Category Archives: GRASS GIS

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 Рexport raster map Рcommon 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.

 

Creating a raster layer with a weighted random sample of points (or, my first attempt to create a python script)

I needed to create a raster map layer with a weighted random sample of all raster cells, using the percentage of crop land as weight. I couldn’t find a function to create such a weighted sample, so I decided to create a script to do this for me. Continue reading

One of those handy GRASS GIS functions I didn’t know about

Recently I needed to create a series of temporally interpolated rasters in between two input raster maps, viz., a suitability distribution map under climate conditions in 2000 and under projected climate conditions in 2020. I though this would be a good time to try out the new temporal database in GRASS GIS and use the t.rast.gapfill function, which replaces gaps in a space time raster data-set with interpolated raster maps using linear interpolation. Continue reading

Add multiple raster or vector map layers to current map display in GRASS GIS

If your mapset contains many raster or vector layers GRASS offers a very handy feature to quickly select the layers you want to add to your current map display. In the layer manager, click¬†Ctrl+Shift+L to open the ‘add selected map layers into layer tree’ window. Continue reading

GRASS 7.0 beta1 is out

After a long wait, GRASS 7.0 beta is out! See here a summary of what is new in this release. Take your time, is is a long list :-).

In fact, GRASS 7.0 has been available for some time now for those willing to compile it themselves. So have I, and out of experience I can tell you, this is a great release, with tons of new features and improvements, including great speed improvements in handling vector layers, a whole new module for time series analysis, numerous interface improvements, etc.

Really, you should go over to the download page and give it a try! Good change you won’t look back after that.

Rescale your raster data layer

Sometimes you want to rescale a raster layer, e.g., to reduce the number of categories, or to create a common scale for different raster layers. Very basic of course, so you can expect to find an appropriate function in any self-respecting GIS software. Just be aware that different terms are being used for the same thing, e.g., scale in gdal, rescale in GRASS and normalize in SAGA GIS. Below a few ways to do this using my favourite GIS programs: GRASS GIS, QGIS, SAGA GIS or gdal. Continue reading