[GRASSLIST:2074] Re: lat/lon -> utm european datum

[Paul Kelly]

Hello there

On Wed, 17 Dec 2003, javier garcia - CEBAS wrote:

> Hi,
> I've got some images (*.gif) and I know the lat/lon coordinates of four
> points in the image (not the corder but in an inner square). And my location
> is projected in European Datum 1950 for Spain and Portugal:

I think r.in.gdal con read GIF files (if not convert to another format
like TIFF in external image processing software first). Then you can
import the images into an unprojected XY location. Create your
latitude-longitude location and make sure to set up the correct datum that
your images are in.

Then you could use i.points/i.rectify with your known co-ordinates
(from the XY location) to rectify the images
into the lat/long location, and finally go to the eur50
location and run r.proj to bring in the images from lat/long. I would
advise re-running g.setproj on the eur50 location first (you need to use
the CVS GRASS 5.3) as I think there are some more accurate datum
transformation parameters available for Spain now than those in your
existing PROJ_INFO.

So, a 3-stage process for each image:
1) import into XY (r.in.gdal)
2) rectify into lat/long (i.group/i.target/i.points/i.rectify)
3) re-project into UTM eur50 (r.proj)

I hope this is some help.

Paul