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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183 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!
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2answers
292 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 ...
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2answers
179 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 ...
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2answers
628 views
How to smooth large vector polygons from Raster
I have a landuse classification raster file (6 classes) of a large area. But I need it in vector polygons so I vectorised it. No problem so far, but the result is - of course - that every pixel is ...
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2answers
143 views
Vectorize cell boundaries in GRASS
I need to vectorize the cell boundaries of a raster map and I have forgotten how to do this.
For instance, if I have a raster map of a region that is just map=1 with a cell size of 500m, I would ...
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2answers
683 views
Quickly create contour polygons from cost points using OSS for web app
This is related to a previous question I've asked:
Create filled contour map with GRASS
I've created a point layer using OpenStreetMap data and pgRouting's driving_distance() function, where the ...
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5answers
442 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 ...
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2answers
455 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 ...
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4answers
1k views
Dissolve ploygons in QGIS or Grass to new polygons of defined population sizes
I have a shapefile with 3800 polygons representing the smallest administrative areas in Ireland. Many of these, in rural areas, have tiny populations, under 100 people. In urban areas, all would have ...
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1answer
945 views
How to do Kernel density analysis in QGIS 1.7?
Do someone have some suggestion? We would like to tray Kernel Density analysis as we did with ArcGis using QGIS?
5
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1answer
729 views
Open software tool or QGIS plug-in to make land cover classification
Is there any tool or plugin for QGIS/GRASS to make an automatic land cover classification from satellite imagery - based on CLC nomenclature for example? Of course, it will not be 100% sure but it ...
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1answer
163 views
How to increase mask buffer and then offset it using r.mapcalc in GRASS?
I'm in the process of learning on how to remove clouds and cloud-shadows from Landsat images using GRASS. So far I was able to remove a lot of clouds from those images using i.landsat.acca, but it ...
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1answer
416 views
What is north-up projection?
How do I know what projection to use for north-up or 0 rotation? I have a gtiff (ND83-nf) that gives me the error when importing to Grass. Should I re-project or recreate the image with the rotation ...
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1answer
158 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 ...
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votes
1answer
187 views
Is it possible to use the Goode Homolosine projection in QGIS?
Is it possible to use the Goode Homolosine projection in QGIS? Both QGIS and GRASS seem to have trouble with the interruptions, squashing the higher latitudes together. I tried +proj=goode ...
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206 views
SEXTANTE toolbox - GRASS error
I am trying to use the SEXTANTE module GRASS (and SAGA) for vector analysis but whatever function I use I always get the same error:"Could not load layer: G:/closest.shp
Check the SEXTANTE log to look ...
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2answers
201 views
Can I split up v.in.ogr into multiple v.clean commands?
I'm trying to load a large set of polygons into GRASS with "v.in.ogr" and am running out of memory at the "Break Boundaries" stage. I'm wondering if I can break into steps all of the different things ...
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5answers
456 views
Elevation correction ASTER GDEM2 (+10m)
My ASTER GDEM2 has a average elevation error of -10m for my area. (I testet it using 90 defferential GPS reference points and compared it with old Topo25, SRTM, and GoogleMaps).
I would like to ...
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4answers
191 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 ...
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4answers
408 views
How to generalize and vectorize a LandUseClassification raster file?
I want to vectorize that rasterfile with its 6 landuse classes. The classification is very noisy and have to be generalized before.
The result should be a polygone vector file.
I use SAGA, (GRASS) ...
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3answers
160 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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3answers
1k 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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2answers
529 views
What's a good toolchain to reproject some PNGs in plate carre to UTM?
I have some PNGs produced from Canadian DEM data. They're 1201px by 1201px heightmaps. Each one represents one quarter of a degree latitude and one quarter of a degree longitude.
But I want to work ...
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3answers
932 views
How do you open/display and extract NetCDF files info?
I am working with NetCDF files using R & Matlab and I would like to know if the GIS community is using them. I know that ArcGIS can open & display, however most of the times the results are ...
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1answer
545 views
How can I calculate the vertical distance to the nearest water?
Summary:
I would like to create a raster where each cell contains the vertical distance to the nearest water (a decent approximation would be acceptable). The problem is that I'm not sure how to go ...
