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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561 views

Steiner tree problem: Optimal routes for Fibre planning on road network

I am trying to solve a large optimization problem where I have a set of nodes on a road network that need to be connected using fibre using the shortest possible amount of fibre. The problem is a ...
6
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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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358 views

Running v.clean tool in QGIS Python Console

How to use v.clean GRASS processing tool for break in QGIS from Python QGIS Console.I have tried using below command: processing.runandload('grass:v.clean', layer,\ 0,0.100000,'8132391.27018,8134827....
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1k views

QGIS cannot open output layers

I have problem with QGIS 2.0.1. Everytime I run tool from SAGA or GRASS, I get exactly the same error, for example: Oooops! The following output layers could not be open Channel Network: /tmp/...
4
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1answer
82 views

Cell Size and nonsensical results from GRASS r.walk

I've been wrestling with two main problems the past six hours. I am using 30m resolution aster/srtm merged dem. When I use the r.walk function to calculate a walking time surface from a point, the ...
4
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225 views

Activating GRASS utilities in QGIS Processing toolbox via text descriptors

This is a new follow-on question from this one. Following the documentation outlined in the answer, it is fairly easy to set up a descriptor text file for standard utilities that exist but aren't in ...
4
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162 views

Drawing “proportional” buffer using QGIS or GRASS?

I'm working on aquatic vegetation and have a shapefile representing floating vegetation in a lake. By some studies, we know that submerged vegetation extends for a certain extension based on floating ...
4
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0answers
337 views

How to build a GRASS network with node IDs from the line dataset?

I have a dataset of street network links (line geometries). Each network link has a link id, start node id, and end node id attribute. I want to use this network in GRASS, so after importing the lines,...
4
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0answers
686 views

Error when using r.watershed in QGIS 2.10.1 with Grass

I am running r.watershed within QGIS processing the I get the error below. I draw your attention to: GRASS_INFO_WARNING(2205,1): Subprocess failed with exit code 256 GRASS_INFO_END(2205,1) Does ...
4
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0answers
443 views

Option for 360 degree movie embedded in Open Source GIS software?

Is there any Open Source GIS software available to embed 360 degree movies with the map? For a COTS example, there is the Active Link Vision (ALV) extension for ArcGIS from IWANE.
4
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755 views

Problem loading output layer QGIS

Every time I run operations with temporary file output from the graphical modeler, I get the following error message: Oooops! The following output layers could not be open CLIP: C:\Users\Amine\...
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0answers
736 views

How to install grass addons when offline?

Can anyone tell me how can I install GRASS (v.7) addons on a windows PC when offline? I manually downloaded the files from http://svn.osgeo.org/grass/grass-addons/grass7/ and copied: - the .py file ...
4
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0answers
2k views

GRASS GIS - r.water.outlet - What is my mistake?

I'm new to GIS - more so in GRASS GIS. I installed GRASS GIS 6.4.3svn in my Windows 7 machine. No problem in installation. Downloaded SRTM-Geotiff file Location, Mapset all o.k Used r.in.gdal to ...
4
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1answer
994 views

QGIS GRASS Processing Not Working on MacOS?

Recently upgraded to QGIS3 (3.0.2) for MacOS (High Sierra) and encountered GRASS (7.2.2) issues. Tried adding a custom variable and now when running GRASS algorithms (e.g. r.reclass) I get the ...
3
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2answers
125 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 : ...
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 ...
3
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0answers
71 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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0answers
350 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 ...
3
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0answers
219 views

QGIS 2.18.17: python warning missing init

Every time I open QGIS 2.18.17, I get the following python warning in the protocol window: 2018-03-02T12:30:52 1 warning:C:/PROGRA~1/QGIS2~1.18/apps/qgis-ltr/./python\qgis\utils.py:607: ...
3
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0answers
52 views

Checking and enforcing downstream Z constraint for synthetic streams?

Assume I've delineated planar (X, Y) stream breaklines to use them for enforcement of bare ground DEM derivation from high density lidar data. The stream features are in a Z and M enabled polyline ...
3
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0answers
179 views

How to show Vector Layer created by v.clean GRASS tool in QGIS

I have created vector layer using GRASS tool v.snap, which resulted in a vector layer as output. I want to display the vector layer in QGIS. How can i view the vector layer created by snap tool in ...
3
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0answers
188 views

Making DTM from contour vectors in QGIS?

I have been using QGIS (2.18.0) for 6 months and now need to make a DEM from contour vectors. From my reading, I know I have to use GRASS. I am in the process of using this tutorial to achieve that ...
3
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0answers
68 views

QGIS - Layer missing polygons after pointsfile transformation

I'm using pointsfile transformation in QGIS for the georeferentiation of my layers. After the transformation the result some times has polygons missing like here: Why is this happening? How do I ...
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0answers
927 views

Using GRASS GIS/QGIS to georeference TIFFs in 3D space, vertically?

