[Qgis-user] Retirement & Future QGIS Support Options

[C Hamilton via QGIS-User]

Hi Everyone,

In a month I will be retiring from US federal government service. For the
last few years my efforts were on promoting open source GIS software for
government use. I've had some success but wish it would have been easier. I
am the author of 12 official QGIS plugins,

https://plugins.qgis.org/plugins/user/hamiltoncj/

There is another organization who is supposed to take over maintenance of
most of these plugins. I don't know whether it will happen or not. In the
near term I will fix any major bugs until they actually take over. If they
don't take over I might be back asking to see if anyone is interested in
supporting them. I can't do it forever and I still need to make a living.

I am interested in continuing working part time with the QGIS community and
open source GIS. I think I am one of the few US QGIS plugin developers. As
a hobby I have worked with the archaeological community in processing Lidar
and magnetometry data. That has been fun.

Please send me a note if you know of any part time job opportunities in
supporting QGIS and other open source GIS software.

Thanks,

Calvin
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Re: [Qgis-user] Advance Digitising Tools- compass bearings

[C Hamilton via QGIS-User]

Phil,

The Shape Tools plugin has an "Azimuth distance digitizer" and for what you
are talking about an "Azimuth distance sequence digitizer". With the latter
function you click on a starting location and then give a list of azimuth,
distance sequences. I have used this for old surveys like this. There is
also an declination offset just in case your surveys were using magnetic
north and not true north. In that case you have to look up what the
declination offset was for your 1880s date.

Regards,
Calvin

On Thu, May 16, 2024 at 9:50 PM Philip Ryan via QGIS-User <
qgis-user@lists.osgeo.org> wrote:

> Hello,
> I am trying to digitise a series of old gold lease "portion plans"
> produced in the 1880s in Australia by a mining surveyor using a compass and
> chain. The data for each gold lease includes a table of  1) compass
> bearings in degrees and 2) distance measurements in links (0.2 m) for each
> vertex of the lease polygon (mostly a rectangle or trapezoid but sometimes
> more complex).
> The Advance Digitizing Tools would seem to be ideal for this data except
> for the angle measure (a) which I can't input as a compass bearing (0-360
> deg). The current settings with 90 deg E as the zero makes conversion of
> compass bearings very tedious.
> Is it possible to change the angle variable (a) to a compass bearing?
> Regards,
> Phil Ryan
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Re: [Qgis-user] Kmz rendering very slow

[C Hamilton via QGIS-User]

Agreed. Google Earth simply cannot handle large amounts of data.

Calvin

On Fri, Feb 23, 2024 at 8:38 AM Kobben, Barend (UT-ITC) via QGIS-User <
qgis-user@lists.osgeo.org> wrote:

> Not really. KMZ/KML is a simple dataformat not suitable for such large
> amounts of data. It eg does not support spatial or other indexing (even if
> it would, Google Earth renderering porbbably cannot use the indexes
> anyway)...
>
> *-- *
>
> *Barend Köbben*
>
>
>
>
>
> On 23/02/2024, 14:07, "QGIS-User" 
> wrote:
>
>
>
> Hello,
>
> I am reposting this question.
>
> I have a geopackage file of about 30MB size. I have converted it into kmz
> which resulted in 13MB size. When I open this kmz in google earth, it is
> very slow and takes about 10 to 15 minutes to load and open. Even after
> opening, I cannot zoom-in or zoom-out quickly. Is there a fix for this such
> that I can open the file in google earth quickly?
>
>
>
> Regards.
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[Qgis-user] Vector layer WKT attribute to new layers

[C Hamilton via QGIS-User]

I came across a point vector layer that had a WKT object as one of the
attributes. The WKT object could be a point, line, polygon, multi-point,
multi-line, or multi-polygon and there could be a mixture of these in the
same vector layer.

I added an algorithm to the Lat Lon Tools plugin that accepts a vector
layer and an attribute field, and can potentially export 3 new layers
representing WKT points found, lines found, or polygons found. If the WKT
objects are all the same type then only one new layer will be created.

You can import WKT geometries from a csv file, but there is no good way to
do this in QGIS from a vector layer with a WKT attribute.

Enjoy,
Calvin
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Re: [Qgis-user] Distance measurement from Center - Buffer

[C Hamilton via QGIS-User]

You can always use the Shape Tools plugins to draw a circle around the
points. It uses Geodesic calculations so you don't need to convert to
another projection.

