NAME

GIS::Distance::Cosine - Spherical law of cosines distance calculations.

DESCRIPTION

Although this formula is mathematically exact, it is unreliable for small distances because the inverse cosine is ill-conditioned.

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

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

FORMULA

a = sin(lat1) * sin(lat2)
b = cos(lat1) * cos(lat2) * cos(lon2 - lon1)
c = arccos(a + b)
d = R * c

SEE ALSO

https://en.wikipedia.org/wiki/Spherical_law_of_cosines

AUTHORS AND LICENSE

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