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3answers
540 views
How to get the elevation of the areas in a raster file from SRTM?
I have an SRTM elevation map. How do I get the elevation of each point in the map? I am using GRASS. Is there a GRASS script to do such?
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5answers
458 views
How to save a raster and vector into a single PNG file in GRASS?
I am trying to save a raster and vector into a PNG file. The vector is overlayed on top of the raster map. I was only able to save the raster file into a png using r.out.png but without the vector.
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2answers
480 views
How do I split polygons into line segments?
How can I split my polygon file into "segements"? The lines should be broken up like this picture shows:
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4answers
451 views
How to automatically plot intermediate contours with QGIS, GRASS GIS or SAGA GIS?
I'm mapping a steep mountain range. My main contour interval is 50 m and my intermediate contour interval is 10 m. In steep areas, the interval of 10 m is too small, so I need to leave ...
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1answer
86 views
Export Region definitions - GRASS GIS
I use two different Landsat datasets in different computers. But the region settings I work is the same. Is it possible to export the region settings in the form of a file in GRASS?
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1answer
146 views
Raster DEM generation
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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2answers
456 views
Altitude Above channel in GRASS 6.4
i'm fairly new to the GIS world and GRASS (come from econometric background), i would like to do some species distribution modeling using R and GRASS.
So i started to read the book of Tomislav Hengl ...
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2answers
185 views
How to select a subset of separate bands in GRASS GIS?
As you know landsat data has separate files for different bands. Creating a
subset is a wise option to work on region of our interest. Therefore, I used
this method to subset my image -
d.zoom || ...
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2answers
86 views
How to do a looping to Interpolate a huge Rainfall Time-series in GRASS GIS or R
In GRASS GIS I have access to a table in PostgreSQL Database with this structure:
Table Name: rainfall_time_series
Columns: id | year | month | day | value_mm | x | y | gauge_code
Setting g.region ...
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2answers
322 views
Monthly Average Solar Maps (R.Sun) in Grass
I'm trying to create monthly average maps as described in R.Sun in Grass. I have my DSM. In reading the page on OSGEO it mentions that it is possible without showing how. Ideas? I assume I will need ...
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920 views
Where can I find a tutorial for installing an addon to GRASS GIS that a six-year-old could understand?
I want to use the r.stream.distance addon in GRASS GIS 6.4 on ubuntu 10.04 (64 bit).
I've installed grass from the repositories and that works fine but I can't seem to figure out how to install this ...
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1answer
476 views
How to extract features from a vector layer?
I have a vector file containing the river lines of an area. I want to extract a specific water line from the vector. I used:
v.db.select but it only displayed:
...
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1answer
113 views
How to repair and clean contours from high data resolution (lidar)?
I'm unsuccessfully trying to make a bathymetric map with contours extracted from Lidar data at 1 m resolution.
The extracted contours have a lot of artifacts like dangles and islands.
First I used ...
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1answer
81 views
Programmatic raster-vector calculation
I currently use GRASS' r.mapcalc to find the difference between vector and raster data using a loop and temporary files and layers.
Is it possible to do the core calculation between raster with a ...
4
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1answer
179 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 ...
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2answers
387 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 ...
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1answer
216 views
Multishading: bring them together to one Raster-Image
I made a multi-hillshade with 4 different light-directions and colors and stacked one above the other, each with its own transparency. Now I want to "save" the result in one raster-image.
Whats the ...
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1answer
169 views
Need to remove small areas, but only if they do not have adjoining boundary
I'm generalizing some lat/lon data in grass64 and as a precursor to the generalization, I am removing small areas from the data using 'v.clean'. The following command is working well:
$ v.clean ...
4
votes
1answer
134 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 ...
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1answer
50 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 ...
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1answer
99 views
Would it be possible to construct a stand-alone grass.script python package?
I would like to migrate dependency on ArcPy to grass.script without requiring the full installation of Grass. Would it be technically possible to have a portable directory containing grass.script and ...
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1answer
1k views
Convert shapefile lines to a polygon in GRASS
I have a shapefile of a map that is the outline of a number of islands. I would like to convert the lines into polygons (ie all islands filled in) using GRASS. I searched on how to do this with GRASS ...
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52 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 ...
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1answer
74 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 ...
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0answers
141 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 ...
