> What can I do to speed this up?

The absolute fastest way to join is to use the Processing tool: Join
Attributes by Location -- no plugins necessary :D

Nyall
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Re: [Qgis-user] Draw Ellipse/Polygons for areas of maximum concentration

[Nyall Dawson]

On Fri, 30 Apr 2021 at 15:01, chris hermansen  wrote:
>
> Krishna and list,
>
> On Thu, Apr 29, 2021 at 7:45 PM chris hermansen  wrote:
>>
>> Krishna and list
>>
>> On Thu, Apr 29, 2021, 15:24 krishna Ayyala  wrote:
>>>
>>> Chris,
>>> Thanks for the reply. Yes, I did run k-means clustering for 4 clusters. It 
>>> is creating a new layer called "clusters". This layer has a field called 
>>> Cluster_id, ranging from 1 to 4. But, this method is considering all the 
>>> points within the circle. I am looking for the points outside the ellipses 
>>> to be omitted (should not be considered). Also K-means clustering is not 
>>> generating any polygons/ellipses. We have to identify a cluster based on 
>>> the Cluster_ID. I am curious if there is any tool within Qgis that can 
>>> produce results similar to the circle with ellipses?
>>
>>
>> If you symbolize your points by colour according to the cluster_id does the 
>> clustering look acceptable to you?
>>
>>>
>
> Thinking about your diagram, maybe you want to fit ellipses to point 
> clusters.  If that's the case, maybe this paper is of some help:
>
> https://www.researchgate.net/publication/276433770_Multiple_ellipse_fitting_by_center-based_clustering/fulltext/56293cc208aef25a243d5d3a/Multiple-ellipse-fitting-by-center-based-clustering.pdf


You could try this plugin : https://plugins.qgis.org/plugins/SDEllipse/

Nyall



>
> I imagine you'd need to program this yourself.
>
>
> --
> Chris Hermansen · clhermansen "at" gmail "dot" com
>
> C'est ma façon de parler.
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Re: [Qgis-user] Draw Ellipse/Polygons for areas of maximum concentration

[Nyall Dawson]

On Fri, 30 Apr 2021 at 08:25, krishna Ayyala 
wrote:

> Chris,
> Thanks for the reply. Yes, I did run k-means clustering for 4 clusters. It
> is creating a new layer called "clusters". This layer has a field called
> Cluster_id, ranging from 1 to 4. But, this method is considering all the
> points within the circle. I am looking for the points outside the ellipses
> to be omitted (should not be considered)
>

In this case "dbscan clustering" is more appropriate.


> . Also K-means clustering is not generating any polygons/ellipses. We have
> to identify a cluster based on the Cluster_ID. I am curious if there is any
> tool within Qgis that can produce results similar to the circle with
> ellipses?
>

What you could do is dissolve the points based on the cluster_id field, and
then generate convex (or concave) hulls enclosing each set of points. You
won't get ellipses, but you'll get polygons describing the boundaries. (And
it would be relatively straightforward to wrap up these steps into a single
graphical model so that you have one tool which gives the desired output!).

Nyall




>
> Regards.
>
> On Thu, Apr 29, 2021 at 3:56 PM chris hermansen 
> wrote:
>
>> Krishna and list,
>>
>> On Thu, Apr 29, 2021 at 2:51 PM krishna Ayyala 
>> wrote:
>>
>>> Hello,
>>> I have a circle in which there are randomly distributed points as below.
>>> Each point is a customer.
>>>
>>> [image: image.png]
>>>
>>>
>>> Is there a tool within QGIS that can automatically generate four
>>> polygons or four ellipses such as below. These polygons are the areas of
>>> maximum concentration of the customers?
>>>
>>> [image: image.png]
>>>
>>> You could try k-means clustering
>>
>>
>> https://docs.qgis.org/3.4/en/docs/user_manual/processing_algs/qgis/vectoranalysis.html#k-means-clustering
>>
>> --
>> Chris Hermansen · clhermansen "at" gmail "dot" com
>>
>> C'est ma façon de parler.
>>
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Re: [Qgis-user] Measure distance along line

[Nyall Dawson]

On Thu, 29 Apr 2021 at 21:53, Prud'homme Jérémie  wrote:
>
> Hi,
>
> I am wondering if it's possible to use the Measure distance tool to measure 
> the distance between two places, following a line.
>
> For example, I click on a first place on the line, I click on a second place 
> and the tool automagically follow the line.
> Same behavior as what we can do with the use of automatic tracing for 
> geaometrie creations.

I'd also love to see this land in QGIS. While the measure tool
currently works with all other layer snapping settings it **doesnt'**
work with the tracing option. I think if QGIS allowed tracing with the
measure tool then this use case would be handled nicely...

Nyall
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Re: [Qgis-user] python(3) script to calculate latitude longitude values from (ESRI) shape file

[Nyall Dawson]

On Thu, 22 Apr 2021 at 06:43, wxgis  wrote:
>
> Hi -
> Wondering if there is existing Python(3) script code that can take an (ESRI)
> shape file as input and then calculate latitude/longitude/elevation values
> for country boundaries.  For example, if the input file is a SHP file for
> France, the output would be the lat/lon/elevation values for the country
> boundaries.  I am quite new to QGIS, looking at version 3.18 (so only know
> about ESRI shape files, maybe there are other types of SHP files?), and read
> that in QGIS  I can edit the attribute table for a given layer and add
> latitude/longitude attributes, but I am hoping to this more
> programmatically, using the QGIS Python console.  I gladly welcome any ideas
> on this.

If you're new to this then I'd suggest skipping the Python part and
instead making a graphical model using Processing tools to do what you
want. The visual aspect of making models will help guide you through
the process, and there's plently of video tutorials on Youtube showing
how to do this.

You can even then take the model and automatically convert it directly
to a Python script with a single button click!

Hope that helps,
Nyall
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Re: [Qgis-user] Changes in Python versions on QGIS 3.18

[Nyall Dawson]

On Thu, 25 Mar 2021 at 10:41, Pedro Camargo  wrote:
>
> Hello,
>
> I am not sure this is the appropriate mailing list to send this, but here it 
> goes.
>
> I have noticed that QGIS 3.18 for Windows has shipped with Python 3.9, after 
> having updated to 3.8 just a couple of versions ago.

I'm curious -- what's the pain in a Python update? They usually have
very little harmful impact on python code.

Nyall
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Re: [Qgis-user] Georeferencer failing - QGIS 3.18

[Nyall Dawson]

On Fri, 19 Mar 2021 at 08:09, Tony Shepherd (FarmMaps NZ)
 wrote:
>
> Hi All
>
>
>
> Has anybody had issues with the Georeferencing tool failing after updating to 
> 3.18

This is (partially) why the 3.18.0 release was withdrawn. Wait for
this week's 3.18.1 patch before upgrading to 3.18 and the issue will
be resolved.

Nyall

>
>
>
> I'm not doing anything different to what I have in the past, start with a 
> basic scan of an image, load into georeferencer, pick a few control points on 
> the image and the map canvas, press the green button, and then it hangs and I 
> have to kill QGIS.
>
>
>
> If I do exactly the same in versions 3.12 or 3.14 it works like a charm.
>
>
>
> Anyone else experiencing this?
>
>
>
> Cheers
>
> Tony
>
>
>
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>
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>
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>
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Re: [Qgis-user] No transform available between XXX and EPSG:4326 when using non-Earth projections

[Nyall Dawson]

On Fri, 19 Mar 2021 at 07:04, Even Rouault  wrote:
>
> Sebastian,
>
> I can reproduce the 2 error messages you got. There's indeed something in 
> QGIS that tries a terrestrial reprojection and should be fixed, but I don't 
> think this is really critical apart of the annoyance of being spammed about 
> that. Please file a QGIS issue to track this.

