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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7 views

GRASS v.to.rast outputs a bounding box of the geographic region

I'm trying to rasterize a vector layer in GRASS after setting the geographic region to the vector layer extent. I also used v.category to add categories to my vector layer. The command I'm using to ...
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2answers
5k views

GRASS GIS Plugin not loading in QGIS 3

When starting up QGIS 3.2.2 (also tested with 3.2.3), I get the following message in the "Plugins" Log Message Window: 2018-10-18T08:03:48 WARNING Failed to load C:/OSGEO4~1/apps/qgis/plugins/...
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1answer
616 views

Install QGIS 3.4 with GRASS support in Ubuntu 18.04

I can install QGIS3.X but cannot run a GRASS process. I get the popup: This algorithm cannot be run :-( GRASS 7 can't be found on this system from a shell. Please install it or configure your ...
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1answer
20 views

v.to.rast command in one shell script with other commands

I am using the latest GRASS Gis and QGis versions. In order for a study project, I have to rasterise a vector layer using v.to.rast. This has to be done in my already existing shell script, in which ...
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1answer
63 views

v.clean is stuck at 0%

So I have a layer with thousands of gaps and overlaps that I want to tidy up, but when I go to run v.clean in order to do so, it just sits there at 0%. I have no warnings or errors in the system, and ...
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91 views

V.Clean is not giving output In QGIS 3.14 Pi

I was trying to clean by removing sliver lines between set of polygons in my KML file. But unfortunately I am getting following error: QGIS version: 3.14.15-Pi QGIS code revision: d5114d2cfa Qt ...
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19 views

How do I update a polygon with values from a line in GRASS

I have a line map generated from r.stream.extract. I also have a polygon map generated from r.stream.basins, using the raster stream layer generated from r.stream.extract. I want to update the ...
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28 views

QGIS 3.18 and 3.16 LTR install. GRASS and SAGA not working. MacOS OSX

I have tried to update QGIS on Mac to either version 3.18 or 3.16 using the installers on the QGIS page. I have been having issues getting the GRASS and SAGA providers running. Error message below. ...
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12 views

QGIS r.regression line F significance

I performed with grass QGIS processing tool "r.regression line" a linear regression between two rasters. The result I got is shown in the picture Can someone explain to me what is the ...
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2answers
46 views

Resample raster to expand extent in QGIS

I am building a groundwater model and I need to assign elevations to the base of geologic units (where the unit is present) and at a minimum thickness where the unit is not present. I have a ...
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1answer
110 views

Using r.reclass.area.lesser in QGIS?

I want to reclass small areas in QGIS 2.18, but it seems to fail calling the algorithm in GRASS GIS. The interesting lines from the Log of the tool: ... C:\PROGRA~1\QGIS2~1.18\bin>g.region n=...
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1answer
176 views

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 - ...
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1answer
676 views

How to import SpatiaLite data into GRASS?

How can I import SpatiaLite tables into GRASS? Are there any restrictions I should be aware of? How does GRASS cope with columns that don't have a specific type (Sqlite tends to create such columns e....
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1answer
42 views

r.watershed error in QGIS (3.16.2) for MAC

I'm trying to use the r.watershed tool, here is the error that is arising. I've tried changing the GRASS path to custom /Applications/QGIS.app/Contents/Resources/grass78 and it doesn't seem to work ...
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1answer
119 views

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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1answer
100 views

How to extract contours from .jp2 DEM dataset?

This will be a little long-winded but I'm including all information I consider relevant. Problem: I have received a data set from a municipality that is a 3-layer LiDAR JP2 DEM and need to extract ...
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2answers
1k views

How to calculate the 3D length of line segment in QGIS?

