GRASS-Wiki - User contributions [en]

PSC Meeting 2025-08-08

2025-08-11T17:23:27Z

Pvanbosgeo:

== Participants ==

* Anna Petrasova
* Helmut Kudrnovsky
* Huidae Cho
* Linda Karlovska
* Nicklas Larsson
* Paulo van Breugel
* Vaclav Petras
* Veronica Andreo

== Agenda ==

The topics proposed are:

* GRASS presence on different events
* Release 8.5
* New docs status
* Website rebranding status
* Mailing list removal? Question from Vicky in chat
* Decide on the Workspace topic and whether the solution suggested [https://github.com/OSGeo/grass/discussions/5916#discussioncomment-14045240 here] can be implemented. This would help to finalize and merge this [https://github.com/OSGeo/grass/pull/3113 PR].
* Discussion on the [https://github.com/OSGeo/grass/discussions/5909 workflow proposal]. Perhaps we need a File Browser pane?

== Minutes ==

* GRASS presence on different events
** FOSS4G EU: Alen presented the state of GRASS talk.
** FOSS4G NL: Paulo gave a presenation about GRASS in education and research
** FOSS4G NA (Nov 3-5)
*** Workshop: GRASS Addon Development with Python, Corey & Caitlin.
*** Talk: GRASS Meets Longest Flow Paths, Shortest Compute Times, Huidae.
*** Talk: State of GRASS, Corey.
** FOSS4G 2025 NZ:
*** Alen and Luca will attend and present the state of GRASS talk (Corey as co-author as he wrote the original abstract).
** FOSS4G.be: Moritz will present a state of GRASS talk

* GRASS 8.5 Release postponed to fall
** Waiting for JSON stuff from GSoC, which needs to be reviewed before release.
** Fix r.mapcalc issues regarding parallelization.
** Mac binaries: There's an issue with code signing. Needs to be solved before the release.
** Release scripts are in addons, and they run in a Docker image. Still several steps need to be manual and they are different depending on the type of release, i.e., major, minor, micro or RC.
** Jupyter notebook integration into GUI. Some things need to be defined/solved first:
*** Where to start the Jupyter server?
*** Where to store the notebooks: current working directory, let users choose, outside projects, within mapsets, provide a good default?
*** What happens when users do not have the dependencies installed?
*** It should work in Windows (both OSGeo4W and standalone installer).
** FHS should be ready for 8.6

* New docs:
** They are up and running, but there's still something missing on the automatic upload part (currently a personal GH token of MN is used which expires every 3 months).
** There’s the question of whether we need to have docs updated all the time or only when we release. In that sense, this is not a blocker for the release, but a nice-to-have.
** For this release, we do not remove the HTML files, which are mostly used locally in the GUI or when called with g.manual from the terminal.
** Addon docs with new format: they work online.

* GSoC:
** The student and mentors are working hard on adding JSON output to C tools.
** They are obsoleting the -g flag and moving to the format option.
** More clean-up should be done before GRASS 9 + Python tools.

* CMake:
** We need 3 steps: FHS ([https://github.com/OSGeo/grass/pull/5630 PR WIP]), GUI (Nicklas has a follow-up PR, but will need help with this), extensions (nothing done so far).
** MSVC binaries are built fine, but they don’t work out of the box because of missing environment variables; Can make them work by manually setting environment variables though; g.gui fails with Python exceptions

* Vicky's questions in the [https://matrix.to/#/!BOjyJgENYOLyXbRKxO:gitter.im/$xIdFsIr_HiEm6ASHtQCEt7GQkIrz_5zlLKOr-UpZLgo?via=gitter.im&via=matrix.org&via=osgeo.org GRASS chat]:
** We need to understand what they want to remove, and why; grass-user and grass-dev archives must not be removed, and neither must other list archives.
** Anna sends an email to Vicky.

* Workspace discussion:
** We agreed on having them within mapsets, but being asked if we want to save them or not - the opposite view is to save them automatically with a timer or so
* Anna proposed to remove the lock to delete maps in different mapsets from the GUI - check if this is independent from the owners of mapsets.

[[Category:PSC]]

Map Reprojection

2024-08-25T09:02:45Z

Pvanbosgeo: correct typo

'''Question''': How to change map/image projections, datums, etc in GRASS GIS?

'''Answer''': For quality reasons, GRASS GIS handles '''one projection per location'''. You can reproject between locations as well as reproject during data import if needed.

