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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Why importing QGIS rasters into GRASS Mapset is not working

I am using GQGIS 3.30. I enabled GRASS and Processing Plugins, and pointed them to the right directory. I created a new mapset and location. Then I used the GRASS toolbox "Import raster into ...
Andrea's user avatar
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13 views

Input/Output Warning and uncompression error during v.rast.stats processing

First I use command r.slope.aspect elevation=dem slope=dem_slope format=percent --overwrite to calculate slopes in percent. I get a warning during slope calculation: WARNING: Unable to flush file ...
Nikolay Yasinskiy's user avatar
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1 answer
106 views

GRASS r.horizon returns nonsense

I am trying to calculate the horizon profile from a point on a mountainside, through the appropriate DTM elevation file and the GRASS function r.horizon.height (via QGIS). However, the output looks ...
elevation_modeller's user avatar
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25 views

Different area between Query raster/vector tool and v.to.db

I found a discrepancy between the select GUI tool "Query raster/vector" and v.to.db, and I do not know why. I attached the pictures. First image (image 1) show that the attribute "...
Pablo Sanhueza's user avatar
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25 views

Using v.voronoi.skeleton in Qgis 3.43 with Grass8

In previous QGIS-versions that used Grass7 I designed a model that used v.voronoi.skeleton. But with the upgrade to 3.43, and Grass8, this model will not work anymore. It complaints that grass7:v....
StefanK's user avatar
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Why new v.dissolve procedure generates new database tables and causes an error on adding columns later?

The new v.dissolve procedure includes, as the documentation states, two independent processes: v.reclass and v.extract, being a front end to those. In my case when v.reclass is called it creates a new ...
Nikolay Yasinskiy's user avatar
1 vote
1 answer
40 views

What is the right way to dissolve vector features in GRASS GIS on attribute values of one column summarizing or averaging others?

The line product of v.overlay contains a column with zones number and a stack of other attributes. What I want: Dissolve features (lines) on attribute column that contains zones number. Other ...
Nikolay Yasinskiy's user avatar
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25 views

How to get zonal statistics of a vector map by areas from another vector map in GRASS GIS?

I have a map with areas (polygons) and another map with lines for example. Lines have multiple attributes and I want some of them to be summed and written to new columns of my areas map. Each polygon ...
Nikolay Yasinskiy's user avatar
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1 answer
30 views

How do I calculate albedo in QGIS from a Landsat 8 image downloaded from EarthExplorer

I'm using QGIS and I'm struggling to calculate the albedo from the images. I don't understand how to use GRASS as every time I use it, I get something that doesn't make sense. Sor far, I have ...
GISNewbie2024's user avatar
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2 answers
75 views

Segment lines by given divider

I a trying to segment lines with specific values that are stored in a field. For example, I need my line 1 which is ~84m long, to be segmented into two segment that are 31m and 53m long. I have a ...
basile's user avatar
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Use v.clean function from GRASS in Jupyter Notebook

I want to automate a process which involves using v.clean tool from GRASS inside a Jupyter Notebook. I've read documentations on how to use Python with GRASS, but it seems impossible to do it or I don'...
Freestyle Season's user avatar
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2 answers
66 views

Fatal Error when trying to download addons for GRASS 8.3.1

I get an error with g.extension r.stream.order: ERROR: Failed to get branch from the Git repository <https://github.com/OSGeo/grass-addons/>. fatal: unable to access 'https://...
Nikolay Yasinskiy's user avatar
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1 answer
29 views

How can I update a column of a vector layer for reversed selection of features using command line?

Let it be two layers: one with multiple polygons, other with one. The task is: to select features of first layer that intersect with the second, then calculate values of a new column (for example: ...
Nikolay Yasinskiy's user avatar
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1 answer
32 views

How to resolve "Rscript not found" error when executing r.futures.potential in GRASS GIS?

