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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132 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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205 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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65 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
79 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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62 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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43 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
191 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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1answer
97 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
82 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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1answer
291 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 ...
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1answer
123 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 ...
3
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1answer
401 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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24 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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249 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
208 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): ...
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104 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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159 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
43 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: ...
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380 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
149 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
84 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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139 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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83 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 ...
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1answer
923 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
225 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. ...
2
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1answer
116 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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1answer
197 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
267 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 ...
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3answers
1k 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
109 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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198 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
368 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 ...
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1answer
92 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
63 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 ...
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1answer
77 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 ...
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3answers
755 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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1answer
24 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
150 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
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1answer
83 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
181 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
171 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
81 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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2answers
312 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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2answers
54 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 ...
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0answers
41 views

GRASS r.out.mat memory issues

we have built a model with pythn/GRASS that calls the r.out.mat module. The area is quite large 25,000x25,000 cells. The machine we are running it on is Windows 7 machine with 16GB of RAM. After a ...
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1answer
242 views

What is the typical v.surf.xxx exicution time?

What is the typical v.surf.xxx exicution time? I am trying to run v.surf.bspline on a set of ~1600 points. It has bee running for about an hour now and is stuck at spot indicated in the image. I ...
3
votes
1answer
662 views

Shortest distance from polygon centroids to a line in QGIS

To get the distance of each polygon centroid from a line, I have tried the Distance to nearest hub algorithm from the Processing Toolbox. The distances I got from the algorithm did not seem correct, ...
3
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1answer
673 views

NVIS module not found in QGis

When I try to use the nvis module in Grass, QGis, pops-up a warning window saying "Module nviz not found". how can I solve this issue and use the nviz?
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1answer
138 views

How to modify existing grass gis tools and run them in QGIS?

I would like to take an existing tool of the grass tool box and modify the code to the specific needs of my task. As I´m struggling to start some kick-off would be great. How to access code? What do I ...
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1answer
219 views

Empty signature file after i.gensig in GRASS

I'm trying to make a supervised classification in Grass 6.4.3 under Linuxmint 16. After digitizing the training areas, I transformed them from vector to raster. Then I've done the following: just in ...