[GRASSLIST:324] Re: GRASS and the Norwegian coordinate systems (NGO48)

[Paul Kelly]

Hello there

It looks like you will need to add the modified Bessel ellipsoid to the
ellipse.table file as it doesn't seem to be included. The file is in
$(GISBASE)/etc/ellipse.table, where $(GISBASE) is the directory GRASS is
installed in.

Add a line something like:

modif_bessel  "Bessel Modified (Norway)"  a=6377492.0176  f=1/299.15281285

to the end of the file and then run g.setproj, selecting 'tmerc' for the
projection and modif_bessel for the ellipsoid. The other parameters you
will need to answer the questions from g.setproj are at
http://crs.ifag.de/crs_national.php
There are actually 8 different co-ordinate systems, and if you have data
in different zones from I to VIII you will need to set up a separate GRASS
location for each zone.

If you are using the latest CVS version of GRASS then you would also be
able to take advantage of datum transformations between the WGS84 and
ngo48 datums. I will look at adding support for the ngo48 datum to the
GRASS CVS tomorrow, although you can always add it as a custom datum or
add the details to the datum.table and datumtransform.table files yourself
if you want, using the details at the above website.

In general it is possible to use almost any projection and datum in GRASS,
although some require a little more setting up than others. For European
countries most of the parameters you need are at
http://crs.ifag.de/crs_national.php, which is a very useful website.

I hope this is some help

Paul Kelly