Re: [Qgis-user] Legend layout editor

[Phil Wyatt]

Hi Camilo,

 

There is a good tutorial on custom legends here - 
https://www.youtube.com/watch?v=rb3EZSs9q4w

 

I assume you are after something over and above what you have created in the 
map window.

 

Cheers - Phil

 

From: Qgis-user  On Behalf Of Camilo 
Aristizabal
Sent: Wednesday, 12 January 2022 12:59 PM
To: qgis-user@lists.osgeo.org
Subject: [Qgis-user] Legend layout editor

 

Hi all,

 

Does someone know how to customize the automatic legend QGis generates? The 
simple one shows no options to edit every single item I'd like to appear as I 
need. 

 

Thanks

 

Camilo 

___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

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
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Re: [Qgis-user] Coordinate Transformation

[Greg Troxel]

tim dunlevie  writes:

> On Mon, Jan 10, 2022 at 9:22 PM Grant Boxer  wrote:
>
>> Is there a plugin for QGIS that takes two pairs of coordinates, one in
>> local (Cartesian) grid and one in real world utm coordinates, that will
>> calculate the real world coordinate transformation parameters? I have a
>> pile of local grid coordinates I need to convert.
>>
>> Cheers Grant
>>
>> Perth WA Australia


> Hi mate,
>
> There's a 'Geoscience' plugin which has a function that allows you to
> create a local grid from coordinates ?
> Local XY, Grid XY...
> Does that help?
>
> Tim
>

I used this and succeeded, but I found it difficult.There did not
appear to be a way to store the coordinates in a file so I could fix
them if I got it wrong, and there did not appear to be a way to have two
layers, one local and one global, and have then join by name as input.


signature.asc
Description: PGP signature
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Re: [Qgis-user] Readonly gpkg

[Greg Troxel]

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?   If I got that wrong which I probably did, I wonder
what you do mean.


signature.asc
Description: PGP signature
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

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.
> ___
> Qgis-user mailing list
> Qgis-user@lists.osgeo.org
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Re: [Qgis-user] Coordinate Transformation

[tim dunlevie]

Hi mate,

There's a 'Geoscience' plugin which has a function that allows you to
create a local grid from coordinates ?
Local XY, Grid XY...
Does that help?

Tim

On Mon, Jan 10, 2022 at 9:22 PM Grant Boxer  wrote:

> Is there a plugin for QGIS that takes two pairs of coordinates, one in
> local (Cartesian) grid and one in real world utm coordinates, that will
> calculate the real world coordinate transformation parameters? I have a
> pile of local grid coordinates I need to convert.
>
> Cheers Grant
>
> Perth WA Australia
>
>
> ___
> Qgis-user mailing list
> Qgis-user@lists.osgeo.org
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Re: [Qgis-user] Readonly gpkg

[Greg Troxel]

 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.

> 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.


signature.asc
Description: PGP signature
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Re: [Qgis-user] Readonly gpkg

[pergler]

Even Rouault  writes:

> The default enabling of WAL even in initial read-only access mode is
> to avoid that potential issue.
>
> There are currently way of disabling WAL (for advanced users) :
>
> - setting the OGR_SQLITE_JOURNALenvironment variable to JOURNAL
> - or setting the QGIS setting "qgis/walForSqlite" to false
>
> See
>
https://github.com/qgis/QGIS/blob/master/src/core/providers/ogr/qgsogrprovid
erutils.cpp#L1005

Greg Troxel  writes:

> Thanks for the pointers; I think I am beginning to follow.

> The use of WAL is a persistent property of a database.  Clients use it
> or not when connecting, normally.

>  As it is, qgis (by default) forces WAL mode, even if the database was
>  not already in WAL, and even if there are other connections open.  Or
>  it forces DELETE mode, similarly without checking.  So the concern
>  about upgrading/downgrading comes from any setting of mode by any
>  connection and any other existing connection.

