Tips and Tricks

Tips and Tricks

Using QGIS as a frontend to GRASS

QGIS can run as a frontend to GRASS. There is support for displaying maps, editing maps, and execution of simple GIS functions. The GDAL/OGR library is a requirement for that (but for GRASS anyway):

• QGIS homepage: http://qgis.org
• GDAL homepage: http://www.gdal.org

To use the two together, the GDAL-GRASS plugin must be installed:

• Compile and install GRASS and QGIS with GDAL/OGR Plugin

Test that the GDAL-GRASS plugin is available with this command:

  gdalinfo --formats

Look for a line like "GRASS (ro): GRASS Database Rasters (5.7+)"

Enable the QGIS GRASS plugin from QGIS:

  GUI: Plugins / Plugin Manager / Check the GRASS checkbox

The GRASS toolbar should now be visible. While not a firm requirement, it is easier to start QGIS from within a GRASS session.

• QGIS GRASS Cookbook - Recipes for common tasks

Exporting GRASS maps to GMT

GMT (Generic Mapping Tools) is a Free software package for creating publication quality cartography.

GMT homepage: http://gmt.soest.hawaii.edu

Exporting GRASS maps to GMT: http://169.237.35.250/~dylan/grass_user_group/#GMT_and_GRASS-overview
(Supplied by the GRASS Users Group of Davis, California)

Interfacing R-Statistics with GRASS

• All the necessary functions for the GRASS 6 interface are now in packages

on CRAN, so that on Linux/Unix (or Mac OSX) installing rgdal from source with PROJ4 and GDAL installed, or Windows installin binary, the required packages are:

sp

maptools (now includes spmaptools)

rgdal (now includes spGDAL, spproj)

spgrass6

now all on CRAN.

• http://grass.ibiblio.org/statsgrass/index.php#grassR

• R-Statistics homepage http://www.r-project.org

• R Spatial Projects http://sal.uiuc.edu/csiss/Rgeo//

• http://r-spatial.sourceforge.net/xtra/xtra.RHnw.html#spgrass6

• Neural Networks with GRASS and R (posted by Markus Neteler on the grass-user mailing list) http://www.uam.es/proyectosinv/Mclim/pdf/MBenito_EcoMod.pdf

• Using R and GRASS with cygwin: It is possible to use Rterm inside the GRASS shell in cygwin, just as in Unix/Linux or OSX. You should not, however, start Rterm from a cygwin xterm, because Rterm is not expecting to be run in an xterm under Windows, and loses its input. If you use the regular cygwin bash shell, but need to start display windows, start X from within GRASS with startx &, and then start Rterm in the same cygwin shell, not in the xterm.

Using GRASS with an on-line Web-GIS

see:

• GRASS and MapServer
• GRASS and PHP
• GRASS and Python

(please expand)

Starting and running GRASS from a script

See GRASS and Shell.

Running GRASS remotely on OS X

Tiger (OS 10.4) changed the default configuration of SSH from previous versions of OS X. You can no longer start an ssh session with the -X flag and display the Tcl/Tk components of the GRASS GUI remotely. If you are running grass on OS X (10.4) between hosts on a network (i.e. running it on one machine but displaying it on another), you will need to use the "trusted forwarding" mode of SSH in order for the Tcl/Tk generated graphics, such as d.m or gis.m in order for the GUI graphics to make it through your connection. This can be done using the -Y flag when you start the ssh session:

ssh -Y remotehost

or add this to ~/.ssh/config:

Host hostname
  ForwardX11 yes
  ForwardX11Trusted yes

Using the -X flag, or simply turning on X11Forwarding in the SSH configuration files, is not enough: the symptoms in this case are that a d.mon window will function fine, but none of the Tcl/Tk dialogues will work, failing with an error message complaining either about Wish not behaving as expected, or a "Bad Atom".