Category Archives: GRASS GIS

Access R from GRASS GIS on Windows

Since I have switch from Windows to Linux, many years ago, things have started to look a lot brighter for those wanting to use GRASS on Windows. I won’t switch back to Windows any time soon, but I recently had to install WinGRASS for somebody else. And it was a whole lot easier than I had feared (or even hoped).

But there is one thing I couldn’t immediately figure out; how to run R from within GRASS. I should add that I installed GRASS using the OSGEO4W installer. When installing GRASS using the stand alone installer, access to R from the GRASS command line should work out-of-the-box (see comment from Helmut in the comment section below).

After a bit of trial and error, I came up with the steps below. It involves editing a file to tell GRASS where to look for executables. In the example below I am adding the path to the R and rstudio executables to this file. Having done that, I can now type R.exe or rstudio.exe on the GRASS command line to open these programs. Continue reading

Recode your raster file in GRASS GIS using a csv file

The two easiest ways to reclassify a raster layer in GRASS GIS are using the r.reclass or r.recode functions. Although both are easy enough to use, sometimes it would be nice if you could just provide the input layer and a simple table with re-class values to create new raster maps. A fairly trivial task, so ideal to make another attempt at creating a python script.

I create a small add-on (r.recode.attr) that let you reclass/recode a raster layer based on values in a csv (comma separated text) file. The csv file should include one column with the raster values and one or more columns with the reclassification values. For each of these columns a new map will be created.  See the manual page for more information. Continue reading

Access GRASS 7 data in QGIS

QGIS supports GRASS in two different ways. 1) For those working with GRASS databases, there is the GRASS toolbox, which basically offered an alternative GUI to GRASS. For those working with other data types, most GRASS functions are now available through the processing toolbox.

I do most of my spatial analysis in GRASS, while I use QGIS amongst others to create maps based on the results. So I mostly used the GRASS toolbox. Unfortunately, the GRASS toolbox doesn’t work (yet) in QGIS 2.6. So what now? Well, as it turns out, QGIS can access GRASS raster layers through the QGIS browser. Continue reading

GRASS GIS 7.0.0 beta 3 is out, bringing further fixes and improvements

GRASS 7 sports very significant improvements and numerous new functions. For example, the improved graphical user interface makes it much easier to carry out complex GIS operations and handling of vector data has become much faster and more efficient with very large files. There is a large number of new analytical raster and vector modules and existing modules are now much faster (some even 1000 x faster). Beta 3 ships 390 fixes and improvements with respect to beta 2. For more details, go to http://grass.osgeo.org/news/37/15/GRASS-GIS-7-0-0-beta3/.

Exporting your GRASS raster using r.out.gdal? Check the createopt options!

GRASS GIS can export your raster layer in most common (and quite a few less common) data formats using the r.out.gdal function (menu: file – export raster map – common raster formats). Exporting is so simple that you may forget that depending on the output format there are different options to optimise your output raster layer. Continue reading

Stable GRASS GIS 6.4.4 released

A new stable version GRASS GIS 6.4.4 has been released. It sports various bug fixes and a number of new features. Go here for more information.

You may be aware that there is also a GRASS GIS version 7. So which version should you go for? Well, it depends. Is long-term support, backward-compatibility with the GRASS 6 line and stability important to you. Or do you use the QGIS GRASS GIS toolbox a lot (which is not yet compatible with GRASS 7)? Go for the new GRASS 6.4 series.

Are you always looking for the latest of the latests, or is speed or the ability to handle very large data sets important to you? Have a look at list of new and improved features in GRASS 7. It is still in beta, so in theory less stable. But I should add that I am using this version for some time now (on Linux) and in my experience it is very stable.

Of course, you can also install both, they should run happily next to each other.