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Questions tagged [grass]

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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pyqgis processing, grass: --overwrite does not work

I have a QGIS plugin that tries to call the v.clean algorithm multiple times in a row and use the same output file each time the algorithm runs through. But even though I set the --overwrite parameter ...
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10 views

GRASS: db.in.ogr fails where v.in.ogr succeeds

This is a follow up on a previous question on the storage of vectors layers imported from PostGIS. To importing a spatial table from PostGIS I use, sucessfully, the following formulation with v.in....
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25 views

Do I need the standalone GRASS app if I have the GRASS Plugin and Processing toolbox enabled in QGIS? [on hold]

What processing abilities does the standalone GRASS GIS application have that aren't available in the QGIS GRASS plugin/toolbox? I'm trying to understand whether you would need/want the standalone ...
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34 views

GRASS: import PostGIS vector layer into SQLite database

I am working with vector layers (points) composed of more than 100 000 geometries. These layers are originally in a PostGis database and I import them with v.in.ogr, using a formulation like: v.in....
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20 views

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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1answer
57 views

Viewing 3D relationships of layered points and DEMs by displaying absolute height for both in QGIS? [on hold]

What are the limits of viewing points and rasters together in QGIS 3D (either in-app or using qgis2threejs) in comparison to ArcScene? Is using GRASS NVIZ the solution? (see end of post) I am using ...
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11 views

Get visible polygon form one point (visibility graph with one point)

Problem I would like to get the visibility of one point in regard to a polygon layer. E.g. which island can I see from the beach. What I found It's possible to get a visibility graph via Grass v....
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26 views

Interpolate 3D raster with Anisotropy

I am building a 3D geological model for soil deposits. I have two approaches to build a 3D raster. My dataset is about 300k points of bh information with texture and permeability at every meter ...
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1answer
20 views

Can I import raster files from GRASS GIS in QGIS versions later than 1.8.0

I have a process that I have used for years where I create .ascii files with a Python process, import them to GRASS GIS 6.4.3 and do some raster calculations (r.mapcalc). This works great but then ...
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3answers
52 views

Calculating the shortest distance coordinate to vector layer

I want to calculate the nearest distance from each coordinate in a vector layer containing more than 17 000 coordinates to another vector layer. I tried the GRASS v.distance tool but it gives the ...
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1answer
21 views

Cost raster/friction map and data extraction

I am in an early stage of least cost paths analysis of a wide area. One part of the operation includes simulation of movement across the grid of previously agreed size of cells and extent of the grid (...
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12 views

Minimize time for snow-covered image with `i.atcorr` module

Did anyone notice the time taken by i.atcorr module when running for a snow-covered image? It is noticed that two to three hours for 30m resolution with the image of 3656*1000 size. Both for VNIR(...
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36 views

Convex boundary of polygon [closed]

Is there any tool that can help me with my problem? I have polygons looking like this : And what I want, is to simplify or gain convex boundary of such polygons. I tried Simplify Polygon in ArcMap, ...
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1answer
34 views

Calculate weighted centroid of a raster layer using GRASS?

I'm trying to calculate the weighted centroid of some raster layers I have, which are basically patches of positive values in a sea of null values. I know I could convert thoses patches to binary ...
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3answers
523 views

GRASS not working with QGIS 3.6

I updated QGIS to version 3.6 using OSGEO4w When I try to run any GRASS script, I get the following error message : This algorithm cannot be run :-( The specified GRASS 7 folder "C:\OSGEO4~1\...
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1answer
48 views

Executing r.viewshed (GRASS) in R

What libraries do I need to execute this GRASS tool (or any other) from an script in R ? Has anybody try to compare performance between using r.viewshed from QGIS and r.viewshed from R ?
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1answer
50 views

Using GRASS 7 in QGIS 2.18 on MacOS

Does anybody found a way to use GRASS 7 in QGIS 2.18 under MacOS? QGIS 2.18.19-2 is the latest version packaged with GRASS 7. For many reasons, all the following versions been have packaged with ...
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1answer
96 views

No output from GRASS 7 r.reclass in Processing Python script

I want to run the r.reclass tool in python on a raster layer to reclassify 1 value (and leave the rest the way they are). Here is my best attempt so far, after trying to reference documentation and ...
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0answers
61 views

