GRASS 6 Tutorial/Raster data management

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Revision as of 04:53, 26 April 2013 by Dmci (talk | contribs) (Data Import)

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Raster data management


This section of the tutorial is intended to provide new users with an introduction to raster data management in GRASS GIS. As with other parts of the GRASS 6 tutorial, the examples are largely based on the GRASS 5.7 tutorial as well as the GRASS GIS presentation at Geostat-2012. The aim is to present the reader with introductory information on handling raster data within GRASS GIS.

Data Import

In a similar way to the vector data management, the import and export of raster data is underpinned by GDAL. As such, the modules,* and r.out.* and specifically, and r.out.gdal are used. The module r.extenal can be used in lieu of importing a raster into GRASS.

A Geotiff can be imported into GRASS using the command line (input represents the full or relative path to the raster file you want to import; output is its raster name in GRASS). The same can be achieved using the GUI. input=elev_input_state500m.tif output=elev_input_state500m

Grass raster import.png

Sometimes, you need to define the region of the Mapset to the extent of your raster. For instance, using the above-mentioned example, you would simply:

g.region rast=elev_input_state500m

A common issue that users are faced with is how to import several GeoTiffs? Obviously the above steps can be repeated using the GUI or copy-pasting the command line or more simply using the following BASH for loop:

for file in `ls *.tif`
 do input=$file output=${file%.tif}

Note - that when you run, the full extent of the map is imported