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
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