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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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1answer
108 views

Replacing multiple polygon features by their shared center point in GRASS GIS

I have three polygon features of the same category in a larger vector layer from which I would like to create a center point (mean coordinate) that holds the same attributes as the three polygons. I ...
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1answer
28 views

Area size of polygons with same value (building id) in GRASS GIS

Is there a way to calculate the area size of multiple polygons having the same value (in this case building number) like group stats in QGIS?
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1answer
45 views

Python scripting in GRASS

A script that worked fine one week ago, has errors and warnings now. I must have changed something. import grass.script as grass import numpy as np def main(): grass.read_command('r.import',input='D:...
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1answer
43 views

Opening .Jp2 image in QGIS on Mac?

I am trying to open a Jp2 file in QGIS 3.4.5 on a macOS 10.14.5 Mojave. I am new to QGIS and have been looking through forums that discuss GRASS and GDAL but I don't understand the connection to QGIS....
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59 views

Using Spyder (Anaconda) environment to execute GRASS Python script in Windows 10 [closed]

How can I set my spyder environment in order to use GRASS Python script in Spyder for Windows 10? I need to use some Python script from GRASS GIS. I am really new in Python and manipulate with scripts....
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9 views

GRASS GIS - r.in.usgs plugin TNM API Error

I'm having a problem with my GRASS GIS r.in.usgs plugin. I've never had this happen before. I'm trying to download any product (NED, NAIP, NLCD), but none of these work. ERROR: TNM API Error - [u'org....
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1answer
163 views

How to install GRASS Add-On after migration from SVN to Github?

I'm new to GRASS and in the past I have had no issue installing add-ons. Recently I tried to install "r.stream.order" and got the following error: g.extension extension="r.stream.order" Extension ...
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2answers
54 views

Creating new GRASS locations while looping in Python script

I am making a Python script for processing my data. import grass.script as grass import numpy as np def main(): f = open("D:\\Glaciers_selected.csv", 'r') fl = f.readlines() for x in ...
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109 views

Grass GIS: g.extension – Not found

I'm having problems trying to compile (r.landscape.evol and another) on the 7.6.1 version of GRASS from the g.extension command. It does not found the file in the default repository. I am running ...
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1answer
18 views

Error when trying to access variables in the GRASS startup program

I am able to create a new location using the Location Wizard, however I would like to create a GRASS location in a Python script, so I was figuring out this can be done from the console. In the ...
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1answer
46 views

GRASS GIS changes shape of tiff file when imported

I do have a raster which shows 13 rows and 16 columns when viewing it with Windows Viewer and also when using imread for loading it into python. I want to work with my dataset in GRASS. My steps: ...
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0answers
22 views

Using V.clean.snap?

I'm working on creating a road network of pedestrian walkways. Since all data were manually drawn, I'll need to snap the vertices together to form a consistent road network on which I can run routing. ...
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2answers
49 views

How to display a map from a script in Grass Gis 7.6.1

I am working with Grass Gis and spyder (IDE) and I am trying to display a map on "Spyder console" from the command line of spyder. I have a raster map call "elevation" and i tried this script: import ...
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1answer
165 views

3D population density map

I'd like to make a 3D population density map about a country. I've got all of the population data of the towns and villages etc. and I've got shp about these areas. I'd like to make a map like this:...
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1answer
88 views

v.voronoi.skeleton error

Recently, I was looking for way to skeletonize buffer and besides solution with PostGIS and Postegre solutions there is algortihm v.voronoi.skeleton. I have tried to use it with different road/rail ...
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1answer
33 views

QGIS i.landsat.toar not reading .txt file

I am having an issue with GRASS i.landsat.toar tool. It will not let me choose my metadata .txt file. I click on the three dots to the right of "Name of Landsat metadata file (.met or MTL.txt) [...
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0answers
47 views

Getting results from processing.run GRASS r.resample in PyQGIS

I am trying to get output from r.resample in a stand-alone PYQGIS application. The code runs and does not show any errors, but it does not save an output file (i.e. 'c:/path/to/output.tif'). As far as ...
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1answer
110 views

