[Proj] Libproj4 manual opinion poll
Gerald I. Evenden
geraldi.evenden at gmail.com
Mon Sep 29 11:35:15 EDT 2008
One thing quickly becomes apparent: the confusion as to what is the difference
between proj.4 and libproj4.
In terms of cartographic projections, nearly nothing. In terms of datum
shifts and other miscellany: everything. libproj4 as with the original
proj.4 software had nothing to do with datum shifts other than the original
distribution had a separate section that dealt only with the NAD datums. The
original proj program also had a mechanism for generating Tchebyshev
polynomials that were designed for use with the mapgen map graphic system.
For the end user, the difference between running proj and lproj is trivial and
the user can use the original report for proj when using lproj without
getting into trouble. There are a few more projections in libproj4 library
and lproj than the old system.
There have been a few peculiarities introduced into the proj.4 material, some
I can understand and some that I cannot (to put it very mildly).
1. Alternate longitude origins. Are not supported in libproj4 (nor original
proj). Some usefulness and a valid suggestion for libproj4.
2. Alternate origins for some projections. I shudder when I see "two standard
parallels" listed for plain ol' Mercator. There is not even one standard
parallel, let alone two. There is a latitude of true scale and that only
adjusts the k_0 factor so that the scale factor is 1. at the selected
latitude. If one wants to shift the origin then use x_0, y_0. Stuff like
that really raises blood pressure.
I am sure there are others but that is a starter list.
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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