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
166 views

Grass r.mapcalc generates 1 cell map

I'm a GIS student and in my project I need to generate vegetation indexes. I've generated it succesfully yesterday using both python2.7 and grass gui .I'm using WinGRASS-6.5.svn-r54428-453 on Win7. ...
3
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1answer
98 views

Showing map in Grass Layer Manager/Map Display via Python

I've created some raster(tif) maps using Grass libraries in Python. I want to opem them automatically in Grass GIS Map Display or Layer Manager after creation. I don't want to use GUI for this. What ...
8
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2answers
2k views

How to correctly install QGIS with plugins and GRASS-integration from source?

I'm running a Sabayon GNU/Linux (based on Gentoo) at my home desktop system and I want to install Quantum-GIS. I'm currently using the qgis-1.7.0-package from the repositories. But this is somehow ...
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2answers
197 views

How to install GDAL/OGR with GRASS vector support?

The GRASS 6.4.3Svn for Windows that i have in my machine does not have GDAL/OGR support. Is there any library (libgrass) for Windows to add into existing GRASS installation. If not, how to build or ...
2
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1answer
253 views

OGR Python bindings

When I try to access one of the GRASS vector files through Python OGR bindings, it gives error: Here is the script code in Python 2.7.3 IDLE (GUI) in Windows 7. from osgeo import ogr ds = ...
0
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1answer
233 views

How do I repair NVIZ error: 'Can't find a usable init.tcl'?

How do I repair the following problem: The error occurred while I was trying to run NVIZ in the GRASS environment in QGIS. NVIZ however runs perfectly in GRASS. On checking the directories ...
6
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2answers
488 views

Calling GRASS functions from external Python

I have GRASS 6.4.3svn installed in my machine running Windows 7. Also in my machine i installed Python 2.7.3 for Windows.Now i need to call GRASS libraries from Python and not within the Python shell ...
2
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1answer
120 views

Error when importing vector layer into GRASS

I am trying to import a vector layer into GRASS, but I keep receiving the same error. The values in the vector layer are important because I would like to use them to create a heatmap. What could I ...
5
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1answer
230 views

How to create a heatmap using values?

How do I create a 'heatmap' in QGIS based on the values of the different points? I did do this once before with rainfall, but can't remember how!
3
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1answer
119 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 ...
5
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5answers
2k views

How to calculate distances in a point sequence?

I'm looking for help calculating the distance between a sequence of points that are in a single Shapefile in QGIS. Below is what my data look like and a blank distance column I've added to show how ...
2
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1answer
82 views

d.rast.edit error when attempting to edit a raster

I always get an error when I try to edit cell values in a raster with the GrassGIS command „d.rast.edit“. The error under Windows XP/GrassGIS 6.4.3 says: Exception in thread Thread-29: Traceback ...
4
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1answer
1k views

Importing shapefile in grass

I have very simple shapefile, which consists of couple of polygons, and I wanted to snap boundaries automatically. Unfortunately qgis doesn't have such function, but grass has according this answer: ...
2
votes
1answer
512 views

How to delete rings automatically using QGIS/Grass

I'm cleaning up a (very) messy shapefile in QGIS/Grass. I now have several large polygons with numerous (100s) of small rings. Is there a quick and easy way to remove/ fill all these small rings. ...
2
votes
1answer
179 views

How to filter or query data in GRASS?

I have a PostGIS dataset with just over 2 million rows. Each row has a PostGIS geometry point value and several attributes. I'd like to do some analysis on certain subsets of the data, but I can't ...
4
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3answers
6k views

Converting a .jpg map into a shapefile

I have a .jpg map of a set of U.S. counties that were affected by a tornado. The map shades where the tornado passed through, resulting in some counties only partially experiencing the tornado. I ...
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1answer
132 views

GRASS-QGIS Linking error

I need few customizations over grass and would use qgis gui for accessing grass. I am building qgis with grass enabled (WITH_GRASS=TRUE). While I am doing that I get the following. Any help is greatly ...
3
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1answer
94 views

How to recategorize features in GRASS by geometry, like the ArcGIS Sort tool?

The ArcGIS Sort tool creates a new feature class with features sorted by geometry. For example, it can number features IDs from north to south, etc. Is there a way to renumber the cat field in a GRASS ...
6
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1answer
326 views

Generalize large polygon-file

I have a large polygone file with landuse information (6 classes). Its vectorised from a raster classification so the polygons are all angular. Any of my tries to generalize with v.generalize (sneaks, ...
6
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2answers
1k views

How to compile QGIS with GRASS on Ubuntu?

I am on Ubuntu building qgis with grass plugin. I have build grass code separately and used --prefix to provide the path GRASS_PREFIX is /usr/local/grass-6.4.2 and GRASS_INCLUDE_DIR is ...
2
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1answer
559 views

How to correctly merge layers with overlapping polygons in QGIS/GRASS?

I have 4 vector shapefile that I would like to join/merge, without worrying about attributes. Here are the shapefiles. I would like to do an union and a spatial dissolve, but everytime I do a dissolve ...
2
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1answer
102 views

How to close and fill Gulfs and inlets in QGIS or Grass?

I have a raster layer from which I extracted only zones with a certain color, then polygonized it with QGis. I just generalized the new vector layer in GRASS to smooth things a bit. There are many ...
3
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1answer
79 views

GRASS r.grow doesn't seem to change raster values at all

I have a raster map in GRASS that looks like this: The red cells have a value of 1, the yellow cells have a value of 0. I am trying to use the r.grow command to 'fill in' the gaps in the red ...
6
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1answer
464 views

How to perform unsupervised classification of LANDSAT time series using Grass?