I'm trying to run a Python simulation script in GRASS GIS 8.3.1 on Windows that utilizes the r.futures module. I get the following error when the r.futures.potential command is reached: ERROR: ...
user22780500's user avatar
1 vote
1 answer
93 views

Cannot install GRASS addons in GRASS 8.2 (Ubuntu jammy)

I am trying to install the r.clip addon in GRASS 8.2 in Ubuntu 22.04.3 LTS (jammy). I installed GRASS 8.2.0-1~jammy0 from https://launchpad.net/~ubuntugis/+archive/ubuntu/ppa and ideally need to use ...
Ernesto561's user avatar
2 votes
1 answer
196 views

PCRaster Tools, GRASS and SAGA installation on QGIS 3.34.2 for MacOS

I have followed the instructions here https://www.youtube.com/watch?v=RaFrXzw7IvI to install PCRaster Tools via conda, which is working. However it appears that all of my previously installed packages ...
Justine's user avatar
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18 views

r.mapcalc in GRASS GIS fails to mask rasters

I have a raster binary map (0-1) where 0 represents unsuitable areas (violet) and 1 represents suitable areas (yellow). I want to crop another raster (red) based on this suitability (for several ...
LT17's user avatar
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4 votes
0 answers
79 views

Install GRASS missing addons within QGIS

I'd like to use r.sun.hourly and r.sun.daily from within QGIS but it doesn't seem to be present in GRASS tools. I tried to install it using g.extension in the GRASS shell, but it says I have to run it ...
Louis's user avatar
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1 answer
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r.cross: max number of input map layers?

r.cross serves for combining multiple maps. The current docu (https://grass.osgeo.org/grass83/manuals/r.cross.html) states in section Parameters: Names of 2-30 input raster maps However, further ...
GISmo's user avatar
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63 views

Hans Der Kwast Derive Streams and Catchments Model - WKT issue

After spending a couple of days fixing this problem: Hans Der Kwast - Derive Streams and Catchments Model (r.to.vector not outputting file) thought i had a working model I am now encountering ...
Alex's user avatar
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1 vote
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35 views

Running grass7:r.watershed in QGIS gives different results to running identical process in QGIS

a former colleague created a QGIS tool in Python for the Team which creates Flow Routes and TWI (Topographic Wetness Indicator) maps for a selected location. I have run through the code and copied the ...
sar_copp's user avatar
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50 views

Hans Der Kwast - Derive Streams and Catchments Model (r.to.vector not outputting file)

I'm using the model created below and following the steps from 17:00 onwards https://youtu.be/ZC0skH4ifsI?list=PLeuKJkIxCDj2Gk0CkcJ-QeviE41aMZd-5&t=1021 I've followed the osgeo4 installation steps ...
Alex's user avatar
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0 answers
43 views

Installing old extension using g.extension of GRASS GIS

I am new to GRASS GIS and trying to get this extension I found working. https://gitlab.com/invafish/r.stream.culvert So, it fails to find if I try g.extension g.extension r.stream.culvert url=” https:/...
SunnyD's user avatar
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25 views

QGIS Grass Raster import using r.in.gdal.qgis: 'Layer data source could not be found'

I'm a QGIS learner following the official QGIS Training Manual. I'm on Module 12.1. My problem is that when I try to add a raster layer to GRASS using r.in.gdal.qgis, the resulting layer shows a red ...
JnomiddlenameHoward's user avatar
1 vote
1 answer
38 views

Why stream numbers generated by r.stream.order go one after other, not succeeding

Subwatersheds and streams corresponding form an 2n+1 series, where n=0,1,2... I don't know for what reason, and I also doubt if it works like that in all cases. It's very useful for me as I would like ...
Nikolay Yasinskiy's user avatar
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0 answers
16 views

Is it possible to split a polygon-subwatershed with a gage point without v.overlay?

