[Geotiff] Datum and Ellipsoid Parameters

[Max Martinez]

Masuo,

If you set the GeographicTypeGeoKey to a standard GCS code like WGS84,
this implies all of the parameters that the specified code comprises
(including the ellipsoid). Any other specified keys will be ignored.

If the parameters you are trying to set cannot be stated in terms of a
standard GCS code, you need to use the UserDefined GeographicTypeGeoKey
and specify a citation, the datum, angular units and prime meridian, and
if your datum cannot be expressed in a standard code, you must use the
UserDefined value for the GeogGeodeticDatumGeoKey and then specify a
citation and ellipsoid.

You cannot selectively "override" parameters implied by standard codes.
The one exception to this in the case of IMAGINE is linear and angular
units...you can configure IMAGINE to allow "units" overrides, but this
is not regarded as standard GeoTIFF.

Max

-----Original Message-----
From: geotiff-bounces at lists.maptools.org
[mailto:geotiff-bounces at lists.maptools.org] On Behalf Of Masuo Takahashi
Sent: Tuesday, September 14, 2010 4:56 AM
To: geotiff at lists.maptools.org
Subject: [Geotiff] Datum and Ellipsoid Parameters

Dear all,

I would like to generate geotiff with several projections as
foolows;

1) Lat/Lon
   Datum: WGS84
   Ellipsod: GRS1980
   
2) Lat/Lon
   Datum: ITRF94
   Ellipsoid: GRS1980

What parameters(GeoTIFF Tags) can I set for generating each data
with these projections ?

At 1), "GeographicTypeGeoKey" and "GeogEllipsoidGeoKey" parameters
were set to 4326(GCS_WGS84) and 7019(Ellipsoid GRS1980), but
Ellipsoid parameter didn't seem to be set to GRS1980 by cheking
ERDAS IMAGINE Viewer ver 9.3. Meanwhile, ellipsoid data seemed to
be set correct in cheking  by listgeo command. 

How can I verify that geo-information is set on the data ?


Best regards,
------------------------------------------------------
Masuo Takahashi  takahashi.masuo at jaxa.jp

Earth Obsercation Research Center
Spave Application Mission Directorate
Japan Aerospace Exploration Agency
------------------------------------------------------

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