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Tag Archives: GRASS GIS
Import GRASS function console output as data.frame in R
In R you can use system calls or the spgrass6 package to run GRASS GIS functions. To do this, you need to run R from within GRASS GIS. This is as simple as starting GRASS GIS and subsequently starting R … Continue reading
Posted in GIS, GRASS GIS, R computing environment
Tagged data I/O, function output, GRASS GIS, R, tutorial
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Point coordinates to polygon – part II
In my previous article, I showed how you can convert point coordinates into a polygon vector layer in QGIS. So how about GRASS GIS? Like in my previous post, let’s assume you have a text file with two columns with … Continue reading
Posted in GIS, GRASS GIS, tools
Tagged GRASS GIS, kml, object type, point coordinates, point vector, polygon vector, vector layer
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Sum up values of neighbouring polygons – a GRASS GIS approach
How to sum up values of neighbouring polygons in QGIS? This question was asked on gis.stackexchange, with two interesting answers. One answer explains how to use Spatialite and SQL to achieve this. The other answer, explained in more detail here, presents … Continue reading
New release candidate for GRASS 6.4.3 is out
The second release candidate of stable release 6.4.3 is available now. It contains a good number of improvements and especially stability fixes, see here for more details.
Calculating the raster cell area of an unprojected raster layer
What if you get a raster layer with number of people per raster cell, like for example the population layer from Afripop, and you want to convert it to a population density layer? Well, obviously, you need to divide the … Continue reading
Posted in GIS, GIS software, GRASS GIS, research tools, tools
Tagged GRASS GIS, R, raster, surface area
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Import MODIS data in GRASS using r.in.gdal
NASA offers access to its MODIS and ASTER data sets through Reverb|Echo. The data comes in HDF format and uses the Sinusoidal grid tiling system. If your gdal is compiled with HDF4 support (use ./configure –with-hdf4), you can use gdal, … Continue reading
Stratified random sampling in GRASS GIS
There are various options to create a vector or raster layers with random sample points, including v.random, r.random and r.random.cells. The first two generate random points within the defined region. However, only r.random will respect the mask if set. The … Continue reading
Multivariate Environmental Similarity Surfaces (MESS) index in GRASS GIS
The Multivariate Environmental Similarity Surfaces (MESS) is an index that represents how similar a point in space is to a reference set of points, with respect to a set of predictor variables (Elith et al 2010). The function was first … Continue reading
Posted in Data handling, GIS, GRASS GIS, R computing environment
Tagged add on, GRASS GIS, MESS similarity index, R, scripting
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Reading GRASS GIS vector attribute tables into R
Linking GRASS GIS and R will give you a very powerful set of geo-spatial analytical tools. The spgrass6 offers a very convenient interface between GRASS GIS and R. You can read more about this package in Bivand, R. 2007. Using … Continue reading
Posted in GIS, GRASS GIS, R computing environment
Tagged attribute table, data export, data import, GRASS GIS, R, spgrass6
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