GRASS GIS (Geographic Resources Analysis Support System) is a free, open source geographical information system (GIS) capable of handling raster, topological vector, image processing, and graphic data.

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3
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1answer
125 views

Get results from using GRASS algorithms with the QGIS processing tool

I am trying to write a plugin in QGIS that uses at some point a GRASS algorithm : "v.split.length", accessible by using the processing class, and here is how I am using it : ...
3
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0answers
54 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 ...
1
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2answers
80 views

Vector to raster conversion [solved]

I'm using GRASS but, in case, I'm also familiar with R and QGIS. I'm trying to convert a vector area map into a raster one. My problem is that the resolution of the raster is too low (and I can't ...
0
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0answers
25 views

A vector object not being replaced in temp folder when using 'for' loop in R

I am currently running GRASS GIS through R interface and got stuck at this point; where I am using a 'for' loop in R, and the code is as follows: for(i in 1:nrow(Snapped_SSP_DSN)) { ...
4
votes
2answers
77 views

How can I calculate flow length in QGiS/GRASS?

I have these rasters: DEM Flow Direction Flow Accumulation I would like to calculate the flow distance of every pixel to the outlet of a basin. In Arc-GIS, I can use the flow length. But I don't ...
0
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0answers
23 views

GRASS: strange classification output and reject map from “i.maxlik”

I am trying to perform a supervised classification with "i.maxlik". I have three bands: 1) elevation (a dem); 2) reflectance (derived from Landsat ETM+ band4); 3) cumulative solar radiation (derived ...
2
votes
1answer
49 views

Error while executing v.rast.stats command in grass plugin in qgis

I have a vector polygon which I imported in grass. I also have a raster from which I have to extract the value. I ran v.rast.stats command in QGIS 2.12. The command was executed with error. The error ...
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1answer
46 views

Unable to open shapefile with GRASS GIS? [closed]

Is GRASS GIS able to work with a shapefile (*.shp)? I can´t open my shapefile (328000Kb) in that program. I want to dissolve a shapefile in GRASS because on QGIS the process is very slow.
4
votes
1answer
112 views

What happened to the GRASS Browser in QGIS?

In the past I could display the imported layers in the GRASS toolbox within QGIS. This was possible under the tab "Browser" as you see in the image. Lately I'm missing this tab. The QGIS version is ...
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0answers
65 views

Making GRASS GIS 7 Ubuntu bash file work on Windows 7

I have created this bash file (.sh) while working on watershed analysis stochastic simulation in GRASS GIS 7.0.2RC1, which is running on Ubuntu. It worked perfectly and I received the correct results. ...
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0answers
34 views

i.spectral tool error

system description: Windows7 32 bıt OS, Grass GIS 7.0.0 Gnuplot 5.0 Solution attempt 01: On the basis of following thread, commented out said path check lines from i.spectral.py script: ...
1
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1answer
71 views

how to calculate the mean value of pixels of a raster in Grass plugin in qgis?

I am using grass plugin in qgis 2.12. I have to estimate the average value of all the pixels but don't know how to do it.
1
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1answer
26 views

Calculating Categorical Raster Areas per Polygon

I've got forest fragmentation data from which I've extracted pixels that correspond to forest edges and patches. I've also got a shapefile of counties in a US state. I'm trying to get the area of ...
1
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0answers
29 views

grass r.watershed to larger rivers parallel lines to same stretch

I'm trying create stream channels with r.watershed grass64. However, it shows two or three parallel lines for the same stretch of river. The river is large in some parts, but is just one river. Does ...
4
votes
1answer
109 views

GRASS 6.4 Reinstallation for Ubuntu

I need to reinstall GRASS 6.4 on this Ubuntu computer due to compatibility issues. I had installed GRASS 6.4 a few weeks ago to work with a simulation program. I used the command apt-get install ...
2
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0answers
36 views

C/C++ function to return minimum set of points required to represent a geometric shape

I am looking for a method from Grass, GEOS, or similar that will delete those points in a geometry which do not affect its shape. Example 1 +----+----+ p0 p1 p2 p1 can be deleted without ...
4
votes
1answer
86 views

Why can't I see v.net in QGIS GRASS tools

I have noticed answers such as Is there an open source tool to planarize graphs? stating you can use GRASS v.net from within QGIS. However I can't see it - my QGIS processing GRASS toolbox contains ...
32
votes
4answers
802 views

Generating equal sized polygons along line with PyQGIS?

