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.

learn more… | top users | synonyms

1
vote
0answers
35 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: https://...
1
vote
1answer
81 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.
0
votes
0answers
1k views

How to resample a raster in QGIS?

I've got a boundary file that I would like to resample the raster file from a 30m grid to a 10m grid inside the boundary file. When I try and do it in Qgis or Grass all I get is one big raster cube ...
1
vote
1answer
30 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 ...
0
votes
2answers
1k views

Why is this SRTM TIFF not visible in GRASS GIS 6.4.3?

I want to use interpolated SRTM data for Germany to generate an STL terrain map for use in a CFD application. My SRTM data comes from the OpenDEM project. SRTM data normally has voids, but this data ...
2
votes
1answer
80 views

Reproducing GRASS GIS network analysis tutorial in QGIS Field Calculator

Im looking to reproduce the assigning of road speeds as denoted in a GRASS GIS tutorial (v.net.alloc tutorial), where the road speed is assigned by road type (i.e. 'interstate' = 75 mph etc.) to then ...
1
vote
0answers
34 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
138 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 ...
3
votes
2answers
111 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?
3
votes
2answers
321 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
220 views

grass gis i.atcorr input should be reflectance or radiance

My question is what should be the input image in i.atcorr for grass 6.4.4 version? I tried giving both reflectance (DN) and radiance as input but values are coming properly. I read some where, it ...
2
votes
0answers
38 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
102 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 ...
1
vote
2answers
2k views

How to remove z & m coordinates from kml files

I've recently received some parcel data in shapefile format that has z & m coordinates (all = 0.0). The WKT for a typical parcel looks like this: "MULTIPOLYGON (((2672464.560700002 711396....
1
vote
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 ...
5
votes
3answers
790 views

LiDAR data density, returns per square meter

How can I compute a raster showing the number of return points per square meter using SAGA GIS or other open source software? My goal is to obtain a mask which would show me the places (cells) ...
1
vote
2answers
783 views

LANDSAT 8 i.landsat.toar error GRASS 7

I am a bit new to GRASS, but I have managed to get a lot of good work done thus far. However, the following error is really throwing me off, because I can't find any help anywhere for it. I am using ...
1
vote
1answer
23 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 ...
7
votes
1answer
426 views

How to create a topologically correct dataset in PostGIS (with GRASS)?

I have shapefiles which I have loaded in postgis and now i am trying to use geometric function in postgis like ST_intersect and they fail because the data is not topological correct. I have tried to ...
5
votes
3answers
6k views

New QGIS install can't find GISBASE

At QGIS startup I get the message: "QGIS couldn't find your GRASS installation. Would you like to specify path (GISBASE) to your GRASS installation?" (Windows 7) No amount of rooting around the ...
1
vote
0answers
37 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 ...
2
votes
1answer
132 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 ...
2
votes
1answer
1k views

How to make GRASS and SAGA tools capable to use in QGIS?

I installed QGIS, GRASS and GDAL by OSGeo4w package, and as I finish the installation, I want to use GRASS tool, I face this problem: But I already installed GRASS and SAGA, how to make those tools ...
2
votes
3answers
89 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 ...
1
vote
1answer
55 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 ...
1
vote
0answers
56 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: grass....
1
vote
2answers
39 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
37 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?
1
vote
0answers
33 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 ...
2
votes
1answer
40 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. ...
0
votes
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
vote
1answer
391 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. ...
6
votes
2answers
280 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 etc....
1
vote
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 ...
0
votes
0answers
99 views

QGIS Training Manual - Lesson 12.2.1 (GRASS GIS) - r.colors.table module does not color raster

I am going through the QGIS Training Manual, Lesson 12.2.1 ("Follow Along: Set Raster Colors) and noticed that the 'r.colors.table' GRASS module did not color my DEM raster layer which I imported via ...
1
vote
2answers
138 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
vote
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 ...
4
votes
2answers
724 views

Is it possible to produce a decent looking shaded-relief map at 50K-scale-or-larger using SRTM3 DEM?

I'm trying to make a decent-looking shaded-relief map of a particular area in 50K-scale-or-larger using open-source tools. The best (and free) option I have for DEM data for that area right now is the ...
1
vote
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
37 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 ...
0
votes
0answers
24 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
120 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 ...
0
votes
1answer
125 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.
1
vote
1answer
803 views

How to fix the grass7 package available from the ubuntugis-unstable PPA?

Out of the blue, grass stopped functioning this morning on one of the Ubuntu 14.04 systems I use: $ grass Starting GRASS GIS... python: can't open file '/usr/lib/grass70/gui/wxpython/gis_set.py': [...
3
votes
1answer
277 views

QGIS 2.10 with ubuntugis dependecies Grass issues Ubuntu 14.04

I saw in How to correctly install QGIS 2.8.3 with GRASS plugin on Ubuntu 14.04? how to get Qgis 2.10 running from the non ubuntugis repository with grass features but I'm still having problems with ...
2
votes
0answers
263 views

GRASS v.overlay.or Error when trying to split a polygon with a line

I am using the Grass plugin in QGIS for Windows (1.8.0). I am trying to split a polygon with a line feature. I am using the v.overlay.or function within the QGIS Grass plugin. I have the line layer ...
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 list_lines=...
1
vote
0answers
39 views

Multiply vector categories

I have imported a Vector map into GRASS GIS. There are some problems with the topology and some polygon areas overlap. I used 'v.clean' to break overlapping polygons and now I have multiple polygons ...
2
votes
1answer
396 views

GRASS 7.1 (dev.) i.landsat.toar error

I am working with Landsat 8 image acquired in 2014. I am trying to convert the raw image (DN) to Top Of Atmosphere Reflectance/Radiance (i.landsat.toar) in Grass 7.1 (still under development). The ...
1
vote
0answers
42 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 ...