[Proj] Transverse Mercator algorithm

Gerald I. Evenden geraldi.evenden at gmail.com
Tue May 27 13:28:28 EDT 2008

On Tuesday 27 May 2008 11:52 am, Frank Warmerdam wrote:
> Oscar van Vlijmen wrote:
> > In my opinion, there are 2 possibilities:
> >
> > * High accuracy.
> > * Speed.
> Folks,
> To state the obvious, computers are pretty fast now, so for many purposes
> a TM variant that is quite a bit slower would be acceptable.
> I would like to see a TM version that is very reversable well outside the
> typical six degree swath around the central meridian.
> Mostly I wish I could have a highly reversable TM variant that was exactly
> the same as the existing TM approximation in at least one direction.  It is
> the failure to reverse that is a nightmare for me.

A minor nit-pick: "inverse" is a better term than "reverse."

arcsine is the inverse of sine.

Another minor aside: an earlier version of proj used with the mapgen program 
used a Tchebyshev(sp) approximations to speed up the projections for larger 
scale map regions (lesser lam-phi extents).  This also alowed the code in the 
mapping program to only deal with bivariate polynomials for all projections 
and not have to carry around the projection library.

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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