There's two parts in particular which cause this warning to be shown,
and indeed make an assumption that lat/lng === EPSG:4326
- The status bar coordinate widget
- The CRS selector "area of use" preview widget

We probably need api for testing "is non earth crs" and "given a
non-earth crs, give me a lat/long crs for the same planetary body" to
resolve these. But as Even has pointed out neither are critical
functionality, and the warning can be ignored.
Nyall


> That said, I managed to do a non-Earth reprojection by adding a custom CRS 
> with the following WKT definition:
>
> GEOGCRS["MARS Geographic",
>
> DATUM["D_MARS",
>
> ELLIPSOID["MARS",3396000,0,
>
> LENGTHUNIT["metre",1,
>
> ID["EPSG",9001,
>
> PRIMEM["Reference meridian",0,
>
> ANGLEUNIT["degree",0.0174532925199433,
>
> ID["EPSG",9122]]],
>
> CS[ellipsoidal,2],
>
> AXIS["longitude",east,
>
> ORDER[1],
>
> ANGLEUNIT["degree",0.0174532925199433,
>
> ID["EPSG",9122]]],
>
> AXIS["latitude",north,
>
> ORDER[2],
>
> ANGLEUNIT["degree",0.0174532925199433,
>
> ID["EPSG",9122
>
> and selecting it as the project CRS. Using ESRI:104905 (GCS_Mars_2000) seems 
> to also work (I haven't deeply checked but I do get a reprojected raster and 
> geographic coordinates), but you'll get each time the warnings about the 2 
> terrestrial coordinate operations. Hopefully in coming months, I'll be able 
> to ingest the IAU catalog into the PROJ database as well.
>
> Even
>
> Le 18/03/2021 à 21:07, Sebastian Walter a écrit :
>
> Hi,
>
> Since Version 3.X I'm not able to perform transformations on planetary 
> (non-Earth) data (from e.g. Mars or Mercury, example dataset: 
> https://maps.planet.fu-berlin.de/mex4/h1104_.ihs.53.tif). The error 
> message is:
>
> No transform is available between SINUSOIDAL MARS and Custom CRS: 
> GEOGCRS["unknown",DATUM["unknown",ELLIPSOID["WGS 8….
> proj_create_operations: Source and target ellipsoid do not belong to the same 
> celestial body
> No transform available between SINUSOIDAL MARS and EPSG:4326
>
> The consequence is that transformations to lat/lon are not possible any more. 
> With the older QGis there was no problem like this. My suspect is the "new" 
> Proj6 database layout, but the above error messages also point to the fact 
> there there is some EPSG:4326 projection hard-coded into Qgis.
>
> Is anybody successfully using Qgis with non-Earth data and proper 
> transformations?
>
> Thanks for any advise...
>
> Sebastian
>
>
>
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Re: [Qgis-user] Save log to file via cmd

[Nyall Dawson]

On Tue, 9 Mar 2021 at 00:41, Christoph Jung  wrote:
>
> Hello everyone,
>
> I created a model and added the function “Save log to file” at the end of my 
> model. If I start the model directly in the QGIS application, it works fine 
> (the log file will be created and contains information).
>
> Now I want to call this model from the command line to schedule this task. I 
> created a batch file, setting up the osgeo4w environment and calling the 
> model via qgis_processing-qgis-ltr in this script. The log file will be 
> created, but there is no information in it. There is no error message or 
> something else in the command prompt too. Does anybody has an idea how I 
> could get the information in my log files when I call my model via command 
> line?

Thanks, fixed here: https://github.com/qgis/QGIS/pull/42208/files

Nyall
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Re: [Qgis-user] [QGIS-Developer] Loading multiple raster images from processing algorithm

[Nyall Dawson]

On Fri, 12 Mar 2021 at 07:26, C Hamilton  wrote:
>
> For one of my QIGS processing algorithms I have a destination folder, 
> QgsProcessingParameterFolderDestination, where one or more GeoTIFF images are 
> created. Once these images are created, how do I load them so that they 
> display in QGIS from the "processAlgorithm" method? I had thought that this 
> might work where I would iterate through each image created?

Definitely DON'T do this in the processAlgorithm method if your
algorithm is running in a background thread. It's not thread safe to
add layers to the main project from a background thread.

You could do it in a postProcessAlgorithm override though, as that is
guaranteed to run in the main thread. Just be ultra-cautious not to
store a layer created on the background thread and then try to access
this from postProcessAlgorithm -- layers have thread affinity to the
thread which created them, and can't just be accessed from any other
thread. To be safe you should always create a new layer from the
desired uri instead.

> path = path_to_the_image
> rlayer = QgsRasterLayer(path, name_of_image)
> QgsProject.instance().addMapLayer(rlayer, True)

also note that you should use context.project() instead of
QgsProject.instance() whenever you are accessing the project from a
processing algorithm -- this will ensure your algorithm works
correctly from the command line qgis_process tool!

Nyall
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Re: [Qgis-user] Do GPX files contain CRS information?

[Nyall Dawson]

On Fri, 5 Mar 2021 at 14:59, jeremy benwell  wrote:
>
> Hi,
>
> I was wondering if GPX files contain CRS information? I saved some waypoints 
> in my garmin gps and then used GPSBabel to upload those waypoints to my 
> computer and create a GPX file. The map datum on my gps was set to GDA 94. 
> Does my GPX file contain the CRS that my GPS was set to when I saved the 
> waypoints (i.e. GDA 94) and if so do I need to make sure my QGIS project CRS 
> is set to GDA 94 also?

No, they don't store CRS. Definitely make sure you set the crs to
GDA94 (but only when the gps was explicitly set to this datum!!). I'd
suggest re-saving the gpx to a format like gpkg which can store the
gda94 crs correctly, so that the dataset will open in future with the
correct CRS and you won't run into issues later.
(GPX files are just text files -- you can open to verify this!)

Nyall
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Re: [Qgis-user] [QGIS-Developer] QGIS Select by Location, but no within a distance of

[Nyall Dawson]

On Wed, 3 Mar 2021 at 04:59, C Hamilton  wrote:
>
> I just had a user tell me he had to go back to ArcGIS so that he could use 
> the Select by Location function and specify a distance from the feature. He 
> could not believe that it was not available in QGIS. See
>
> https://desktop.arcgis.com/en/arcmap/10.3/map/working-with-layers/using-select-by-location.htm
>
> What he is looking for is the "Are within a distance of" operator. Am I 
> missing it in QGIS if not this is a really important operator to include. I 
> know you can always prebuffer the layer, but for an analyst who does this 
> regularly ours will go back to using ArcGIS.
>
> Would this be fairly easy to implement?