I would like to create polygons along a line to use them for AtlasCreator in a next step. ArcMap has a tool called Strip Map Index Features. With this tool I can choose the height and width of my ...
2
votes
1answer
75 views

windows can't open the file, v.in.ascii

I am using GRASS 7 for windows, and I'm having trouble running v.in.ascii, although I'm fairly sure I've run it successfully before. When I run v.in.ascii, I get an error: Windows can't open this ...
3
votes
2answers
282 views

Least cost path between various points QGIS

Is there an easy way to find the least cost path (LCP) between various points in an open source GIS? This question has actually already been asked here: How to find a least cost path through several ...
1
vote
1answer
22 views

What projections and input file parameters are supported by r.resamp.rst?

I always get ERROR: Unable To Seek after I run r.resamp.rst r.resamp.rst input=map30 ew_res=10m ns_res=10m elevation=map10 It actually starts to work but after it finish I get the error and no ...
3
votes
2answers
510 views

How to make GRASS 7 addon available in QGIS 2.12?

I stumbled across the GRASS-Tool i.segment but could not find it in my QGIS processing toolbox. I found out that it is an addon for GRASS 7 that I already installed in GRASS 7 standalone. How can I ...
3
votes
2answers
101 views

Grass GIS: Number of CPU cores to use

E.g. in SAGA GIS it is possible to set with one click the number of CPU cores to use during processing. Is this also possible in Grass GIS?
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0answers
43 views

Issues related to lack of Landsat 8 Metadata usage in i.landsat.toar run [duplicate]

In my application of i.landsat.toar, I am coming across an issue for which there is previous precedence. LANDSAT 8 i.landsat.toar error GRASS 7 Computer Basics: Data Used: Landsat 8; Operating ...
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0answers
36 views

How to determine Grass (i.atcorr) tool control file's “visibility for the aerosol model [km]” value

In Grass, the Atmospheric Correction tool (i.atcorr) reference do not provide information with regards to the parameter "visibility for the aerosol model [km]"stated in the control file.I have ...
1
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1answer
51 views

Regarding Atmospheric correction and Elevation DEM Projection system

I am trying to conduct atmospheric adjustment of Landsat 8 image bands using 6s algorithm (i. atcorr grass gis tool). It seems, in the input section, an elevation raster map should be provided. In my ...
2
votes
2answers
129 views

How to calculate the distance to the nearest water source?

I have a polygon hydro layer of my study area and am trying to calculate the distance to nearest water bodies from my site. Since my site are 2km*2km grids I am not sure how to calculate it? Whether ...
2
votes
1answer
36 views

Why there is no “View Output” button for the command “v.to.points” in Grass plugin in QGIS?

How do i get or where do i get my output vector point layer after i run the command v.to.points to my vector line layer?
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2answers
38 views

Resetting 'cat' column in GRASS?

I've got a regular polygon file that looks like this: Unfortunately, this file stems from a v.overlay so that the 'cat' values are are a bit messed up. I would like them e.g. to start in the upper ...
2
votes
1answer
39 views

Matching raster regional extent with vector region in GRASS?

In Grass GIS, I am able to import bathymetry .tif raster data however the region coordinates are not in lat/lon formar and therefore, do not overlay with my vector points which are in lat/lon format. ...
2
votes
1answer
46 views

Problems to use v.what.vect in GRASS7

I have problems to use the function v.what.vect and I'm not sure what is the issue. I have a simple forest polygon and try to determine if a point is in the forest or not. # check the output of the ...
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0answers
36 views

GRASS: Site Analysis using address lists in vector maps

My objective is to analyze and optimize the distribution of sites (e.g. shops) in a certain area.In the end I want to be able to answer questions such as: How much farther or less will customers ...
1
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0answers
31 views

Extracting distances along a line from postcode a centroid to the nearest point (bus stop)

I'm looking to measure the distance from postcode centroids (point file) in a city to the nearest bus stop (point file) along the road network (line file). In Qgis I can calculate the distance but ...
6
votes
2answers
248 views

