[OSRS-PROJ] PROJ and ellipsoid shifts

Jean-Paul Berroir jean-paul.berroir at inria.fr
Wed Jan 9 05:03:00 EST 2002

> Jean-Paul,
> I get the same problem, and I have found it is a botched change I made

> to the Convert_Geodetic_To_Geocentric() routine in September.  As far
> I can tell this will always screw up any conversion from geodetic to
> geocentric.   I have correct the geocent.c file and now I get values
> to your reference position, but still off by 12 meters.  I am assuming
> is due to the +towgs84 transform being only an approximation of the
> transformation.
> I have committed the fixed geocent.c, and also place it at:
>  ftp://gdal.velocet.ca/pub/outgoing/geocent.c
> I would appreciate your trying the fix and verifying things are OK for
> I think I had better issue a PROJ.4.4.5 soon since this is a very
> flaw in the datum shifting support.

Thank you Mark
I've tried your fix and as you say, the results agree with reference
points by less than 12 meters -even less with other points-, which is
more than enough for me.  And more, the +towgs84 specification now has a
normal behavior

many thanks again -  and happy new year (with version 4.4.5?)



AIR project - INRIA - BP 105 - F78153 Le Chesnay Cedex
Tel: +33 1 3963 5703 Fax: +33 1 3963 5880
jean-paul.berroir at inria.fr

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