[Proj] Global Gauss-Kruger and libproj4---the final story

Gerald I. Evenden geraldi.evenden at gmail.com
Wed Aug 27 11:45:53 EDT 2008

Thanks to a reader I have a copy of the Lee-Thompson material for the 
Transverse Mercator projection.

After perusing the material it is clear that no bivariate function operation 
such as libproj4 can handle the general case of the global extent of the 
Gauss-Kruger projection.  This is because of the nature of the equator 
graticule line and the fact that it branches into two parts as it approaches 
90 degrees from the central meridian.  That is, all points with 0 latitude 
and with a delta longitude near 90 degrees will have *two* resultant 
Cartesian coordinates---one for the northern hemisphere and one for the 
southern hemisphere.  Proj_fwd returns only one Cartesian point.

I had a suspicion that this was the case from viewing the "tombstone" 
illustrations of TM referenced many weeks ago but had to wait to learn the 
details of what was tranpiring.

So case closed.

The whole religious complexion of the modern world is due
to the absence from Jerusalem of a lunatic asylum.
-- Havelock Ellis (1859-1939) British psychologist

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