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.