[GRASS-user] importing geotif in grass, transformation parameters

[Martina Schaefer]

Hi,

thanks first for all your fast answers, I'm still a bit lost in GRASS. 
I'll come back to your answers to my other questions later, I have first 
to work a bit more on your suggestions.

For nearly all data that I try to import with r.in.gdal, I get 
warnings/error messages like this:

"A datum name wgs84 (WGS_1984) was specified without transformation 
parameters. Note that the GRASS default for wgs84 is 
towgs84=0.000,0.000,0.000."

or

"WARNING: No projection name! Projection parameters likely to be
          meaningless.
A datum name nad83 (North_American_Datum_1983) was specified without 
transformation parameters. "

or

"WARNING: No projection name! Projection parameters likely to be
          meaningless.
WARNING: Datum 'unknown' not recognised by GRASS and no parameters found.
          Datum transformation will not be possible using this projection
          information."


I don't have any idea to what refers this "transformation parameter". 
Which information is missing?
And, if I would know which information is missing and get to know it, 
would there be any possibility to get this information into GRASS after 
or during the import process?
Even if I can open the files ignoring these warnings, I'm struggling in 
the most cases later on other operations. For example I can't project 
the UTM data in LongLat (or viceversa) as Grass complains again about 
missing parameters.
But my main problem is really that I don't understand with which 
transformation parameters I'm dealing!

Thanks again for your help,
	Martina