[Proj] libproj4 update

Gerald I. Evenden geraldi.evenden at gmail.com
Sat Jun 7 16:37:32 EDT 2008

Libproj4 home web site:


has a new release of the libproj4 libary: new20080604.tar.bz2.

Besides a few corrections the principle item of note are the inclusion of two 
wide-latitude versions of Transverse Mercator: ftmerc and etmerc.  Their 
latitude range extends well beyond the range of tmerc and, except for some 
cases, to and beyond 90 degrees.

etmerc is based upon code by K. Engsager, K. Poder and the kind assistance of 
Thomas Knudsen.

After installation time trials were made along with accuracy tests where tmerc 
excelled in all tests within UTM ranges. For speed:

tmerc: 0.562 usec./forward projection
etmerc: 1.449 usec./forward projection
ftmerc: 2.906 usec./forward projection

Timing was based upon 10,000,000 operations for each trial on a
Intel(R) Pentium(R) 4 CPU 3.00GHz.

tmerc obviously remains the version of choice for UTM because of proven 
accuracy over the legal range of UTM as well as performance speed.

I will add some comments on accuracy on later emails.

Note: there is another version, stmerc, in the library but accuracy does not 
appear to be a strong point.

As always please email me about any portability and other performance 
problems.  Bitches will be ignored and kudos will be welcomed.

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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