=== Rationale ===

Reprojection on the fly can easily introduce artifacts. Especially,
* vector maps: lines and polygons need to have a sufficiently high amount of vertices which is not guaranteed, hence {{cmd|v.split}} be used;
* raster maps:
** categorical maps need to be reprojected with nearest-neighbor method, while
** floating point data might be better reprojected with bilinear or cubic convolution methods)
Since many GIS users tend to blindly go ahead without selecting proper methods, the simple approach was adopted: put data which are in different projections into separate locations. That's it.

=== Reprojecting data in GRASS GIS ===

Variant 1: 
# first create a location from the dataset itself (e.g. using the [[GRASS Location Wizard]])
# second: use {{cmd|r.import}} or {{cmd|v.import}}

Ready.

Variant 2: 
# first create a location in the source projection/geodetic datum (using the [[GRASS Location Wizard]]; note that you can generate the location from the dataset itself)
# [[Importing data|import]] the map/image into the location,
# create a second destination location in the projection/geodetic datum you want to reproject the map/image into,
# Within the destination location session, use {{cmd|r.proj}} or {{cmd|v.proj}} (depending on whether the map/image is raster or vector) to reproject the map/image '''from''' the import location '''to''' the destination location.

Ready.

Variant 3: 
Another (similar) strategy frequently needed when maps need to be imported using, e.g. {{cmd|v.in.ogr}} or {{cmd|r.in.gdal}}, is to tell these programs to create a new location (argument "location"). If the imported data contains proper <code>PROJ_INFO</code> files, they can be reprojected into the current mapset, using the the projection in the current location/mapset.

=== Raster data: GDAL alternative ===

Export as a GeoTIFF, use <code>gdalwarp</code> to change the projection and then import the new GeoTIFF file into GRASS GIS. If you have installed <code>gdal</code>, you almost certainly have <code>gdalwarp</code> as well. Indications for <code>gdalwarp</code> are found at http://www.gdal.org/gdalwarp.html. The options for <code>gdalwarp</code> may be a bit confusing for newbies. In the following example of projecting a GeoTIFF based on SRTM elevation data to UTM 37N, <code>-t_srs</code> is the output file projection, <code>AfricaHornElev.tif</code> is the input file and <code>AfricaHornElev37n.tif</code> is the output file.

<source lang="bash">
# use bilinear resampling (-r; use bilinear for floating point maps)
# use 2GB of RAM as cache
# target resolution (-tr): ensure 100m pixel resolution
gdalwarp --config GDAL_CACHEMAX 2000 -t_srs '+proj=utm +zone=37 +ellps=WGS84 +datum=WGS84 +units=m +no_defs' \
-r bilinear -tr 100 100 AfricaHornElev.tif AfricaHornElev37n.tif
</source>

==== Extracting spatial subset (subregion) ====

If you just want to reproject a part of the image, you may extract a spatial subset first
<source lang="bash">
# projwin order: W N E S
gdal_translate -of GTiff -projwin 636861 5152686 745617 5054047.5 \
p192r28_5t19920809_nn1.tif test1_utm.tif
</source>

=== Vector data: have enough vertices in your vector data ===

When reprojecting vector data, it is important to have enough vertices in the data. Starting from GRASS GIS 7 the vertices are automatically densified.

Example: Box (polygon) created with {{cmd|v.in.region}}:

g.region n=60 s=40 w=0 e=30 res=10 -p
v.in.region box_latlong_10deg

[[Image:V proj input unsplit boundaries.png|450px|center|thumb|4 corner rectangle, LatLong (no further vertices)]] 

Update 12/2014: vertex densification is now automatically done in {{cmd|v.proj}} of GRASS GIS 7! Just use v.proj and it will be right.
<strike>v.split -n box_latlong_10deg output=box_latlong_10deg_vertices_200km length=200 units=kilometers</strike>

[[File:V proj input split boundaries.png|450px|center|thumb|Split rectangle, LatLong]] 

As obvious from the results, enough vertices must be present in the map to avoid (severe) distortion. Note that this applies likewise to "ogr2ogr" and QGIS:

# switch to a different location.
# Properly reproject in GRASS GIS (when having used v.split):
grass70 -c box_latlong_10deg_EU_LAEA.shp ~/grassdata/eulaea
v.proj box_latlong_10deg location=latlong_wgs84 mapset=neteler
v.proj box_latlong_10deg_vertices_200km location=latlong_wgs84 mapset=neteler

[[File:V proj result.png|450px|center|thumb|Results in EU LAEA (EPSG: 3035)]]

# Test in OGR/QGIS
v.out.ogr box_latlong_10deg dsn=box_latlong_10deg.shp
ogr2ogr -t_srs epsg:3035 box_latlong_10deg_EU_LAEA.shp box_latlong_10deg.shp
qgis box_latlong_10deg_EU_LAEA.shp
# ... oops... (result not shown here).