After creating a clean map of subwatersheds I want to split some where control gages are located. If I try to do this with v.overlay (AND) - clipping subwatersheds previously generated with r.basins ...
Nikolay Yasinskiy's user avatar
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0 answers
24 views

Using gdal_translate to convert 32-bit raster to byte is black

I have a 32-bit float raster in GRASS. It is a single channel Sentinel 2 raster. I can export to geotiff with r.out.gdal: g.region rast=orthoimage_red r.out.gdal input=orthoimage_red output=...
Jeshua Lacock's user avatar
1 vote
0 answers
43 views

GRASS paths in Python standalone from QGIS install

I am trying to access GRASS from Python (Spyder). I have: Installed via pip install grass-session Started GRASS from OSGEO4W, loaded the mapset and location Started Spyder from Anaconda Tried to ...
william3031's user avatar
1 vote
1 answer
50 views

Creating relation for duplicate lines

I have two datasets with some duplicate lines. I can select the duplicates with GRASS v.select: v.select ainput=map1 binput=map2 output=duplicates operator=equals or QGIS Select by Location: ...
Jeshua Lacock's user avatar
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0 answers
29 views

Exporting .LAS file after using v.lidar.correction

Question I want to use the GRASS GIS LIDAR modules (v.lidar.edgedetection, v.lidar.growing, and v.lidar.correction) to classify points for LAS files. I'm very new to working with databases, and the ...
mozmoz3737's user avatar
0 votes
1 answer
36 views

Why is r.grow.distance in GRASS GIS returning a raster with all values = 0?

I'm trying to create a raster map that contains "Euclidean" distances to roads from another raster that contains said roads, by using r.grow.distance in GRASS GIS. The command executes ...
user22780500's user avatar
0 votes
1 answer
30 views

GRASS build polylines based on category/ID (v.net.distance)

I have calculated shortest routes between citywide origin-destination pairs with GRASS and v.net.distance. These routes are segmented, however, and I would like to turn them into polylines based on ...
SPet's user avatar
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1 answer
79 views

Running GRASS GIS from PyCharm

I follow the Working_with_GRASS_without_starting_it_explicitly with GRASS 7.8.8 (2023), but it did not work as intended. The Python line "gs.message" runs, but the line "gs.run_command('...
Pablo Sanhueza's user avatar
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0 answers
31 views

Exporting records with more than 250 characters in a field to GML

I am trying to export OSM vectors to the GML format like: v.out.ogr input=network output=network.gml format=GML I get an error that the field a_other_tags has more than 250 characters: ERROR 1: ...
Jeshua Lacock's user avatar
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0 answers
12 views

r.mfilter not applying to raster map

I tried applying r.mfilter to my raster map and it is saying error and not creating any filtered layer. I have tried closing the app and redid project again and upgraded grass as well but still the ...
sathisha's user avatar
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0 answers
32 views

Specify pixel data type importing raster into GRASS with r.in.gdal

When I import 8-bit grayscale images into GRASS with r.in.gdal the datatype used is float32 and is unnecessarily 4 times larger. I can specify the datatype when I export with r.out.gdal but I can't ...
Jeshua Lacock's user avatar
2 votes
0 answers
82 views

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 ...
Geo7's user avatar
  • 21
0 votes
1 answer
20 views

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: ...
user3063547's user avatar
0 votes
1 answer
51 views

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/...
user3063547's user avatar
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0 answers
40 views

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 ...
user230328's user avatar
0 votes
1 answer
80 views

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 ...
Pablo Sanhueza's user avatar
1 vote
1 answer
46 views

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 ...
Hartje's user avatar
  • 133
1 vote
0 answers
35 views

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 ...
Nikolay Yasinskiy's user avatar
0 votes
2 answers
73 views

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 ...
akvilas's user avatar
  • 103
0 votes
1 answer
14 views

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....
Nikolay Yasinskiy's user avatar
0 votes
1 answer
109 views

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 ...
H Tai's user avatar
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0 votes
0 answers
40 views

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 ...
user13966694's user avatar
1 vote
1 answer
101 views

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 ...
Comrade Che's user avatar
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0 answers
44 views

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 ...
Nikolay Yasinskiy's user avatar
0 votes
0 answers
72 views

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 ...
Bayes Rule's user avatar

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