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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1answer
63 views

Underwater terrain modeling

My task is to model the surface of a lake bed, calculate volume of it and visualize it as 3D a surface. I have acquired depth measurements in a small lake using echosounder. The precision should be ...
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0answers
48 views

best method for gridding or interpolating elevation data

I wonder if someone can recommend the best method for gridding elevation data in QGIS, GRASS or similar. The elevation data I have is collected along 1m spaced lines at approximately 1 reading per ...
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1answer
25 views

3D rubber sheeting using ground control points

I have 3d lines that I would like to rubber sheet or rectify in 3D (including z rectification). I used ogr2ogr with -gcp, however all the vertex of a polyline were set to a single elevation, and since ...
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1answer
42 views

Import shapefile into GRASS in QGIS

I am using the GRASS interface in QGIS 2.4. I have successfully imported my shapefiles into GRASS using v.in.ogr, but when I try to then use a GRASS tool, like v.net Network maintenance, the select ...
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1answer
27 views

Create Addons for GRASS GIS

Is there a complete guide - example describing how to create an add-on/plugin for the GRASS GIS? I would like to extend the GUI with extra menus and toolbars creating extra functionality.
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18 views

Cost Surface No sense Results. GRASS

I have some doubts with the generation of a cost surface with r.walk of GRASS. It's assumed that the resulting layer is measured in seconds, but when I try to convert seconds in days march (6h per ...
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1answer
25 views

How to batch export using r.out.gdal command in GRASS

I created a list of files (NPPFILES) using g.mlist command in GRASS 7. Now I would like to export these files as .tiff files. I tried this command in GRASS prompt for files in $NPPFILES; do ...
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0answers
21 views

PostGIS commands in GRASS

How does the geometry get referenced in GRASS when using a PostGIS command like st_within? e.g: echo "UPDATE file SET within=(select file2.name from file, file2 where st_within(file.geom,file2.geom) ...
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1answer
41 views

r.sun delievering unrealistic Values

I need your help. I'm trying to calculate the global irridiation for a specific area. I'm interested in the results for rooftops in special. I have a DEM, calculated slope, aspect and horizons and ...
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1answer
26 views

Preserve polygon boundaries when vectorizing a raster according to a polygon vector

I have a raster which I clip by some polygons and then convert to polygon. I would like to obtain the same number of polygons in both my vector files. The problem is that some areas in the vector ...
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0answers
37 views

How to reference a number variable in r.mapcalc within QGIS graphical modeler

I need to run the following formula in r.mapcalc: (xor(abs(A-B),abs(A-C))>120)*A I would like to however use a user defined number input variable instead of the 120. I already have this variable ...
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0answers
71 views

How to create least-cost path between two polygons with GRASS?

I am completely a beginner in GRASS but I would like to use it to have the cumulative cost of moving between two polygons. More exactly, I would like to get the smallest cost from any point situated ...
0
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1answer
43 views

removing spurious lines in raster before or after vector conversion?

I'm looking for a feature/function in either python opencv/ndimage/gdal/etc. or qgis/saga/grass that will help clean up a skeletonized image that I'd like to vectorize into a shapefile of ...
2
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0answers
80 views

Pan sharpen Landsat 8 using Grass 7

I have followed this great tutorial on pan sharpening using Grass GIS 7 (I'm using beta 3). Everything in the tutorial seemed to have worked, but my final output is not as expected (pictured below). ...
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0answers
19 views

Free And Open Source Software Tools to orthorectify Pleiades imagery [duplicate]

Are there Free And Open Source Software Tools to orthorectify Pleiades, Worldview And Quickbird imagery as we do with COST tools such as ERDAS Imagine, PCI, ENVI, etc.?
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63 views

3D visualization of terrain data and orthophoto using GRASS NVIZ via QGIS

How can I make 3D visualization of terrain data and orthophoto using GRASS NVIZ via QGIS? I am quite new with GRASS. I have only managed to get a 3D view of the terrain so far.
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0answers
71 views

QGIS Grass Processing toolbox

I'm trying to use some of the GRASS tools from the processing toolbox in QGIS. I get the following Python error: An error has occured while executing Python code: Traceback (most recent call last): ...
3
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0answers
35 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.
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33 views

QGIS doesn't recognize GRASS commands

When I try to use GRASS commands in QGIS, I get the following error message: Missing dependency.This algorithm cannot be run :-( This algorithm requires GRASS to be run. Unfortunately, it seems ...
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0answers
24 views

Can't run SAGA or GRASS commands from QGIS processing toolbox [duplicate]

I can't run anything from this toolbox. I tried running SAGA dissolve polygons and got the following error : Oooops! The following output layers could not be open Dissolved Polygons: ...
2
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0answers
100 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: ...
3
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1answer
41 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 ...
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1answer
36 views

R.Mapcalc giving only blank maps as result

No matter what function I put in the r.mapcalc in the GRASS GUI I get a blank map full of null values. I even tried DEM+0 (I can see my DEM) and this also yielded a blank map.
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0answers
61 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 ...
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0answers
23 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 ...
1
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1answer
188 views

QGIS GRASS Missing Dependancy

I want to perform a view shed analysis in QGIS using GRASS 7 r.viewshed. When I double click on r.viewshed in GRASS GIS 7 commands in the processing toolbox of QGIS I get the following message: ...
2
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3answers
70 views