Calvin

On Mon, Feb 12, 2024 at 9:31 PM krishna Ayyala via QGIS-User <
qgis-user@lists.osgeo.org> wrote:

> Chris,
> Thanks for the reply. By rectangular coordinate system, can you mention
> which specific rectangular coordinate system?
>
> Regards.
>
> On Mon, Feb 12, 2024 at 5:52 PM chris hermansen 
> wrote:
>
>> Epsg 4326 is lat long. Make your buffers in a rectangular coordinate
>> system.
>>
>> On Mon, Feb 12, 2024, 16:29 krishna Ayyala via QGIS-User <
>> qgis-user@lists.osgeo.org> wrote:
>>
>>> Hello,
>>> I have a point shape file with the projection as shown below. I have
>>> created a buffer of 16km using this point shapefile. When I measure it
>>> vertically, it reads as 32km. But when I measure it horizontally, it reads
>>> as 26km only. I have reprojected the buffer to the projected coordinate
>>> system. Despite of this, I am getting the same values. What should I do
>>> such that I can read 32kms both horizontally and vertically?
>>> Regards.
>>>
>>> [image: image.png]
>>>
>>> [image: image.png]
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Re: [Qgis-user] Should my QGIS 2 Plugins be removed from plugins.qgis.org?

[C Hamilton via QGIS-User]

I'm surprised that QGIS 2 is still being used. In that case I will leave my
QGIS 2 plugins in the repo.

Calvin

On Fri, Jan 26, 2024 at 12:41 PM Andrea Giudiceandrea via QGIS-User <
qgis-user@lists.osgeo.org> wrote:

> > Greg Troxel gdt at lexort.com
> > Fri Jan 26 07:21:47 PST 2024
>
> > It will be interesting to see if anyone says they are using qgis 2.
>
> Looking at the number of plugins downloads, it seems there are still
> users using QGIS 2. For example, today the number of downloads of the
> "Shape Tools" plugin version 0.7.12 for QGIS 2 is 14736 [1], while it
> was 14168 one years ago [2]
>
> Best regards.
>
> Andrea
>
>
> [1] https://plugins.qgis.org/plugins/shapetools/#plugin-versions
> [2]
>
> https://web.archive.org/web/20230212152411/https://plugins.qgis.org/plugins/shapetools/#plugin-versions
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Re: [Qgis-user] Should my QGIS 2 Plugins be removed from plugins.qgis.org?

[C Hamilton via QGIS-User]

I don't know about that question for sure, but I suspect that if they were
not ported to QGIS 3 then they are not likely being used. Some plugins
became deprecated because QGIS 3 integrated their capabilities into
its core algorithms. In my case I ported all my QGIS 2 plugins to QGIS 3.


On Fri, Jan 26, 2024 at 11:22 AM Andrea Giudiceandrea via QGIS-User <
qgis-user@lists.osgeo.org> wrote:

> > Greg Troxel gdt at lexort.com
> > Fri Jan 26 07:21:47 PST 2024
>
> > Another question is if the plugin repo should simply remove all qgis 2
> > plugins en masse and desupport 2 entirely.
>
> What about the plugins working with QGIS 2 that had not been ported to
> work with QGIS 3?
>
> Andrea
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[Qgis-user] Should my QGIS 2 Plugins be removed from plugins.qgis.org?

[C Hamilton via QGIS-User]

I am wondering whether it is time to remove my QGIS 2 plugins from
plugins.qgis.org. It seems like everyone should be using QGIS 3 now and if
they are not, they should be. What are your thoughts? All of my QGIS 2
plugins are much less capable than my version 3 plugins.

Thanks,
Calvin
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[Qgis-user] New Shape Tools Processing Algorithms

[C Hamilton via QGIS-User]

I added two new Shape Tools (https://plugins.qgis.org/plugins/shapetools/)
processing algorithms. Shape Tools has a number of geodesic shapes that can
be generated from a point vector layer using parameters from the processing
dialog box or from the vector layer's attribute table. What Shape Tools has
lacked is the ability to click on a location and generate a shape at that
location.

I am testing out the capability of doing this from a processing algorithm
using QgsProcessingParameterPoint. I would like your reaction to this
capability. Is it worth doing this for the other primitive shapes?

The two new algorithms draw a concentric band or donut shape about the
clicked canvas point. I also added a processing algorithm to generate N
number of concentric circles with optional radial lines. This is somewhat
similar to the ArcGIS "Generate Range Rings" function. Here is an example
image:

https://drive.google.com/file/d/1a_-iFiOaHG9ucHx2rsdcCb0L3i3qO5mv/view?usp=drive_link

Let me know what you think about these kinds of algorithms.

Thanks,
Calvin
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[Qgis-user] Earth, Sun, Moon, and Planets Field Calculator Expressions

[C Hamilton via QGIS-User]

I updated the Earth, Sun, Moon, and Planets plugin to include some field
calculator expressions. If there are other expressions that you think
should be made available, let me know.

https://plugins.qgis.org/plugins/earthsunmoon/

Note that you need to "pip install timezonefinder skyfield" libraries from
your OSGeo4W shell for these functions to be available.