Skeletonize vectors in QGIS/Python

I am trying to find a tool to create a skeleton of a large vector dataset using QGIS and its bundle. It should be directly programmatically callable through Python or commandline (QGIS, GRASS, OGR ...
1
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0answers
49 views

GRASS GIS i.landsat.toar hangs & holds CPU at 100%

I use python scripting to automate processing of several Landsat 8 scenes. I use a VPS (4 core, 8GB memory, SSD) running Ubuntu 14.04 with GRASS 7.0.1 Line in script for i.landsat.toar: ...
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0answers
27 views

Best way to store, elaborate and query raster data [closed]

I have created multiple raster images with GRASS-GIS (~150Gb), that I'll need to multiply for a certain coefficient, and query the results that need to by saved just temporally. The portions of the ...
1
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0answers
46 views

G_Malloc error for Grass module(r.stream.extract) in R

I am having a big issue of this G_malloc Error while using a module of Grass (6.4.4) (r.stream.extract) in R. Initially I thought my computers configuration was low, So I switched to 8gb Ram 64-bit ...
1
vote
2answers
125 views

Tool or program to clean polygon dataset

I have a polygon dataset (shapefile, mapinfo tab file) which I would like to "clean" to be topologically correct. The polygons are assigned an ID which represents a specific class. For example ID 3 is ...
1
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0answers
28 views

Raster statistics change after re-projection — which one is correct

I'm looking into some global DEMs (like ETOPO1 - http://www.ngdc.noaa.gov/mgg/global/global.html), and noticed that the statistics for the elevation values can change quite a bit after reprojecting ...
2
votes
0answers
36 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 ...
2
votes
1answer
124 views

Atmospheric Correction Model Output for Landsat 8 Image?

Following are my procedure, observation and question/ request: Data Source: Earth Explorer Landsat 8 Grass GIS Version: 7.0.2 RC1 Windows 7 32 bit OS I have been trying to conduct an Atmospheric ...
0
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0answers
21 views

TIF file is black in GRASS when imported

I'm trying to input a TIF file into GRASS. Dimensions: 11617 x 15489 Size: 514 mb Color Palette: 2 colors (black background, white polygons). Layers: one layer Compression: none Software used for ...
2
votes
2answers
97 views

Missing v.in.ogr module of GRASS in QGIS Processing toolbox?

I am a new user to QGIS/GRASS and I am having a problem utilizing GRASS. I have several files that I generated in QGIS that I want to import into GRASS so I can use some of the Grass modules. ...
0
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1answer
98 views

Determination of Soil Moisture for a Region Using open Source Data

I want to derive soil Moisture for a region using Landsat and Microwave data could you please help me with the procedure.
3
votes
1answer
121 views

Get ID for each single v.to.points point in GRASS?

How do I get for each v.to.points point an ID in the database (DB). So far I splited the line (each 10m) but it returns only one DB entry for each original line. v.db.select line cat|Id|Name ...
2
votes
2answers
107 views

Points that get created in the wrong order when using e.g. QChainage?

I have a polyline layer (road) that I want to use to get a point layer with 1 km between the points. I have tried both 'QChainage' and 'Locate points along lines' to do this. They both work, I get ...
1
vote
1answer
67 views

Reading files from grass into R with loop

I have a connection between GrassGIS and R. I want to read thousands files from my mapset into R. I have lines with names "line1","line2"... I know I have to use a loop for this so I did ...
1
vote
1answer
373 views

How do I install qgis lyon with grass access

I am working wit a win10 64 bits 16mb of ram. I want to install Lyon on my computer and not get rid of 2.83. My 2.83 is a stand allone install. I thought I could install Lyon usion OSGEO 4w installer. ...
1
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0answers
39 views

How to determine aerosol model value for i.atcorr in GRASS? (Using Aeronet data)

I am trying to conduct atmospheric correction of landsat 8 image using i.atcorr of Grass GIS. In thıs regard, I need to know Aerosol Optical Depth (AOD) as stated in Grass wiki page. I've found some ...
2
votes
3answers
84 views

Storing large number of mapsets with many raster maps

OS X El Capitan, GRASS GIS 7.0.1 I have a location with about 530 read-only mapsets with each about 2600 raster maps (plus PERMANENT and one link to a read-write mapset), overall 11.255.481 raster ...