Questions tagged [grass-gis]
GRASS GIS (Geographic Resources Analysis Support System) is a free, open source geographical information system (GIS) specialized in handling raster, topological vector, image processing, and graphic data. GRASS GIS is a high performance analytical GIS and remote sensing with focus on modularity. Users can process both day-to-day data as well as massive time series.
527
questions with no upvoted or accepted answers
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Calculate volume of space defined by multiple overlapping 3D polygons
I have thousands of 3D polygons scattered in space but they mostly overlap with many of their neighbors in big extent.
Is there any way how to compute volume they define effectively?
I would love to ...
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11
votes
2
answers
2k
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QGIS GRASS Processing Not Working on MacOS?
Recently upgraded to QGIS3 (3.0.2) for MacOS (High Sierra) and encountered GRASS (7.2.2) issues. Tried adding a custom variable and now when running GRASS algorithms (e.g. r.reclass) I get the ...
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8
votes
1
answer
810
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GRASS v.clean tool in QGIS gives empty output
I am trying to run v.clean in QGIS 3.10.7. I have a 2D LineString dataset saved in GPKG format and I want to run v.clean to clean up some messy topology.
But whenever I run it, I get the same result - ...
- 3,460
7
votes
0
answers
1k
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QGIS cannot open output layers
I have problem with QGIS 2.0.1. Everytime I run tool from SAGA or GRASS, I get exactly the same error, for example:
Oooops! The following output layers could not be open
Channel Network: /tmp/...
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6
votes
1
answer
675
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Dealing with no-data values in raster calculator of QGIS
I am trying to patch two rasters with raster calculator but I am not finding the way to work with no-data values.
Lager@1 has some information I need as first option, this has as no-data -9999 (...
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6
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0
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526
views
Running v.clean tool in QGIS Python Console
How to use v.clean GRASS processing tool for break in QGIS from Python QGIS Console.I have tried using below command:
processing.runandload('grass:v.clean', layer,\
0,0.100000,'8132391.27018,8134827....
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6
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0
answers
268
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Activating GRASS utilities in QGIS Processing toolbox via text descriptors
This is a new follow-on question from this one. Following the documentation outlined in the answer, it is fairly easy to set up a descriptor text file for standard utilities that exist but aren't in ...
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5
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How to load/enable r.stream.distance and r.lfp in QGIS 3.6.1 with GRASS 7.6.1 (Windows 10)?
I am new to QGIS and GRASS. I would like to use r.lfp in QGIS with GRASS.
So far I installed addons extensions r.stream.distance and r.lfp in GRASS (Settings/Addons extension/Install extension from ...
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5
votes
1
answer
1k
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r.viewshed Raster map not found
I wanted to test the r.viewshed module from grass via the Toolbox in QGis. But no File is generated. This is the log output:
Algorithm r.viewshed - Computes the viewshed of a point on an elevation ...
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4
votes
1
answer
2k
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Using GRASS GIS/QGIS to georeference TIFFs in 3D space, vertically?
I am a geophysicist working for a small shallow surface geophysics firm. We create 2D slices of the ground showing data collected from various surveys. These are generally cross sections (TIFFs) of ...
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4
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0
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40
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What does the blocking option do in GRASS r.watershed?
What does the blocking option do to the r.watershed program in grass? According to the manual, it should stop water from being routed past that location, but it appears to have no effect. I'm trying ...
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4
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0
answers
2k
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how to orthogonalize building outlines
I'm looking for a way to orthogonalize building outlines which I've extracted from a high-res DEM. I'm using the FOSS GIS stack (QGIS, GRASS, SAGA, PostgrSQL, PostGIS) and can code in Python (or Java)....
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4
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276
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Drawing "proportional" buffer using QGIS or GRASS?
I'm working on aquatic vegetation and have a shapefile representing floating vegetation in a lake. By some studies, we know that submerged vegetation extends for a certain extension based on floating ...
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4
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0
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380
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How to build a GRASS network with node IDs from the line dataset?
I have a dataset of street network links (line geometries). Each network link has a link id, start node id, and end node id attribute. I want to use this network in GRASS, so after importing the lines,...
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4
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857
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Error when using r.watershed in QGIS 2.10.1 with Grass
I am running r.watershed within QGIS processing the I get the error below.
I draw your attention to:
GRASS_INFO_WARNING(2205,1): Subprocess failed with exit code 256 GRASS_INFO_END(2205,1)
Does ...
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4
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0
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554
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Option for 360 degree movie embedded in Open Source GIS software?
Is there any Open Source GIS software available to embed 360 degree movies with the map?
For a COTS example, there is the Active Link Vision (ALV) extension for ArcGIS from IWANE.