   - *esm_local_datetime()* - Returns the current date and time as a python
   datetime object with the local computer's timezone settings.
   - *esm_local_qdatetime()* - Returns the current date and time as a
   standard QGIS QDateTime object with the local computer's timezone settings.
   - *esm_moon_phase()* - Given a date and time, return the moon's phase in
   degrees where 0° is the New Noon, 90° is First Quarter, 180° is Full Moon,
   and 270° is Last Quarter.
   - *esm_moon_zenith()* - Given a date and time, return the EPSG:4326
   coordinate point where the moon is directly overhead.
   - *esm_sun_moon_info()* - Given a date and time, latitude and longitude
   in EPSG:4326, output format type, and optional timezone of the date and
   time object, it returns a python dictionary or JSON string of solar and
   lunar information.
   - *esm_sun_zenith()* - Given a date and time, return the EPSG:4326
   coordinate point where the sun is directly overhead.

Best wishes,
Calvin
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[Qgis-user] New Day/Night Terminator Algorithm

[C Hamilton via QGIS-User]

I released a new "Day/Night terminator" algorithm as a part of the "Earth,
Sun, Moon, & Planets" plugin. I was able to get some help to implement the
algorithm that does the work.

https://plugins.qgis.org/plugins/earthsunmoon/

The new algorithm creates vector layers for the day/night terminator line,
polygon layers associated with sunrise/sunset, civil twilight, nautical
twilight and astronomical twilight, and the position of the sun directly
overhead. Since I can't include images, here are some links to images
representing the plugin's capabilities.

https://drive.google.com/file/d/1oeT6xtLOBkIp5QN2q2FH2bd94V7XRU2Z/view?usp=drive_link
https://drive.google.com/file/d/1E1JDBlQGqE9Wi3qs34jNX5IIaYtT4kxw/view?usp=drive_link
https://drive.google.com/file/d/148oAwFt7zpL1OChm3GWUq4FtxTckctjr/view?usp=drive_link

The "Day/Night terminator" and "Sun position directly overhead" work as is,
but the rest of the plugin's capabilities require installing Time Zone
Finder and Skyfield (pip install timezonefinder skyfield).

Let me know if you encounter any problems.

Thanks,
Calvin
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Re: [Qgis-user] Dot Density Symbology

[C Hamilton via QGIS-User]

This may not be an answer to your question, but the Density Analysis plugin
(https://plugins.qgis.org/plugins/densityanalysis/) will create a uniform
set of polygons over an area of interest with a NUMPOINTS attribute of the
number of points are contained within the polygon. The NUMPOINTS value can
be weighted using some other attribute. It will automatically style the
density map as well from a given color ramp.

Calvin

On Wed, Jul 26, 2023 at 8:06 PM Shinoto, PD Dr. Maria via QGIS-User <
qgis-user@lists.osgeo.org> wrote:

> Hi,
>
> I have a similar research problem, and the dots seem to be a wonderful
> solution.
>
> So, this email does not give any assistance re the original question, just
> an answer to the question below:
>
> Am 2023/07/27 um 03:45 schrieb chris hermansen via QGIS-User <
> qgis-user@lists.osgeo.org>:
>
> Here's (apologies for the closed source link) an example of the type of
>> map/symbology I'm trying to describe.
>> https://www.arcgis.com/apps/mapviewer/index.html?webmap=30d2e10d4d694b3eb4dc4d2e58dbb5a5
>>
>> Thanks for any suggestions!
>>
>
> What about just shading the polygons using a gray scale?
>
> Given that your polygons should generate a uniform density of dots within
> the area they bound, I don't see value in generating the dots for symbology.
>
>
> The polygon area may vary, as it does in my research (distribution of
> burials in administrative areas). Therefore, a small area always looks
> underrepresented as compared to a larger area, and vice versa. I have large
> administrative areas with low densitiy, but they look well populated even
> with a very light shade of grey.
>
> So I would like to try to find a solution to Chris' problem since the
> representation with dots is closer to reality than colouring areas. I will
> report when I found a solution for my use case -- though this may be
> autumn...
>
> Maria
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[Qgis-user] New Earth, Sun, Moon, Planets QGIS Plugin

[C Hamilton via QGIS-User]

I developed most of this plugin some time ago, but have never liked
publishing a plugin that was not self contained meaning that it has no
depancies on other Python libraries not supplied by QGIS or data too large
to include.

Meet the Earth, Sun, Moon, and Planets plugin. For a particular date & time
it displays the location of the Sun, Moon, and planets where they would be
at their zenith, directly overhead as seen from the surface of the Earth.
It also has another tool that given a date, time, and coordinate it will
display solar and lunar information such as azimuth, elevation, twilights,
etc.

https://plugins.qgis.org/plugins/earthsunmoon/

This plugin requires two additional libraries to be installed. Open the
OSGeo4W Shell and install timezonefinder and skyfield.

pip install timezonefinder skyfield

I am in the process of passing the baton for my QGIS plugins to another
organization but wanted to get this released. The one algorithm I really
wanted to include was to generate an accurate day/night line or polygons
including different twilights. I never found an algorithm that I liked.
There are ones based on a spherical earth, but can be as much as 10 degrees
off towards the poles.

