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.
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PostGIS (hopefully faster) alternative to v.overlay with or condition from GRASS
I have two distinct tables, one called rpg(id, code_culture, geom --polygons) and the other called ia(id, classe, geom --also polygons)
Like this :
How should I proceed to get a single table with a ...
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Errors building GRASS
I am trying to build grass-8.3.0 on a Debian Linux system. The configuration portion has only one flag:
--without-pdal
because Debian 12 does not have that package. The compilation finishes with:
...
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Getting errors on startup of GRASS
I downloaded the Mac/Intel chip binary for GRASS 8.3 and put it in my Applications folder. On startup, I am seeing this in the terminal--
MacBook-Pro:~ me$ /Applications/GRASS-8.3.app/Contents/MacOS/...
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Better solution for simplification of shape polygon with python than GRASS [closed]
I want to simplify a shape containing several adjacent polygons. There are a lot of solutions there to do it, but I found GRASS is the only one that preserves topology and keeps adjacent polygons ...
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GRASS GIS v.out.ogr too many export too many feature shp
I have a vector maps that contains 16 points (from v.information) I would like to export them in Shapefile format, but when I use v.out.ogr I got this message :
Exporting 16 features... 28 features ...
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GRASS GIS Encoding
I want to know if there is a way to change the default GRASS GIS 7.8.7 encoding (UTF-8) to (ISO-8859-1).
My problem is that I have accent words in my "attribute data" (á,é,í, etc), so when I ...
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QGIS Raster resampling without label changes
I am working on raster data that which is in a 5x5 meter resolution. I need to resample this to a 25x25 meter resolution. I have used resample.stats which works, but changes the label numbers into one ...
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In GRASS GIS db.execute IN statement works, but NOT IN doesn't
Here is my command:
db.execute sql="UPDATE table SET factor=number2 WHERE label IS NOT NULL AND number2 IN (SELECT label FROM table)"
This command sets TRUE on those rows, where label in ...
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Find distance from point to coastline
I have a layer of ~2 million line segments representing rivers, and a layer of ~300 000 line segments representing the coastline. I want to extract the river outlets.
I've tried a bunch of different ...
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v.db.update doesn't write values to a column
I use v.db.update map=myfile column=label query_column=cat (areas) to copy column values. This command works well. But when I try do do the same thing for another file which is a product of streams....
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How to get centerline of the mask images
I am working on the centerline extraction, I have tried skeletonize, RivGraph and several other methods but could not get a good centerline. First the line on the ends are not following the center and ...
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r.stream.order returns error
GRASS Version 8.3
OS Win 10
I have a python script that I am using to process data to create hydro outputs, in the past it has worked without error but recently it has returned an error.
The script ...
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Missing tool `i.points.auto` in the QGIS GRASS provider
I have the latest version of QGIS 3.32.2-Lima installed.
I have installed GRASS 7.8 and 8.3, which is confirmed in OSGeo4W.
GRASS plug-in is enabled in QGIS.
But I cannot find the i.points.auto tool ...
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How to set up r.watersheds if it generates too short streams on river valley sections that are too wide
Related to this question too
I am delineating a very big watershed with very wide river valley.
When I tried to perform with PCRaster, the directions map wasn't generated properly, as sticks upon ...
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GRASS GIS 7.6.1 version
How can I download GRASS GIS 7.6.1 version while I can't find the open access online?
I am trying to install GRASS 7.6.1 for my Windows, 64-bit laptop. However, I could not find setup file for it in ...
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How to convert raster to vector by generating center lines?
I need to vectorize the raster by keeping one center line trough the boundary pixels. My solution would need to be very similar to this question: Converting raster to vector by generating center lines?...
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Exporting ldd raster from grass to PCRaster fails
I successfully exported Float32 SCALAR data with
r.out.gdal input=$file output=$file.map format=PCRaster type=Float32 createopt="PCRASTER_VALUESCALE=VS_SCALAR"
but for ldd data (previously ...
