boost::geometry::cs::geographic
cs.hpp
typename DegreeOrRadian
core_detail::coordinate_system_units< DegreeOrRadian >::units typedef core_detail::coordinate_system_units< DegreeOrRadian >::units boost::geometry::cs::geographic< DegreeOrRadian >::units units

Geographic coordinate system, in degree or in radian.

Defines the geographic coordinate system where points are defined in two angles and usually known as lat,long or lo,la or phi,lambda

http://en.wikipedia.org/wiki/Geographic_coordinate_system

might be moved to extensions/gis/geographic

- boost::geometry::cs::geographic
  units