GRASS not working with QGIS 3.7

Like the author of GRASS not working with QGIS 3.6, I am unable to use Grass plugins, with the error: This algorithm cannot be run :-( The specified GRASS 7 folder "C:\OSGEO4~1\bin\bin" does not ...
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2answers
130 views

Automatically fill gaps and merge freshly generated polygons with the longest adjacent polygon

I get polylines automatically generated from AutoCAD from a colleague. Converting them into polygons with QGIS 3.6, I find out some sliver polygons and gaps in between, as shown in the picture below : ...
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1answer
43 views

GRASS 7.6 v.net.iso not providing output in QGIS 2.18

There are simply two layers in EPSG:31469 both are located on the Server side, see image below: points 'HST_Bestand_GK5' polylines 'vwESKN_1_25000_Teil' On my Windows 10 with QGIS 2.18 and GRASS 7.6,...
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1answer
26 views

start GRASS 7.6.1 with OpenCl from windows prompt

I desperately tried this code and variations: grass76 LOCATION_NAME=32632 GISDBASE=C:\Users\706774\Desktop\xxx\grass_database MAPSET=PERMANENT --with-opencl --gu but I get this error: ERROR:...
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0answers
135 views

QGIS GRASS plugin not found?

I have seen this question come up before and have tried the related fixes as best as I could but nothing seems to work. I am running the most recent LTR of QGIS, 3.4.8 but my GRASS plugin cannot be ...
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1answer
29 views

How to mask raster image (DEM) on QGIS Grass

I am doing research at graduate school. Using QGIS GRASS, I made a raster image (DEM) by spline interpolation from point data. Next, I decided to limit the range to within the vector (within the point ...
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1answer
55 views

R.Viewshed Not Working

Getting the following error message when running r.viewshed Processing algorithm… Algorithm 'r.viewshed' starting… Input parameters: { '-b' : True, '-c' : True, '-e' : False, '-r' : False, '...
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1answer
27 views

Extruding vector using one of its attributes in GRASS?

I'm following this tutorial: https://grasswiki.osgeo.org/wiki/Extrude_2D_polygons_to_3D. This is what I've done so far (inside GRASS): - Import a DEM HGT file: > r.in.srtm input=S23W043.hgt --...
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1answer
95 views

Retrieving lines radiating from point with v.select in GRASS GIS 7.6

I am attempting to select lines that radiate from a point using v.select in GRASS GIS 7.6 (also tested with 7.4.4) in Windows 10. I start out with 48 lines radiating from a point every 7.5 degrees. ...
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0answers
47 views

GRASS GIS: Time series of overland flow from r.sim.water

I am trying to perform an overland flow routing on a large area using r.sim.water in GRASS GIS. I've looked at other answers and made sure to set my computational region to the elevation raster I'm ...
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1answer
57 views

Generate a viewshed and merge it with another image using GRASS/GDAL command line? [closed]

I've found a tutorial showing exactly what I want to do (merge viewshed and hill shade or map) but unfortunately it is for QGIS users and I need it in pure command line instructions because I'm in a ...
3
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1answer
87 views

r.surf.contour for large area

I have a vector file containing contour with 2m accuracy, covering a large area (All Hong Kong). I tried to generate an elevation raster map with the file, by first rasterized the vector, using v.to....
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1answer
147 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
49 views

Error installing r.stream extension, GRASS GIS on MacOS

When I attempt to run: g.extension r.stream.order I get the following error: Fetching <r.stream.order> from GRASS GIS Addons repository (be patient)... Compiling... clang: warning: no such ...
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1answer
54 views

How to use GRASS v.buffer function in QGIS?

Trying to use the v.buffer function to create a 500-foot buffer (map units are in metres, which is why I put 152.4 meters as the buffer distance) around the boundary of a property parcel (not the ...
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0answers
38 views

GRASS GIS: From multiple lines to single line

This seems like a simple process but somehow I am not able to solve this. The situation is as follows: I have three separate lines which form visually 1 line. As I want to further process these lines ...
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3answers
105 views

Creating square buffers with v.buffer in GRASS GIS

I do not seem able to create a square buffer around a point feature with v.buffer in GRASS GIS v.7.4.4. The documentation states that "Using -s with a point vector map as input data, square buffers ...
3
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1answer
159 views

GRASS GIS producing different slope than GDAL?

