[Proj] Status of projection inverses
Gerald I. Evenden
geraldi.evenden at gmail.com
Sat Oct 25 22:43:04 EDT 2008
Several days have gone by without any comments on the subject but that does
not mean that I am not working on it.
1. trying to get a better initial guess process via some rough polynomial
method pretty well went up in flames.
2. but using the gsl library of multidimensional root finding shows a great
deal of progress and converges faster than the simple Newton-Raphson and is
more tolerant of poor initial conditions.
3. gsl can also do the same job without a Jacobian requiring derivatives. For
those who have not already noticed, there are many inverseless projections
where the derivatives would be impossible or nearly so---even with help from
Conclusions here are that I am going to finish up this project with the gsl
methodology in order to preserve my own sanity. ;-)
The gsl library already requires gsl for one projection so there is nothing
new in the gsl option.
For those who cannot abide by the gsl license I will continue to use the
switches in the Makefile to eliminate code that uses that library. The
bottom line is that some inverse projections will not be available to non-gsl
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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