[GRASSLIST:4101] wanting to define a spherical earth

[Charles Krouse]

I want to import and use NOAA CoastWatch sst raster data.  It is 
projected in mercator with a spherical earth with a radius of 
6371200.0m.  I thought that I had it defined but it appears a sphere can 
not be used.  After the mercator projection definition, I get the following

projection: 99 (Mercator)
zone:       0
datum:      ** unknown (default: WGS84) **
ellipsoid:  ** unknown (default: WGS84) **


When displaying the data the projection is not accurate for the 
CoastWatch projection, and it appears to have used WGS84 as the default 
ellipsoid.

Can anyone sugguest a work around?  Possibly define a = b in the 
ellipse.table?   This method worked in other software that we used.  


Thanks.

                                                                        
                                                Charlie