What am I missing to get GRASS 7.6 tools to run in QGIS 3.4.4 Processing (linux)? [closed]

I can't seem to get any GRASS 7.6.0 algorithms to run inside QGIS 3.4.4 Processing toolbox on Arch Linux (kernel 4.20.8). I have GRASS installed at /opt/grass. Launches fine standalone with tools ...
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1answer
23 views

How to import coincide table of r.coin tool of QGIS in Excel

I am trying to do a crosstabulation analysis with QGIS. I have used the grass tool r.coin and I have got the coincide report in txt format. However, I want to work with that report in excel, but I don´...
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1answer
40 views

Can GRASS export an ESRI ASCII?

I have a raster in GRASS GIS and want to export it as a ASCII file following the ESRI format. This is my code r.out.ascii --overwrite input=XX@PERMANENT output="...\XX.asc" null_value=-9999 The file ...
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1answer
29 views

Raster clipping error with GRASS

I'm using GRASS 7.6 to clip a raster (i.e. big_raster) layer on a smaller one (i.e. small_raster). Both the rasters are made by nan and 1 values. I used the map calc tool r.mapcalc expression="...
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36 views

GRASS function “V.net.centrality” Error env: python3: No such file or directory

I am using QGIS 3.4 (just updated) on a Mac OSX Mojave 10.14. I am trying to use the grass function "v.net.centrality" but I keep getting an error. The error is ... env: python3: No such file or ...
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47 views

Importing several LiDAR (.las) files in GRASS using v.in.lidar?

I'm building a DEM of a terrain in GRASS and have 48 LiDAR (.las) files. I know I can do this by using r.in.lidar (including the list of files as a .txt) and then r.fillnulls However, I want to ...
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1answer
28 views

Writing GRASS location at predefined directory

I need to write location, mapset and information in defined directory which has write permision. How can I do this? Presently the location and mapset are written at GISDBASE directory. I would like to ...
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1answer
41 views

r.horizon GRASS tool missing in QGIS list of GRASS tools

I would like to run the r.horizon tool from GRASS in QGIS 3.4.4 but it does not show up in the list of GRASS tools in QGIS. Is there some way to add it?
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1answer
16 views

Get Border (Cells) of Polygon GRASS

I have a raster area which i could also convert into a vector area. I need all cells which lie in direct vicinity of the edge(s). My first try was to convert the vector area to lines and then the ...
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1answer
161 views

Calculating shadow of trees with DEM in QGIS?

I have a DEM with a good precision (0,5 x 0,5 m/pix LiDAR) and I´m looking for the way to obtain a raster (or shapefile) with the shadow of the trees located in that place for a whole day (ideally ...
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20 views

SQL Error while using v.distance through simple python editor in grass

I try to execute the following code: grass.run_command('v.distance', from='tramstop', to='iso_tram', upload='cat',column='first_tram_distance', overwrite=True) but i get the "SyntaxError: invalid ...
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1answer
57 views

PyQGIS processing: Overwrite not possible

I have a QGIS plugin that runs the v.clean algorithm two times (first time snap, second break) on a chosen layer: output = self.dlg.directory.text() params_snap = { 'input' : input, ...
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21 views

Grass-v.buffer error [duplicate]

I want to create oval buffers 450 by 350 m tilted by 45° using the v.buffer-tool from the GUI. When I enter everything necessary and click run, in return I get the following error message (same pops ...
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1answer
100 views

QGIS 3.4.4 PATH pointing to grass-7.4.4, but I have 7.6.0 installed thru OSGEO4W

How do I change this PATH (it says read-only and won't stick) or use the network installer to make this work correctly on Windows 10? All I want to do is use QGIS and Grass? I've honestly been ...
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1answer
45 views

Assign “No data” to some pixel values

I have a GeoTIFF Float32 raster DEM with some pixels with value -9999. How can I assign "No data" to those pixels using GRASS 7.4?
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1answer
75 views

Adding extra parameter in QGIS processing in grass to close files after processing

The code below works but as this involves averaging thousands of files, grass shows an error message: Too many open files The code: ymax=31.4648437503 ymin=17.4068080185 xmax=-80.4330407378 xmin=-...
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1answer
55 views

Getting GRASS 7.4.4 Working in Python 3

I'm trying to get some GRASS functionality in a Python Script, specification r.series, but I'm struggling to import GRASS. I'm trying to uses the method outline on the GRASS Wiki, Working with GRASS ...
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2answers
54 views

Import BMP raster with worldfile (tfw) into QGIS

I need to get a few non-georeferenced bmp files into QGIS, Grass or any open source platform. I have tfw files available with no indication on the projection but cannot seem to find a procedure (gdal) ...
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27 views

Creating DEM in GRASS?

