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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Combine duplicate geometries into single records with v.clean in QGIS 3.6

I have a points file that contains multiple duplicate geometries. I am using the QGIS "Processing Modeller" to clean up data, and want to identify duplicate point geometries and combine so that I ...
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Running pygrass on Linux(Mint) based on GRASS 7.8

I want to try out the pygrass API and I dont want to use GRASS cli. I would like to write a python script, import the pygrass and play around with common algorithms eg distance, buffer etc. On my ...
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7 views

basin layer from r.water.outlet Tool has values but is not rendering anything

I'm trying to deliniate a watershed with QGIS and used this tutorial to do so https://geogeek.xyz/catchment-delineation-with-qgis.html 1) r.fill.dir to create depressionless DGM 2) use r.watershed ...
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Incorrect result when using v.net.distance on grass76

As shown in the image below I need to connect the points in yellow to the respective nearest point in brown via the shortest path on the road network in blue. I decided to use v.net.distance on ...
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Combining cost analysis and voronoi-like area interpolation regarding slopes

I have DEM raster data of an island and I have 10 points (cities). My task is to map the island into areas. Inside these areas everything must be nearest to the corresponding city/point, and each ...
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23 views

Routing for Waste Collection (U-Turn problem)

A general question about routing problem: I am working on waste collection problems and I am having some trouble with some routing problems (the truck has to pass by every bin). So far I have tried a ...
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28 views

GRASS error after installation

I have installed GRASS GIS 7.6 and when launching it, the next error shows: ERROR: The APPDATA variable points to directory which does not exist, ask your operating system support Exiting... Press ...
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28 views

Connecting points to lines via network layer in QGIS

So I have a set of three layers: A set of points A road network layer A line layer (e.g. which represents a cable) I need to find the shortest paths which connect the points (Layer 1) to the line ...
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Wang's Bend Simplify in QGIS

I am looking for an alternative to ESRI's Simplify Polygons - Bend Simplify method (I only have a Basic License). Is there an existing QGIS plugin which supports this specific polygon simplifying ...
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27 views

Get error using r.reclass in QGIS 3.4

I am trying to use r.reclass function on a Land Cover raster in QGIS 3.4. The operation is quite basic stuff and the settings are attached below. However, I get an error that prevents the creation of ...
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22 views

Using v.net.connect on QGIS 3?

I am trying to find out if the v.net.connect GRASS tool is on QGIS 3.4 because I'm not finding it anywhere in the toolbox. I have to be reverting to QGIS 2.18 to run this tool.
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72 views

Getting the 'memory:' layers after grass7:v.clean processing using PyQGIS?

To repair geometries errors, I'm now trying processing (grass7) using PyQGIS. For one polygon layer (QgsVectorLayer: 'hn_pg'), I wrote the below script and run the grass7:v.clean algorithm. The ...
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Error with v.net

When running v.net on CentOS 7 I ran into the following error: GRASS 7.6.0 (srilanka2):/tmp/final > v.net input=roads points=bs output=network op=connect thresh=5000 Copying features... 100% ...
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86 views

QGIS 3.8 not running GRASS

I am having trouble initializing the GRASS plugin.I've tried un-installing and re-installing QGIS already. But the following message keeps appearing. GRASS init error : GRASS was not found in '/usr/...
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12 views

Error when running v.net.distance

I'm running grass76 on CentOS 7. When I have a network map (generated using v.net) with layer 1 having the arcs and layer 2 and 3 having the sets of nodes that I need to connect. Details are as ...
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29 views

GRASS functions doesn't work on QGIS 3.8.1-Zanzibar

I have been trying to run some GRASS functions on QGIS 3.8.1-Zanzibar. But the following message keep appearing as the algorithm doesn't compile well. The following layers were not correctly ...
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19 views

Shortest Paths Between Adjacent Points on a Network

With the project I'm currently working on I need to calculate how much the total length of the network increases as I expand it from one node to the next. I have the road network as a line layer (...
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15 views

QGIS changes CRS for new layers using GRASS toolbox functions. Is that normal?

I noticed that QGIS changes the CRS of newly generated layers, that is, I have a layer in my desired CRS, then I use a toolbox function with that layer as input, and the resulting layer is often in a ...
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49 views

Nearest line to polygon based on equal attribute

I have a polygon shapefile and a line shapefile with several thousand features each. I want to get: The nearest distance between a polygon and a line that have the same attribute (e.g. ID). Example ...
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33 views

Least Cost Path in QGIS: Plugin or SAGA or GRASS?