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Is it possible to edit stream network to correspond a new subwatersheds raster and then run r.stream.order?
All rasters are created with r.watershed. So, I have:
streams raster,
accumulation and
directions.
We know, that streams raster should correspond exactly to directions raster in order to use r....
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ERROR: Invalid input <n=n+0> appears for too big holes on SRTM when filling nulls in grass (r.fillnulls)
Related to this question
In the link above I described a case, when there is no null cells in raster, but there are some empty tiles that are also treated of course as nulls. This time, I have ...
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Cannot use r.recode directly in powershell
I am trying to use elements of GRASS in the terminal (PowerShell). I have added the relevant directories to $env:path so that get-command r.recode returns an executable. However, when I try and run r....
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Error: r.walk GRASS function in QGIS (Mac)
I've been trying to run the r.walk GRASS function in QGIS on my Mac, but got several error messages (unable to open datasource, raster map not found). I used two different DEMs just to be sure, but ...
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Access Terminal Commands with QGIS
I'm working with QGIS3.22 and I want to use GRASS and GDAL directly from the terminal. Primarily, this is so that I can gain a better understanding of the tools by viewing the get-help output (if it ...
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db.out.ogr duplicates items and adds an empty one
I export an attribute table of streams_order layer to CSV.
My attribute table in GRASS is ok:
But my CSV file has all features duplicated and an odd 0 feature with no information:
What's wrong and ...
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Download GRASS GIS addons and install from local machine
I use GRASS GIS from a Docker container, and every time I rebuild the image, addons like r.stream.order and r.stream.snap are installed from the GRASS repository. Maybe it's an improper way and I ...
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Issue with compilation of rdenoise for GRASS
I would like to use r.denoise an external tool of GRASS.
So I tried to install it following instructions from this page r.denoise manual
But the terminal returns me an error during compilation:
...
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Calculating flow path length in R
I am currently trying to calculate the flow path length in a DEM towards a streamnetwork. My desired outcome would be a raster with values of how long the flowpath to the nearest streamcell would be ...
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Error calling GRASS from R Studio (Mac)
I am trying to call GRASS GIS from R Studio.
GRASS_path <- ("Applications/GRASS-8.3.app/Contents/Resources")
gisDbase <- ("Users/PS/grassdata")
location <- ("TH_N32&...
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How can I create a new raster from two different rasters like v.patch does?
I have two rasters with zones and I want a patched product from these two as a new classification like:
Zone1 Zone2 Result
12 14 1
15 21 2
15 23 3
17 14 4
54 1 5
etc
each ...
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Why r.to.vect process takes too much time with topology analysis?
My task is to vectorize a standard landuse map (PROBA-V discrete classification) for extent 118.747182 54.231218 124.946218 60.060467 degrees. Raster is too detailed for me, so I generalize it.
I use:...
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Masked raster is completely black when reprojecting and masking in GRASS GIS
I have a global raster of railways networks in Mollweide CRS (resolution 1000x1000) and I want to reproject it to Europe (EPSG:3035), crop it to Europe, and change the resolution to 30x30 km (0.25°).
...
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v.clean (GRASS) creates additional features
I am working with a large road dataset (approx. 1 million features) with a high number of overshoots and dangles.
To address the overshoots and dangles, I am using the v.clean tools (break, snap, ...
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wxnviz.py: No module named 'grass.lib.ogsf'
I'm getting the following error on starting GRASS using the GRASS 8.2.1 Docker container (source: docker pull mundialis/grass-py3-pdal:8.2.1-ubuntu):
Launching <wxpython> GUI in the ...
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Is it possible to add attributes to a vector layer from csv table based on class name?
I have a vector for the region of interest, where each polygon has a class value. Also I have a classification table there each row contains a class name and class parameters in other columns. I want ...
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Check if a file exists in a GRASS mapset
Is it possible to simply check if a file exists in a GRASS mapset and return FALSE or TRUE?
My task is to process a large file, so I don't want to overwrite it every time, because of resources ...
