GIS::Distance::Fast::Vincenty - C implementation of GIS::Distance::Vincenty.
See GIS::Distance::Vincenty for details about this formula.
The results from GIS::Distance::Vincenty versus this module are slightly different. I'm still not sure why this is, as the C code is nearly identical to the Perl code.
Normally this module is not used directly. Instead GIS::Distance is used which in turn interfaces with the various formula classes.