Anyway I hope you enjoy this plugin.

Best wishes,
Calvin
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[Qgis-user] New Date/Time Tools Plugin Update

[C Hamilton via QGIS-User]

I updated the Date/Time Tools plugin.

https://plugins.qgis.org/plugins/datetimetools/

The functionality is the same, but I needed to update the timezonefinder
python library. Unfortunately or fortunately depending on how you see it,
because of changes in the library, it is no longer practical to include the
python dependencies with the plugin. When you update the plugin, you will
also need to open the OSGeo4W console and install 3 additional python
libraries. On windows just type in the following. I don't know if you do
the same on Mac and Linux distributions or not.

pip install timezonefinder astral reverse_geocoder

You don't need to be a system administrator to do this.

Best wishes,

Calvin
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[Qgis-user] Jobs supporting QGIS

[C Hamilton via QGIS-User]

Hi Everyone,

Since 2016 I have been supporting QGIS within the US Federal Government.
You can see my QGIS plugin contributions here:

https://plugins.qgis.org/plugins/author/C%20Hamilton/

Unfortunately, I have been told to quit further QGIS development by my
current organization and I have a limited time to provide bug support. I
have held this off for about 9 months and suspect that I have another 6
months to formalize what to do. One option is to try and find another US
government job that needs a QGIS plugin developer (anyone out there?). The
other options are to simply move on to non QGIS related projects, retire (I
am eligible), or find some other organization I could work with. I will
make sure that the plugins are either transferred to some other
organization for support or I will do it myself. I won't let them just be
dropped.

I took "The Road not Taken" by supporting open source GIS. Certainly, many
of you here have done the same, but it is not necessarily the most
profitable. For me it has been fun and I have really enjoyed it.

If any of you have any job leads please let me know. I have at least 6
months to make this decision.

Thanks,
Calvin
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[Qgis-user] Shape Tools New Capabilities - Compass cardinal directions

[C Hamilton via QGIS-User]

I thought I would highlight a couple of updates to the Shape Tools plugin.
For those who are not aware, Shape Tools has a measuring tool that not only
includes the distance from point A to B, but also displays the azimuth from
A to B and from B to A. It shows each segment with these features and the
total distance. It also has a measurement layer algorithm that creates a
new layer from a polygon or line layer with already styled measurements of
the line segments.

The recent addition is to also include the compass cardinal directions such
as N, S, E, W or NE, WSW, or NEbE depending on the number of compass points
that are selected. This has to be enabled from Vector->Shape
Tools->Settings and then look for "Points of the compass" and you can
select None, 4, 8, 16, or 32. It defaults to None.

The other addition is a related expression function with some examples

st_compass( azimuth[, number_of_points, mode] )

st_compass(33) → 'NNE'
st_compass(33, 8) → 'NE'
st_compass(33, 32) → 'NEbN'
st_compass(33, 16,'full') → 'north-northeast'
st_compass(33, 32,'full') → 'northeast by north'
st_compass(33, 32,'trad') → 'Quarto di Greco verso Tramontana'

Enjoy,

Calvin
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[Qgis-user] What QGIS plugin development should I work on this year?

[C Hamilton via QGIS-User]

Hi QGIS users,

I am looking for ideas for what QGIS development I should be working on
this year. My plugin development over the years has focused on capabilities
that were missing at the time or algorithms that made QGIS user's lives
easier. Here are the plugins I've developed so far.

https://plugins.qgis.org/plugins/author/C%2520Hamilton/

I am interested in algorithms that may be in commercial software but not in
QGIS that people need. I am also interested in different ways to visualize
and analyze data. Last year I released the Density Analysis plugin
. It added additional
density analysis algorithms including a fast H3 histogram of an area. I
never got any feedback on the plugin so I don't know whether it is
useful or not to users, but it has had 11,608 downloads since last June. I
always appreciate feedback as it is what encourages me to continue
development.

I have been debating on updating the D3 Data Visualization plugin
 to use plotly to create the
graph and perhaps add additional graphs. That was one of my early plugins
where I created my own D3 graph of the data. It could probably be done
better.

Are there any algorithms that you would like to have developed? It may be
that QGIS is getting sufficiently advanced that there is not much that is
really needed any more, but if you have any ideas I would appreciate them.
Anything I work on needs to benefit a sizable number of users. It can't be
too specific. It also needs to be constrained enough that I can complete in
a reasonable amount of time.

If you have any ideas for improving my existing plugins that could be an
option as well.