Reasonably so - the bulk of the required changes would all sit within
QgsLocationBasedAlgorithm , specifically in
QgsLocationBasedAlgorithm::processByIteratingOverTargetSource and
QgsLocationBasedAlgorithm::processByIteratingOverIntersectSource
(there's two code paths there, and the one called will depend on
whether its more efficient to iterate over the first or second layer
-- this dual-logic approach is why these algorithms and join by
location are much faster then the intersection algorithm as previously
discussed!). In both of these you'd basically expand out the size of
the bounding box used to request matching features via
QgsRectangle::grow (so the larger bounding box is handed off to the
underlying data provider spatial index for filtering), and then change
the "isMatch" test to use engine->distance(  ) <= buffer distance.
(Might also be worth first testing if the geometries intersect before
calculating the distance as it may be more efficient to do this, but
would need to be tested to verify.). On GEOS >= 3.9 based builds the
distance(... ) check is optimised and uses indexes, so it should be
very fast to perform this check! (As opposed to the inefficient
"buffer the geometries" approach). Basically we'd want to follow
PostGIS ST_DWithin approach, not a ST_Intersects(ST_Buffer(...))
approach.

If I was quoting for a customer I'd estimate 5 hours total for the
change, but of course YMMV.

Nyall


>
> Calvin
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Re: [Qgis-user] QGIS 3.18 image problems in geopackage file

[Nyall Dawson]

On Tue, 2 Mar 2021 at 15:32, Grant Boxer  wrote:
>
> Does version 3.18 see raster images in geopackage files differently to
> v3.16? I have created geopackages with raster and vector files in 3.16,
> but now when I try to open the raster images in 3.18, it puts two
> explanation marks (!!) in front of the raster image file name and won't
> open the images. I can open these images if I go via the Open Data
> Source Manager > Raster option, but not ODSM > Geopackage option. Is
> this a bug?

It's a known issue, will be fixed in 3.18.1.

QGIS 3.18.0 has proven to be quite a buggy mess -- the installers have
been removed from the website as a result pending the fixes present in
3.18.1. I'd recommend downgrading back to 3.16 for the time being.

Nyall
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Re: [Qgis-user] Performance problems with the ogr file-gdb driver

[Nyall Dawson]

On Thu, 25 Feb 2021 at 23:44, Thomas Struller
 wrote:
>
> Hallo List,
>
> since installing QGis 3.16.3 and now continuing 3.18 i have serious 
> performance problems when using the OGR file-gdb Driver.
>
> When i use the ogr file-gdb driver QGis becomes very slow. Not only when I 
> try to edit a file geodatabase, even when i zoom in or out or try to change 
> from the layer-view to the browser-view.
>
> On start up QGis now needs minutes to scan „former project connections“. Is 
> it possible to avoid this scan on startup?
>
> We have a mixed enviroment with arcgis installations and qgis. Sometimes i 
> have to edit a filegeodatabase.
>
> I’m on windows 10 pro, amd ryzen 4750, 32 GB
>
> Does anyone have the same experiences? Is there a solution besides 
> uninstalling the ogr-file-gdb driver?

You could go into Settings - Options - GDAL - Vector Drivers and
disable the filegdb driver whenever you're not actively editing a gdb
file. I.e. use the stable, optimised openfilegdb driver most of the
time and only switch to the filegdb driver when you have a specific
need to use it.

The GDAL driver page for the FileGDB driver lists a whole lot of known
issues with that driver, which can't be addressed by anyone except for
ESRI (as they come from the underlying ESRI SDK). I don't see any
likelihood that this driver can/will be improved in the future.

In the long term, there's two reasonable solutions for this setup that I see:
1. With the improved Geopackage compatibility that recent ArcGIS Pro
versions bring you may have luck in moving your arcgis workflows away
from gdb files and to gpkg, which of course work great in QGIS and
other non-esri applications.
2. If funding is available, there's a good chance that edit support
can be added to the open source openfilegdb GDAL driver. While this
hasn't yet been tested, the gdb format is sufficiently reverse
engineered and understood well enough to make this a good possibility.

Nyall


>
> On a imac machine and a linux-mint machine I did not have these performance 
> issues. But as far as i now, there it is not possible to edit esri file 
> geodatabases.
>
> Mit freundlichen Grüßen
>
>
> Thomas Struller
> Diplom Geologe (Univ.), BDG, V18
>
> Sachverständiger nach BBodSchG §18,
> SG1 Historische Recherche
> SG2 Pfad Boden – Gewässer
> Akademischer Geoinformatiker
>
>
>
>
> Tel:0049 911 12076 111
> Mobil:  0049 170 33 20 494
> Mail:   thomas.strul...@lga-geo.de
>
>
> LGA Institut für Umweltgeologie und Altlasten GmbH
> Christian-Hessel-Straße 1
> 90427 Nürnberg
> i...@lga-geo.de
> www.LGA-geo.de
>
>
>
>
>
>
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>
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Re: [Qgis-user] Problem to open Raster files

[Nyall Dawson]

On Sat, 20 Feb 2021 at 06:43, Bernd Vogelgesang
 wrote:
>
> seems this a ESRI File Geodatabase (sorry, left the ESRI stage 10 years
> ago, so not sure).
>
> As far as I know, rasters can't be exctracted from this with QGIS.

This is the ONLY way to use these data formats from open source
software: https://github.com/r-barnes/ArcRasterRescue

I've long been seeking a financial sponsor to fund development of a
GDAL driver for GDB raster layers, but to date have not had any luck.
If raster GDB support is important to your organisation, can you
please contact me off list to discuss sponsoring this development?

Thanks!
Nyall


>
> List of supported raster formats: https://gdal.org/drivers/raster/index.html
>
>
> Am 19.02.21 um 21:00 schrieb Cassia Pahim:
> > They are in those formats
> >
> > .gdbindexes
> > . gdbtable
> > . horizon
> > . gdbtablx
> > . freelist
> > . atx
> > . spx
> >
> > Cassia
> >
> >
> >
> >
> >
> >
> >> Le 19 févr. 2021 à 14:58, Bernd Vogelgesang  a 
> >> écrit :
> >>
> >> could you possibly share a little more details about what type of rasters 
> >> you are dealing with? There is a bazillion of different raster formats!
> >>
> >> Am 19.02.21 um 20:47 schrieb Cassia Pahim:
> >>> Hello,
> >>>
> >>> I am trying to create a map and I have 15 datasets that were sent to me 
> >>> in a zip folder and I can’t open them into QGIS. When using the icon « 
> >>> add rater layer » I get an error message telling me the files are not 
> >>> valid or recognized. What should I do to be able to work with those 
> >>> datasets ? Please note that I am using macOS Catalina 10.15.7 and I have 
> >>> installed QGIS 3.16.
> >>>
> >>> I appreciate your help,
> >>>
> >>> Cassia
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
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Re: [Qgis-user] Symbol lines every km, moving when changing scale or moving map

[Nyall Dawson]

On Fri, 19 Feb 2021 at 23:00, Andreas Neumann  wrote:
>
> Hi Jérémie,
>
> Ah good to hear!
>
> I'm not a big fan of this fact that line simplification is turned on by 
> default in QGIS. I believe that users should consciously turn it on if they 
> want it!

I'd be interested to see some benchmarks of disabling vs enabling
simplification for the marker line symbol layer alone. If it's not too
expensive, we could skip it automatically for line marker symbol
layers (it makes a HUGE difference to the rendering speed for simple
line layers and other symbol layer types, but the intention is that
the results should be visually identical to no simplification).