I've been looking through all of the GRASS commands in the QGIS 2.10 processing toolbox and it seems like one of these must be able to do this but I haven't found one yet. There is 'v.sample' which ...
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1answer
56 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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3answers
1k views

GRASS New/Open Mapset not available ( QGIS 2.18.7) on Mac OS

I have QGIS 2.18 and the option to create a New Mapset is unavailable to me. GRASS is installed but when I go to the Plug-Ins>GRASS only Open GRASS Tools and GRASS Options are available to me. ...
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1answer
66 views

Creating cumulative friction map

I am looking at bottom friction (Manning's n) values in relation to storm surge as large volumes of water flow over a surface. In order to calculate total head loss occurring as water passes from the ...
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1answer
47 views

Running QGIS Processing Algorithms in Standalone Python Script in Windows

I want to run this code outside qgis as a standalone python script. import processing, os os.chdir('C:/Users/User/test/25') alg_params = { '-c' : False, '-f' : False, '-i' : False, '-n' : False, '...
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1answer
102 views

GRASS: Can v.buffer use geodesic distance like r.buffer does?

Question: In GRASS GIS, can v.buffer use geodesic distance like r.buffer does? If v.buffer can't use geodesic distance, is there a way to do vector geodesic buffering (ideally in GRASS, but I can ...
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8answers
43k views

How to set all pixels with value <= 0 to “nodata” in DEM raster?

I have a DEM raster with pixel values between about 3000 and -0.0003. I need to set all pixel with a value of 0 and smaler (<=0) to "nodata" (for later raster calculations and to reduce the ...
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1answer
45 views

v.clean cleaning topology

I'm doing some tests with the v.clean but getting some results that I don't really know if I am the one doing something wrong or what. As you can see in the image bellow I created 3 features, one with ...
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1answer
25 views

GRASS GIS, r.li modules: How to fix “ERROR: Illegal areas disposition”?

While trying to run commands in examples of GRASS GIS r.li module, I get the error. This is the output I get from commands in the examples grass_cmd_output(Language:Japanese) (Fri Sep 4 13:12:18 2020)...
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1answer
17 views

GRASS GIS v.surf.idw not working correctly

I have recently been struggling with an issue in GRASS. I am a new GRASS user and recently downloaded version 7.8.5 for my MacBook (macOS Catalina). I converted this sample dataset to a shapefile. I ...
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1answer
89 views

Georeferencing CAD drawing and setting ground control points in GRASS?

I'm fairly new to QGIS and Grass GIS, and learning the interface. I have a CAD drawing that has no coordinate system assigned and needs to be georeferenced to NAD83 HARN Northern Colorado (feet). I'...
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1answer
19 views

r.thin (GRASS) not giving correct result

I have raster image of road feature. I want to extract line feature from it. So I run r.thin tool on it of parameter - { 'GRASS_RASTER_FORMAT_META' : '', 'GRASS_RASTER_FORMAT_OPT' : '', '...
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1answer
103 views

Generating Hough transform (Hough line transformation) of binary image using QGIS

How do I generate a Hough transform (Hough line transformation) of a binary image in QGIS? I tried in GRASS and I got Error: unable to fetch interface description for command I found from the link: ...
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2answers
253 views

PYQGIS 3 Using the ouptut from GRASS v.distance algorithm

I have a script which is trying to run v.distance on two existing shape files, buildings.shp which containing some polygons and singleasn.shp which contains a single point. This will be run from the ...
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21 views

GRASS - Create 3d Raster map with time as vertical unit

I'm working with 2d climatic (annual max temperature) raster maps. I have 1961-1990 time period and I want to calculate 90th percentile of the climatic value within that period (so 30 maps) and inside ...
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1answer
47 views

r.grow.distance with r.mask returns errors on a global scale, but not with a smaller extent or without a mask

We are trying to calculate distances to settlements on a global scale (with a 10 arc second resolution), to eliminate 2/3 of the area (water/ocean) to calculate we used land as a mask (r.mask) but ...
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0answers
36 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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23 views

QGIS - Network join issue with cost allocation using OSM dataset

I've been trying to create a cost allocation map, using the v.net.alloc tool on QGIS with Grass. Some of the results don't connect to the network fully, even though they should in real life. This has ...
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2answers
44 views

Running parallel r.mapcalc in GRASS

I have thousands raster maps (3652, named raster_name.1, raster_name.2,... raster_name.x,... raster_name.3652) and for each map I want to do the r.mapcalc-threshold operation below here: ...
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0answers
13 views

r.watershed: How does the convergence parameter and “AT”- lcp work?