By the way is there a better forum than this qgis-user group to reach out
to QGIS users or is this the best way?

Thanks for your input!

Calvin
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Re: [Qgis-user] Coordinate display in different coordinate systems

[C Hamilton via Qgis-user]

The Lat Lon Tools plugin has a coordinate display dialog where you click on
a point and it displays it in many different coordinate systems.

On Fri, Oct 28, 2022 at 9:30 AM Tanja Hartinger via Qgis-user <
qgis-user@lists.osgeo.org> wrote:

> Hello
> I have a question about the coordinate display. Is it possible that I
> can display the coordinates in several coordinate systems (I am in
> Germany and therefore in my case it is about the coordinate systems
> Gauß-Krüger and UTM) somewhere on a map at the same time? I don't want
> to set an object there. Ideally, I click somewhere and then the
> coordinates are displayed in several coordinate systems. Is this
> possible in any way?
> Thank you very much in advance.
> Many greetings,
> Tanja
>
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[Qgis-user] Proper Way to Unload A Toolbar

[C Hamilton via Qgis-user]

I see several ways developers have created custom toolbars and then removed
them and I am wondering if there is a preferred way.  In the initGui of the
plugin we would have something like this:

self.toolbar = self.iface.addToolBar('My Toolbar')
self.toolbar.setObjectName('MyToolbar')

When we add an action it is:

self.toolbar.addAction(self.myAction1)
self.toolbar.addAction(self.myAction2)

In unload() I see two methods used:

Method 1:

self. myAction1  .deleteLater()
self. myAction1  = None
self. myAction2  .deleteLater()
self. myAction2  = None
self.toolbar.deleteLater()
self.toolbar = None

Method 2:
self.iface.removeToolBarIcon(self. myAction1)
self.iface.removeToolBarIcon(self. myAction2)
del self.toolbar

It is unclear to me in Method 2 whether removeToolBarIcon() applies to a
custom toolbar or not. I have used that in my plugins but am wondering if
it only is to be used if you are using the Plugins toolbar.

Thanks,

Calvin
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[Qgis-user] Lat Lon Tools Gets New Capabilities

[C Hamilton via Qgis-user]

Yesterday, Lat Lon Tools was updated to version 3.6.5 (
https://plugins.qgis.org/plugins/latlontools/). This release includes the
following:

1. Lat Lon Tools can now snapshot H3 geohash coordinates and zoom to H3
coordinates. H3 is a fantastic library that I have started working with,
but you currently need to 'pip install h3' from the OSGeo4W Shell to get
this capability. Lat Lon Tools detects whether H3 is available or not and
works as it always has without it.
2. Some coordinate formats represent a point on the earth's surface where
others represent an area. Previously when using Lat Lon Tools' zoom to a
coordinate tool it would zoom to the location and add a marker at the
center of area coordinate formats. Now it marks the center but also
displays the actual area the coordinate represents based on the resolution
of the coordinate. This applies to H3, Geohash, Google Open Location Code
(Plus Codes), and the amateur radio Maidenhead grid format. I would like to
apply this to MGRS and UTM, but the MGRS library was developed by the
defunct Boundless geo and there is no function to return the boundary. The
same is true with my implementation of UTM.
3. You can now choose the color of the marker used with the zoom to tool.
It can be selected from the Settings dialog.

Enjoy,

Calvin
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Re: [Qgis-user] Jenks Raster Styling?

[C Hamilton via Qgis-user]

Andrea,

Thanks for your response and glad to see someone else interested in this. I
was asked about how difficult it would be to implement as a plugin, but I
think it would be best as a core capability. Like always there needs to be
a funding source. I reached out to some of my colleagues to see if anyone
has funding for this type of QGIS development, but in the last few years
interest in our organizations for non-ESRI GIS software has really
diminished so I suspect that the people I know do not have the funding.

Is it a correct assumption that this feature request is not currently being
implemented in QGIS?

Thanks,

Calvin

On Wed, Sep 14, 2022 at 11:51 PM Andrea Giudiceandrea via Qgis-user <
qgis-user@lists.osgeo.org> wrote:

> *C Hamilton* adenaculture at gmail.com
> 
> *Wed Sep 14 10:46:38 PDT 2022*
> --
>
> Is it possible to implement similar styling methods such as Jenks in raster
> as you have with vector?
>
>
> Hi Calvin,
> there is also a feature request on the same matter:
> https://github.com/qgis/QGIS/issues/39746
>
> Best regards.
>
> Andrea Giudiceandrea
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[Qgis-user] Jenks Raster Styling?

[C Hamilton via Qgis-user]

With Graduated vector symbology there are various modes such as Equal
Count, Equal Interval, Logarithmic scale ,Natural Breaks (Jenks), Pretty
Breaks, and Standard Deviation to apply the graduated style to the vector
data.

