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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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52 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
2k 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 ...
5
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1answer
719 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
381 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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126 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
62 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
44 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
71 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
51 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
249 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 ...
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1answer
39 views

Empty results from r.fuzzy.set in GRASS 7.4.2

I am trying to fuzzify a distance to roads tiff file using r.fuzzy.set in GRASS (installed with QGIS). I input the parameters (input layer, output, inflection points, fuzzy range, fuzzy boundaries etc ...
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1answer
65 views

Error - Grass 7 doesn´t run because isn´t not sucessfully installed

I am having problems to run GRASS7 from the processing tool. Always run the following error that is not corrected instaled. I ve reinstall QGIS several times, even tried different versions,as also ...
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0answers
208 views

Grass algorithm r.neighbors doesn't work in Qgis 3.4. How can I solve this? [duplicate]

When I try to run the algorithm it gives me this error: Traceback (most recent call last): File "C:/OSGEO4~1/apps/qgis/./python/plugins\processing\algs\grass7\Grass7Algorithm.py", line 411, in ...
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2answers
43 views

Breaking lines in PostGIS?

I have a roads table and I want to break the lines in the intersections like the v.clean tool from GRASS (I'm talking about how the break tool in the parameters works). How can I do the same process ...
2
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1answer
198 views

How do v.distance 'upload' parameters actually work?

I'm trying to use v.distance (using QGIS 3.4) to calculate the distance in meters between a layer of water shutoff points and the boundary of the nearest building footprint polygon. Even better would ...
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0answers
194 views

r.recode error with QGIS 3.4

Yesterday, I successfully ran the r.recode Grass-command from QGIS 3.2 Bonn on a Windows 10 machine to recalculate a DEM-geotiff. Today, I installed QGIS 3.4 Madeira and de-installed all older QGIS-...
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3answers
93 views

r.in.gdal tries to create file in incorrect repository

I am trying to import a DEM in GTIFF format with: r.in.gdal --overwrite input=$user_filename output=srtm_mosaik_utm -o but I get the message: Input contains an invalid SRS. WKT definition: LOCAL_CS[...
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2answers
103 views

supervised classification in grass gis

I am currently using GRASS GIS 7.4.1. I need some help here: when loading a geotiff made in QGIS to GRASS GIS, the bands that make the image are split (e.g.clip1@permanent, clip2@permanent, & so ...
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2answers
73 views

Splitting catchments in GRASS

I have the polygon of my catchment of interest, I call it catchment A (Reyran in the schema). (format *.shp). I have also the x-y coordinate of a dam that is situated in the catchment. I have also a *...
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2answers
100 views

Workaround for Intersection with points is not yet supported' GRASS Error

I am dealing with a line layer which I am unable to import properly into GRASS. After some work solving dangles and invalid geometry issues I managed to import it, nevertheless when I try to use v....
2
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1answer
70 views

Relating input data to output data in GRASS in QGIS 3

In QGIS 3 there are a number of useful vector tools available via GRASS functions. However, the output of many of these only contain 'cat' attribute in their output. For example, if I run the routing ...
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2answers
2k views

GRASS GIS Plugin not loading in QGIS 3

When starting up QGIS 3.2.2 (also tested with 3.2.3), I get the following message in the "Plugins" Log Message Window: 2018-10-18T08:03:48 WARNING Failed to load C:/OSGEO4~1/apps/qgis/plugins/...
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2answers
135 views

QGIS 3 r.texture no output

I cannot solve the mystery of no outputs in any case and in any experiment I have done with all kinds of parameters in the latest QGIS 3.2.3 Bonn and GRASS 7. r.texture does not provide any output. ...
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2answers
50 views

Specific methodology to call a GRASS function like v.transform with Python

I cannot understand if and how I can call with its parameters a GRASS function like v.transform through a Python script from e.g. PyCharm etc. Is there something comprehensible to understand? An ...
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2answers
102 views

GRASS algorithm in QGIS: v.to.lines

I'm using the v.to.lines algorithm (GRASS algorithm) to convert a layer from polygons to lines in QGIS. The algorithm works without problems but the output layer only has an attribute called "cat", I ...
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2answers
36 views

Purpose of comma in r.mapcalc in GRASS GIS 7.4

I would like to know the purpose of a comma in r.mapcalc of GRASS GIS. Consider this example - r.mapcalc "noise = if(landuse96_28m==1 || landuse96_28m==2, roads_buffers, null())" In the above ...
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4answers
216 views

Have DEM, need polygon outlining region above a certain elevation

I have a DEM in HGT format. I need to isolate all areas above a certain elevation and view them as polygons. Something like this (let's say the pink polygon is everything above 1000m): Seems like ...
4
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1answer
64 views

GRASS v.qcount in QGIS is returning insanely high counts

I'm trying to use GRASS's v.qcount command through the QGIS processing toolbox to conduct a simple quadrat point pattern analysis. I've run the tool on some projected point data, but I keep getting ...
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1answer
59 views

Error when importing data source from web using GDAL/OGR in GRASS 7.4.1

I am running the latest bundle of OSGeo4W with GRASS 7.4.1 I am following the tutorial in the following URL: Analysing the ECA&D climatic data, where I am trying to import data from web using ...
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2answers
240 views

