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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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 ...
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0answers
155 views

What open source solution would work best for auto extracting features from satellite images? [duplicate]

Possible Duplicate: Feature Extraction - Land cover I have been looking for an open source solution which would allow me to define a region (or collection of images) and extract features ...
4
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2answers
229 views

95 percent volume contour

I generated, from point data, a kernel density map using GRASS, and I would like to identify the 95% volume contour in it. Is it possible in GRASS? Thank you
3
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2answers
514 views

How to determine aerosol model value for i.atcorr in GRASS?

The i.atcorr module in GRASS requires aerosol model data to perform atmospheric correction using the 6S algorithm. It seems like I need a value from one of these parameters to continue: Estimate ...
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2answers
2k views

1'' DHM: Hillshade is too rough - how to “generalize”?

I got this hillshade from my DHM (I used the hillshade-module from qgis). For my purpose there is too much relief detail (roughness). How can I get rid of this in QGIS or GRASS? Thanks! Martin
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3answers
2k views

How to set all pixels with value <= 0 to “nodata” in DEM raster?

I have a DEM raster with pixel values between about 3000 and -0.0003. I need to set all pixel with a value of 0 and smaler (<=0) to "nodata" (for later raster calculations and to reduce the ...
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2answers
192 views

Is there a shortcut in GRASS for importing vector files?

Is there a keyboard or command shortcut in GRASS for importing vector files? If you know link where I can find maybe whole list of shortcuts for GRASS, that would be awesome. Thank you.
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3answers
856 views

Convert 800 .hdf4 files to Tiff using GRASS/QGIS/SAGA/GDAL/R

I've have MODIS ndvi data (MODIS_Grid_16 days NDVI) from the iberian peninsula, from February of 2000 to August of 2012 (really big data). How do I batch convert about 800 .hdf MODIS files to .tif ? ...
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1answer
2k views

How do I find vector line bearing in QGIS or GRASS?

How can one extract the bearings from a set of lines in a vector file? I'm trying to find the bearings of several straight vector line segments (simplified contour lines, actually) and can't figure ...
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3answers
485 views

Can a raster map in GRASS be saved in JPEG/BMP format?

I'm trying to save a raster map in GRASS in jpeg/bmp format without using the GUI for d.out.file/d.save. Is there a script to do it? I tried r.out.gdal but it produced a map that is black and white.
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1answer
224 views

Combining Geological Grids and extruding between them?

I have a situation where I have 3 Geological grids, each showing a different horizon + the Seabed Grid. I need to extrude between these grids in order to make the 3D polygon for the geological ...
3
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1answer
210 views

SVN Version of GRASS and QGIS

I have GRASS6.5 SVN installed and wanted to go for SVN installation of Quantum GIS in Ubuntu 11.04. So as instructed in QGIS Wiki, I added the qgis repository to my sources.list file. Now I am able to ...
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2answers
575 views

Creating square buffer in qgis

How can I create a buffer with square ends along a line segment in qgis? I've buffered lines using v.buffer in the GRASS plugin, but the -c option for square ends is not exposed in that interface. ...
3
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2answers
271 views

Create network from shapefile without ArcGIS?

I want to perform shortest-path analysis on a network whose edges represent real-world roads and whose nodes are buildings or other locations. I have the shapefile for the area I'm interested in. ...
3
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4answers
363 views

Has anyone else been unable to locate and install the GRASS plugin in QGIS 2.0.1?

After uploading and installing QGIS 2.0.1, I am unable to locate and install the GRASS plugin. The plugin is not listed in the 'Plugin Manager'. The 'Plugin_Installer' is also shown in red, ...
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4answers
907 views

GRASS 6.4.3 Crashes on Startup; libintl-8.dll cited

I recently installed QGIS 2. I used the advanced OSGeo4W installer that I downloaded from the QGIS download page. GRASS is included in the stack. When I attempt to open GRASS, I receive the following ...
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2answers
243 views

How do I tell GRASS where to find Python?

