[GRASSLIST:1019] Re: Georeferencing without the mouse?

Glynn Clements glynn at gclements.plus.com
Fri May 5 19:46:00 EDT 2006


David Ottina wrote:

> New to GIS, and new to GRASS. Trying to learn using GRASS 6.0.1/GDAL
> under ubuntu dapper
> 
> On importing a .jpg, .tif, etc. that is not georeferenced the tutorial
> explains using i.group i.target, i.point, i.rectify, which I can do. 
> But I'm wondering if it is possible to avoid the mouse by specifing
> both sets of points textually.
> 
> For instance if I'm trying to georeferece a global image of a known
> pixel resolution and projection like NASA's blue marble:
> http://visibleearth.nasa.gov/view_rec.php?id=2430

If the projection is known, it's simpler to create a new location with
the correct projection, import the image there, then set the map's
corners with r.region.

If you want to use the map in a location with a different projection,
you can use r.proj to create a re-projected copy of the map.

> Then I'd prefer some way to say:
> 
> x,y = lat, long
> 0,0 = -180,90
> 0,1024 = -180,-90

If the image is a whole-earth lat/lon map, import it into a lat/lon
location then use "r.region n=90 s=-90 e=180 w=-180".

However, some import modules have problems importing into lat/lon
locations as the default bounds result in a north value greater than
90. In that case, switch the location to x/y by editing the WIND file
before importing, then change it back afterwards.

-- 
Glynn Clements <glynn at gclements.plus.com>




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