> After digesting it all, I am left thinking that whether to use a
  geopackage in WAL mode or DELETE mode is a user decision, ...
> Therefore, I think the right approach is:
>  1) let the user do "pragma JOURNAL_MODE=WAL;" if they want
>  2) when opening the database, don't do anything about JOURNAL_MODE;
  just use it the way it is set.

You've left me in the dust, which is fine. But it sounds that

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. In the distant future,
I could see
the Browser providing a UI wrapper to send the right pragma JOURNAL_MODE if
user requests.
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.
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).

Do I have that right? Thanks!
Martin 




___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

[QGIS-it-user] punti regolari in tre dimensioni

[Claudio]

Salve,
mi scuso fin da subito se non sarò chiaro e tecnico, ma uso QGis in
modo abbastanza dilettantesco come supporto a ricerche sull'ecologia
degli animali.
Ho questo problema: vorrei posizionare delle fototrappole in posizioni
equidistanti (diciamo km 1), e l'ho fatto così:
vettore-->strumenti di ricerca-->punti regolari

Tuttavia, per essere più preciso, vorrei che le distanze fossero delle
distanze misurate sul terreno, cioè in 3D.
Immagino che si debba costruire un layer geometrico, in cui le distanze
siano su un piano, e poi drappeggiare un rilievo tridimensionale.
Come si fa? (Naturalmente va bene anche qualsiasi altro metodo, la
questione del drappeggio l'ho introdotta per spiegarmi meglio)
grazie e saluti
Claudio 

___
QGIS-it-user mailing list
QGIS-it-user@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/qgis-it-user

Re: [Qgis-user] Readonly gpkg

[Greg Troxel]

Even Rouault  writes:

> The main issue I see is that it is unknown (and non documented AFAICS
> in SQLite documentation) what happens if :
>
> - reader A has opened the file with default journaling mode (for read-only)
>
> - reader B (other QGIS process for example, or possibly the same QGIS
> process like a renderer thread) has opened the file with default
> journaling mode (for read-only)
>
> - let's say A wants to edit and we thus enable WAL to avoid
> reader/writer blocks
>
> - is B which has opened without WAL still in a safe state ? Does it
> react properly to WAL having been enabled behind its back ?
>
> The default enabling of WAL even in initial read-only access mode is
> to avoid that potential issue.
>
>
> There are currently way of disabling WAL (for advanced users) :
>
> - setting the OGR_SQLITE_JOURNALenvironment variable to JOURNAL
>
> - or setting the QGIS setting "qgis/walForSqlite" to false
>
> See
> https://github.com/qgis/QGIS/blob/master/src/core/providers/ogr/qgsogrproviderutils.cpp#L1005

Thanks for the pointers; I think I am beginning to follow.

  The use of WAL is a persistent property of a database.  Clients use it
  or not when connecting, normally.

  WAL or DELETE (the normal rollback) are both sound for multiple
  writers, with different speed proeprties.

  sqlite3 docs say "WAL does not work over a network filesystem." but
  they do not say if this leads to an error, to corruption, or something
  else.

  I see what you mean about the docs being silent on existing processes
  and mode switching.  As what is being changed is the mode *of the
  database* and not the access mode of a single connection, it would
  seem a clear bug in sqlite3 if changing the mode isn't safe.


  As it is, qgis (by default) forces WAL mode, even if the database was
  not already in WAL, and even if there are other connections open.  Or
  it forces DELETE mode, similarly without checking.  So the concern
  about upgrading/downgrading comes from any setting of mode by any
  connection and any other existing connection.

  After digesting it all, I am left thinking that whether to use a
  geopackage in WAL mode or DELETE mode is a user decision, and that
  it's only safe to pick WAL if it's on a fs that supports it and it is
  known that no processes access the database via a remote filesystem.
  It's not enough for it to be local with respect to a writer that wants
  to use WAL; it has to be guaranteed that there aren't any remote
  writers (or even readers I think).

