Geography Reference
In-Depth Information
Figure 8.7: Georeferencing an image with QGIS
in QGIS after the world file has been generated. Once you have the layer
up in QGIS, check it against any reference layers you may have to make
sure the georeferencing was a success.
Georeferencing with GRASS
There are two ways to georeference an image using GRASS. You can
use what's termed the “old” way, or you can use the
gis.m
GUI. The
old way involves a sequence of commands as described on the GRASS
FAQ:
8
i.group + i.target + i.points/i.vpoints + i.rectify
. The “new way” is to use
gis.m
and the
Georectify
item under the
File
menu.
The process is pretty much like that we used with QGIS. We won't look
at an example here, but you can explore the “old” and “new” ways on
your own if you decide to use GRASS for georeferencing rasters.
Of course, the best option is to find rasters that are already georefer-
enced. In many cases, you can do this—if not, you have to use your
newly acquired skills to get the job done.
8.
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