I'm using GRASS to perform an unsupervised classification on a time series of LANDSAT images (monthly temporal res, over 30 years), in order to compare land cover change in a particular area. I'm ...
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0answers
61 views

GRASS error reading raster map: request for row 1 is outside region [closed]

I'm a rather inexperienced GRASS user, and am trying to use an addon module called r.geomorphon (see http://sil.uc.edu/downloads.html#software). I've managed to get it installed and am trying to run ...
2
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1answer
197 views

Raster Analysis - Identifying features from Raster

I have an IDW, tension spline and hill-shade rasters that show an archaeological landscape and from these rasters I want to identify new features which are seen in the landscape as depressions. And ...
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1answer
167 views

Undefined reference errors installing GRASS addon

I am trying to install the r.geomorphons GRASS addon (available from http://sil.uc.edu/pdfFiles/jarek/r.geom.zip) in GRASS. I tried on Windows but gave up and decided the best thing to do was to try ...
1
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0answers
29 views

How do you change units from meters to kilometres? [duplicate]

Possible Duplicate: Using ‘gdalwarp’ in Python script for Grass I wonder how i could fit my cells to 10 km... Therefore is in meters... and the resolution is different (0.16164). I need ...
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0answers
122 views

i.maxlik cannot read i.class output signature file

I'm trying to perform a supervised classification using i.class. I'm then using i.maxlik, but this is returning the following error: GRASS 6.4.3svn (India_01):~ > i.maxlik group=test_group@test ...
3
votes
1answer
81 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 ...
5
votes
2answers
577 views

How to batch import GDAL supported raster files into GRASS?

I am trying to import some GDAL supported raster files into a binary raster map layer using the r.in.gdal module from QGis Grass tool. As I have multiple files to import, I would like to batch import ...
2
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1answer
362 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
votes
1answer
80 views

V.kernel not working correctly in grass-6.4.2

I am using grass-6.4.2 for generation of heat maps of crime data. For testing purpose, I created a vector layer from my places shapefile which is a point data.The places shapefile contains more than ...
6
votes
2answers
259 views

How do I compute v.kernel maps in less than 16 hours?

I am using the GRASS GIS 6.4.2 bundled with QGIS 1.8.0, using a PostGIS dataset exported via v.in.org.qgis from QGIS, to create kernel density maps. The layer has 738,288 points. My problem is the ...
3
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1answer
126 views

Creating rasters?

I am doing my masters in archaeology, but have used GIS for some time now, however this is my first attempt at generating and using rasters. I appear to have been successful for some, but not so well ...
7
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4answers
762 views

Calculate polygon field based on neigboring polygon attribute

I have a vector shape with many different sized polygons each possessing an own class name (for instance "houses", "houses with offices", etc ...) I want to assign a new field to each polygon ...
1
vote
1answer
108 views

extract data from several images to different shapefile columns using GRASS

I am now working in grass and I want to extract raster values from several images to a shapefile. I have already created the columns in the .shp where the raster values will be stored but I am facing ...
4
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1answer
3k views

Convert Shapefile to MySql

I have used Grass GIS imported a .shp file; I now want to export this file to MySQL. I understood that MySQL will contain the function of all three the files necessary in a Shape file system (.shp - ...
2
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1answer
56 views

What units are used in GRASS Rasterize?

What units are used in GDAL Proximity or GRASS Rasterize? - 'new size' parameter
3
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2answers
237 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 ...
5
votes
1answer
306 views

How to call GRASS modules in pyQGIS?

I wish to use a Grass module (v.to.db) in QGis, without the grass toolbox. I tried with the Python console, but to no avail : Using Sextante plugin but obviously it didn't know all the grass ...
16
votes
4answers
588 views

How to do kernel density estimation with a physical barrier/ boundary in QGIS?

Does anyone know of a programme that will allow kernelling that takes a boundary into account in its calculation rather than simply masking areas that are impossible? So far I have found: GME add on ...
1
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1answer
168 views

Why is transparancy of GRASS rasters missing when imported into QGIS?

I have a raster map in QGIS imported from a GRASS mapset with the QGIS GRASS plugin. The problem is that I have null() cells in the GRASS map that appear "colored" in QGIS. How can I set the ...
5
votes
2answers
678 views

How to color-balance false-composites of pan-sharpened Landsat images in GRASS?

Whenever I try to pan-sharpen composites of some Landsat images in GRASS using i.pansharpen, i.fusion.brovey or the IHS sharpening method, the output will have some or all of the following ...
14
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6answers
3k views

What's the best way to produce a density map from weighted points in QGIS?

I'd really like to repeat the functionality of the ArcGIS Kernel Density tool - how could I do that? I would like to limit answers to easy-to-install free-and-open-source software – i.e. QGIS ...
5
votes
3answers
2k 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 ...
8
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1answer
654 views

How to pan-sharpen Landsat images for image-classification in GRASS?

I'd like to learn how to do an unsupervised classification of a Landsat scene using i.cluster > i.maxlik in GRASS using pan-sharpened 15m-resolution images (the example given in its Wiki uses the ...
3
votes
2answers
326 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
votes
1answer
284 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 ...
4
votes
1answer
76 views

How are r.horizon results aligned?

I used r.horizon to calculate horizon on a raster every 10° without any offset. I have got 36 files now. Is the first file from 0° to 10° (then centered on azimuth=5°) or is it centered on 0°, in ...