Nyall

>
> Your example shows that it can lead to confusion (understandably).
>
> Good that it works now. Note that you can override this setting on a per 
> layer base in the layer properties - so not all layers need to have the same 
> setting.
>
> Greetings,
>
> Andreas
>
> On 2021-02-19 13:40, Prud'homme Jérémie wrote:
>
> Hi,
>
> I had simplification turned on, indeed...
>
> I deactivated it :
> - in the Options as you mention, so that it is deactivated for newly added 
> layers
> - in my layer options (Rendering properties)
>
> And it is ok now.
>
> It makes sense that if the line is simplified the distance vary !
>
> Thanks Andreas.
>
>
> Jérémie.
>
> Le ven. 19 févr. 2021 à 11:12, Andreas Neumann  a écrit :
>
> Hi Jérémie,
>
> Do you have geometry simplification turned off? See "Settings" --> "Options" 
> --> "Rendering" --> "Enable feature simplification ..."
>
> Make sure this is deactivated (I think it is enabled by default).
>
> Greetings,
>
> Andreas
>
>
> On 2021-02-19 11:05, Prud'homme Jérémie wrote:
>
> Tested too fast :(
>
> Behavior is ok when zooming in, but still problems when zooming out (whereas 
> the entire feature is visible !).
> See here : https://www.zupimages.net/viewer.php?id=21/07/ehlo.gif
>
> Circles should follow the strokes generated with the tool "Points along 
> geometry".
>
>
> Jérémie.
>
> Le ven. 19 févr. 2021 à 10:03, Prud'homme Jérémie  a 
> écrit :
>
> Hi,
>
> Thank you very much Nyall, this one was pretty well hidden.
>
> With clipping unchecked, behavior is as expected for my use case.
>
>
> Jérémie.
>
> Le jeu. 18 févr. 2021 à 23:29, Nyall Dawson  a écrit :
>
> On Wed, 13 Jan 2021 at 06:33, Prud'homme Jérémie  wrote:
> >
> > Hi,
> >
> > I'm using QGIS 3.10.
> >
> > I tried to use only symbology to display a stroke every km along a road.
> > The project CRS is 2154 (Lambert 93).
> >
> > When adding a ""symbol line" with an interval of 1000 map units (meter for 
> > 2154) – or 1000 meters at scale, same result – I achieve to display symbols 
> > every km.
> >
> > Problem is when I move the map or change scale, the symbols do not always 
> > stay in place. They are sometimes misplaced.
> >
> > I've been told that problem can be that the first node of the line is not 
> > always the reference to calculate the intervals.
>
> From the bottom of the symbol widget, click the "Advanced" button and
> uncheck "Clip features to canvas extent".
>
> Nyall
>
>
>
> >
> > You can find a GIF here that displays my problem : 
> > https://zupimages.net/viewer.php?id=21/02/nvr2.gif
> >
> > Circles are symbols via Symbology.
> > Strokes are symbos on points generated vith the tool "Points along 
> > geometry".
> >
> > You can see that circles are not always at the same place as the strokes.
> >
> > Is it a "normal" behavior ?
> > Anyway as a user I would expect that symbols are always generated at the 
> > same place from the starting node.
> >
> > Thanks for your enlightments on this.
> >
> > Jérémie.
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Re: [Qgis-user] Layout without initializeDefaults()

[Nyall Dawson]

On Fri, 19 Feb 2021 at 11:03, Mayo Rubiano  wrote:
>
> Hello everyone.
> I'm new in QGIS.
> My question is: I'm trying to layout with PYQGIS, I understand that there is 
> one way to initialize automatically the layout configurations that is with 
> the function initializeDefaluts(), that adds a A4 page in landscape 
> orientation. But I want to layout without this function because I need a 
> different page size and orientation.
> I tried with this code in the python console:
>
> project = QgsProject().instance()
> layout = QgsPrintLayout(project)
> page = QgsLayoutItemPage(layout)
> #set page orientation vertically and a letter size
> page.setPageSize("Letter", 0)

layout.pageCollection().addPage( page )

(you don't use addLayoutItem for pages -- add it directly to the page
collection instead)

Nyall


> layout.addLayoutItem(page)
> #set the layout name for the layout manager
> layout.setName("MyLayout")
> #add the layout to the layout manager
> project.layoutManager().addLayout(layout)
>
>
> When I open the layout made with this code in the the layout manager I note 
> that the variable layout_numpages is set to 0, that means that I can't add 
> guides because there are no pages to link guides and I can't use the rulers 
> because the 0 of y rulers is at the coordinates (0,10)mm. Then, there are 
> other variables with different values (layout_pageheight, layout_pageoffset 
> and layout _page width).
>
> Could someone tell me what is needed to build a layout without that function 
> and correcting the rulers and the layout_numpage variable?
>
> Thanks
>
> M. Rubiano
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Re: [Qgis-user] Setting a project variable from processing modeler

[Nyall Dawson]

On Fri, 19 Feb 2021 at 09:12, Francesco Pelullo  wrote:
>
> Hi list,
>
> is there an algorithm for setting a project variable from a modeler algorithm?

A native one was added in 3.16 - look under the "modeler tools" group.

Nyall

>
> I found this:
> https://gis.stackexchange.com/questions/359386/is-there-a-way-to-edit-project-variables-with-modeller-in-qgis
>
> but if I add this script to the modeler, QGIS 3.10 shows error:
> AttributeError: type object 'QgsProcessingAlgorithm' has no attribute 
> 'FlagSkipGenericModelLogging'
>
> Any help appreciated.
> Thank you
> Francesco
>
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Re: [Qgis-user] Symbol lines every km, moving when changing scale or moving map

[Nyall Dawson]

On Wed, 13 Jan 2021 at 06:33, Prud'homme Jérémie  wrote:
>
> Hi,
>
> I'm using QGIS 3.10.
>
> I tried to use only symbology to display a stroke every km along a road.
> The project CRS is 2154 (Lambert 93).
>
> When adding a ""symbol line" with an interval of 1000 map units (meter for 
> 2154) – or 1000 meters at scale, same result – I achieve to display symbols 
> every km.
>
> Problem is when I move the map or change scale, the symbols do not always 
> stay in place. They are sometimes misplaced.
>
> I've been told that problem can be that the first node of the line is not 
> always the reference to calculate the intervals.

From the bottom of the symbol widget, click the "Advanced" button and
uncheck "Clip features to canvas extent".

Nyall



>
> You can find a GIF here that displays my problem : 
> https://zupimages.net/viewer.php?id=21/02/nvr2.gif
>
> Circles are symbols via Symbology.
> Strokes are symbos on points generated vith the tool "Points along geometry".
>
> You can see that circles are not always at the same place as the strokes.
>
> Is it a "normal" behavior ?
> Anyway as a user I would expect that symbols are always generated at the same 
> place from the starting node.
>
> Thanks for your enlightments on this.
>
> Jérémie.
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Re: [Qgis-user] file qpj non creato

[Nyall Dawson]

On Wed, 17 Feb 2021 at 08:34, Bernd Vogelgesang
 wrote:
>
> Isn't the correct answer, that in newer versions, there is no qpj created, 
> cause it is not needed anymore?

Exactly -- it was a hack in place for many years because the whole
open-source geo software stack lacked robust CRS handling, but after
proj 6/gdal 3 this was all completely rewritten and the hack is no
longer required.

