projecting rasters

[Cosyn Bart]

> Hello,
> 
> Has anyone done any projection conversions on raster files?
> If so, I would like to hear how you went about it, it seems
> a bit complicated to me.

Hi  Steve,
I worked a few months ago on some problems to change from our Belgian 
Lambert projection to UTM and vice versa. As far as I know there was no 
conversion tool to do so in Grass. The way I solved the problem was by 
rectifying the image from one location to another. I used the module 
i.rectify for that but in stead of using i.points or i.vpoints to 
determine my rectifying points I just made the POINTS file myself. F.I 
you pick out the 4 corner points and determine the position of the points 
in the two different systems. You make the file by hand using tools of 
yourself or an other institute! the points file is located in
$GISDBASE/group/???/POINTS
First you need i.group and i.target to run. In fact it works fine but 
take care of the use of the allocation of the points over the image! They 
need to be well distributed. This procedure looks to be quite time 
intensive but as you are never using an interface program you can do it 
thru a script! Hope it helps and gives you at least some ideas!

			Bart

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	| ir. Bart Cosyn				  |
	| ERS1/2 project				  |
	| Laboratory for Hydrology and Water Management	  |
	| University of Gent 			 	  |
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        | Belgium 					  |
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	| E-mail: bcosyn at allserv.rug.ac.be		  |
        | Http: http://sung.rug.ac.be/			  |
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