For some reason, when I start GRASS on my Mac it says that it has found Python 2.6.7. However, /usr/bin/python version is 2.7.2 and I can't find a lower version anywhere on my system. Potentially ...
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2answers
642 views

Using 'gdalwarp' in Python script for Grass

I'm writing a Python script that aims to re-project various LANDSAT tiles into a common projection and then import the tiles into Grass. The script at present is shown below: #!/usr/bin/python ...
3
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2answers
2k views

How to calculate LS Factor of Watershed for RUSLE Calculation?

I managed to get subbasins for my catchment (7 km^2) with their areas but I haven't figured out how to get the LS factor (see Revised Universal Soil Loss Equation) from it. I have the vector file ...
3
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1answer
94 views

Can two versions of GRASS be installed in a computer and still run independently?

GRASS 6.4.0 is currently installed in my computer. The script that I am trying to run is present in 6.4.1. It is stated in my previous post. If I installed 6.4.1, will my 6.4.0 still run? I don't want ...
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2answers
955 views

How to delete a base map in GRASS?

I'm trying to delete a map that I used as a mask before, but I cannot delete it using g.remove. It displays this: g.remove rast=raster_Mnorzagaray@PERMANENT [raster_Mnorzagaray@PERMANENT@PERMANENT] ...
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2answers
206 views

How to make the arrows in d.rast.arrow GRASS script visible?

I'm trying to create a Flow or directional raster map (with arrows) from an SRTM elevation map that I downloaded from CGIAR. I already created an aspectMap to be used for the d.rast.arrow. I used ...
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1answer
246 views

How to reproduce Smoothing from Generalizer Plugin in v.generalizer in Processing Toolbar using QGIS?

I´d like to reproduce the smoothing operations done with the Generalizer Plugin inside the v.generalizer Toolbox so I can use them on a polygon layer instead of only on a line layer. I tried ...
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2answers
249 views

How to fix unreachable nodes in QGIS GRASS network?

I have created a network with the GRASS module v.net. But when I try to create the travelling salesman path with v.net.salesman, I get: Destination node 9383 is unreachable from node 9398 If I ...
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3answers
417 views

GRASS v.generalize method=douglas not working as expected

I'm frustrated with v.generalize trying to simplify polygons. Those polygons stem from ArcGIS's raster to vector function (imported into GRASS from Shapefile), so they are pretty zigzag like this: ...
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3answers
508 views

How to calculate peaks in a DEM

How could I extract all peaks from a DEM (large mountainous area)? Peak means something like: a pixel which is sourrounded by other pixels with smaler elevation numbers in a area arround the ...
3
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1answer
589 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 ...
3
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3answers
683 views

Topographic correction (for land use classification) with SAGA or GRASS

Is there a module in GRASS or SAGA (or a alternative open program) to do a topographic correction of a landsat image to enhance the land use classification? Thanks! Martin
3
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1answer
617 views

Correct ASTER with SRTM or Topographic Map

I have a problem with my DEM again. I decided to use ASTER GDEM2 (for different reasons). ASTER GDEM2 have its problems, I know, and I dont want to discuss that again. I have to use it, because SRTM ...
3
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1answer
695 views

Cell calculations; QGIS,GRASS,GDAL,SAGA

I recently asked a question about trying to calculate the slope over distance (manually) using QGIS, but then I came up with another way of solving the problem, but I would have to get some help for ...
3
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1answer
486 views

Change raster value for an area based on a class of another raster

I would like to change all raster values in raster A that fall into the locations of category/class 1 of raster B. Here, some more details. I did a calculation on a DEM resulting in different ...
3
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2answers
223 views

Can GRASS v.net.iso split between nodes?

Can GRASS's v.net.iso module split networks between nodes on the network, i.e., if I am finding the area within a cost of 400, and there is a line segment with a cost of 800 leaving the center node, ...
3
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3answers
766 views

How do I draw on a vector map in GRASS?

I have a vector map that has two lines. I want to have the two connected. Is there a way for me to draw a line to connect the two? I am using GRASS gis by the way. The two lines that I want to connect ...
3
votes
1answer
469 views

Slope, aspect and beam in R.Sun (GRASS)

I'm starting to mess about with the solar radiation packages of GRASS and ArcGIS and have become rather stuck on the GRASS side of matters. I have a DSM area, and that is feeding into GRASS well ...
3
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1answer
502 views

How to get the Flow or directional raster map using GRASS?

