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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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12 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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15 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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37 views

Error whilsted using QGIS 3.4.4 r.series batch processing

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
40 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
32 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
18 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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29 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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12 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
25 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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0answers
22 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
50 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
62 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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27 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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0answers
24 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=...
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2answers
37 views

GRASS r.viewshed from Python with multiple raster tiles

I'm new to GRASS and struggling to do a viewshed across multiple tiles. I have got the GRASS r.viewshed function working from Python as follows for a single tile: gis_path = os.path.join(output_dir, '...
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1answer
38 views

DEM File “not found” Error when running r.watershed with Processing Toolbox in QGIS 3.4.2 with GRASS

I have downloaded a DEM from the NASA server with "SRTM Downloader". I want to find the watershed area, so I run the "r.watershed" function form the Processing Toolbox. However, I got a multi- "...
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0answers
61 views

Convert NetCDF(.nc) (TROPOMI Sentinel-5p) to GeoTIFF (GDAL, GRASS)

I tried converting NetCDF (Sentinel-5p) file to GeoTIFF file but I'm getting: D:\>gdalinfo 20181119T121048.nc Warning 1: Recode from UTF-8 to CP_ACP failed with the error: "Invalid argument". ...
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0answers
56 views

Clip raster by mask layer not working in QGIS 3.4.2?

I've been successfully using QGIS 2.18.21 to "clip raster by mask layer" and then run v.rast.stats. However recently v.rast.stats has stopped working in QGIS 2.18.1. The log does not show an error, it ...
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0answers
110 views

GRASS r.slope.aspect via QGIS 2.18 vs QGIS 3.4 - not working

I seem to be unable to replicate actions with GRASS tools when I access them through QGIS 3.4. In particular the r.slope tool. I receive error messages and it fails in QGIS 3.4. They seem to work fine ...
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1answer
20 views

d.rast.edit not yet implemented in the WxGUI

Am using GRASS to modify a raster and tried using d.rast.edit but am getting the following error when using it in the WxGUI Command 'd.rast.edit' not yet implemented in the WxGUI. Try adding it as a ...
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0answers
18 views

How can I get an HTML output on GRASS GIS?

I'm using GRASS GIS to create a simple map with some text (d.text) and vector maps (d.vect) and I can have a .png output with the PNG Display Driver (which I looked it up on https://grass.osgeo.org/...
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0answers
32 views

Unable to make use r.drain

I want to calculate a cost distance model between a source of raw material and a group of sites. Raster and vector data are in the same CRS (EPSG 32615). I was able to use r.walk and get my cost and ...
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1answer
60 views

point thinning/point selection based on distance threshold in QGIS/GRASS

I need to thin a point vector later based on the distances amongst points. So I have a threshold and wish to omit all records but one that is below a distance D representing a distance between points. ...
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0answers
43 views

Cannot see GRASS Processing Error(s) in QGIS?

I'm trying to run r.neighbors in QGIS 3.4.1-Madeira and can't find the log that comes up with what looks like a red error message. I've also tried a couple of other GRASS processing tools and they ...
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0answers
13 views

outputs of r.sim.water tool in GRASS GIS not showing

I was trying to simulate a water discharge process using the r.sim.water tool in GRASS under the hydrology tab. These were all the parameters used in the r.sim.water tool: r.sim.water -t elevation=...
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1answer
39 views

Blocking areas from consideration when running r.drain to calculate walking path from cost map?

r.drain was obviously originally intended to be used for drainage catchment, which is a problem when trying to find a least-cost walking path, as r.drain is happy to send you walking down a riverbed. ...
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1answer
51 views

Distance vs cost in QGIS network analysis

I'd like to calculate shortest route and distance in QGIS 3.2. In the past I have used the v.net.iso, v.net.distance and v.net.path tools. However, I've noticed that there is no distance parameter ...
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1answer
77 views

Using v.split in GRASS?

I'm trying to split several lines into bits of a maximum given length using v.split. First, I got this bug: UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe8 in position... which was ...
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0answers
47 views

Distance calculation with v.net.path in QGIS 3.2

I have 3 layers: origin and destination point shapefiles and network line shapefiles. I want to calculate the shortest path on the network between the origin (250 features) and destinations (20 ...
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0answers
10 views

GRASS supervised clasiffication

I tried classifying a certain satellite image to various land cover classes using the GRASS tool known as "interactive input for supervised classification". Prior to this I had incorporated the ...
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1answer
249 views

GRASS Processing not working on QGIS?