DEM from Vector to Raster in GRASS GIS

I am using GRASS GIS 7.4 and I have a DEM as points in a vector format and want to turn it into a raster. I tried using v.to.rast and v.to.rast3, but the elevation is not one of the attributes so am ...
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0answers
108 views

Error with QGIS and Grass Tools

I wanted to use the r.viewshed tool in QGIS. Everytime I want to start the tool there is a error (german): Dieser Algorithmus kann nicht ausgeführt werden run :-( GRASS GIS 7 ist anscheinend nicht ...
2
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1answer
197 views

Can't call GRASS commands with Python on QGIS 2.18

I'm trying to run a grass command (v.split.length) using the processing library in pygis. The script is as follows: import processing layer = r'path\to\shp.shp' extent = QgsVectorLayer( layer, '', '...
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1answer
67 views

Install GRASS GIS extension r.pi including r.pi.prox and implement the Addon in QGIS

I would like to install the GRASS GIS addon r.pi within QGIS, I only have access to basic GRASS commands I installed QGIS using the osgeo4w-setup-x86_64.exe advanced installation using the http://...
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0answers
93 views

Convert polygons to lines ignoring redundant vertices in QGIS

Provided the following Polygons layer with 6 polygons (see image below), I would like to calculate each line's segment's angle (amongst other things), so I should convert those six polygons into lines,...
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1answer
72 views

Extract a line segment out of a polyline on the basis of numeric values (distances) defined as attributes [QGIS]?

I have a set of points (red in the picture) in a shapefile containing an ID as well as two numeric values representing distances in Meters for each point. After creating polylines for each point via ...
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0answers
28 views

v.surf.idw raster file conversion into a vector with same colours style

Is it possible to convert from raster to vector the raster file resulting from grass interpolation algorithm "v.surf.idw" coloured with the quantile method and maintain such colours in the vector file ...
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0answers
301 views

How to automate topology check/fix in QGIS?

Short version: I have a layer with 19483 features with plenty of topological errors and I would like to fix/review them as many as possible in an automated way but don't know how to do it. ...
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1answer
65 views

GRASS: Can v.buffer use geodesic distance like r.buffer does?

Question: In GRASS GIS, can v.buffer use geodesic distance like r.buffer does? If v.buffer can't use geodesic distance, is there a way to do vector geodesic buffering (ideally in GRASS, but I can ...
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2answers
67 views

Issue with exporting GRASS visibility graph to shapefile

I am rerunning code in GRASS that has worked in the past (about six months ago) and am now having problems. In the GUI, I have created a new mapset and imported the 'SimplifedCoastline' file to the ...
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1answer
29 views

How can I interact with PyGrass after a script is launched?

From Grass GUI 7.4.1, I launch a .py script (File > launch a script) that builds maps. How can I interact with the maps viewer, selecting the coordinates of some features, giving them as a new input ...
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1answer
296 views

Error creating Terrain in HEC-RAS

I am struggling to produce a terrian file with RAS Mapper. I have a .tif file produced from a .asc raster elevation and when I tried to add a New Terrain Model as described in the documentation I get ...
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1answer
104 views

Adding GRASS module to QGIS 2.18.21

I did a module in grass wich I called r.out.haralickFeatures.py. I did a .qgm. I can't get the parameters rigth. #!/usr/bin/env python #%module #% description: Compute asm, contrast, var, idm and ...
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2answers
165 views

v.surf.bspline and Interpolation(cublic spline) persistent errors in QGIS 3.2 & 3.3

I'm new to QGIS and as such I'm pretty hesitant to post anything, but I cannot for the life of me figure out why two raster creation techniques are not working. For the v.surf.bspline GRASS algorithm:...
2
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2answers
34 views

Translate manual operations to GRASS commands

I am new in GRASS GIS and i wanted to know how i could translate GRASS manual operations to GRASS commands in the console. I imported a raster and i was able to see the command r.import input=XXXXX\...
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0answers
118 views

QGIS Processing v.net.distance Error

I am hoping that someone can point me in the right direction. I am wanting to calculate the distances from a point to each point in another layer along a road network using v.net.distance. I have done ...
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1answer
153 views

Loading ADF file from National Elevation Dataset into GRASS with Python?

I'm trying to load data from the National Elevation Dataset into GRASS/Python, using this Python script (outside of GRASS): # Imports import os import grass_session from grass.script import setup as ...
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1answer
41 views

Entry point not found Error initiating GRASS GIS from Python

I cannot run any GRASS tools from within Python 2.7.15. While the GRASS environment, grass.script etc. are loading correctly and I can run basic checks like gscript.read_command('g.gisenv') gscript....
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1answer
45 views

Georeferencing CAD drawing and setting ground control points in GRASS?

I'm fairly new to QGIS and Grass GIS, and learning the interface. I have a CAD drawing that has no coordinate system assigned and needs to be georeferenced to NAD83 HARN Northern Colorado (feet). I'...
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1answer
96 views

Grass averaging raster not working with: Could not read georeferenced file error

I am trying to average geotiff using grass files using r.external and r.series. The geotiffs are georeferenced with wgs84. The command is below. grass74 g.proj -c proj4="+proj=longlat +datum=WGS84 +...
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3answers
2k views

Convert dwg (CAD) to shp in any open source GIS software?

I would like to do what's needed in a GIS (GRASS, QGIS, etc) alone, no other converters-only. The process is to read the dwg files that would be located in a folder and read them as shp and perform ...