== See also ==

* [[Location and Mapsets]]
* [[WxGUI]]
* [[Projection]]s

Other publications and sites:
* [https://crs-explorer.proj.org CRS Explorer - PROJ codes]
* [http://projections.mgis.psu.edu Interactive Album of Map Projections 2.0]
* Compare Map Projections: [https://map-projections.net/singleview.php View Map Projections]

[[Category:FAQ]]
[[Category:Raster]]
[[Category:Vector]]

GRASS Community Meeting Prague 2024

2024-06-16T08:38:27Z

Pvanbosgeo: /* Online */

{{toc|right}}
The ''GRASS GIS Community Meeting'' for contributors and developers will be happening from '''June 14 to June 19, 2024''' in Prague, Czechia.

[[File:Prague-Community-Meeting-2023-crop.jpg|500px|frameless|center]]

== Sponsor us! ==

We welcome financial contributions to support the meeting and we are looking for sponsors to cover costs such as meals or to help reducing travel and accommodation expenses for GRASS developers who volunteer their time. If you are interested in sponsoring the GRASS Community Meeting, please go to:

::: '''[https://opencollective.com/osgeo/projects/grass/contribute/community-meeting-2024-71849 Open Collective: Community Meeting 2024]'''

Any surplus at the end of the event will be used for future activities of the GRASS GIS project such as the [[Student Grants|Student Grant program]].

This GRASS Community Meeting is a great occasion for you to support the development of GRASS. With your contribution you'll enable more developers to meet. Community meetings are important opportunities for developers to discuss, fix bugs, plan the direction for the project and work on new features. The developers and other contributors or their employers are donating their valuable time, so it would be great if funding can be made available from within the community to cover out-of-pocket expenses. All of the work that takes place at the community meeting will be directly contributed back into the GRASS project to the benefit of everyone who uses it. Note that while we have our general plan, we can't accept any earmarked donations, i.e., we can't make any promises for a specific work to be done, please contact specific developers or support commercial providers for that.

We are grateful to the following sponsors for their support and commitment!

* U.S. National Science Foundation, award 2303651. (Travel for 5 participants and their time, event venue.)

[[File:NSF Official logo.png|none|left|200px|alt=Logo of US NSF|U.S. National Science Foundation]]

* [https://www.osgeo.org/ OSGeo]: 5500 USD (approved budget contribution, [https://www.loomio.com/p/W9Qz5cf1/motion-to-approve-5-500-for-the-grass-community-meeting-2024-budget motion])

[[File:Osgeo logo.png|none|left|alt=Light and dark green logo of OSGeo saying Your Open Source Compass|Open Source Geospatial Foundation]]

* [https://www.fossgis.de/ FOSSGIS e.V.]: 3500 EUR (approved budget contribution, [https://www.fossgis.de/wiki/F%C3%B6rderantr%C3%A4ge/GRASS_GIS_Community_Meeting_2024 request])

[[File:FOSSGIS_eV_logo.png|none|left|400px|alt=Logo of FOSSGIS e.V.|FOSSGIS e.V.]]

* [https://opencollective.com/osgeo/projects/grass/contribute/community-meeting-2024-71849 Community Meeting 2024 goal contributors at Open Collective]
* In-kind contributions will be acknowledged here.
* Personal time and/or financial contributions will be acknowledged here.

== Purpose ==

The ''GRASS GIS Community Meeting'' is a great occasion for folks to support the development by actively contributing to the project in different ways. These include source code updates, documentation (manuals, wiki, tutorials), translations, website improvements or likewise. The community meeting is also a get-together where supporters, contributors, power users and developers make decisions and tackle larger problems related to the project, discuss and collaboratively resolve bugs, plan the direction for the project and work on new features. We welcome people committed to improving the GRASS GIS project and the interfaces to QGIS, GDAL, PostGIS, R, OGC Services and others.

In this meeting, building on momentum from the 40th birthday meeting, we will continue the revisions of the maintenance processes and infrastructure - a process which highly benefits from the current maintainers being in one place (and time zone). Topics which require highly synchronous collaboration will be included such as Markdown documentation and CMake build transitions. Other contributors are expected to enhance existing tools and their documentation. A [https://grass.osgeo.org/news/2023_08_13_grass_community_meeting_prague_june_2023_report/ press release] gives an overview of last year's event.

We do require participants to work on GRASS GIS or connections to other projects. However, we leave them the freedom to work on what they think is the best contribution to the project given their skills and time available.

For the detailed agenda and individual's plans, see below.

