Geo::Inverse - Calculate geographic distance from a lat & lon pair. use Geo::Inverse; my $obj = Geo::Inverse->new(); # default "WGS84" my ($lat1,$lon1,$lat2,$lon2)=(38.87, -77.05, 38.95, -77.23); my ($faz, $baz, $dist)=$obj->inverse($lat1,$lon1,$lat2,$lon2); #array context my $dist=$obj->inverse($lat1,$lon1,$lat2,$lon2); #scalar context print "Input Lat: $lat1 Lon: $lon1\n"; print "Input Lat: $lat2 Lon: $lon2\n"; print "Output Distance: $dist\n"; print "Output Forward Azimuth: $faz\n"; print "Output Back Azimuth: $baz\n"; This module is a pure Perl port of the NGS program in the public domain "inverse" by Robert (Sid) Safford and Stephen J. Frakes.

new
The new() constructor may be called with any parameter that is appropriate to the ellipsoid method which establishes the ellipsoid. my $obj = Geo::Inverse->new(); # default "WGS84"

ellipsoid
Method to set or retrieve the current ellipsoid object. The ellipsoid is a Geo::Ellipsoids object. my $ellipsoid=$obj->ellipsoid; #Default is WGS84 $obj->ellipsoid('Clarke 1866'); #Built in ellipsoids from Geo::Ellipsoids $obj->ellipsoid({a=>1}); #Custom Sphere 1 unit radius

inverse
This method is the user frontend to the mathematics. This interface will not change in future versions. my ($faz, $baz, $dist)=$obj->inverse($lat1,$lon1,$lat2,$lon2); Add more tests. Please send to the geo-perl email list. No guarantees that Perl handles all of the double precision calculations in the same manner as Fortran. Michael R. Davis qw/perl michaelrdavis com/ Copyright (c) 2006 Michael R. Davis (mrdvt92) This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. Net::GPSD Geo::Ellipsoid GIS::Distance::GeoEllipsoid