Therefore, I think the right approach is:
  1) let the user do "pragma JOURNAL_MODE=WAL;" if they want
  2) when opening the database, don't do anything about JOURNAL_MODE;
  just use it the way it is set.

(nI personally will leave it off, because 1) I don't like "read leads to
write" and 2) my workload is mostly reading for display and when I edit,
I'm clicking the UI and speed is not important.)

I am guessing that if OGR_SQLITE_JOURNAL is not set, the mode is not
changed, meaning the mode that the file already is in is used.  The gdal
docs didn't seem to explain and I'll have a look in the sources.



signature.asc
Description: PGP signature
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Re: [Qgis-user] information depth from landsat

[Madry, Scott]

Passive electro-optical imagers in orbit like Landsat have no penetration 
ability into ground or vegetation. It only measures the very top surface 
properties. There is well understood water penetration in the visible bands, 
primarily the blue band, and there are several articles in the literature. If 
you wish to actually penetrate soil you need to move into the microwave (radar) 
bands, and even there, it is severely attenuated by moisture and only works in 
very dry areas, also well describes in the literature. Ground penetrating radar 
dragged by sleds on the ground do have very good penetration generally, but not 
from airborne or satellite sensors.

I hope this helps,

Scott Madry

On Jan 11, 2022, at 2:16 PM, jean Lukusa 
mailto:luku...@gmail.com>> wrote:

Hi all .
As you know , we usually  extract some informations from landsat . For instance 
, lineaments , alterations , etc.
So I want to know , what is the maximum depth undeground the above-mentionned 
informations are collected ?


[https://ipmcdn.avast.com/images/icons/icon-envelope-tick-round-orange-animated-no-repeat-v1.gif]





___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

[Qgis-user] information depth from landsat

[jean Lukusa]

Hi all .
As you know , we usually  extract some informations from landsat . For
instance , lineaments , alterations , etc.
So I want to know , what is the maximum depth undeground the
above-mentionned informations are collected ?

>
>
>
> 
>
>
>>
>>
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Re: [Qgis-user] Readonly gpkg

[Greg Troxel]

Even Rouault  writes:

> The main issue I see is that it is unknown (and non documented AFAICS
> in SQLite documentation) what happens if :
>
> - reader A has opened the file with default journaling mode (for read-only)
>
> - reader B (other QGIS process for example, or possibly the same QGIS
> process like a renderer thread) has opened the file with default
> journaling mode (for read-only)
>
> - let's say A wants to edit and we thus enable WAL to avoid
> reader/writer blocks
>
> - is B which has opened without WAL still in a safe state ? Does it
> react properly to WAL having been enabled behind its back ?

Perhaps each read needs to be a transaction with taking and release a
shared-read lock.  And/Or the writer needs to wait until the readers
have released the read locks.

In a way this complaint of writing is not fair if sqlite3 is a 'real
database', but the attraction of it is specifically that it is less than
a full database management wise.

> The default enabling of WAL even in initial read-only access mode is
> to avoid that potential issue.
>
>
> There are currently way of disabling WAL (for advanced users) :
>
> - setting the OGR_SQLITE_JOURNALenvironment variable to JOURNAL
>
> - or setting the QGIS setting "qgis/walForSqlite" to false
>
> See
> https://github.com/qgis/QGIS/blob/master/src/core/providers/ogr/qgsogrproviderutils.cpp#L1005

It seems then that sqlite3 itself needs to be enhanced to avoid writing
until there's a write, in such a way that it can deal with the
cross-user locking.   Either that or move all that locking and
signalling into the above-sqlite access layer.

When I use pgsql, I expect to deal with a db, don't back up the data
dir, and run a pg_dumpall before backups and do backup that.  But
sqlite3 files in random places are files and treated like that, except
here they are acting more or less like pgsql in that reads lead to
writes, and one should use a different backup strategy.


