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NAME

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

DESCRIPTION

This formula uses Math::Trig's great_circle_distance function which at this time uses math almost exactly the same as the GIS::Distance::Cosine formula. If you want to use the GIS::Distance::Cosine formula you may find that this module will calculate faster (untested assumption). For some reason this and the Cosine formula return slight differences at very close distances. This formula has the same drawbacks as the Cosine formula.

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

FORMULA

As stated in the Math::Trig POD:

    lat0 = 90 degrees - phi0
    lat1 = 90 degrees - phi1
    d = R * arccos(cos(lat0) * cos(lat1) * cos(lon1 - lon01) + sin(lat0) * sin(lat1))

AUTHORS AND LICENSE

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