I am a geophysicist working for a small shallow surface geophysics firm. We create 2D slices of the ground showing data collected from various surveys. These are generally cross sections (TIFFs) of ...
3
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0answers
634 views

GRASS 7 commands in PyQGIS without results (QGIS 2.18)

I have tried to run different GRASS commands as part of a PyQGIS script in QGIS 2.18 and 2.14, without obtaining any result, e.g. for the following code: # Open raster fileInfo = QFileInfo(raster) ...
3
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0answers
157 views

How to accelerate v.generalize on massive vector data?

I have a big problem with my vector dataset (more than 1 million entities) and v.generalize in grass 7.0.5 and 6.4 (64 bits for both). I try to use Douglas method on this dataset but it is very very ...
3
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0answers
324 views

GRASS v.net.iso does not include all lines

I want to define catchment area for bus stops in small city. As a result of v.net.iso in QGIS with GRASS I don't get all highways in that city. Here are my steps: importing above layers into GRASS ...
3
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0answers
32 views

What does the blocking option do in GRASS r.watershed?

What does the blocking option do to the r.watershed program in grass? According to the manual, it should stop water from being routed past that location, but it appears to have no effect. I'm trying ...
3
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0answers
226 views

r.sun from QGIS toolbox doesn't give realistic value about the hours of insolation

I have a problem with the GRASS module r.sun when I run it in QGIS. I would calculate the hours of insolation in a specific site during a specific day. When I ran the algorithm "r.sun" from GRASS, it ...
3
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0answers
104 views

Calculating a specific distance from points along a network - GRASS

I'm currently using the v.net.iso function in GRASS (no access to network analyst in ArcMap). Does anybody know of a way to export the result to shapefile so that you have an individual line feature(s)...
3
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0answers
207 views

Wrong area using Albers Equal Area Projection in GRASS for Java, Indonesia

I am just getting to know GRASS 7.0 and I am struggling finding a good projection to work on a spatial analysis of Java, Indonesia. I am new to the forum, so if information's are missing for a better ...
3
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0answers
101 views

QGIS - WHERE SQL within a processing.runalg statement for v.surf.rst in python console

I'm creating lots of raster files with grass:v.surf.rst so rather than using the graphical interface I wanted to use the python console (and potentially put in in a script at some point). However ...
3
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0answers
87 views

v.clean batch process within QGIS 2.10 (PISA)

I get an error message when I try to create a batch for v.clean operation.. Algorithm v.clean - Toolset for cleaning topology of vector map. starting... local variable 'filename' referenced before ...
3
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0answers
1k views

how to orthogonalize building outlines

I'm looking for a way to orthogonalize building outlines which I've extracted from a high-res DEM. I'm using the FOSS GIS stack (QGIS, GRASS, SAGA, PostgrSQL, PostGIS) and can code in Python (or Java)....
3
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0answers
618 views

Performance difference between focal statistics (ArcGIS) and neighbor (GRAS or QGIS)

I tested minimum, maximum, and average neighbor (circle radius = 161 pixel) using ArcGIS, GRASS and QGIS: ArcGIS (10.1): it takes only one minute GRASS (6.4.3): it takes 123 minutes for every output ...
3
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0answers
269 views

3D interpolating

Our final year project domain is soil contamination modeling. We collected soil samples at the depths of 0.3 cm ,0.5cm , 1cm , 1.5 cm in about 25 locations. We considered 8 contaminants- p h, sodium, ...
3
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0answers
919 views

Import vtk file in grass or qgis

last summer I made the relief of a cave, and at this time I returned with Therion software. This survey is in 3d and I can save it in the formats .Lox, .3d, vtk. I would like to import it in grass or ...
3
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0answers
165 views

Extract representative slope profiles from hillslope polygons

With the help of the Whitebox Geospatial Analysis Tools I was able to easily extract hill slopes from a river network in combination with a flow direction map. Now I would like to extract ...
3
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0answers
483 views

QGIS 2.4 NVIZ Solution

I am going to ask this question better: What happened with NVIZ? I do not know the exact version that nviz stopped working but it seems around version 2 of QGIS. There are two ways to get to nviz in ...
3
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0answers
487 views

Why GRASS 7.0.0 can't create a table while importing shapefiles from QGIS?

I use GRASS7.0.0Beta1 and QGIS 2.4.0 on Windows8. With v.in.ogr, when I import a shapefile, I get the error message "Unable to create table". When I put the option of not importing the table, the ...
3
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0answers
183 views

IS it possible to run GRASS commands in the QGIS graphical modeler?

I have a geoalgorithm set up in the graphical modeler and everything runs except for the GRASS commands. It is really frustrating because when I execute these commands on their own they work just fine ...
3
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0answers
206 views

R.Neighbors with large neighborhoods?

I'm running into problems running the r.neighbors GRASS command in QGIS. Although it will run for small neighborhoods as soon as I increase my neighborhood above a certain number it becomes unbearably ...
3
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0answers
413 views

Getting an error when I try to import a loaded vector file to the QGIS GRASS Plugin

I am getting an error code when I try to import a contour line vector file GRASS via QGIS. I have been trying to create a DEM from the contour lines following this tutorial: http://linfiniti.com/2010/...
2
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0answers
33 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 ...
2
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0answers
48 views

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 ...
2
votes
1answer
161 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/...
2
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0answers
43 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? ...
2
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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. ...
2
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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 ...
2
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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....