# GIS::Distance::MathTrig

## NAME

GIS::Distance::MathTrig - Great cirlce distance calculations using Math::Trig.

## DESCRIPTION

This formula uses Math::Trigâ€™s "great_circle_distance()" which at this time uses math almost exactly the same formula as the GIS::Distance::Cosine formula. And the Cosine formula is about 5% faster than this formula.

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

## FORMULA

lat0 = 90 degrees - phi0

lat1 = 90 degrees - phi1

d = R * arccos(cos(lat0) * cos(lat1) * cos(lon1 - lon01) + sin(lat0) * sin(lat1))

As stated in the Math::Trig documentation.

## SUPPORT

See " SUPPORT" in GIS::Distance.

## AUTHORS

See " AUTHORS" in GIS::Distance.

## LICENSE

See " LICENSE" in GIS::Distance.