sorry that this is not completely grass related but I wan't to create a location in the 'Laos National Datum 1997'. All information I have is from http://ocean.csl.co.uk/ and is listed below.
I hope somebody can help me.
Thanks
Wolfgang
datum_code= 6678 (Lao National Datum 1997)
datum_name= Lao National Datum 1997
datum_type= geodetic
origin_description= Fundamental point: Vientiane (Nongteng) Astro Pillar. Latitude: 18 deg 01 min 31.3480 sec N; Longitude: 102 deg 30 min 57.1376 sec E (of Greenwich).
realization_epoch= 1997
ellipsoid_code= 7024 (Krassowsky 1940)
prime_meridian_code= 8901 (Greenwich)
area_of_use_code= 1138 (Lao People's Democratic Republic (Laos).)
datum_scope= Cadastre, topographic mapping, engineering survey.
remarks= Supersedes Lao 1993.
information_source= National Geographic Department
data_source= EPSG
revision_date= 2004-04-27
change_id=
deprecated= 0
6678,Lao National Datum 1997,geodetic,"Fundamental point: Vientiane (Nongteng) Astro Pillar. Latitude: 18 deg 01 min 31.3480 sec N; Longitude: 102 deg 30 min 57.1376 sec E (of Greenwich).",1997,7024,8901,1138,"Cadastre, topographic mapping, engineering survey.",Supersedes Lao 1993.,National Geographic Department,EPSG,2004-04-27,0,
I found some dx,dy,dz values on the net. But now I have an other question: I want to calibrate a scanned map. The grid on the map is in this Laos Datum, but finally I want to have it wgs84. Do I really have to go the way: xy->lao97->wgs84?
Thanks
Wolfgang
Wolfgang schrieb:
Hi,
sorry that this is not completely grass related but I wan't to create a location in the 'Laos National Datum 1997'. All information I have is from http://ocean.csl.co.uk/ and is listed below.
I hope somebody can help me.
Thanks
Wolfgang
datum_code= 6678 (Lao National Datum 1997)
datum_name= Lao National Datum 1997
datum_type= geodetic
origin_description= Fundamental point: Vientiane (Nongteng) Astro Pillar. Latitude: 18 deg 01 min 31.3480 sec N; Longitude: 102 deg 30 min 57.1376 sec E (of Greenwich).
realization_epoch= 1997
ellipsoid_code= 7024 (Krassowsky 1940)
prime_meridian_code= 8901 (Greenwich)
area_of_use_code= 1138 (Lao People's Democratic Republic (Laos).)
datum_scope= Cadastre, topographic mapping, engineering survey.
remarks= Supersedes Lao 1993.
information_source= National Geographic Department
data_source= EPSG
revision_date= 2004-04-27
change_id= deprecated= 0
6678,Lao National Datum 1997,geodetic,"Fundamental point: Vientiane (Nongteng) Astro Pillar. Latitude: 18 deg 01 min 31.3480 sec N; Longitude: 102 deg 30 min 57.1376 sec E (of Greenwich).",1997,7024,8901,1138,"Cadastre, topographic mapping, engineering survey.",Supersedes Lao 1993.,National Geographic Department,EPSG,2004-04-27,0,
datum_code= 6678 (Lao National Datum 1997)
datum_name= Lao National Datum 1997
datum_type= geodetic
origin_description= Fundamental point: Vientiane (Nongteng) Astro
Pillar. Latitude: 18 deg 01 min 31.3480 sec N; Longitude: 102 deg 30
min 57.1376 sec E (of Greenwich).
realization_epoch= 1997
ellipsoid_code= 7024 (Krassowsky 1940)
prime_meridian_code= 8901 (Greenwich)
area_of_use_code= 1138 (Lao People's Democratic Republic (Laos).)
datum_scope= Cadastre, topographic mapping, engineering survey.
remarks= Supersedes Lao 1993.
information_source= National Geographic Department
data_source= EPSG
revision_date= 2004-04-27
change_id=
deprecated= 0
EPSG is a very good sign for finding an answer.
I found some dx,dy,dz values on the net. But now I have an other
question: I want to calibrate a scanned map. The grid on the map is in
this Laos Datum, but finally I want to have it wgs84. Do I really have
to go the way: xy->lao97->wgs84?
project/transform your grid coordinates to WGS84 using a tool like
PROJ's cs2cs or GRASS 6.1's m.proj before the i.points step. This may or
may not be an appropriate method depending on the map projection(s)
involved.
Be aware that there is a new georectification module in the GRASS 6.1
GUI which could use some testing (File->Georectify [pull into target
location from xy]). Also the old i.vpoints module has had many
improvements in the last few weeks. (i.rectify [push to target location
from xy])