I need to create DSM and DEM with resolution 0.4 m. I tried to create DSM with resolution of 1m, everything was ok, but when I set higher resolution, then raster have a stripes with No Data values. ...
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20 views

r.grow in GRASS not working at all

Everytime i try to use the r.grow module from GRASS in QGIS (3.0.0 "Girona") i get this error Any tips?
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98 views

Error whilsted using QGIS 3.4.4 r.series batch processing [closed]

I'm having some trouble using the Batch Processing to perform r.series, Could anyone explain what I'm doing wrong? I'm using QGIS 3.4.4. Output Log: Processing algorithm 1/1… Algorithm r.series ...
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1answer
50 views

i.atcorr [GRASS] - has anyone used it and actually had success?

I am trying to apply i.atcorr to a landsat mosaic with GRASS. These are my 6S parameters: 18 01 31 22.10 178.940 -17.263 1 1 0 0.115 -0.270 -1000 116 Everytime I run it, it returns me a raster ...
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1answer
48 views

GRASS console doesn't open

I'm currently stuck in a project because whenever i try to open GRASS console (shell) it doesn't appear anything, and i cant find the reason why. Im using QGIS Desktop 3.4.3 with GRASS 7.4.2 What i ...
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1answer
21 views

GRASS Error: WARNING: segment zero_fill(): Unable to write (No space left on device)

I was trying to define the drainage patterns and to delineate some catchments based on a 30m DEM using r.watershed --overwrite elev=DEM accumulation=Accum drainage=Drainage -m but grass would ...
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40 views

Recommended resources for viewshed generation using Grass GIS 7.4

I am working on a project where I need to create viewshed areas around towers with a radius of 5000 meters. The underlying DEM I created using free Lidar data. Uptill now I did all this on a laptop ...
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26 views

grass-session 1.0 produce ImportError cannot be imported in Spyder IDE

I am trying to use the recently developed grass-session package inside Spyder in Linux Mint with GRASS 7.4.3 installed with a aim to do some geoprocessing without starting GRASS explicitly. I ...
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1answer
31 views

-32768 in flow direction values of Grass GIS

I was checking the values of a flow direction tiff created with Grass GIS and the values were: -32768, -4, -3, -2, -1, 1, 2, 3, 4, 5, 6, 7, 8. This answer explains clearly the meaning of the values ...
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58 views

QGIS r.reclass batch processing error

I am reclassifying 43 rasters in Grass r.reclass function and am getting the following error: Processing algorithm 1/43… Algorithm r.reclass starting… Input parameters: {'GRASS_RASTER_FORMAT_META': ''...
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1answer
93 views

QGIS Madeira 3.4.3 running GRASS tool v.net.distance producing ERROR: Unable to open vector map

I have been trying to use the v.net.distance from GRASS in the QGIS toolbox. I have a road layer with two sets of points I want to calculate the shortest distance between. I have checked the validity ...
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1answer
89 views

Consistent Errors with QGIS using GRASS tools?

I have recently started using QGIS after using Arc for years. I downloaded QGIS Madeira 3.4.3 and have been working with road layers. After working with my project for a month in QGIS, I started ...
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37 views

Getting an error while using GRASS GIS from R

I have installed GRASS in my Ubuntu system. Library "rgrass7" is successfully installed and imported. but, while running the code I am getting an error : Error in parseGRASS(cmd, legacyExec = ...
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35 views

GRASS v.out.ogr append to a postgresql table does not work

I'm using the following command to export a GRASS layer to a PostGIS table: v.out.postgis input=elevation_profile output="PG:dbname=spatialdbnew user=postgres password=postgres" output_layer=...