Nyall

>
> Am 16.02.21 um 22:56 schrieb Nicolas Cadieux:
>
> Hi,
>
> I created a shp file today. I specified the CRS in the new Shapefile Layer 
> dialog.  The .prj was created.  I am using qgis 3.16 on Windows 10.  Did you 
> specify the CRS?
>
> Nicolas
>
>
> "Dear users of the list
> today wanting to make a comparison with some old shapefiles I created a new 
> one with QGIS 3.10.2 and I realized that the .qpj file is no longer created 
> in addition to the classic .prj.
>
> Can anyone tell me from which version of QGIS this happens?
>
> Antonio Valanzano"
>
> On 2021-02-16 2:14 p.m., Antonio Valanzano wrote:
>
> Cari utenti della lista
> oggi volendo fare un confronto con alcuni vecchi shapefile ne ho creato un 
> nuovo con QGIS 3.10.2 e mi sono accorto che non viene più creato il file .qpj 
> in aggiunta al classico .prj.
>
> Qualcuno sa dirmi da quale versione di QGIS accade ciò ?
>
> Antonio Valanzano
>
>
>
>
>
>
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[Qgis-user] QEP 209: Expose OGR feature styles via a new "Embedded styling" renderer

[Nyall Dawson]

Hi all,

Please see https://github.com/qgis/QGIS-Enhancement-Proposals/issues/209
for a newly filed QGIS Enhancement Proposal: "Expose OGR feature
styles via a new "Embedded styling" renderer".

Some vector data formats have native support for embedding feature
styling information, such as MapInfo TAB files. These formats allow
embedded symbology to be set on a feature-by-feature basis. This
proposal concerns exposing this per-feature styling information via
the QGIS API and creation of a new "embedded styling" renderer for
compatible vector layers, which allows users to view features using
the closest possible match to their original symbology.

Comments and discussion welcome! (please keep discussion on
https://github.com/qgis/QGIS-Enhancement-Proposals/issues/209 and not
via email replies in order to keep all conversation centralized!).

Regards,
Nyall
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[Qgis-user] A nice task for a community member: revamping the QGIS github landing page

[Nyall Dawson]

Hi all!

If someone's been looking for a great introductory task to start
contributing to QGIS, I'd like to put a call out for a volunteer to
have a go at re-working the landing page (the README) that you see
when you visit

https://github.com/qgis/QGIS

While the current text is all accurate, it's very dry and technical,
hasn't had a major update in years, and doesn't really paint QGIS in
an "exciting" light! I'd love to see this revamped into something more
visual which really showcases QGIS' capabilities. I'm thinking
something more like what you see for the alternative QGIS albireo
frontend at https://github.com/kadas-albireo/kadas-albireo2...

It'd be a great task for someone who is well familiar with QGIS'
capabilities and has a good English writing style, and it doesn't
require any technical capabilities between simple markdown editing.

Thanks in advance!
Nyall
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Re: [Qgis-user] GRASS and UK LIDAR

[Nyall Dawson]

On Wed, 10 Feb 2021 at 00:20, Dave Marshall <43carn...@gmail.com> wrote:
>
> Nyall,
>
> The first error which appears is "WARNING: Datum 
>  not recognised by GRASS and no 
> parameters found ".I think all subsequent errors stem from this. This error 
> message occurs whether I choose a CRS transformation or not.

Ok - that's an error coming straight from GRASS itself. You'll need to
ask the GRASS project about this one and raise a ticket on their issue
tracker!

Nyall

>
> Cheers,
>
> Dave
>
> On Tue, 9 Feb 2021 at 02:05, Nyall Dawson  wrote:
>>
>> On Tue, 9 Feb 2021 at 05:57, Dave Marshall <43carn...@gmail.com> wrote:
>> >
>> > Hello,
>> >
>> > I use QGIS 3.4 to visualise LIDAR tiles from the UK which use EPSG:27700 
>> > as the CRS. I put height contours on the images using the r.contour 
>> > feature in GRASS. This works extremely well. I have tried a couple of 
>> > times to move to a more up-to-date version of QGIS but in each case, the 
>> > version of r.contour associated with later versions does not work. These 
>> > later versions seem to require some sort of co-ordinate transformation on 
>> > opening the LIDAR files (I think to EPSG:4326) and I wonder if this is 
>> > part of the problem. Running r.contour generates an error message which 
>> > seems to suggest it does not recognise or cannot work with the CRS being 
>> > used (there is a reference to Airy Spheroid).
>>
>> What's the error?
>>
>> Nyall
>>
>>
>>
>> >
>> > What I would like to do is to be able to use a more up-to-date version of 
>> > QGIS but with the same version of GRASS which I get when I use 3.4. This 
>> > version would seem to be 7.6.1 rather than 7.8.5.
>> >
>> > There is a similar contour feature in QGIS under \Raster\Extraction but 
>> > this does not allow the specification of height ranges which is essential 
>> > for the work I am doing to avoid the routine from taking a very long time 
>> > to run.
>> >
>> > Any help or advice would be much appreciated,
>> >
>> > Dave Marshall
>> > ___
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Re: [Qgis-user] [QGIS-Developer] timzonefinder vs point in polygon

[Nyall Dawson]

On Wed, 10 Feb 2021 at 03:32, Matthias Kuhn  wrote:
>
> Hi Calvin,
>
> If you are looking for speed I would consider putting things into memory.
> I have seen that timezonefinder has an in_memory option which makes it even 
> faster.
> On QGIS side you can also load features into a memory layer and add a spatial 
> index to that.

Just to add to this -- if you pre-prepared the timezone polygon
geometries and cached all the results then that's the fastest speed
you'll ever achieve :) (at the cost of memory usage, however!)