I downloaded a SRTM file and followed this tutorial and now I have a hillshade layer and a color layer. It looks like this. I want to calculate the least cost path between p1 and p2. But I'm not ...
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9 views

Terminal connection error when running v.net.steiner

I am using GRASS 7.6.0 on a CentOS server. I've attempted to run the v.net.steiner function on the map layer with the following properties: Layer/table: 1/network type count min ...
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1answer
24 views

Passing a parameter to GRASS_BATCH_JOB shell script?

This sort of builds off of my previous question about GRASS but it is a different issue. I have a Python script which should kick off a GRASS batch job in a docker container like so: grass_batch_job ...
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30 views

GRASS GIS: creating raster with a certain gradient and extent

Constraints - Use only GRASS GIS - Automated using pyGRASS Input DEM River raster OR river as vector (both are computed) gradient of the valley (as a float) vector line with direction and magnitude ...
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1answer
36 views

Create multiband raster from a single band raster with fields

I have a raster which has a single band containing what is effectively a lookup code. When I open the raster in ArcMap and open the attribute table I can see several fields which I guess come from the ...
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7 views

i.landsat.dehaze add-on for Grass 7.x

What happened to the landsat add-ons i.landsat.dehaze and i.landsat.trim in grass7? I keep seeing references to them but cannot find them in the repository.
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39 views

Creating a GRASS GIS Docker container with a mounted volume

I'm attempting to build a Docker container (based on an image that includes an installation of GRASS 7.6) which includes a mounted directory into which the outputs of analysis are stored for later use....
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41 views

GRASS GIS Segmentation issue on UAV image

I tried i.segment to perform segmentation on a part of UAV orthophoto image, but this always results in stripe-like rectangle segments which I do not expect. Could anyone figure out what happens? ...
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32 views

GRASS command line: r.thin produces no output

I am trying to use GRASS on the command line, specifically the r.thin module. It seems to execute properly but I have no output raster dataset to work with afterwards, it is as if it just gets ...
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16 views

Running v.net.steiner in segments?

I am using GRASS GIS 7.6 on a CentOS server with 157 GB of RAM. The vector categories of the network layer that I need to run the Steiner tree algorithm on are as follows: Layer/table: 1/network type ...
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1answer
32 views

Error when importing shapefile as vector layer into GRASS GIS

I'm tried to importing an Esri shapefile into GRASS GIS using both v.in.ogr and v.in.import however methods fail with the following error message: WARNING: Table <roadsSriLanka> linked to ...
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11 views

QGIS Network - OD matrix within local neighborhood based on line feature length

I have a given road network dataset as polylines and want to create a network out it. For that, I found v.net from the GRASS GIS toolbox. Now (1) I'd like to get the OD matrix from the intersections ...
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26 views

Running GRASS GIS on Text-based interface alone

I'm required to run GRASS GIS functions on a CentOS 7 server using the GRASS Text-based interface as it is not possible to use the GUI. I basically want to import some shapefiles as vector layers and ...
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8 views

Category Values parameter for v.net.steiner

So I need to extract the steiner tree along a line network connecting a set of points. The one part I don't quite get is what to add for the required Category values parameter. I initially thought ...
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18 views

Error when using v.net in GRASS GIS

I'm new to using GRASS GIS and GIS in general. I have a point layer and a line layer which I added on to the layer tree using two .shp files. I need to use v.net tool to create a network by connecting ...
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1answer
19 views

GRASS: r.to.vect outputs empty layer when creating lines

I am trying to convert a binary raster to polyline using r.to.vect in QGIS 3.4. It keeps giving me an empty output, however. This is my input raster: And I am expecting an output (more or less) like ...
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25 views

Raster analysis , Proximity (raster distance)

This is my first message here. I am trying to create a proximity map with the Raster analysis tool. My problem is that I only get two options for distance units , pixels coordinates and georeferenced ...
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16 views

Identify incorrect boundaries in GRASS GIS

I have used v.overlay option=not to find the intersection between two very large polygon layers. When I run v.build -e errors=filename_err I get WARNING: Number of incorrect boundaries: 2 Using ...
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1answer
32 views

Using data from 30-meter DEM map to fill into missing pixels in 8-meter DEM map

I have a DEM map of 8-meter resolution, where some groups of pixels are blank due to the clouds (I guess). Is there a way in ArcGIS or GRASS to fill into those null areas with data from 30-meter DEM ...
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35 views

GRASS GIS r.mblend: Data base element issue

I'm using r.mblend within Grass GIS v7.6.1 on Windows, attempting to merge higher resolution raster files (1 m) with lower resolution (5m). All is running until the print out step "Dropping extra ...
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21 views

Associating file with data point? [closed]

Is it possible with GRASS or QGIS to link a data point on a map with a report of some kind (photo, pdf, graph etc)? I am interested in this feature, to facilitate data entry from the field, ...
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1answer
107 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
27 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
41 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
36 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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45 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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8 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
157 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
45 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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101 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
17 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 ...