== Agenda ==
These are some of the identified project priorities:
* Develop the project roadmap to better communicate project vision and priorities.
* Discuss the GRASS GIS integration with QGIS with its maintainers to identify next steps.
* Test the CMake and conda packaging implementations.
* Finalize the HTML to Markdown documentation conversion.
* GSoC students will showcase their projects and seek feedback. We also search for fostering their engagement with community members participating in the meeting and others that want to join online.
* Test and review onboarding documentation for developers, maintainers and other contributors.
* Develop use cases and tutorials on the use and integration of STAC related modules into data processing workflows.
* Get feedback on ongoing GRASS website UX improvements and add missing content.
* Address issues discussed last year about GRASS-R integration: https://github.com/rsbivand/rgrass/discussions/78
* Discuss mailing list (mailman) vs [https://discourse.osgeo.org/ discourse] (forum)
* Simplify [[Working with GRASS without starting it explicitly#Python:_GRASS_GIS_8_with_existing_location|working with GRASS 8.4+ in Python wiki page]], then improve [https://gis.stackexchange.com/a/457875/687 here on GS]
* Create release artifacts by GitHub CI (for inspiration, see [https://github.com/OSGeo/libgeotiff/pull/115 libgeotiff] and [https://github.com/libgeos/geos/blob/main/.github/workflows/release.yml GEOS])

=== Thursday, June 13 ===

Day of arrival. Contact organizers if you are interested in individualized program or helping with organization.

=== Friday, June 14 ===

* Welcome.
* Refine shared goals.
* 5 pm: PSC meeting ([https://www.timeanddate.com/worldclock/meetingdetails.html?year=2024&month=6&day=14&hour=15&min=0&sec=0&p1=207&p2=204&p3=25&p4=197 See local times]):
** Elections' date, contributors that will vote, who steps down.

=== Saturday, June 15 ===

* morning: GRASS in Windows
* 2 pm: Project roadmap discussion

=== Sunday, June 16 ===

* 11am or 4pm: Group photo
* 2 pm: Documentation discussion
** html - md conversion status
** Programming manuals
** Guidelines: contribution, submission, translation, etc.
** Tutorials: feedback on topics, where to include them, etc.

=== Monday, June 17 ===

* Morning: Status of GRASS-QGIS integration
* Afternoon:
** Session, projects and mapsets, Python API, subcommands in CLI (Vashek leads)
** GSoC students presentations

=== Tuesday, June 18 ===

* 9:15am-9:45am: Nix, Ivan Mincik, Geospatial Nixpkgs maintainer
* 10am: GeoSPARQL in GRASS
** SPARQLing Unicorn modularisation
** on-line with Timo Homburg

* 2pm: Website redesign discussion
** UX feedback
** Content

=== Wednesday, June 19 ===

=== Thursday, June 20 ===

Day of departure.

== Participation ==

Please add your name here or contact [[User:wenzeslaus|Vaclav Petras]] <tt><wenzeslaus at gmail com></tt>:

=== In person ===

{|class="wikitable sortable" border="2" cellspacing="0" cellpadding="4" rules="all" style="margin:1em 1em 1em 0; border:solid 1px #AAAAAA; border-collapse:collapse; background-color:#edf9c7; font-size:95%; empty-cells:show;"
!width=50px|'''Number'''
!width=130px|'''Participant '''
!width=100px|'''Country'''
!width=100px|'''Arrival'''
!width=100px|'''Departure'''
!'''Topics'''
!'''Notes'''
|-
|1
| [[User:wenzeslaus|Vaclav Petras]]
| United States
| June 13
| June 20
| review PR, reduce PR queue, Python API topics (also for QGIS and R), funding
|
|-
|2
| [[User:Annakrat|Anna Petrasova]]
| United States
| June 13
| June 20
| grass.jupyter, R and QGIS integration
|
|-
|3
| [[User:Ctwhite|Corey White]]
| United States
| June 13
| June 20
| STAC, JSON outputs, connections with other tools (OpenPlains)
|-
|4
| [[User:Chaedri|Caitlin Haedrich]]
| United States
| June 13
| June 20
| grass.jupyter, GRASS on Windows
|
|-
|5
| [[User:Veroandreo | Vero Andreo]]
| United States
| June 13
| June 20
| tutorials, website, documentation, contributing guidelines
|
|-
|6
| [[User:florisvdh | Floris Vanderhaeghe]]
| Belgium
| June 13
| June 18 (morning)
| Interfacing GRASS from R (parts of the [https://github.com/rsbivand/rgrass/discussions/78 todo-list])
|
|-
|7
| [[User:martinl | Martin Landa]]
| Czech Republic
| June 14
| June 19
| GUI, Modeler, Markdown, ...
|
|-
|8
| [[User:hellik | Helmut Kudrnovsky]]
| Austria
| June 14
| June 16
| ...
| Arrival on Friday evening.
|-
|9
| [[User:neteler | Markus Neteler]]
| Germany
| June 13
| June 19
| Infrastructure, Markdown, mailman vs discourse...
|
|-
|10
| [[User:lads | Luís de Sousa]]
| Portugal
| June 14
| June 20
| r.mblend, [https://github.com/OSGeo/grass/issues/2187 issue 2187], GeoSPARQL plug-in, DGGS free thinking, ...
| Arrival on Friday evening.
|-
|11
| Edouard Choinière
| Canada
| June 13
| June 20
| CI, checks, code quality
|
|-
|12
| [[User:pesekon2 | Ondřej Pešek]]
| Czech Republic
| June 13
| June 20
| Modeler, refactoring, i.atcorr, ...
| Not joining on June 15
|-
|13
| [[User:Mazingaro | Alen Mangafić]]
| Slovenia
| June 13
| June 20
| LiDAR tutorial, hyperspectral discussion
|
|-
|14
| Ivan Minčík
| Slovakia
| June 17
| June 19
| packaging
|
|-
|15
| Linda Karlovska
| Czech Republic
| June 15
| June 15
| GUI, refactoring
| Maybe joining also on June 16
|-
|16
| Chung-Yuan Liang
| Taiwan
| June 13
| June 20
| Tools parallelization
|
|}