Nyall

>
> Hope that helps to squeeze the last bit of performance out of this
> Matthias
>
> On Tue, Feb 9, 2021 at 5:52 PM C Hamilton  wrote:
>>
>> It is highly likely that you have a much faster machine than mine so I can 
>> only look at comparative times between timezonefinder and the PyQGIS code 
>> included below. You will notice that I take a snapshot of the time before 
>> and after I iterate through the 10,000 points using both timezonefinder as a 
>> look up and the code Nyall proposed. That is how I am getting the times. 
>> What I am really trying to determine is the fastest way to look up a point 
>> using either timezonefinder or PyQGIS code. Perhaps what I have with PyQGIS 
>> code is fast enough, but I am not satisfied if it is not close to the speed 
>> of timezonefinder.
>>
>> Ultimately, I am trying to determine whether I should continue to use 
>> timezonefinder as the method to look up time zones in my datetimetools 
>> plugin or should I have the gpkg time zone polygon layer as a part of the 
>> plugin and do lookups using it. Right now I am just doing single point 
>> lookups and it is probably fast enough, but I don't like that it is slower 
>> than timezonefinder. I am likely to expand datetimetools plugin to have a 
>> processing algorithm to do a lookup on a whole layer and in that case the 
>> PyQGIS method is better.
>>
>> Those are my thoughts and if there is a faster method using the gpkg time 
>> zone polygon to do the lookup, let me know.  One thing I just tried was 
>> using the shapefile from  
>> https://github.com/evansiroky/timezone-boundary-builder. It appears it is 
>> not spatially indexed and was taking too long. I resaved it as a shapefile 
>> and made sure it had a spatial index, but the gpkg conversion of the 
>> shapefile is even faster to access.
>>
>> Calvin
>>
>> On Tue, Feb 9, 2021 at 11:19 AM  wrote:
>>>
>>> Hi Calvin,
>>>
>>>
>>>
>>> Thanks for sending me this from the Developers list. I am not a part of the 
>>> Developer list, so I did not see the Join attribute by location tip from 
>>> Andrea.
>>>
>>>
>>>
>>> Anyway, what do you mean with not getting fast result with single point 
>>> lookups?
>>>
>>> When I select a single point from the 1 point layer and run the same 
>>> algorithm (check the selected features only option in the dialogue box), 
>>> the result takes 0.05 seconds (12 seconds for all 1). At least that is 
>>> what is says in the log tab of the algorithm. And it sure looks quick.
>>>
>>>
>>>
>>> Jeroen
>>>
>>>
>>>
>>>
>>>
>>> Van: C Hamilton 
>>> Verzonden: dinsdag 9 februari 2021 16:25
>>> Aan: Nyall Dawson 
>>> CC: Andrea Giudiceandrea ; qgis-developer 
>>> ; Groene Bij 
>>> Onderwerp: Re: [QGIS-Developer] timzonefinder vs point in polygon
>>>
>>>
>>>
>>> Nyall,
>>>
>>>
>>>
>>> Using "Join attributes by location" on a large set of points is fast, but 
>>> if you are doing single point lookups it bothers me that I am not getting 
>>> that fast of results in comparison to timezonefinder. The 10,000 points is 
>>> intended to test the speed of many single point lookups. If I were going to 
>>> actually do 10,000 point lookups I would use the Join attributes by 
>>> location, but here are my results of single point lookups using 
>>> timezonefinder vs. your method. Note that the assumption is that they can 
>>> be anywhere in the EPSG:4326 bounding box. I am not trying to constrain 
>>> them to the QGIS canvas.
>>>
>>>
>>>
>>> timezonefinder: 44 seconds
>>>
>>> Your method: 144 seconds
>>>
>>>
>>>
>>> Here is my code for each:
>>>
>>>
>>>
>>> timezonefinder
>>>
>>> from timezonefin

Re: [Qgis-user] GRASS and UK LIDAR

[Nyall Dawson]

On Tue, 9 Feb 2021 at 05:57, Dave Marshall <43carn...@gmail.com> wrote:
>
> Hello,
>
> I use QGIS 3.4 to visualise LIDAR tiles from the UK which use EPSG:27700 as 
> the CRS. I put height contours on the images using the r.contour feature in 
> GRASS. This works extremely well. I have tried a couple of times to move to a 
> more up-to-date version of QGIS but in each case, the version of r.contour 
> associated with later versions does not work. These later versions seem to 
> require some sort of co-ordinate transformation on opening the LIDAR files (I 
> think to EPSG:4326) and I wonder if this is part of the problem. Running 
> r.contour generates an error message which seems to suggest it does not 
> recognise or cannot work with the CRS being used (there is a reference to 
> Airy Spheroid).

What's the error?

Nyall



>
> What I would like to do is to be able to use a more up-to-date version of 
> QGIS but with the same version of GRASS which I get when I use 3.4. This 
> version would seem to be 7.6.1 rather than 7.8.5.
>
> There is a similar contour feature in QGIS under \Raster\Extraction but this 
> does not allow the specification of height ranges which is essential for the 
> work I am doing to avoid the routine from taking a very long time to run.
>
> Any help or advice would be much appreciated,
>
> Dave Marshall
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Re: [Qgis-user] File based Geopackage bugs

[Nyall Dawson]

On Tue, 2 Feb 2021 at 12:12, Patrick Dunford  wrote:
>
> I recall going back someway we were sold this Geopackage idea being
> implemented into Qgis because it was going to be so much better than
> shape files that everyone has been using up to now. I bought into these
> ideas by converting shape files in most of my Qgis projects into
> Geopackage files.
>
> However there appear to be some serious bugs in Qgis' implementation of
> Geopackages as a file based system, and since SQlite has an impeccable
> reputation, it is a reasonable conclusion that there must be significant
> uncorrected bugs in the Qgis code that deals with file based Geopackages.
>

Please have a read over the threads at
https://lists.osgeo.org/pipermail/qgis-developer/2020-March/060584.html
and  https://lists.osgeo.org/pipermail/qgis-developer/2020-May/061162.html

All your issues were discussed at length in those threads -- so
there's lots of background info there. Suffice to say, as you've
realised, many of the issues are still outstanding and yes, geopackage
can be a pain (a nightmare?) to use for some workflows.

Nyall


>
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Re: [Qgis-user] What is postgresql client version and does it have anything to do with different postgresql versions

[Nyall Dawson]

On Wed, 3 Feb 2021 at 06:37, Groene Bij  wrote:

> I did notice in the info screen for qgis3.16.3 it says PostgreSQL Client 
> version 11.5
>
> Does that mean QGIS3.16 might work best with PostgreSQL 11.x? Or are they 
> completely unrelated?

They are unrelated -- the client version refers to the library which
QGIS uses to access any postgres database. It doesn't have to be
matched to the version of the database you connect to at all. QGIS
should connect perfectly to later database versions too!

Nyall

>
>
>
>
>
> Kind regards,
>
> Jeroen Hovens
>
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Re: [Qgis-user] QEP: Layer Notes

[Nyall Dawson]

On Mon, 1 Feb 2021 at 14:47, Nyall Dawson  wrote:
>
> Hi all,
>
> I've just submitted a new QGIS enhancement proposal detailing support
> for user created "notes" for map layers. You can read the details
> here: https://github.com/qgis/QGIS-Enhancement-Proposals/issues/206
>
> I'm after feedback on this proposal and am trying to determine how
> widespread the use-case is, and how desirable it is to have this
> functionality available in QGIS out-of-the-box (vs as a plugin).

Thanks everyone for the great feedback so far! Can I please request
that we keep the comments and replies on the github proposal page in
order to keep everyone's comments centralised?

Thank you!
Nyall
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Re: [Qgis-user] QEP: Layer Notes

[Nyall Dawson]

On Tue, 2 Feb 2021 at 05:35, Garth Fletcher  wrote:
>
> Stewart Holt brings up an important distinction between
> Meta Data, which belongs with the layer, and Layer Notes which
> would belong with the project.
>
> I agree that having both would be very valuable as each serves
> a different and important role in documenting a project an
> its data sources.
>
> I would use Meta Data to document data source and its manipulation
> which are important if the file is imported into a different project,
> while I would use Layer Notes for information about layering and
> such in the current project.

Exactly, thanks for adding this clarification!

Nyall

>
> Kudos to Nyall for his proposal!
> --
> Garth Fletcher
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[Qgis-user] QEP: Layer Notes

[Nyall Dawson]

Hi all,

I've just submitted a new QGIS enhancement proposal detailing support
for user created "notes" for map layers. You can read the details
here: https://github.com/qgis/QGIS-Enhancement-Proposals/issues/206

I'm after feedback on this proposal and am trying to determine how
widespread the use-case is, and how desirable it is to have this
functionality available in QGIS out-of-the-box (vs as a plugin).

