NAME

GIS::Distance::Haversine - Exact spherical distance calculations.

DESCRIPTION

This is the default distance calculation for GIS::Distance as it keeps a good balance between speed and accuracy.

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

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

FORMULA

    dlon = lon2 - lon1
    dlat = lat2 - lat1
    a = (sin(dlat/2))^2 + cos(lat1) * cos(lat2) * (sin(dlon/2))^2
    c = 2 * atan2( sqrt(a), sqrt(1-a) )
    d = R * c

RESOURCES

http://mathforum.org/library/drmath/view/51879.html

http://www.faqs.org/faqs/geography/infosystems-faq/

AUTHORS AND LICENSE

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