I've been having several issues making GRASS algorithms work from the Processing toolbox. When you fresh install QGIS 3.4 (MacOS High Sierra), first it doesn't find python -- which I solved by ...
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0answers
40 views

How to delete little geometries without hole in python script

I'm writing a python standalone script from a old PyQGIS script. Input data is a raster of which I would like to delete little areas. In the PyQGIS script, I vectorized it and used GRASS v.clean to ...
2
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1answer
34 views

Deleting floating lines from network using GRASS 7 in QGIS

I'm trying to find a way to remove floating line segments from a road network shapefile. Is there a relatively fast way to identify and delete these features? I've been using GRASS 7 in QGIS to ...
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33 views

Grass Gis: What is the meaning of a TARGET LOCATION?

I am attempting to follow a guide on creating ortho-photos in Grass GIS, available here: https://grassbook.org/extra/sample-chapter/ The chapter suggests that a separate cartesian LOCATION should be ...
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1answer
22 views

Why is i.histo.match missing from QGIS 3.x?

I'm trying to normalise and then mosaic two ASTER scenes (multiple bands in each). The GRASS tool i.histo.match has been suggested in a few places, but it isn't listed in the processing toolbox for ...
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1answer
30 views

TypeError during compilation of extensions in GRASS GIS using g.extension

I am using GRASS 7.4.0 on Ubuntu 18.04. I installed grass-dev using sudo apt-get install grass-dev, and then used g.extension v.centerpoint to try to install v.centerpoint. The output is below: $g....
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1answer
40 views

Remove overlaping vertices in lines - QGIS

I am currently working with data that has a huge amount of topological errors. These are lines that are closed, in the place where the beginning of the line meets the end, someone added more than 2 ...
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0answers
61 views

Error when trying to run GRASS 7 via processing toolbox in QGIS 2.18 on Mac

I have gone through the following steps: Installed the following packages that came with QGIS 2.18: 1 GDAL Complete.pkg 2 NumPy.pkg 3 matplotlib.pkg 4 Install QGIS.pkg Installed GRASS-7.4.1 from ...
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1answer
66 views

Clustering spatially connected polygons so all clusters have approximately the same size

I want to group together polygons from a shapefile a way that all the clusters formed contained approximately the same number of polygons. The problem is that the source polygons have vastly ...
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1answer
17 views

Erasing part of line vector outside raster region using GRASS?

I need to delete all the vector 'part' that it's outside the yellow raster region. How can I do it?
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1answer
21 views

how can interior basins be modified in the r.watershed GRASS function?

This is a follow up question to How does "Minimum Size of Exterior Watershed Basin" work in r.watershed command in qgis 2.18.12? I understood that the threshold parameter is used to ...
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2answers
399 views

QGIS 3.4 error: utf-8' codec can't decode byte 0xe8 in position 50: invalid continuation byte

I have the following error message every time I try to run a GRASS algorithm in QGIS 3.4. I unistalled the software and installed it again but I did not solve anything. Traceback (most recent call ...
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1answer
200 views

Error using grass v.clean: “ 'utf-8' codec can't decode byte… ”

I try running the v.clean tool using QGIS 3.4. As input I use a vector line layer (I checked the validity and everything is fine), but running the algorithm I get the following error: Traceback (most ...
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0answers
97 views

Dissolving large sets of polygons [closed]

We have many datasets, each containing about 150'000 polygons. We would like to dissolve each dataset down to about 2500 polygons, based on a given attribute. We've successfully done this using the ...
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0answers
30 views

Calculate the area of the drainage basin upstream of a point [duplicate]

I have the point location of vegetation surveys conducted on a river network. I would like to calculate the area of the contributing drainage basin upstream of each point using a DEM. This image ...
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2answers
33 views

How do I work with GRASS regions?

Every time I think I've started to get a very basic handle on QGIS, I get thrown for a loop. I tried to run r.flow today, and got the following error: ERROR: Elevation raster map resolution differs ...
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2answers
28 views

Cumulative cost upstream a raster stream network with GRASS

I have a river network in raster and locations of many dams on the river. In the image above, the BLUE point represent one random cell. Dam 1 is downstream to the cell. I am looking to calculate ...
5
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1answer
46 views

Getting WHERE statement to work in v.generalize?

I have a shape (its topology is terrible but I don't think it's the problem). I'm trying to simplify it to reduced it's size using v.generalise. I succeeded at reducing the whole shape but I ...
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0answers
45 views

Determining distance to nearest location along stream network by each cell using GRASS?

I have a river network in raster and locations of many dams on the river. In the image above, the BLUE point represent one random cell. Dam 1 is downstream to the cell. I am looking to calculate ...
3
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1answer
121 views

Batch distance calculation with v.net.distance

I have three shapefiles: one containing destinations the second containing postcodes the third containing the road network I want to calculate the distance between the postcodes and destinations ...