Geocentric Datum of Australia 1994, was - Re: [GRASS-user] Convert OGR vector layer to GRASS vector map

[Paul Kelly]

On Wed, 15 Jul 2009, Markus Neteler wrote:

> On Wed, Jul 15, 2009 at 3:43 AM, benton101<benton.davies at gmail.com> wrote:
>> 2. The command output pane states "Datum <GDA_1994> not recognised by GRASS
>> and no parameters found". How can I give imported data the correct meta data
>> for projection? I gather that this will be an EPSG identifier?

Were you creating a new location while importing the file? If not, this 
message is of no significance - the projection of the location is what 
will be used.

> I found this:
> Maps and the GDA, http://www.icsm.gov.au/gda/mapsgda.pdf
>
> +---------------------------------------------------
> | This map was produced on the Geocentric Datum of Australia 1994 (GDA94).
> | Heights are referenced to the Australia Height Datum (AHD).
> | For most practical purposes GDA94 coordinates and satellite derived (GPS)
> | coordinates based on the World Geodetic Datum 1984 (WGS84) are the same.
> |
> | Example 1: Datum information on new map.
> +---------------------------------------------------
>
> Should we add WGS84 as short-cut in the datum table?

No it's a datum in its own right and should have an entry in datum.table 
with ellipsoid GRS80 and dx=dy=dz = 0. Before adding it we would need to 
check what the proper EPSG-based long name should be. I suspect it might 
be "Geocentric_Datum_of_Australia_1994" but will need to make sure.

Paul