projections in GRASS

[Cosyn Bart]

Hi,


> Hi,
>
>         has anybody out there any experience transforming raster data
> between projections?
>
As Grass is not transformable from f.i Non-projected data to Lambert
Conic projection I am a bit afraid you will need to combine own written
programs with the Grass tools for image processing. i.points and i.rectify

I had a basically identical situation to transform my data to the Belgian
Lambert projection.
I wrote a program that allowded me to calculate points from one system to
another. This you should be able to get from a local geographic institute
or at least you would need to have the refernce points and meridian.
After having written this you should do the following.

Make a group with i.group so in this way grass creates the subdirectory
group and a subdir with the name of the group. Normally using i.points or
i.vpoints you create a file POINTS. You can skip the module i.points and
create the file POINTS yourself with your calculated data. Then just run
i.rectify. Be sure that you have good distributed points over the area.
It should work but it will take time to develop your own transformations!

                        Bart


        ---------------------------------------------------     
        | ir. Bart Cosyn                                  |
        | ERS1/2 project                                  |
        | Laboratory for Hydrology and Water Management   |
        | University of Gent                              |
        | Coupure 653, B-9000 Gent                        |     
     | Belgium                                    |
        | Tel: +/32/9/2646137                             |
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        | E-mail: bcosyn at allserv.rug.ac.be                |
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