With raster styling there are only "Interpolation" options Discrete, Linear
and Exact, and then the "Mode" of Continuous, Equal Interval, and Quantile.

Is it possible to implement similar styling methods such as Jenks in raster
as you have with vector? Can these styles at least be simulated in some way
with how QGIS is now?

Thanks,

Calvin
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[Qgis-user] More QGIS Density Analysis Updates and Some Time Comparisons

[C Hamilton via Qgis-user]

Anyone dealing with heatmaps or density estimation will be interested in
this plugin.

https://plugins.qgis.org/plugins/densityanalysis/

QGIS natively has the Heatmap (Kernel Density Estimation) algorithm
which is powerful and produces a heatmap image that can then be styled and
displayed. Each pixel in the image represents an area with an accumulated
intensity of the density from the input point layer data.

The Density Analysis plugin adds 3 vector gridded density map algorithms.
1) One of these can be done with a series of steps using QGIS algorithms
such as "Create grid" over the point layer extent, followed by "Count
points in polygon", "Extract by attribute", and then style it. The Density
Analysis plugin does this in one step. If the input point layer is not
spatially indexed then the "Count points in polygon" can be painfully slow.

The next algorithm takes the point layer and generates a geohash string for
each coordinate and creates a dictionary of geohash strings with their
counts. These geohashes are then turned into polygons with a NUMPOINTS
count attribute. The third algorithm makes use of the H3 geohash library
(which you must pip install). H3 geohashing produces hexagon boundaries and
is ideal for density analysis and is blazing fast. Here are some time
comparisons on my computer with these three algorithms. I ran this on a
layer containing 193401 points and there are two different grid cell sizes.

Algorithm 4km grid  1.22 km grid
    -
QGIS count points in polygon  8.16 seconds  63.18 seconds
Geohash   4.89 seconds  5.6 seconds
H3 geohash3.56 seconds  3.79 seconds

When the grid gets more dense the time it takes to count points in
polygons really goes up but the geohashing doesn't change much. We tested
the H3 algorithm against the similar capability in ArcGIS. Here are those
results.

Grid Resolution   ArcGISQGIS H3 geohash
---   --
400m  50 seconds2.93 seconds
50m   3:20 minutes  12.51 seconds

The latest Density analysis plugin includes the following updates:
1. Added a settings dialog that allows the user to choose the default color
ramp used in the algorithms. The setting is persistent from one launch of
QGIS to the next.
2. Added  an invert color ramp check box.
3. Added a styled polygon density algorithm.
4. Added a styled heatmap (kernel density estimation) algorithm. This is a
wrapper on the QGIS Heatmap algorithm, but you specify the grid/pixel cell
size in terms of km, m, mi, etc and not in terms of the CRS of the input
layer. It then automatically styles the layer.
5. Added a H3 grid algorithm.

For a more complete list of capabilities install the plugin and select Help
from "Plugins->Density Analysis".

Best wishes to everyone,

Calvin
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Re: [Qgis-user] Shapefile to KML conversion

[C Hamilton via Qgis-user]

Creating a KML that large is usually not a good idea, but if you still want to 
try it install the KML Tools plugin. It can usually handle larger data sets. 

Best wishes,

Calvin

> On Jul 9, 2022, at 6:19 PM, krishna Ayyala via Qgis-user 
>  wrote:
> 
> Hello,
> I have a shapefile of size 5GB. I have added it onto qgis map. Right 
> click>Export> Save Feature as and I picked kml format and saved the 
> file. The resulting kml has a size of 1.67GB. But when I open the kml file, I 
> get the following error. No results - empty kml file.
> 
> Regards.
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[Qgis-user] QGIS Density Analysis Plugin Update

[C Hamilton via Qgis-user]

I recently released the Density Analysis plugin and today I had a new
update that provides a polygon raster density analysis algorithm along with
a processing algorithm to style the raster with a heatmap.

https://plugins.qgis.org/plugins/densityanalysis/

I have a very narrow window in which I can make updates to this plugin. It
meets my needs, but perhaps you might see something I have missed. I am
being reassigned from QGIS development to other projects. Unfortunately, a
certain company, who shall not be named, has ultimately prevailed even
though it is really expensive and QGIS free. I will be allowed to fix bugs
in my plugins, but no new development.

If anyone has any comments or would like something done a little
differently with the Density Analysis plugin please let me know now. Next
month, unless it is a bug, I won't be allowed to make any changes.

It has been a pleasure working with the QGIS community. You are all great.
I will miss being able to spend full time working with QGIS. Hopefully, my
contributions have provided you with some useful tools.

https://plugins.qgis.org/plugins/author/C%2520Hamilton/

I wish you all the very best!

C Hamilton
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Re: [Qgis-user] PyQGIS code on raster image - What am I doing wrong?

