Bruce Raup wrote:
All,
We at NSIDC had the EASE-Grid projections added to the EPSG code list
last year or so, and I recently noticed that in the "share/proj/epsg"
file in FWTools, for the entry for 3410, it says:
# NSIDC EASE-Grid Global
# Unable to translate coordinate system EPSG:3410 into PROJ.4 format.
I don't understand why it says this, especially since the Proj.4
parameters are defined at
Bruce,
It says this because EPSG projection method 9834 (Lambert Cylindrical
Equal Area) has no translation support in gdal/ogr/ogr_fromepsg.cpp.
If you file a ticket on this issue I can add it.
http://nsidc.org/data/atlas/epsg_3410.html
as pointed out by Jose. Can anyone say why the epsg file says that?
Proj.4 doesn't deal with datums, so it can handle EASE-Grid just fine,
but it should be noted that EASE-Grid maps lon/lat, usually defined on
the WGS-84 datum, to a projection that uses a non-standard spheroid.
In other words, the datum ellipsoid and the projection ellipsoid are
not the same. This is common for satellite-era data. Unfortunately,
lots of software and data formats do not properly make this
distinction, or allow for this distinction, and so one can run into
problems. For example, display software can display the wrong lon/lat
under the cursor by erroneously doing a datum shift after
unprojection.
This is most annoying since there seems to be no standard way of representing
such a coordinate system in WKT (for instance).
Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up | Frank Warmerdam, [EMAIL PROTECTED]
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Programmer for Rent
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