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4
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0
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829
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Problem loading output layer QGIS
Every time I run operations with temporary file output from the graphical modeler, I get the following error message:
Oooops! The following output layers could not be open CLIP:
C:\Users\Amine\...
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4
votes
0
answers
885
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How to install grass addons when offline?
Can anyone tell me how can I install GRASS (v.7) addons on a windows PC when offline?
I manually downloaded the files from http://svn.osgeo.org/grass/grass-addons/grass7/ and copied:
- the .py file ...
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3
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0
answers
512
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Both GRASS and SAGA fails on QGIS 3.28
After having trouble with GRASS and SAGA on my Windows laptop, I have just reinstalled QGIS but it has not solved anything. Hopefully I'm missing something obvious, but I cannot for the world figure ...
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3
votes
0
answers
62
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Any advice on how to use r.stats in QGIS
I am trying to run r.stats in QGIS to get all unique combinations of data values from 2 raster layers. The process runs, outputs an HTML file, and does not throw any errors. However the files are ...
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3
votes
0
answers
191
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Network analysis in QGIS with nodes at start and end point
I have a dataset form a national agency with a topologically correct road-network. However, I have a problem when applying network analysis within QGIS to the dataset.
I have tried both the native ...
3
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0
answers
184
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Error: Algorithm not found using grassprovider in PyQGIS standalone script
With QGIS 3.22 the GRASS algorithms got its own provider (grassprovider.Grass7AlgorithmProvider) and are no more part of processing.algs. Knowing this, in a standalone pyqgis-script I am trying to add ...
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3
votes
0
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109
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QGIS 3.12.3: V.to.3d: Number of centroids exceeds number of areas
QGIS.3.12.3 | CRS = WGS 84 | Grass downloaded
Making a habitat survey map 3d using height values stored in attribute using v.to.3d.
Parameters
Name of vector map: Habitat layer
Input feature type: 4 ...
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3
votes
0
answers
116
views
How does grass r.viewshed take into account the Earth curvature?
Up to now I always had to do such analysis in a local Cartesian Coordinate System and on relatively small datasets, but today, I want to compute a viewshed analysis on a large raster DEM which is ...
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3
votes
0
answers
147
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CalledModuleError: Module run None g.gisenv -n ended with error
I am trying to use r.horizon GRASS module(version GRASS 7.8) in Python script. But I couldn't able to access the grass modules. Everytime, I am getting the following error.
File "C:\OSGEO4~1\apps\...
3
votes
0
answers
54
views
Line along points with no continous ID and creation date/time
I have a huge points file. The points are along a route network. I would like to build lines by going from point to point - but there is no chronology given!
The "ID"s seams to be chaotic ...
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3
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0
answers
204
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r.to.vect is not responding in QGIS GRASS
NLCD data entered for half of Illinois, all of Michigan and Wisconsin, plus additional along borders.
Used r.neighbors to simplify, then r.to.vect with "smooth corners" feature selected.
Got ...
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3
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0
answers
143
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GRASS 7 problem
I am working with QGIS 3.8.3. I want to split my lines into intersections and for this, I tried to use the command v.clean in GRASS - Processing Toolbox. However, an error msg appears:
"This ...
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3
votes
0
answers
143
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Problems importing raster to GRASS from QGIS (error: Datum ETRS89)
When I try to import raster from QGIS to GRASS with r.in.gdal.qgis an error of projection appears.
Raster is in EPSG::25831 - ETRS897UTM zone 31N and mapset is supposed to be defined with the same.
...
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3
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0
answers
106
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GRASS GIS Segmentation issue on UAV image
I tried i.segment to perform segmentation on a part of UAV orthophoto image, but this always results in stripe-like rectangle segments which I do not expect. Could anyone figure out what happens?
...
3
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186
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Using v.net.flow in QGIS/GRASS GIS?
When I try to use the v.net.flow tool in QGIS, the output datasets have a value of 0 for every feature in the flow column. Almost every other v.net tool works, such as v.net.steiner and v.net.distance....
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3
votes
0
answers
979
views
Convert NetCDF(.nc) (TROPOMI Sentinel-5p) to GeoTIFF (GDAL, GRASS)
I tried converting NetCDF (Sentinel-5p) file to GeoTIFF file but I'm getting:
D:\>gdalinfo 20181119T121048.nc
Warning 1: Recode from UTF-8 to CP_ACP failed with the error: "Invalid argument".
...
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3
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0
answers
1k
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Clip raster by mask layer not working in QGIS 3.4.2?
I've been successfully using QGIS 2.18.21 to "clip raster by mask layer" and then run v.rast.stats. However recently v.rast.stats has stopped working in QGIS 2.18.1. The log does not show an error, it ...