[C Hamilton via Qgis-user]

Andrea,

Thanks so much. I'm not sure I would have figured that out on my own. I
also found that I needed to include the min and max values from the
statistics. Here is my final code if anyone else is trying to do this.

layer = iface.activeLayer()
provider = layer.dataProvider()
stats = provider.bandStatistics(1, QgsRasterBandStats.Min |
QgsRasterBandStats.Max)
min = stats.minimumValue
max = stats.maximumValue

# Get the Reds default colorramp
style = QgsStyle.defaultStyle()
ramp = style.colorRamp('Reds')
color_ramp = QgsColorRampShader(min, max, ramp,
QgsColorRampShader.Interpolated)
color_ramp.classifyColorRamp()

raster_shader = QgsRasterShader()
raster_shader.setRasterShaderFunction(color_ramp)

# Create a new single band pseudocolor renderer
renderer = QgsSingleBandPseudoColorRenderer(provider, layer.type(),
raster_shader)

layer.setRenderer(renderer)
layer.triggerRepaint()



Thanks,

Calvin

On Wed, Jun 22, 2022 at 9:47 PM Andrea Giudiceandrea 
wrote:

> *C Hamilton* adenaculture at gmail.com
> 
> *Wed Jun 22 08:36:45 PDT 2022*
> --
>
> color_ramp.setColorRampType(QgsColorRampShader.Interpolated)
>
>
> Hi C Hamilton,
> I think you are missing to classify the color ramp here:
>
> color_ramp.classifyColorRamp()
>
>
> Best regards.
>
> Andrea Giudiceandrea
>
>
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[Qgis-user] PyQGIS code on raster image - What am I doing wrong?

[C Hamilton via Qgis-user]

I am trying to automatically style a singlebandgray raster image with one
of the singlebandpseudocolor color ramps. When I run this code in the QGIS
Python console the raster image disappears. If I look at the image
"Properties" everything seems to be set correctly and it does appear when
Apply or OK buttons are clicked on. I must be missing something.

layer = iface.activeLayer()

style = QgsStyle.defaultStyle()
# Get the Reds default colorramp
ramp = style.colorRamp('Reds')
color_ramp = QgsColorRampShader()
color_ramp.setSourceColorRamp(ramp)
color_ramp.setColorRampType(QgsColorRampShader.Interpolated)

raster_shader = QgsRasterShader()
raster_shader.setRasterShaderFunction(color_ramp)
# Create a new single band pseudocolor renderer
renderer = QgsSingleBandPseudoColorRenderer(layer.dataProvider(),
layer.type(), raster_shader)

layer.setRenderer(renderer)
layer.triggerRepaint()
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[Qgis-user] New Density Analyses Plugin

[C Hamilton via Qgis-user]

I want to share a new vector based density analysis plugin sooner rather
than later. My work priorities are being rearranged so that I will not be
able to do new development or new features, but only fix bugs if they
arise. Here is the new plugin. Please test it out and give me any feedback.
I have about a month where I can optimize it more, but after that I will
not be able to do further development.

https://plugins.qgis.org/plugins/densityanalysis/

You can read the Density Analyses Documentation
,
but here are the highlights.

This plugin currently has 3 vector based density algorithms:

   1. *Create density map grid* - This one creates a grid of polygons and
   counts the number of points in those polygons using the QGIS *Create
   grid* processing algorithm followed by the *Count points in polygon* and
   then styled appropriately. It is very important that the input point data
   be spatially indexed. This algorithm provides the most flexibility,
but *Count
   points in polygon* is time consuming.
   2. *Create geohash density map* - This makes use of the geohash
   algorithm to geohash each point and count the number of points for each
   geohash and create the geohash polygons. Depending on the density of the
   map this can be an order of magnitude faster than the above algorithm. The
   disadvantage is that you are limited to the geohash grid resolutions.
   3. *Create H3 density map* - This is the fastest of all 3 algorithms. It
   creates a hexagon density map grid and is similar in that it uses a H3
   geohash index to count all the points in each geohash. Unfortunately, H3 is
   not a part of the QGIS standard python libraries and you will need to 'pip
   install h3' to be able to access these algorithms, but it will be worth it.
   QGIS developers, you may want to consider including H3 as a part of QGIS.

Here are some running times of the 3 algorithms with a data set of around
194,000 points.

   - Create density map grid - 63.18 seconds
   - Create geohash density map - 5.6 seconds
   - Create H3 density map - 3.7 seconds

Once the heatmaps are created (note that they are automatically styled),
then there is a heatmap explorer that allows you to load in the N highest
grid counts and by clicking on them it will pan or zoom to the heatmap
polygon to examine the data that is there.

There are also 3 other utilities.