I generated streams with GRASS GIS r.watershed, executed in RStudio. Now, I want to explain the functionality behind that function. The GRASS- manual explains a lot here: https://grass.osgeo.org/...
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2answers
69 views

Calculating furthest distance from a pipeline line segment to a road line segment in QGIS

I am currently using the v.distance GRASS tool to calculate distances, but it naturally gives the nearest (shortest) distances. Oddly enough, I would like to find the furthest distance from a ...
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1answer
109 views

Does GRASS GIS work on latest Macs with M1 chip?

Does GRASS GIS work on Macs with M1 chip?
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1answer
54 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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1answer
43 views

Error while performing actions in GRASS GIS in Python

While performing actions in python console as described in the module of GRASS GIS,am getting following error: import grass.script as gs r.in.gdal -e input="D:...\ASTGTMV003_N19E073_dem" ...
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1answer
69 views

Error launching GRASS GUI : error message related to gcmd.py or gi_set.py

I am trying to run GRASS GIS for the first time. However, when I try to run GRASS (by clicking on the icon in the start-up menu), I get the following error message: > Starting GRASS GIS... ...
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1answer
104 views

Install GRASS GIS extension r.pi including r.pi.prox and implement the Addon in QGIS

I would like to install the GRASS GIS addon r.pi within QGIS, I only have access to basic GRASS commands I installed QGIS using the osgeo4w-setup-x86_64.exe advanced installation using the http://...
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1answer
27 views

r.slope.aspect grass gis datum format on dx and dy analysis

I'm performing terrain analysis due to photovoltaic installation on QGIS with r.slope.aspect plugin. I'm interested in evaluate differently N-S slope and E-W slope based on the PV system I would ...
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1answer
25 views

Installing GRASS >7.0 and its addons to use in R session

I am hoping to use the openSTARS package that relies on GRASS 7.0 within R. However, I do not understand how to proceed with the initial steps. From: https://github.com/MiKatt/openSTARS A functional ...
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1answer
309 views

How to use GRASS GIS in Python standalone?

I'm trying to use GRASS module in a Python Skript. I already checked this: Is it possible to use GRASS GIS in Python stand alone scripts? and this Using Python script to control GRASS GIS from outside?...
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3answers
52 views

Rescale Sentinel2 data to 8 bit

I need to rescale Sentinel2 data (both lvl 1C and 2A) to 8 bit, because of the requirements of a GRASS GIS module (i.histo.match) that only works with values from 0:255. All the documentation of ...
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1answer
75 views

gdal_calc raster calculation fails on 28 GB GeoTiff

I am trying to do a raster calculations on a 28 GB GeoTiff using gdal_calc.py (3.0.4) but the process fails gdal_calc.py -A DEM_0.tif --outfile=DEM_1.tif --calc="A+0.33" --format=GTiff --...
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1answer
42 views

GRASS 7.8.3 problem with r.watershed and r.water.outlet

I need to find the basin of a small river and this is what I did: I found the drainage direction with r.watershed I used r.water.outlet to find the basin for the coordinates of the water outlet point....
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2answers
49 views

Problem with integration of GRASS-Gis in creating a process for PyWPS

Hey everyone:) It's possible that I have some kind of miss-conception in my head and just wanted to ask it here. I have a space-time-datacube in GRASS-Gis and now I'd like to create a process in PyWPS ...
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2answers
22 views

GRASS - r.mask analogous for vectos

I am working with r.stats. My analysis is about overlap Extreme Climatic Events (ECE) raster map with mammals range maps. I used to do my analysis first creating r.mask on ECE map and then applying r....

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