NAME

       GIS::Distance::GreatCircle - Great circle distance calculations.

DESCRIPTION

       A true Great Circle Distance calculation.  This was created because the
       GIS::Distance::MathTrig formula uses Math::Trig's "great_circle_distance()" which doesn't
       actually appear to use the actual Great Circle Distance formula (more likely Cosine).

       A faster (XS) version of this formula is available as GIS::Distance::Fast::GreatCircle.

       Normally this module is not used directly.  Instead GIS::Distance is used which in turn
       interfaces with the various formula classes.

FORMULA

           c = 2 * asin( sqrt(
               ( sin(( lat1 - lat2 )/2) )**2 +
               cos( lat1 ) * cos( lat2 ) *
               ( sin(( lon1 - lon2 )/2) )**2
           ) )

SUPPORT

       See "SUPPORT" in GIS::Distance.

AUTHORS

       See "AUTHORS" in GIS::Distance.

LICENSE

       See "LICENSE" in GIS::Distance.