Are you saying that if we disable the WAL option, then accesses are
still safe, but we have lower concurrency, because there is some locking
scheme to interlock writing and reading?That seems better to me, for
most uses.   Perhaps a property in the layer to use WAL, otherwise not?

If so, it seems WAL mode should be taking that lock in shared-write
mode, where multiple can write but all must be in WAL mode, vs single
writer vs multiple reader.


signature.asc
Description: PGP signature
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Re: [Qgis-user] Readonly gpkg

[Even Rouault]

Le 11/01/2022 à 18:58, Greg Troxel a écrit :

Jürgen E. Fischer  writes:


On Tue, 11. Jan 2022 at 09:10:57 -0500, perg...@gmail.com wrote:

I've tried making the gpkg read-only, which hasn't crashed anything in brief
testing and generates no warnings. However, it feels risky, and clearly QGIS
or OGR aren't fully happy, since the temporary shm and wal files don't get
deleted on exit. So I'm hesitant to continue doing this for fear of a crash
when I'm actually doing something useful.

We do the same with world_map.gpkg - see
https://github.com/qgis/QGIS/issues/35383.

I had seen that (NetBSD 9, pkgsrc, qgis 3.16.x) and wondered if it was a
packaging error I should look into.  Now I understand.   I have long
found it problematic that the wal/shm files exist and persist for long
periods, and that gpkd files I don't intend to change are modified at
the OS level.

It strikes me that the basic bug needs one of two things:

   1) The geopackage driver should have a read-only access mode, and qgis
   should start out that way, trying to change to read/write only when
   the user hits the edit button on one of the layers.  And, if the file
   is read only, there should be a nice error like "can't make this layer
   writable" and the toggle to write should fail.


The main issue I see is that it is unknown (and non documented AFAICS in 
SQLite documentation) what happens if :


- reader A has opened the file with default journaling mode (for read-only)

- reader B (other QGIS process for example, or possibly the same QGIS 
process like a renderer thread) has opened the file with default 
journaling mode (for read-only)


- let's say A wants to edit and we thus enable WAL to avoid 
reader/writer blocks


- is B which has opened without WAL still in a safe state ? Does it 
react properly to WAL having been enabled behind its back ?


The default enabling of WAL even in initial read-only access mode is to 
avoid that potential issue.



There are currently way of disabling WAL (for advanced users) :

- setting the OGR_SQLITE_JOURNALenvironment variable to JOURNAL

- or setting the QGIS setting "qgis/walForSqlite" to false

See 
https://github.com/qgis/QGIS/blob/master/src/core/providers/ogr/qgsogrproviderutils.cpp#L1005




   With this option, there perhaps needs to be some kind of lock outside
   of sqlite, which can be multireader and single writer.

   2) somehow, the geopackage layer could hide all this and logically open
   the layer read/write, but refrain from writing to the filesystem.
   Then, when there is an actual write, the db open-for-write can
   happen.   After the database is written, if no layers [are
   editable]or[have unwrittend changes] for some period of time (5m?) the
   database should be changed back to read only.   This is sort of like 1
   but at the gdal layer vs the qgis layer.


Because of this I'm starting to think about moving all my data into
postgis, and not use geopackages any more.


___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user


--
http://www.spatialys.com
My software is free, but my time generally not.

___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Re: [Qgis-user] Readonly gpkg

[Greg Troxel]

Jürgen E. Fischer  writes:

> On Tue, 11. Jan 2022 at 09:10:57 -0500, perg...@gmail.com wrote:
>> I've tried making the gpkg read-only, which hasn't crashed anything in brief
>> testing and generates no warnings. However, it feels risky, and clearly QGIS
>> or OGR aren't fully happy, since the temporary shm and wal files don't get
>> deleted on exit. So I'm hesitant to continue doing this for fear of a crash
>> when I'm actually doing something useful.
>
> We do the same with world_map.gpkg - see
> https://github.com/qgis/QGIS/issues/35383.