Nyall
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Re: [Qgis-user] [QGIS-Developer] New QGIS Date/Time Tools Plugin

[Nyall Dawson]

On Fri, 29 Jan 2021 at 01:13, C Hamilton  wrote:
>
> Nyall,
>
> What you mention has merit, but I was not kidding about trying to keep a 
> plugin self contained for government use. To set up automatic downloading on 
> our networks would require PKI authentication and that opens up another can 
> of worms. I know how to deal with PKI because I already maintain plugins that 
> use authentication. It would be easier for our users to have them download a 
> data pack and have some manual installation process, but it is even easier if 
> the data is already a part of the plugin. The other option would be to 
> produce two different versions of the plugin. One for government use and the 
> other for community use, but my sponsor would probably frown on that and not 
> want me to use my time to maintain the community version.
>
> The author of timezonefinder has done a number of optimizations to provide 
> fast lookups. See
>
> https://timezonefinder.readthedocs.io/en/latest/3_about.html
>
> I wonder what the difference in time would be to use a gpkg and QGIS point in 
> polygon look up vs timezonefinder lookup. Will it be faster or slower? I'm 
> not sure without testing. What are your thoughts? I would choose the faster 
> of the two.

I'd certainly hope a dedicated GIS application can do this faster than
a random Python library :D

> I just converted the timezone data to a gpkg and its size is 102Mb. The data 
> size for timezonefinder using the same data set is 49Mb. The optimization in 
> timezonefinder can produce a maximum error of 1cm at the equator as they use 
> 32 bit ints for the data. It might actually be better to use the gpkg file, 
> but it is double in size. I will investigate using the gpkg data.

You may want to try a shapefile too, just in case...!

Nyall


>
> It seems to me that if a plugin requires a certain dataset to function then 
> that data should be included with it and not require an additional download, 
> but I understand the issues that this could cause so I am not sure of the 
> best way forward. For our use it is definitely better to include the data 
> with the plugin.
>
> I guess what I would like you to take from this conversation is that some 
> users have a completely different environment and face different challenges 
> then what you do when it comes to dealing with software. I wish that it was 
> easier for me to get QGIS acceptance in our workforce but ArcGIS still rules.
>
> Thanks for your ideas and all of the hard work that you do to keep QGIS 
> moving forward.
>
> I wish you all the very best!
>
> Calvin
>
>> Given that the size of the python library is almost entirely the size
>> of the timezone boundaries themselves, have you considered:
>> - avoiding the library entirely, and insteading using a standard
>> shapefile/gpkg/... of the boundaries and using QGIS vector layer
>> methods to determine the timezone for a point
>> - deferring the download of the boundary spatial data, so that it's
>> not supplied with the plugin but instead the plugin automatically
>> downloads it on first launch?
>>
>> This would avoid the need for the large size plugin, allowing it to be
>> supplied via the standard QGIS repo while still providing its full
>> functionality...
>>
>> Nyall
>>
>>
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Re: [Qgis-user] [QGIS-Developer] New QGIS Date/Time Tools Plugin

[Nyall Dawson]

On Thu, 28 Jan 2021 at 00:32, C Hamilton  wrote:
>
> Tim,
>
> I understand the position you are in and I really struggled in even wanting 
> to put in the time to develop this plugin knowing that there would probably 
> be a problem getting it accepted by the QGIS developers because of its size, 
> but our users have a very real need for this capability which is why I 
> consented to develop it at all.
>
> In order to deal with locating time zones based on a coordinate there is 
> simply no way to get around the size of the python library required if 
> accuracy of the results is desired. That feature alone requires 42Mb. I 
> struggle to convince our GIS analysts to use QGIS over ArcGIS and so I try to 
> provide solutions that work better than those in ArcGIS, but if there is any 
> sort of complication that makes it more difficult for one of the analysts to 
> get the resources they need for QGIS then I have lost the battle. This 
> includes having them pip install additional python libraries because most of 
> them do not have system admin privileges.

Given that the size of the python library is almost entirely the size
of the timezone boundaries themselves, have you considered:
- avoiding the library entirely, and insteading using a standard
shapefile/gpkg/... of the boundaries and using QGIS vector layer
methods to determine the timezone for a point
- deferring the download of the boundary spatial data, so that it's
not supplied with the plugin but instead the plugin automatically
downloads it on first launch?

This would avoid the need for the large size plugin, allowing it to be
supplied via the standard QGIS repo while still providing its full
functionality...

Nyall


>
> I can easily set up the ability for users to point to a separate repo that 
> houses this plugin, but once again that is an additional complication. Every 
> once in a while I find some QGIS repo of plugins that are not a part of the 
> official QGIS repo and I think that it is too bad that they are probably not 
> used much outside of the organization who hosts them. Unless a plugin exists 
> on the official QGIS repo it will not be discoverable and will not likely be 
> used by many.
>
> I think the plans I have with this plugin will make it very useful to the 
> QGIS community, but if it cannot be a part of the QGIS repo it will not be of 
> much use to the community. Our users will make use of it because we will 
> provide it to them. I would like to swap out the astral library for the 
> Skyfield library with the JPL ephemeris data to provide more precise sun and 
> moon calculations, but that adds an additional ~20Mb.
>
> I would love it if you would provide timezonefinder and Skyfield libraries by 
> default with the QGIS distribution, but that increases the size of the QGIS 
> download. When you are dealing with time zones and astronomical calculations, 
> there is no way in getting around the plugin size to get the best accuracy 
> available. I personally am not interested in providing tools with less 
> accuracy.
>
> I don't know how important it will be for the QIGS community to have these 
> tools available, but I know that there will be a number of users who have 
> been looking for these capabilities in QGIS and will be valuable to them. 
> Right now I have coded only one of a number of tools that I have planned, but 
> part of my plans will be determined by the QGIS acceptance of a larger 
> plugin. I think my other QGIS plugins I have provided including "Lat Lon 
> Tools", "Shape Tools" & "KML Tools" shows how useful my plugins have been.
>
> If there is something I am missing or some other way around this let me know, 
> but keep in mind I hold to two fundamental principals with my plugins. 1) 
> They are as accurate at possible. 2) They are self contained meaning that OUR 
> users don't need to install any software to run them. The functionality in 
> Date/Time tools is simply going to take up space and there is no way around 
> it that I can see. I think your "unwritten expectation" of small plugins 
> prevents some capabilities from being introduced, but I also agree that in 
> most instances plugins should be kept small. What I am trying to accomplish 
> simply does not come small.
>
> Let me know if you want me to just provide the capabilities for our users 
> alone or to expand it for use by the QGIS community.
>
> I await the QGIS developers decision on this.
>
> Thanks!
>
>>> Personally I would be more on the -1 on upping the limit for plugins - 
>>> currently at 10mb I think - since large plugins will consume more space on 
>>> our plugins server and our user's bandwidth. There is an unwritten 
>>> expectation that plugins should be small and quick to fetch. If others feel 
>>> strongly with a contrary opinion, contact me offlist and I will help you 
>>> get it published without generally changing the limit.
>>
>>
>> Regard
>>
>> Tim
>>
>> ___
>> Qgis-user 

Re: [Qgis-user] v.transform Tool

[Nyall Dawson]

On Thu, 7 Jan 2021 at 07:31, krishna Ayyala  wrote:
>
> I have created a polygon shape file with CRS of EPSG:4326-WGS 84. I ran the 
> v.transform Tool on this polygon by increasing the xscale to 1.5 and yscale 
> to 1.5. I see a polygon generated. But, this is not falling on top of the 
> original polygon. It is falling in completely in a different location i.e 
> beyond the map limits. What should I do to have this fall at the right 
> location?