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3
votes
1
answer
975
views
How do v.distance 'upload' parameters actually work?
I'm trying to use v.distance (using QGIS 3.4) to calculate the distance in meters between a layer of water shutoff points and the boundary of the nearest building footprint polygon. Even better would ...
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3
votes
0
answers
280
views
Convert polygons to lines ignoring redundant vertices in QGIS
Provided the following Polygons layer with 6 polygons (see image below), I would like to calculate each line's segment's angle (amongst other things), so I should convert those six polygons into lines,...
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3
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0
answers
237
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r.stream.basin in qgis
I am trying to generate subbasin with provided multiple outlets points by using r.stream.basin. I have install r.stream.basin addon in grass but it does not appear in qgis. Is there any ways to use ...
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3
votes
0
answers
66
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GRASS GIS Error Flags
I am attempting to run a GRASS command from the terminal and eventually a bash script, in which it links rasters in a folder to the Mapset previously defined. I was able to successfully create the ...
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3
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0
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255
views
QGIS 2.18.17: python warning missing init
Every time I open QGIS 2.18.17, I get the following python warning in the protocol window:
2018-03-02T12:30:52 1 warning:C:/PROGRA~1/QGIS2~1.18/apps/qgis-ltr/./python\qgis\utils.py:607: ...
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3
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86
views
Checking and enforcing downstream Z constraint for synthetic streams?
Assume I've delineated planar (X, Y) stream breaklines to use them for enforcement of bare ground DEM derivation from high density lidar data. The stream features are in a Z and M enabled polyline ...
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3
votes
0
answers
216
views
How to show Vector Layer created by v.clean GRASS tool in QGIS
I have created vector layer using GRASS tool v.snap, which resulted in a vector layer as output. I want to display the vector layer in QGIS. How can i view the vector layer created by snap tool in ...
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3
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0
answers
227
views
Making DTM from contour vectors in QGIS?
I have been using QGIS (2.18.0) for 6 months and now need to make a DEM from contour vectors. From my reading, I know I have to use GRASS.
I am in the process of using this tutorial to achieve that ...
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3
votes
0
answers
78
views
QGIS - Layer missing polygons after pointsfile transformation
I'm using pointsfile transformation in QGIS for the georeferentiation of my layers. After the transformation the result some times has polygons missing like here:
Why is this happening? How do I ...
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3
votes
0
answers
790
views
GRASS 7 commands in PyQGIS without results (QGIS 2.18)
I have tried to run different GRASS commands as part of a PyQGIS script in QGIS 2.18 and 2.14, without obtaining any result, e.g. for the following code:
# Open raster
fileInfo = QFileInfo(raster)
...
- 1,536
3
votes
0
answers
194
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How to accelerate v.generalize on massive vector data?
I have a big problem with my vector dataset (more than 1 million entities) and v.generalize in grass 7.0.5 and 6.4 (64 bits for both). I try to use Douglas method on this dataset but it is very very ...
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3
votes
0
answers
362
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GRASS v.net.iso does not include all lines
I want to define catchment area for bus stops in small city. As a result of v.net.iso in QGIS with GRASS I don't get all highways in that city. Here are my steps:
importing above layers into GRASS ...
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3
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0
answers
276
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r.sun from QGIS toolbox doesn't give realistic value about the hours of insolation
I have a problem with the GRASS module r.sun when I run it in QGIS.
I would calculate the hours of insolation in a specific site during a specific day. When I ran the algorithm "r.sun" from GRASS, it ...
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3
votes
0
answers
134
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Calculating a specific distance from points along a network - GRASS
I'm currently using the v.net.iso function in GRASS (no access to network analyst in ArcMap). Does anybody know of a way to export the result to shapefile so that you have an individual line feature(s)...
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3
votes
0
answers
266
views
Wrong area using Albers Equal Area Projection in GRASS for Java, Indonesia
I am just getting to know GRASS 7.0 and I am struggling finding a good projection to work on a spatial analysis of Java, Indonesia. I am new to the forum, so if information's are missing for a better ...
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3
votes
0
answers
118
views
QGIS - WHERE SQL within a processing.runalg statement for v.surf.rst in python console
I'm creating lots of raster files with grass:v.surf.rst so rather than using the graphical interface I wanted to use the python console (and potentially put in in a script at some point). However ...
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3
votes
0
answers
98
views
v.clean batch process within QGIS 2.10 (PISA)
I get an error message when I try to create a batch for v.clean operation..
Algorithm v.clean - Toolset for cleaning topology of vector map. starting...
local variable 'filename' referenced before ...
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