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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6
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0answers
73 views

Calculate volume of space defined by multiple overlapping 3D polygons

I have thousands of 3D polygons scattered in space but they mostly overlap with many of their neighbors in big extent. Is there any way how to compute volume they define effectively? I would love ...
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51 views

Computing Moran's I for vector data in GRASS

Does GRASS allow for computing Auto-Correlation using Moran's I statistic from vector files. GeoDa and ArcGis can do this. But seems grass lacks this functionality https://grass.osgeo.org/grass76/...
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1answer
34 views

Can exporting geodata to OSM data format with less precision cause self-intersections? How to address it?

I have my geodata layers processed in GRASS GIS. Its internal tools report that the topology has no problems, such as self- and mutual intersections. Then I export the data to a GML file which then ...
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0answers
31 views

Wrong layer analysis using GRASS v.clean tool

I am using QGIS version 3.6 in macOS Mojave, version 10.14. I am trying to fix the topology of a vector layer using the GRASS tool v.clean. The first time it worked well. I forgot to save the ...
2
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1answer
129 views

Exposing GRASS GIS add-on in QGIS Processing framework?

Having QGIS and GRASS GIS 7 installed, how can I expose a GRASS GIS add-on, which has been installed using g.extension, in QGIS' Processing framework?
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1answer
30 views

How to apply smoothing filter only to way bigger than specified number of nodes, length, area?

I am try to smooth data obtained by vectorization of a raster image by applying a series of filters in GRASS GIS. Once of steps involves using the Douglas-Peucker filter. However, I need to apply it ...
0
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0answers
12 views

configuration file not found

Every time at startup this message shows (and reappears a second time after clicking it away). And everytime I quit QGIS 2.18 the same message shows. How do I get rid of it ? I imagine it has to do ...
3
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1answer
50 views

Cheapest path through polygons and lines from point to point

I want to find the cheapest path or the least cost path from one point to another point. The points are part of a vector map and do not lie on a network. All features being part of the map have ...
0
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1answer
325 views

Installation of QGIS 3.4.4 on Ubuntu 16.04 fails to install qgis-plugin-grass because of uninstallable grass760 dependency

I have used the instructions here marked Tested 29/06/2018 to install QGIS 3.4.4 on Ubuntu 16.04. While QGIS installs nicely I get an error on installing qgis-plugin-grass. Subsequently the Grass ...
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0answers
17 views

GRASS GIS - V.VOL.IDW interpolation interpolates same property vertically

When interpolating a 3D raster using v.vol.idw (ref), the vertical cross section show that the properties are the same vertically. v.vol.idw input=GEOMOD_March24@Toronto output=...
2
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0answers
40 views

Splitting line into two lines with GRASS GIS?

I converted a raster to polygon, after converting polygon to lines I have one line of the channel of a river which border a river. But I need to split this line in two lines: left border and right ...
0
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0answers
16 views

GRASS GIS - V.VOL.RST avoid segmentation (paneling)

In order to reduce the segmentation effect where the interpolation appears to have different square regions, is this due to segment that are too small (segmax?). Is the solution to avoid this to ...
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0answers
9 views

GRASS GIS - 3D raster, make voxels above DEM NULL (or remove them)

I am currently using r3.out.vtk to export a 3D raster to view Paraview (several million cells). With r3.out.vtk, you can create a 3D raster with a top and bottom, which is fine in itself. However, if ...
1
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1answer
25 views

Adding attribute based on Function in GRASS GIS

I would like to create a new attribute based on another attribute using a formula in GRASS GIS. I would like to do multiple 'if' functions embedded example: if attribute x = 1.2: 1e-6 if attribute x ...
1
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1answer
51 views

Connect two Shapefiles

I have two shapefiles which should be connected to one single shapefile without a gap, unfortunately there is a gap between them: I tried to use v.cleanin Grass GIS but because of the shape of the ...
-1
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1answer
360 views

GRASS GIS tools cannot perform on QGIS 3.6 Noosa

I am a fresh-hand to QGIS 3.6 Noosa. When I want to use GRASS GIS tools like r.recode, r.cost and so on, I am confronted with error information like this: The specified GRASS 7 folder 'C:\OSGEO4~1\...
0
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1answer
148 views

Opening Esri Geodatabase file with GDAL/QGIS/Grass?

EDIT: I have a 64-bit installation of QGIS but 32-bit Microsoft Office Access drivers. It has been suggested that this is the cause of the problem, which is also indicated in this post: https://www....
3
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1answer
73 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 ...
0
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1answer
40 views

CGIAR SRTM to xyz using GRASS GIS, with sampling

I have used CGIAR interface to select the tiles, like so: This resulted in a bunch of *.zip-files, and I have extracted them all into a directory. Next, I followed the instructions as https://...
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0answers
16 views

GRASS GIS - Create Mask for 3D raster using 2D raster interpolated Surfaces (top and bot)

I created a 3D raster using V.VOl.RST with GRass GIS, and i noticed that using r3.mapcalc, we cannot include 2D raster. I would like to keep the portion of the 3D raster that is between a DEM (top ...
2
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1answer
373 views

GRASS not working in QGIS, standalone

*Running QGIS 3.6, GRASS 7.6; have both Python 2 and 3 I'm trying to run a GRASS algorithm in QGIS, and none of the GRASS tools are working. GRASS also isn't working in the standalone version. I have ...
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1answer
110 views

r.stats output parameter error

The "r.stats" tool gives "ERROR: r.stats: Sorry, is not a valid parameter" error and it creates empty file.
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1answer
28 views

GRASS GIS - Keep raster below/above surface

I would like to clip raster where the surface intersect another surface and keep elevations that are below only. I am interpolating a vector into a 2D raster (v.surf.rst) for properties at a given ...
1
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1answer
188 views

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 ...
1
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1answer
38 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....
2
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0answers
45 views

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

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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0answers
66 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....
3
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0answers
69 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....
1
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1answer
154 views

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

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 ...
0
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0answers
15 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....
0
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0answers
47 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 ...
0
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1answer
25 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 ...
1
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3answers
74 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 ...
1
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2answers
114 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 (...
2
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0answers
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(...
1
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0answers
46 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, ...
3
votes
1answer
88 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 ...
12
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4answers
6k 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\...
1
vote
2answers
101 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 ?
1
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1answer
104 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 ...
2
votes
1answer
150 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 ...
3
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0answers
128 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 ...
1
vote
1answer
32 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´...
1
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1answer
100 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 ...
0
votes
1answer
32 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="...
0
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0answers
78 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 ...
2
votes
0answers
74 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 ...
0
votes
1answer
33 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 ...
0
votes
1answer
56 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?
1
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1answer
19 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 ...