I had seen that (NetBSD 9, pkgsrc, qgis 3.16.x) and wondered if it was a
packaging error I should look into.  Now I understand.   I have long
found it problematic that the wal/shm files exist and persist for long
periods, and that gpkd files I don't intend to change are modified at
the OS level.

It strikes me that the basic bug needs one of two things:

  1) The geopackage driver should have a read-only access mode, and qgis
  should start out that way, trying to change to read/write only when
  the user hits the edit button on one of the layers.  And, if the file
  is read only, there should be a nice error like "can't make this layer
  writable" and the toggle to write should fail.

  With this option, there perhaps needs to be some kind of lock outside
  of sqlite, which can be multireader and single writer.

  2) somehow, the geopackage layer could hide all this and logically open
  the layer read/write, but refrain from writing to the filesystem.
  Then, when there is an actual write, the db open-for-write can
  happen.   After the database is written, if no layers [are
  editable]or[have unwrittend changes] for some period of time (5m?) the
  database should be changed back to read only.   This is sort of like 1
  but at the gdal layer vs the qgis layer.


Because of this I'm starting to think about moving all my data into
postgis, and not use geopackages any more.



signature.asc
Description: PGP signature
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Re: [Qgis-user] Readonly gpkg

[Jürgen E . Fischer]

Hi Martin,

On Tue, 11. Jan 2022 at 09:10:57 -0500, perg...@gmail.com wrote:
> I've tried making the gpkg read-only, which hasn't crashed anything in brief
> testing and generates no warnings. However, it feels risky, and clearly QGIS
> or OGR aren't fully happy, since the temporary shm and wal files don't get
> deleted on exit. So I'm hesitant to continue doing this for fear of a crash
> when I'm actually doing something useful.

We do the same with world_map.gpkg - see
https://github.com/qgis/QGIS/issues/35383.


Jürgen

-- 
Jürgen E. Fischer   norBIT GmbH Tel. +49-4931-918175-31
Dipl.-Inf. (FH) Rheinstraße 13  Fax. +49-4931-918175-50
Software Engineer   D-26506 Nordenhttps://www.norbit.de
QGIS release manager (PSC)  Germany IRC: jef on Libera|OFTC


signature.asc
Description: PGP signature
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Re: [Qgis-user] QGIS Model Designer

[Ujaval Gandhi]

The batch processing and modeler are mising the 'iterate' feature, and this
type of batch processing + merge functionality will be useful. I have a
tutorial on how to write a bit of pyqgis code to do this that shows exactly
the use case you have. But it can be used with any other processing
algorithm.
https://www.qgistutorials.com/en/docs/3/processing_algorithms_pyqgis.html
[image: Logo] 
Ujaval Gandhi
Spatial Thoughts
mobile: +91-8095684687
email: uja...@spatialthoughts.com
[image: LinkedIn icon]   [image:
Twitter icon] 



On Mon, Jan 10, 2022 at 4:52 PM Richard McDonnell 
wrote:

> Hi All,
>
> Apologies, but I think I have found a Plugin, which looks promising “Point
> sampling tool” which seems to do what I want.
>
> 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 *Richard
> McDonnell
> *Sent:* 10 January 2022 11:18
> *To:* qgis-user@lists.osgeo.org
> *Subject:* [Qgis-user] QGIS Model Designer
>
>
>
> Hi all.
>
> I have been asked to sample over 100 raster pixel values using a single
> point file.
>
> I can use the “Sample raster values” Tool, but this only outputs for one
> Raster. I have looked at batching this, but it will produce 100’s of point
> files which I will have to merge together. So I was looking at using the
> Model Designer, but again it can’t accept multiple raster inputs.
>
>
>
> What I would like to know, is how I might easily create a single shapefile
> with a column for each raster containing the sampled value. The easiest way
> would be to somehow sample the first raster saving the output then loop
> back to the second raster, but this time using output from the first
> sampling to sample the second. This looping would continue until all
> raster’s had been sampled.
>
>
>
> Any help appreciated.
>
> 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/
>
>
> ___
> Qgis-user mailing list
> Qgis-user@lists.osgeo.org
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