   1. *Apply style to selected layers* - You can copy a style to the
   clipboard or select a .qml file and apply it to all selected layers or
   groups of layers.
   2. *Apply graduated style* - This applies a graduated style to a layer,
   but it is done as a processing algorithm so it can be used in the model
   builder.
   3. *Apply random categorized style* - This applies a random categorized
   style to a layer, but it is done as a processing algorithm so it can be
   used in the model builder.

I plan on also adding a raster based polygon density algorithm that seems
to be missing from QGIS.

If you have any suggestions or find any problems with the plugin please let
me know.

Thanks,

C. Hamilton
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Re: [Qgis-user] visualize and export coordinates of centroids

[C Hamilton via Qgis-user]

Once you have your centroids you can use the Lat Lon Tools plugin and run
the "Point Layer to Fields" algorithm to extract the geometry and add it to
one or two attribute fields. You can also specify the CRS that you want it
in and what format (ie. decimal degrees, DMS and a lot of other formats)
you want it in.

Best wishes,

Calvin

On Tue, May 24, 2022 at 2:53 PM Thayer Young via Qgis-user <
qgis-user@lists.osgeo.org> wrote:

> Hi Francesca,
>
> Assuming that your layer has a geographic coordinate system like 4326. And
> you have found your centroids already:
> Use the field calculator to add a new or virtual field with a numeric data
> type, e.g. double, and name it something like "lat". Then in the expression
> area enter the expression: $y
> and press OK. Do the same for "lon" and the expression will be: $x
>
> If you want to find the centroid of a polygon and its latitude in one step
> your expression would be: y(centroid($geometry))
> For longitude it would be: x(centroid($geometry))
>
> Note that different methods will give you different coordinates for your
> centroid. So you may need to use a spatial join to do your match.
>
> -Thayer
>
>
> On Tuesday, May 24, 2022, 06:22:46 AM EDT,
> qgis-user-requ...@lists.osgeo.org 
> wrote:
>
> --
> Date: Tue, 24 May 2022 09:52:26 +0200
> From: Francesca Parente 
> To: QGIS User List 
> Subject: [Qgis-user] visualize and export coordinates of centroids
> Message-ID:
> 
> Content-Type: text/plain; charset="utf-8"
>
> Hello group,
>
> I would like to ask you what is in your opinion the best way to identify
> the lat-lon attributes of derived centroids in order to export them to an
> extra-QGis database where corresponding coordinates should match with
> identified locations.
>
> So far I've tried with Geocoding and MMQGIS plugins, but the resulting
> attributes table doesn't inlcude the coordinates of geocoded points.
>
> Thanks a lot for any advice!
> Francesca
>
> --
> 
> Francesca Parente
>
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Re: [Qgis-user] Change properties of multiple layer at once

[C Hamilton via Qgis-user]

I have been working on a plugin and as a part of its capabilities is to be
able to use a .qml file or the style on the clipboard to apply it to all
selected layers including groups of layers. It would be a very similar
process to adjust the opacity or stroke style.

On Fri, Apr 1, 2022 at 6:04 AM Roland Spielhofer via Qgis-user <
qgis-user@lists.osgeo.org> wrote:

> Hi,
> thanks for the tip!
> The layers are all of the same type (content is the same, they represent
> different days).
> I wanted to preserve the different fill colors and just change the opacity
> and pen stroke.
> Therefore copy stlye does not work.
>
> Anyway, I adjusted the layers manually meanwhile - was just curious if
> there is an elegant way to do this and save time next time.
>
> Regards,
> Roland
>
>
> *Gesendet:* Freitag, 01. April 2022 um 10:37 Uhr
> *Von:* "L.W. via Qgis-user" 
> *An:* "Raymond Nijssen" , qgis-user@lists.osgeo.org
> *Betreff:* Re: [Qgis-user] Change properties of multiple layer at once
> May you change the style itself and set the same style to all layers.
>
> You can change i.e. color of lines by "type of line" / attribute values
> so you can use one style for multiple layers.
>
>
> Am 01.04.2022 um 10:13 schrieb Raymond Nijssen via Qgis-user:
> > Don't know how to do that using the GUI, but for the opacity you can
> > use these 2 lines of python in the QGIS python console. It will set
> > all your selected layers to 50% opacity.
> >
> >
> > for layer in iface.layerTreeView().selectedLayers():
> > layer.setOpacity(.5)
> >
> >
> > I think the stroke style is harder to change because all these layers
> > can have different symbologies.
> >
> > Hope it helps!
> > Raymond
> >
> >
> > On 01-04-2022 09:47, Roland Spielhofer via Qgis-user wrote:
> >> Hi,
> >> I have a set of similar layers where I would like to change certain
> >> properties for all layers in the same way.
> >> * change opacity to 50%
> >> * change stroke style to "no pen"
> >> When I select multiple layers and open properties -> symbology, I
> >> just change the styling of the first layer, not for all.
> >> Is there a way to do this?
> >> Regards,
> >> Roland
> >>
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