importing raster maps

[Gerald I. Evenden]

>Date:         Wed, 04 May 94 15:48:13 +0200
>From: Ralf Kunkel <STE077 at ZAM001.ZAM.KFA-JUELICH.DE>
>Organization: Forschungszentrum Juelich GmbH
>Subject:      importing raster maps
>To: Office of GRASS integration <grassu-list at max.cecer.army.mil>
>
>There are a couple of raster maps I want to import into GRASS 4.1.3. These
>maps are referred to a Gauss-Krueger Projection (central meridian 9.0 degrees
>east, speroid=bessel) with equidistant spacing in N-S and W-E directions in
>this projection.
>As far as I could get out of the GRASS-manuals, importing ASCII-data using
>r.in.ascii or r.in.ll uses an equidistant spacing of lat-lon coordinates.
>Although I dont't know exactly how to arrange this, it should be possible to
>convert the GK coordinates of each single raster cell or it's boundaries into
>lat-lon coordinates with PROJ. But then, the geographic locations of the
>cells should be changed significantly when importing into GRASS.
>Right now, I'm stucked on this problem. I wonder if somebody can give me some
>hints in importing the data into GRASS.
>
>Thanks in advance
>Ralf Kunkel

A couple of partial answers.

First: Gauss-Krueger is synonymous with Transverse Mercator.  The former
	nomenclature is more common in Europe and the latter in North America.

Second: the central meridian of 9 degrees makes it similar to UTM.
	BUT do not use UTM unless you determine that a scale factor of
	0.9996 (k_0) was spec'ed for the CM.
	Regardless, you are going to need the CM scale factor.  If you can't
	determine what it is you're going to have to guess 1.0.

Third: check the datas easting to see if the zone was prepended as
	N,000,000 meters.  That is, the easting will have a number larger
	than about 800,000m (probably in the range of 2,000,000+).

Knowing these factors, getting the data into GRASS ought to be possible.

Gerald (Jerry) I. Evenden   Internet: gie at charon.er.usgs.gov
voice: (508)563-6766          Postal: P.O. Box 1027
  fax: (508)457-2310                  N.Falmouth, MA 02556-1027