[Qgis-user] Readonly gpkg

[pergler]

I've packaged a number of read-only layers (e.g. contours, watercourses) for
my area of interest into one gpkg. However, QGIS writes changes to this gpkg
every time it is opened, even if the layers themselves are never edited. I
think this is related to SQLite wal journaling. 

 

It's an annoyance since it's a large file that gets unnecessarily reuploaded
in every incremental backup, and when I'm in the field, that's sometimes
over a bad 3G cell connection. 

 

I've tried making the gpkg read-only, which hasn't crashed anything in brief
testing and generates no warnings. However, it feels risky, and clearly QGIS
or OGR aren't fully happy, since the temporary shm and wal files don't get
deleted on exit. So I'm hesitant to continue doing this for fear of a crash
when I'm actually doing something useful.

 

Is there a better way to tell QGIS to not write to a gpkg in which all
layers are only being accessed read-only?

Thanks!

 

---

Martin Pergler

 

___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Re: [Qgis-user] NULL value in a table

[Ujaval Gandhi]

This looks like a bug, but I could find a workaround. In the Print Layout
Table's Item Properties, choose 'Attribute' and for the column that you
have NULL values, enter an expression like below under the 'Attributes'
heading. Replace 'my_col' with the name of your attribute.

CASE WHEN "my_col" is NULL
THEN NULL
ELSE "my_col"
END

After you enter the expression, change the 'Heading' to the original column
names. Now you should have blank entries where there were NULL values.

[image: Logo] 
Ujaval Gandhi
Spatial Thoughts
mobile: +91-8095684687
email: uja...@spatialthoughts.com
[image: LinkedIn icon]   [image:
Twitter icon] 



On Mon, Jan 10, 2022 at 10:30 PM Dario C  wrote:

> Hi,
> I have a table in my layout, which has  a column set as integer. Is there
> any chance to have void attribute where I have NULL values? At the moment I
> have everything with "0".
>
> Thanks
> ___
> Qgis-user mailing list
> Qgis-user@lists.osgeo.org
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Re: [Qgis-user] [QGIS-Developer] Step-up for OGC compliance

[Marco Bernasocchi]

Hi Paul,
Thanks a lot for stepping up, we couldn't wish better!

I still think that organisations for which the certification is important
should step-up financially, and we^ll still work in that direction.

Probably the best is if you get in touch directly with me and Régis to see
how to move things forward.

Cheers
Marco

On Wed, 5 Jan 2022 at 09:12, Paul Blottiere 
wrote:

> Hello everyone,
>
> > maintaining the OGC compliance for QGIS server is a very time consuming
> > undertaking that up to now was completely relying on the volunteer work
> of very
> > few community members. Unfortunately Régis cannot follow this anymore
> (Thanks
> > a lot Régis for all the work you put in!).
>
> > We therefore are looking for community members to take over the lead on
> this.
>
> Considering that I already take care of the underlying "technical
> infrastructure" for the OGC compliance (server admin,
> QGIS-Server-CertifSuite,
> ...), I propose to also take care of the formal request.
>
> What do you think?
>
>
> > Ideally, we'd also like to see organisations that rely on QGIS server
> > certification to step-up financially to support the big workload needed.
>
> It'd be nice :).
>
>
> Regards.
> --
> Paul Blottiere
> QCooperative: https://www.qcooperative.net/
> Hytech Imaging: https://hytech-imaging.fr/
>


-- 
Marco Bernasocchi

QGIS.org Chair
OPENGIS.ch CEO
http://berna.io
___
Qgis-user mailing list
Qgis-user@lists.osgeo.org
List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user