[Proj] Geodesics on Saturn's moons
Charles Karney
ckarney at sarnoff.com
Wed Apr 1 05:39:11 EST 2009
I've updated my geodesic routines. For documentation go to
http://charles.karney.info/geographic/geodesic.html
The code itself (C++ classes and the Geod utility) is available at
http://charles.karney.info/geographic
The main changes are:
* code has been sped up modestly (about 25-30%) by trimming the
orders of the series used and by improving the starting guesses
for Newton's method for the inverse problem.
* a prolate spheroid can be specified by a negative reciprocal
flattening.
* the Geod utility accepts the following new options (type Geod -h,
for details):
-e a r, to set the ellipsoid parameters,
-b, to report azi2 as a back azimuth,
-a, to accept and report distances in terms of arc length on the
auxiliary sphere.
Example: to determine a geodesic for a pair of points on Tethys, one of
Saturn's moons (which is prolate on account of tidal forces?), do
echo 30N 0E 28S 180W | ./Geod -e 529300 -47.7 -i -p 0
=>
44.80204 136.31245 1660275
Still to do:
* More documentation (probably at least a month off)
* More thorough analysis of Newton's method for inverse problem
--
Charles Karney <ckarney at sarnoff.com>
Sarnoff Corporation, Princeton, NJ 08543-5300
URL: http://charles.karney.info
Tel: +1 609 734 2312
Fax: +1 609 734 2662
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