NAME

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

DESCRIPTION

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

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

FORMULA

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

AUTHORS AND LICENSE

See "AUTHORS" in GIS::Distance and "LICENSE" in GIS::Distance.