GRASS v.distance - Getting meters instead of degrees

I'm trying to measure the distance between points to a coastline. I have a shapefile of the "High Seas" which I got from NOAA's website here. ...
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0answers
24 views

r.walk: Incorrect cost parameter values on GRASS GIS Windows version 6.4.3

GRASS GIS 6.4.3 (MS Windows OS): When I run r.walk (from command line), the cost parameters (a,b,c,d) come back like this: Walking costs are a=0.000000 b=-0.000000 ...
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1answer
36 views

repeating steps in GRASS r.mapcalc

I simply cannot find out the following: I want to repeat a calculation in GRASS GIS several times. Is there a command for r.mapcalc to repeat a calculation x times (similar to this possibility in ...
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2answers
44 views

Qgis map composer shows a huge red cross

I can show this best by a picture: This cross also shows when I export it as raster or pdf. What is it and how can I get rid of it? I am using Qgis 2.4 and the map was done with the help of the ...
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1answer
51 views

How to increase the resolution of a 3D image in QGIS GRASS NVIZ

I'm trying to display 3D data in NVIZ within QGIS, but the result appears very low resolution in comparison to the same data in ArcScene. Any ideas as to how to improve the quality would be greatly ...
2
votes
3answers
139 views

Converting Landsat8 DN to TOA reflectance for use in envi

I am used to working in envi, however my current version does not support Landsat8. I downloaded GRASS for the express purpose of converting Landsat8 DN to TOA reflectance for use/analysis in envi. ...
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0answers
30 views

QGIS DEM Output cell size does not match DEM input cell size

As my first post I offer a humble apology if this is such a basic question as to make any of you cringe. I feel like I have exhausted my search skills and read through the QGIS documentation ...
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0answers
63 views

r.stream.* commands do not work in qgis environment

I have been working for a while with some grass commands in QGIS environment (r.watershed, r.terraflow, r.thin, r.to.vect etc) with out any problem. I haven't been able to get any results at all from ...
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1answer
129 views

Loading GRASS gives error installing QGIS Chugiak on Windows 8.1?

I am experiencing a problem installing QGIS 2.4 Chugiak on Windows 8.1, resulting in a error loading Grass. This may be a problem only affecting certain installations, I'm not sure. I am a noob on ...
0
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1answer
38 views

Trouble with r.out.gdal in GRASS GIS

I'm processing some landsat 8 files. I'm using this scene LC82260982013325LGN00 and I have to apply i.landsat.toar and export the result as a GTiff. However when I use r.out.gdal it takes a very long ...
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1answer
15 views

GRASS: v.drape, v.split and v.to.db on spearfish sample data

I am new to GRASS and started training on the spearfish sample data set in GRASS 6.4.3. I selected a bicycle tour and transformed it into a polyline. My next goal is to read out the slope and ...
1
vote
1answer
46 views

What's the difference between Processing GRASS and the GRASS toolbar?

Preparing a QGIS-course for my colleagues I stumbled over the following question: What is the difference between the GRASS commands in the processing toolbar and the GRASS Tools, that you access via ...
4
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3answers
183 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) ...
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0answers
31 views

Problem with Command Console (GRASS GIS 7.0,0 beta2 on Windows 8.1)

I have a problem with Command Console. When I do for example, File-> Map display-> Add raster-> elevation, it works. But when I write into Command Console d.rast map=elevation@PERMANENT, it ...
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0answers
24 views

Execute Spyder within Grass GIS

I'm using GRASS Gis with a small Python script. Is there a way (for windows users) to use the sypder ide within grass? I looked at http://grasswiki.osgeo.org/wiki/Tools_for_Python_programming but ...
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vote
1answer
18 views

Is my code for changing the resolution correct?

I have a raster files of daily minimum temperature (tmin) for the period 1962-2011 at a resolution of 1.125. I need to convert each single day raster file into 0.5 using inverse distance ...
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0answers
50 views

GRASS and r.viewshed

I'm trying to run the r.viewshed command using co-ordinates held in a .csv file I imported using v.in.ascii. It has over 200 rows and I'm looking to run viewsheds from each line, without doing it ...
2
votes
1answer
50 views

Compute number of days with snow

I have a project and I want to map the effective number of days with snow cover for a year in some mountain area. Until now, I have processed the MOD10A2 (8 days snow cover) product derived from MODIS ...
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1answer
43 views

How to check the resolution of converted raster file

I have a raster file whose resolution I need to change to 0.5. I do this using this: g.region rast=my_raster res=0.5 After running this command, how do I verify whether the resolution has actually ...
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0answers
24 views

v.clean in QGIS Python console

I have tried to use v.clean and v.clean.advanced (by GRASS GIS) within a script in QGIS, and was not able. I followed instructions here:, but was not able to do so. I got message: "No module named ...
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1answer
31 views

Why is the raster information No Data value set to -1.#IND?

I have a couple rasters that have been atmospherically corrected using the "landsat.toar" tool in Grass. When these rasters are output and I open up their properties in ArcCatalog, the NoData Value ...
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1answer
58 views

QGIS – Raster Calculator: Using flat (no data) areas of an aspect-raster in the raster calculator

I´m playing around with the Raster tools, following more or less the qgis-tutorial but using my own data. When I calculate the aspect of a DEM, flat areas are (logically) left without data. However, ...
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0answers
34 views

Does somebody has a Python script for a Multiple Flow Algorithm?

I´m looking for for a python script for a multiple flow algorithm assigning flow to all lower cells from one central cell. This algorithm is part of the r.terraflow and would need it to start at a ...
0
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2answers
27 views

Adjacency matrix in GRASS

I have a line shapefile that I use as network. I connect a set of point to it using "v.net operation connect" command. . My questions are: (i) how can I get the list of neighbors for each ...