Category Archives: GRASS GIS

Checking the analogies of known places

Posted on May 11, 2012 by

On the GRASS user email list, a new script for GRASS GIS was just announced; r.finder. The script can be used to check the analogies of places with known characteristics and to show the most similar areas in the region. … Continue reading →

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Find and select duplicate values in your vector attribute table

Posted on May 4, 2012 by

Suppose you have a vector layer in your GRASS GIS database and you want to find all duplicate values in one of the columns of the attribute table of that layer? If you are using SQLite or PostgreSQL as the … Continue reading →

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Creating polar diagrams with confidence intervals in R

Posted on April 24, 2012 by

The function r.polar in GRASS GIS allows you to create simple polar diagrams of e.g., the slope aspect or wind directions. These polar diagrams make it easy to spot directional bias, for example in the distribution of the slope aspect … Continue reading →

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Creating polar diagrams in GRASS GIS

Posted on April 11, 2012 by

There are so many functions in GRASS GIS that it is easy to miss one or two. One functions I recently came across through this tutorial is the d.polar function. This function draws a polar diagram of angle map such … Continue reading →

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If you run out of memory, split up your data

Posted on April 5, 2012 by

Most functions of GRASS can handle very large data sets. With a few functions you might run out of RAM though. One of these is the r.random.cell. This is a function that generates a random sets of cells with spatial … Continue reading →

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Sexante toolbox for QGIS

Posted on March 30, 2012 by

QGIS already has very strong analytical capabilities through its GRASS toolbox. Now, this is further extended by a new plugin that offers direct access to the Sextante toolbox. With this toolbox, QGIS can tap into 300+ functions from SAGA GIS … Continue reading →

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Changes in the r.mapcalc syntax in GRASS GIS 7

Posted on March 21, 2012 by

After some frustrating failed attempts to do some simple raster calculations in GRASS (version 7.0), I found out there is a small change in the syntax for r.mapcalc in GRASS GIS 7:

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Add geometry values to vector layer in GRASS GIS

Posted on March 17, 2012 by

In my previous post I explained how to add geometry values to the attribute table of a vector map in QGIS. You can do the same in GRASS GIS. It is slightly more complicated (don’t worry, it is still easy … Continue reading →

Posted in Data handling, GIS, GRASS GIS | Tagged , , , , , | 1 Comment

Start R inside GRASS but keep the terminal prompt

Posted on June 17, 2011 by

I often run R from within GRASS GIS. For example using R as a scripting language to automate GIS analysis. Or to use statistical models in R on spatial data in GRASS. I used to open R in the terminal. … Continue reading →

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GRASS GIS: creating cross products of multiple raster map layers

Posted on June 11, 2011 by

I am looking at vegetation distribution in east Africa, using a map we have developed based on historical vegetation maps from the region, and I wanted to know the surface area per vegetation type per country. In ‘spreadsheet terms’, I … Continue reading →

Posted in Data handling, GIS, GIS software, GRASS GIS | Tagged , | 4 Comments