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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108 views

GRASS i.landsat.toar returns empty raster

I am trying to use the GRASS module i.landsat.toar. Currently the files created are empty and it spits out: So it seems that it is not picking up something? The location is set to the extent of ...
3
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1answer
230 views

How to prepare road network for routing in QGIS or GRASS

I have been working on a road network and I want to run shortest path algorithms on it. One problem is that some lines come very close to each other, but are not connected. Is there a way to connect ...
3
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2answers
147 views

Is r.cost equivalent to diffusion interpolation with barriers?

I want to perform interpolation using cost distances rather than euclidean distances similar to Greenberg et al. (2011). In that paper they use r.cost in GRASS to compute cost distances for each ...
4
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1answer
225 views

How can I avoid reprojection gaps when merging DEM rasters?

I have two raster DEMs in same resolution I want to bring together. I was using the merge-function in SAGA, GRASS and QGIS but I always get the following result: What do I need? Where could the ...
1
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1answer
133 views

How to remove terracing from Civil3D GeoTIFF export?

I've received a GeoTIFF DEM that was exported from Civil3D and at every contour there is a distinct terrace created when I process an aspect or slope in QGIS with the GRASS plugins. I've looked ...
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1answer
61 views

GRASS: Loss of data using v.net

I'm trying to build a network in GRASS in order to find the shortest path from any settlement out of 1120 (points), to one waste treatment facility out of 27 (points). I plan to use v.net.distance ...
3
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1answer
134 views

Issue with Sextante r.map calculator and modeler

I am trying to build a model with Sextante modeler and the r.mapcalculator algorithm but when I run the model I get the error message: ‘Could not load layer: ‘….’Check sextant log to look for errors ...
4
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3answers
313 views

How to install GRASS on Linux Mint?

I'm trying to figure out an error in GRASS network analysis, for several days now. I started to suspect that it has something to do with my OS, namely Windows 7. Hence I installed Linux-Mint 14 ...
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0answers
99 views

GRASS python script runs twice

Is there a reason that every script I have written for GRASS in python runs twice? I start them using the GUI script launcher tool, and they all begin with: #!/usr/bin/python import grass.script as ...
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0answers
218 views

How to handle/ avoid intersect errors when clipping the difference between two layers?

Using QGIS + Grass, I've added a shapefile of coastline and islands to my map. I then buffer this shapefile to create a coastal zone of a known width. At this stage the buffer consists of the ...
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0answers
719 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 ...
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2answers
106 views

Error using Grass v.net

I'm trying to connect my network to a points layer with a threshold of 4500 meters. I have about 11000 or so entries in my polyline and about 24 in my points layer. I have alreday used v.distance, ...
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1answer
291 views

Installing GRASS on MINT 14?

I'm very new to mint/linux/GRASS and have no clue how to deal with these errors. Can I just change the URL somewhere? Here is the simplest reproducible command to produce a failure: sudo apt-get ...
4
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1answer
164 views

Help installing add-on in GRASS, I get an error message

My Grass gives me this error message, Grass_info_error(4816,1):'make' required. Please install 'make' first. This happens when I attempt to fetch an add-on (r.viewshed). What am I doing wrong? and ...
6
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4answers
1k views

How to find dead-ends in a road network

I'm trying to remove all the dead-end roads in a road dataset (lines) that are less than 100m long. How do I identify roads that are dead-ends (no exit)? The 100m part is easy. I know how to use Arc ...
1
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1answer
115 views

Set certain amount of pixels to 1 inside of a polygon (GRASS)

I have a rather coarse vector map with polygons and want to calculate a (sufficiently) finer raster map defined by spatial extension and resolution. Every polygon of the vector map has a value ...
9
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1answer
321 views

Is there a way to use ArcPy and PyGRASS tools in the same Python script?

I´m trying to write a Python script, that includes different ArcPy / ArcGIS commands and want to combine it with GRASS geoprocessing tools. Unfortunately importing the GRASS libraries doesn´t work. ...
7
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1answer
330 views

How to generate a DEM from isolines and spot heights?

I have two shape files containing height information of a certain area and I need to create a raster DEM with GRASS using them. file 1 consists of height information in contours (isolines) file 2 ...
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1answer
454 views

Raster operation with grass.mapcalc

I need to iteratively add each raster map of viewshed analysis obtained from a series of single observer locations. For this i used grass.mapcalc with Python (GRASS 7 for Windows). However, my ...
2
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1answer
434 views

Integrated viewshed analysis

I need to do integrated viewshed analysis of a target with several observer locations. I am going to use r.viewshed analysis function in GRASS. With this function, it is possible to perform analysis ...
7
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1answer
813 views

How to enable GRASS-modules in QGIS?

I have the latest QuantumGIS-1.9.0-master from Github with python-modules support and full GRASS-integration (GRASS-4.6.3-RC2) on Linux. When opening the GRASS-tools plugin, it only displays six ...
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1answer
194 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
104 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
211 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
284 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 = ...
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1answer
258 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
560 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
130 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
239 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
128 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
93 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
2k 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
614 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
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1answer
202 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
8k 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 ...
-1
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1answer
150 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
102 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
361 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
votes
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
votes
1answer
677 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
votes
1answer
108 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
votes
1answer
82 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
votes
1answer
550 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
71 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
223 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 ...
1
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1answer
177 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 ...
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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 ...
1
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0answers
134 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 ...