If you are arriving or departing on the days of the event, please specify the time, too.

=== Online ===

Join our [https://app.gitter.im/#/room/#grassgis_sprint:gitter.im Gitter chatroom: grassgis/sprint]

Gitter has a video (and backup will be Zoom).

Participating virtually:

{|class="wikitable sortable" border="2" cellspacing="0" cellpadding="4" rules="all" style="margin:1em 1em 1em 0; border:solid 1px #AAAAAA; border-collapse:collapse; background-color:#edf9c7; font-size:95%; empty-cells:show;"
!width=50px|'''Number'''
!width=130px|'''Participant '''
!width=100px|'''Country'''
!'''Topics'''
!'''Times, synchronous or fully asynchronous'''
!'''Notes'''
|-
|1
| Loïc Bartoletti
| France
| QGIS Integration, CMake, C
| Part of 15th and 17th
|
|-
|-
|2
| Paulo van Breugel
| Netherlands
| Documentation, tutorials
| Part of the 16th
| Will join discussion at 2pm
|-
|}

== Venue ==

[[File:Ncsu logo.jpg|240px|frameless|left]]
[https://prague.ncsu.edu/about/ NC State European Center in Prague] 
Malé náměstí 144/1 
Praha 1 – 110 00 
Prague, Czech Republic 

[https://en.mapy.cz/s/fohulovaha Map] 

Prague, the capital of Czechia (Czech Republic) has an international [http://www.prg.aero/en/ airport]. It's location in the middle of central Europe makes it easily reachable by train, bus or car. The city itself has great public transportation.

== Accommodation and Costs ==

''Participation is free of charge''. However, participants should plan for the following costs:

* Travel
* Lodging
* Food and drink (some may be covered)

'''Please note''': The currency in Czech Republic is {{wikipedia|Czech crown}} (CZK, koruna, Kč). 100 Czech crowns are about 4 Euros (see [https://www.cnb.cz/cs/financni-trhy/devizovy-trh/kurzy-devizoveho-trhu/kurzy-devizoveho-trhu/ current rates]).

== Individual Preparation ==

* Bring your own computer
* Bring {{wikipedia|AC adapter|power connector adapter}} if needed (Czech Republic: 230V, 50Hz, {{wikipedia|File:Euro-Flachstecker_2.jpg|Type C Europlugs}} are common and also {{wikipedia|File:French_plug_and_socket.jpg|Type E}})
* Install git and the compiler tools, and come with a working GRASS development environment if possible. See [https://github.com/OSGeo/grass/blob/main/CONTRIBUTING.md here] for details.

== FAQ ==

* ''How was it last time?''
** Splendid! See [[GRASS Community Meeting Prague 2023]]!
* ''Is the meeting just a coding event?''
** It is mainly a coding and documentation event. It is a working session for people who are already participants in the GRASS project and/or are committed to improving the GRASS project. Committed newcomers are welcome!
* ''Is the GRASS Community Meeting for developers only?''
** No, anybody can help, with testing, checking out bugs and fixes, documentation and more.
* ''Where can I get help and more information about the community meeting?''
** Contact [[User:wenzeslaus|Vaclav Petras]] <tt><wenzeslaus at gmail com></tt>.