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

GRASS GRASS user
1

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.

I hope that someone has experience with "Hong_Kong_1980_Grid", can confirm,
what I found so far and maybe add the missing datum transformation parameters
or knows where I can find more about it?

thanks a lot
Otto

2

Does this help... http://spatialreference.org/ref/epsg/2326/proj4/ ?

On Thu, 2007-12-13 at 11:51 +0100, 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.

I hope that someone has experience with "Hong_Kong_1980_Grid", can confirm,
what I found so far and maybe add the missing datum transformation parameters
or knows where I can find more about it?

thanks a lot
Otto
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--
Nikos Alexandris
.
Department of Remote Sensing & Landscape Information Systems
Faculty of Forestry & Environmental Sciences, Albert-Ludwigs-University Freiburg
.
Tel. +49 (0) 761 203 3697 / Fax. +49 (0) 761 203 3701 / Skype: Nikos.Alexandris
.
Address: Tennenbacher str. 4, D-79106 Freiburg i. Br., Germany

3

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

4

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@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