When producing a slope in GRASS GIS 7.4 the results are different than with QGIS (GDAL) and ArcMap for the same input data and same parameter (Z ratio is 1.0 and degrees). QGIS and ArcMap generate ...
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0answers
22 views

How to work with a freshly imported vector?

I have a text file with points coordinates: $ cat ControlPoints.txt -10153967|8326376 -10621243|8176811 -11122894|8184333 -9657869|8379692 -10014696|8056719 -10014696|8056719 I import them with v....
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0answers
39 views

PyGRASS: storing attribute table values to variables

Goal: to store the sum of all values (lengths) of a vector map in a variable inside a Python script. This variable will later be shown to the user in a GUI. The computation time has to be as low as ...
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1answer
34 views

Computing x and y distances between two raster maps using GRASS GIS?

I am working with a maximum water elevation raster in which, similarly to using r.grow.distance, I am trying to extract the distance from the each null cell to the nearest water elevation cell. ...
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2answers
78 views

GRASS GIS: Computing center line of raster feature representing a river

My goal: Convert a raster layer representing a river feature (see picture) to the center line of the river stored as a polyline feature. Limitation: The whole process has to be automated. I can ...
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0answers
111 views

GRASS GIS: connecting vertices with lines along following Node Number

My goal: Convert vertices to a poly line describing the general route to have 1 line describing the center line of a river. Limitation: The whole process has to be automated. The raster can ...
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0answers
23 views

r.surf.area is underestimating area and giving negligible area

I am using r.surf.area in GRASS GIS to estimate surface area of a DEM. DEM is in EPSG4326 WGS84. It is giving a negligible area. Please give solution to this. Following is the output of r.surf.area.
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1answer
50 views

Creating Vector Attribute Field with Raster Value in QGIS

I want to create a new attribute field contains data coming from a raster in a vector file. I tried the GRASS v.drape tool but the analysis did not create any new field in shapefile. Also, I tried the ...
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0answers
23 views

Importing GRASS [closed]

I tried to run i.atcorr in a system in which GRASS GUI was not installed. I copied all the required libraries to one folder and set environment variable to that location. But while importing raster ...
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0answers
53 views

GRASS r.sun returns “ERROR: insol_time and incidout are incompatible options”

I'm trying to measure irradiance on a DEM using the r.sun tool in QGIS 3.6. I have grids for the elevation (EPSG:32735 - WGS 84 / UTM zone 35S), the slope and aspect (EPSG:4326 - WGS 84). I've tried ...
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1answer
90 views

r.surf.area command of GRASS GIS is giving a very small area

I am a beginner to GIS systems and am trying to calculate the surface area of a dem using r.surf.area command of GRASS GIS. The surface area it is giving me is unacceptable as it is very small. It is ...
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0answers
32 views

How to use the GRASS GIS v.net.timetable tool in QGIS?

The GRASS GIS v.net.timetable tool needs the following input information: (a) a vector layer with the network (b) a vector layer of points (from - to) (c) and the timetable. The GRASS manual on the ...
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1answer
74 views

GRASS: what to do when the SQLite database becomes busy?

Every now then the SQLite database used internally by GRASS becomes unavailable or locked and the modules do not finish (see example below). This happens with different modules, primarily when ...
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0answers
25 views

Converting vector to raster on-the-fly using GRASS?

EDIT: I later realized that, instead of creating multiple 256 x 256 tiles, I could just create a single image to overlay on the entire map. However, I'd still like to know if there are better ways to ...
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1answer
23 views

Regrouping raster values from range to one value using GRASS GIS?

Using GRASS GIS is there a way to give a certain value for 3D raster cells that fall within a certain range, whether it's by using module (reclass, recode, r3.mapcalc)? Another alternative would be ...
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0answers
59 views

Getting error running GRASS GIS 7.6.1

Here is the error notice I receive after starting GRASS GIS 7.6. I am not sure what is the source of these errors. I had reinstalled the application but it didn't fixed these errors. What are ...