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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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How to create elevation profile using SRTM and OSM?

I have a route came from OSM data ( lets say a line geometry ). And I have elevation files from Nasa's SRTM ( DEM files ). Is it possible to calc the elevation profile from that route line? It must ...
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12 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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26 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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Importing GRASS [on hold]

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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20 views

r.surf.area in GRASS GIS is giving issues [on hold]

I have generated a DEM and on running r.surf.area. It is giving a very small area.
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11 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
37 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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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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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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22 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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9 views

GRASS GIS - regroup raster values from range to one value

Using GRASS GIS is there a way to give a certain value for 3D raster cells that fall within a certain range, whether its by using module (reclass, recode, r3.mapcalc. Other alternative would be to ...
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Calculating Horton ratios on GRASS GIS?

I need to calculate the Horton´s ratios (bifurcation, lengh and area) for a group of basins. Is there a way to calculate them on GRASS GIS or with some other software that allows me to use the ...
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35 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 ...
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1answer
16 views

v.generalize in QGIS throwing “Unable to create table” error

I am trying to smoothen few polyline shapefiles using v.generalize in QGIS 3.4. But it's not working. Even i tried the same in QGIS 2.18. Getting the same error. Tried the same process in GRASS 7.4.2....
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1answer
52 views

Find radius of curve?

Using QGIS with GRASS I have found a route through r.drain but it has many sharp curve. the maximum radius of curve allowed to me is 176m. Is there any to reduce the curve sharpness to 176m or at ...
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11 views

Meaning of required parameters for Morans I of raster in GRASS

I have used the Polygon to Raster tool in ArcGis a convert a vector inside shape file to a raster in TIFF format using one of the vector attributes Using https://grass.osgeo.org/grass76/manuals/...
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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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18 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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24 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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11 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 ...
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1answer
87 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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27 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 ...
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9 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 ...
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1answer
41 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 ...
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1answer
73 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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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=...
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29 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 ...
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14 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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6 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 ...
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1answer
18 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 ...
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1answer
40 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 ...
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108 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\...
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1answer
56 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....
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1answer
42 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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1answer
38 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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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 ...
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1answer
156 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
36 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
21 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 ...
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1answer
124 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 ...
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1answer
24 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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38 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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60 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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42 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
81 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 ...
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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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34 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
21 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
63 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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2answers
54 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 (...