[GRASS-user] towgs84 datum parameters for "Hong Kong 1980"

[Otto Dassau]

Hi Nikos and Paul

thanks a lot for your help and notes. I will test the parameters and write back
then. Maybe then, we can add the datum parameters to grass svn.

 Regards,
  Otto

On Thu, 13 Dec 2007 13:51:17 +0000 (GMT)
Paul Kelly <paul-grass at stjohnspoint.co.uk> wrote:

> On Thu, 13 Dec 2007, Otto Dassau wrote:
> 
> > Hi,
> >
> > I need some help to add support for "Hong Kong 1980" datum in GRASS. I
> > have a wkt file with following information:
> >
> >
PROJCS["Hong_Kong_1980_Grid",GEOGCS["GCS_Hong_Kong_1980",DATUM["D_Hong_Kong_198
> >
0",SPHEROID["International_1924",6378388.0,297.0]],PRIMEM["Greenwich",0.0],UNIT
> >
["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["Fal
> >
se_Easting",836694.05],PARAMETER["False_Northing",819069.8],PARAMETER["Central_
> >
Meridian",114.1785555555556],PARAMETER["Scale_Factor",1.0],PARAMETER["Latitude_
> > Of_Origin",22.31213333333334],UNIT["Meter",1.0]]
> >
> > The datum D_Hong_Kong_1980 does not exist in GRASS yet. I found following
> > parameters and added them to the datum.table file:
> >
> > # Hong Kong Datum 1980
> > hk80     "Hong_Kong_1980"   international    dx=-156    dy=-270    dz=-189
> >
> > Now I am missing the Datum Transformation Parameters to add to the
> > datumtransform.table.
> 
> Just to note that you do not necessarily need to add parameters to both 
> datum.table and datumtransform.table. If dx=-156    dy=-270    dz=-189 are 
> the only parameters you have, that is fine and they will be the only ones 
> used. An entry in datumtransform.table is only needed if you have multiple 
> sets of parameters for the datum, or if the only set you have available is 
> not a 3-parameter set.
> 
> Paul