This tool literally just takes the coordinates in the features and
scales them by the value -- so a vertex at 30.5, 70 will scale to 70,
140 if you scale with 2/2 scaling values. (In other words, it will
appear to move). To scale around a center point you'd need to
translate the feature back to the origin, scale it, and then translate
back to its original location.

>
>
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Re: [Qgis-user] Confusion with ellipsoidal method of $area

[Nyall Dawson]

On Wed, 6 Jan 2021 at 07:40, Rahkonen Jukka (MML)
 wrote:
>
> Hi,
>
>
>
> Sorry, I am amateur on this area and I do not know what is the difference 
> between spheroids and ellipsoids. Do you mean that QGIS is using more 
> accurate method than PostGIS for calculating the lengths and areas over the 
> WGS 84 ellipsoid?

You're definitely not alone in this, but I'd strongly recommend doing
a bit of research into the differences and how they affect
measurements. There's no single "right" answer to how things should be
accurately measured, so the decisions regarding this are the user's
responsibility, and it's up to you to make an informed choice here.

Suffice to say that both QGIS and geographiclib can do either
spherical or ellipsoidal calculations -- to compare them you need to
ensure that the exact same sphere/ellipsoid parameters are used.

Nyall


>
>
>
> The article that is used as a reference on the GeographicLib page (Charles F. 
> F. Karney, Algorithms for geodesics,
>
> J. Geodesy 87(1), 43–55 (Jan. 2013) does not use word spheroid in the text at 
> all but ellipsoid appears there 29 times. So perhaps the library deals 
> actually with ellipsoid but PostGIS and Spatialite documentation talks about 
> spheroid?
>
>
>
> Could you give one linestring and one polygon as reference geometries and the 
> most accurate lengths and areas that you know for some of your favorite 
> ellipsoids to be used as true values?
>
>
>
> -Jukka Rahkonen-
>
>
>
>
>
>
>
> Lähettäjä: Nicolas Cadieux 
> Lähetetty: tiistai 5. tammikuuta 2021 22.52
> Vastaanottaja: Rahkonen Jukka (MML) ; 
> qgis-user@lists.osgeo.org
> Aihe: Re: [Qgis-user] Confusion with ellipsoidal method of $area
>
>
>
> Hi,
>
> QGIS is currently built on Proj version 6.3.2-1.  If the other libraries are 
> using a spheroid by default, then they use a sphere for speed and not an 
> ellipsoid for precision.  You can probably force this measurement in QGIS by 
> creating a custom CRS with a spheroid rather than an ellipsoid. The other 
> option is to use the python in QGIS and to force a geoid.
>
> Nicolas
>
> On 2021-01-05 1:33 p.m., Rahkonen Jukka (MML) wrote:
>
> Hi,
>
>
>
> I suppose that PostGIS is using the WGS 84 ellipsoid but I am not sure where 
> from the documentation I could find that information. The ST_Area document 
> https://postgis.net/docs/ST_Area.html says only “For geography types by 
> default area is determined on a spheroid with units in square meters”. Same 
> thing with Spatialite, documentation suggests just that it is “the” spheroid 
> http://www.gaia-gis.it/gaia-sins/spatialite-sql-latest.html.
>
>
>
> I did not notice this paragraph in the ST_Area document earlier “Enhanced: 
> 2.2.0 - measurement on spheroid performed with GeographicLib for improved 
> accuracy and robustness. Requires Proj >= 4.9.0 to take advantage of the new 
> feature.” So no wonder that the web app and PostGIS give the same results 
> because they both use GeographicLib. And SpatiaLite 5.0 is using RTTopo that 
> is a library that is based on LWGeom so close connection in there too.
>
>
>
> So perhaps the way to get identical areas from QGIS would be to make it to 
> use GeographicLib as well. I have no idea if it is a realistic approach and 
> worth making a feature request.
>
>
>
> -Jukka Rahkonen-
>
>
>
> Lähettäjä: Nicolas Cadieux 
> Lähetetty: tiistai 5. tammikuuta 2021 20.04
> Vastaanottaja: Rahkonen Jukka (MML) ; 
> qgis-user@lists.osgeo.org
> Aihe: Re: [Qgis-user] Confusion with ellipsoidal method of $area
>
>
>
> Hi,
>
> Your method in QGIS is sound.  Area is calculated using the wgs84 ellipsoid 
> EPSG 7030. If you reproject to wgs84 zone 35N (I think this is close), area 
> goes from 249566957499.7546m2  to 249566957499.721m2 or a difference of 
> 0.0336 m2.  I don't think densification would change things much.
>
> My question is the following: You know that QGIS uses the WGS84 Ellipsoid.  
> What Ellipsoid are using used in the other software???  If you don't know, I 
> would proceed until you figure that out.
>
> This is the currently used ellipsoid in the proj database in QGIS 3.16.  You 
> can get this by typing proj -le in the OSFeo4W Shell.
>
>
> MERIT a=6378137.0  rf=298.257   MERIT 1983
> SGS85 a=6378136.0  rf=298.257   Soviet Geodetic System 85
> GRS80 a=6378137.0  rf=298.257222101 GRS 1980(IUGG, 1980)
> IAU76 a=6378140.0  rf=298.257   IAU 1976
>  airy a=6377563.396rf=299.3249646   Airy 1830
>APL4.9 a=6378137.0  rf=298.25Appl. Physics. 1965
> NWL9D a=6378145.0  rf=298.25Naval Weapons Lab., 1965
>  mod_airy a=6377340.189b=6356034.446Modified Airy
>andrae a=6377104.43 rf=300.0 Andrae 1876 (Den., Iclnd.)
>danish a=6377019.2563   rf=300.0 Andrae 1876 (Denmark, Iceland)
>   aust_SA a=6378160.0  rf=298.25Australian Natl & S. Amer. 1969
> GRS67 a=6378160.0  rf=298.2471674270 GRS 67(IUGG 1967)
>   GSK2011 

Re: [Qgis-user] change pixel value from no data to zero

[Nyall Dawson]

On Wed, 16 Dec 2020 at 13:36, Azzurra Lentini  wrote:
>
> Hi to all,
> I am using qgis 3.16.
> I have a raster file that I created from shapefile of polygons (rasterize of 
> GDAL) using a column that has the number 9 every where there are the 
> polygons. This raster  has 2 different values in the pixel: not data and 9.
> I need to have 0 (zero) instead of no data.
> What can I do? Can I change the pixel value from no data to zero?
>  Before when I used the version 2.18 I could create directly with rasterize a 
> file with these two values.

Run the "Fill NoData Cells" tool from the Processing Toolbox, and
enter "0" as the fill value.

Nyall


>
> Many thanks, Azzurra
>
>
>
> --
> Lecturer GIS University "Roma Tre"
> Consultant Environmental Risk Prevention and Hydrogeology
> AZZURRA LENTINI
> ++
> Italy Mobile Tel.: **(39) 338 24 40 676
> ++
> SKYPE azzurrahydro
> ++
>
> azzurralent...@gmail.com
>
> azzurra.lent...@uniroma3.it
>
> ++
> *Par respect pour l'environnement,*
>
> *n'imprimez ce mail qu'en cas d'absolue nécessité*
>
>
>
>
>
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