Aside from using r.fill.dir in GRASS, is this the script to produce the Flow or directional raster map? Is this the output for the script ...
3
votes
1answer
38 views

Generate a raster with a uniform value using QGis

I'm working on a project using the qgis-modeler and i want generate a raster with a uniform value. i'm using r.surf.random function of GRASS which need min and max value but i want have only one ...
3
votes
1answer
108 views

It is possible to verify landsat reflectance values?

My question is really wide today, as I am still beginner in Remote sensing. I´ve asked a GRASS programmer to prepare for me Landsat reflectance values from raw DN values (1 scene per year from 1987 to ...
3
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2answers
195 views

QGIS GRASS shell commands not working in Yosemite

First time asking a question here. Running GRASS 6.4.3 within QGIS 2.4.0 on Mac OS 10.10 Yosemite. I'm trying to run v.net.iso within the GRASS shell, but the following error is returned every time: ...
3
votes
1answer
152 views

Practical tools to delineate large scale watershed?

I would like to do some watershed delineation at national/regional level (using SRTM-90 data). I have experimented with r.watershed (GRASS 6.4.3) but it fell over when I tried to do big stuff. I ...
3
votes
3answers
240 views

Can a shapefile, or other file, be made from Excel without coordinates

I have two Excel spreadsheets I'd like to make into shapefiles, or some equivalent. I have access to ArcGIS at work and want to try using GRASS as well. I have seen the help on doing so, but only if I ...
3
votes
2answers
2k views

QGIS GISBASE specify location

I am just a beginner at this QGIS and GRASS and I am using this QGIS 2.0.1 Dufour which throws a error at the startup that "QGIS couldn't find your GRASS installation. Would you like to ...
3
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2answers
900 views

How to set output resolution for gdalwarp to that of source file?

I have a large raster, which I want to re-project and crop for a new location that I'm creating in GRASS. I seem to have gotten the re-projection and cropping right with this call to gdalwarp: ...
3
votes
1answer
823 views

How to cluster Raster data

I have thousands of Raster data concerning the ice coverage at the pole at different times (days) over several years. Now I would like to perform a cluster analysis. I want to split the data into ...
3
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2answers
237 views

Resolution difficulties in Grass

I have gone through similar questions to mine here, but I didn't find a solution. Please help! When cropping a raster image by using g.region & r.mapcalc, I get a new image but the resulting ...
3
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3answers
657 views

How to clean layers from non topological databases?

I'm doing my internship in a consulting office which is switching from MapInfo to QGIS/GRASS 1.8.0. I posted here a few days ago about the way to clean a polyline from a Lidar data with v.clean. ...
3
votes
1answer
144 views

Temporal GRASS GIS framework

I am trying to follow the tutorial posted here. When I get to this part "Extraction of seasonal mean temperature" and run this code: t.rast.extract \ input=temperature_mean_1950_2011_seasonal \ ...
3
votes
1answer
153 views

v.dissolve to multipolygon

Using v.dissolve in GRASS, I'd like to get a multipolyon as a result. However, I end up with distinct polygons with the same 'dissolve value.' For example; lets assume I have two polygon features ...
3
votes
1answer
107 views

Is there an easy way to taper huge amounts of drainage vectors?

I've performed hydrological analysis using r.watershed using GRASS and now I have some stream vectors for a large area. Next, I'm planning to taper these streams to varying width to make them appear ...
3
votes
1answer
487 views

How to reproject a raster to Winkel Tripel projection?

I'm trying to project a raster map (in ASCII grid format) from longlat to the Winkel Tripel projection. But I'm running into errors, for instance gdalwarp won't accept the proj-string. $ gdalwarp ...
3
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1answer
570 views

Where to change GRASS GIS wxGUI language?

I use GRASS 6.4.2 on Russian version of Windows 7 x64. As I start wxGUI it is shown in Russian. But I don't like its translation and want to work with English interface. I have no clues how to solve ...