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Resample() function in R's terra package and the r.resamp.interp module in GRASS GIS yield such different rasters
Comparing the results from the resample() function in R's terra package (version 1.7-29), and the r.resamp.interp GRASS GIS module (version 8.2), I find differences in how they apply bilinear ...
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How to remove the first header line when creating a csv with ogr2ogr?
I use the great approach to large rasters as described here
gdaltindex an_index.shp *.tif
ogr2ogr -f CSV list.csv an_index.shp -spat xmin ymin xmax ymax
gdalbuildvrt -input_file_list list.csv mosaic....
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r.fillnulls throws "Invalid input"
I use GRASS 7.8.7 (2022).
For a DEM raster
r.fillnulls input=file1 output=file2 I get:
Registering primitives...
Using RST interpolation...
Locating and isolating NULL areas...
100%
Growing NULL areas
...
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Real-sky radiation with r.sun in GRASS: Why do atmospheric factors (e.g. cloudiness) reduce diffuse radiation?
r.sun in GRASS (enter link description here) makes it possible to calculate real-sky radiation (as opposed to clear-sky) with the coeff_bh and coeff_dh parameters. The relevant part of the ...
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Calculating r.li.shannon with vector grid on GRASS GIS
I looked up baker and cai (1992) and throughout the internet to find my answer, but my novice level makes it hard to find concrete solutions.
I am trying to calculate the shannon diversity index (r.li....
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Interpreting r.regression.multi
I cannot find a source that explains how to interpret the output of r.regression.multi. Can someone explain what the different lines mean; specifically how do I see if the results are significant?
X=...
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Flow pathways during a flood event in QGIS
I have a river and a field next to it (with its DEM). I want to determine the water's pathways in the field, when the water in the river reaches a certain level , based on the DEM only.
I am thinking ...
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2
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g.gui.rlisetup configuration file missing
I am trying to calculate the shannon diversity index (r.li.shannon) for a landscape using the r.li tool in GRASS GIS 7.8.7. My input file is a raster of my different land covers with an assigned ...
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How to if a polygon is within a concave area of another?
Is there a method where I can detect if a polygon is inside the concave area of another (in this case a bay), then output the bay itself?
It's hard to explain with words so I'll demonstrate below:
...
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GRASS r.texture :g.proj symbol lookup error
--Problem Description
I am trying to use grass within a python code thanks to the grass_session and grass_scirpt packages.
I am not very familiar with the "session" part. From what i ...
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R.regression.multi land-use data not enough valid cells
What I want: run r.regression.multi between land-use change and bumblebee occurrence.
What I did:
X coefficients: cov_all.0 of North, East, South and West SSP1 -4 layers in total. (I projected the ...
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No path found between two points
I'm trying to find a path between different pairs of points,
But within the thousands of pairs tried only a few actually result in a path.
I find this odd but maybe it's normal.
(note that when I'm ...
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Linear regression t-value missing in r.series QGIS
I am using QGIS 3.22.15, but I noticed that in the GRASS r.series tool there is no tvalue function (see image) as described instead in the manual here https://grass.osgeo.org/grass82/manuals/r.series....
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How create voxel 3d (x,y,z,attribute) in GRASS GIS from CSV file
I have a csv file with (x,y,z,attribute) x,y,z,attribute are float value, and I want to do a voxel 3D in Grass Gis, the documentation and examples are poor, so please I need some help.
I am using ...
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Using v.distance to classify points far from overlapping polygons always return the same set of polygons
I have two vector layers with the distribution of an animal species. EDIT: I'm showing how the maps look in QGIS, but I'm working in GRASS GIS. First dataset:
Second dataset:
As you can see, these ...
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1
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How to update string column of a shapefile GRASS GIS
I'm relatively new in GRASS GIS and I want to update a column of a shapefile.
I use GRASS GIS (version 7.8.6 on Ubuntu 20.04 .4 LTS), not the GRASS extension in QGIS.
I'm workin on a shapefile. In ...
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