[GRASS-user] DAtum Warning while using r.in.gdal

[Paul Kelly]

On Mon, 31 May 2010, Kim Besson wrote:

> Greetings
>
> Following a few suggestions made at this list I'm using gdalwarp to project
> a few landsat images and only then yusing r.in.gdal.
>
> I'm using this expression to reproject image:
> gdalwarp -t_srs "+proj=tmerc +lat_0=39.66825833333333
> +lon_0=-8.133108333333334 +k=1 +x_0=0 +y_0=0 +ellps=GRS80 +units=m +no_defs
> " L71203033_03320001023_B10.TIF  landsat_out.tif
>
> And when I run r.in.gdal I get this warning:
> Datum <unknown> not recognised by GRASS and no parameters found
> Projection of input dataset and current location appear to match
>
> What does this means?

It is a warning that there is no datum information in the reprojected 
file. It may not be a problem, unless if the original image (before you 
reprojected it) was in a different datum there could be small errors in 
it. Since the ellipsoid is GRS80, you can add the correct datum 
information by adding "+towgs84=0,0,0" to the projection parameters. If 
you import that image with r.in.gdal then there should be no warning.

Paul