...one of the most highly
regarded and expertly designed C++ library projects in the
world.

— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards

Tag defining the unit of plane angle for spherical coordinate systems. This tag specifies that coordinates are defined in radians (-PI .. PI). It has to be specified for some coordinate systems.

struct radian { // ... };

Either

`#include <boost/geometry/geometry.hpp>`

Or

`#include <boost/geometry/core/cs.hpp>`

Specify two coordinate systems, one in degrees, one in radians.

#include <iostream> #include <boost/geometry.hpp> using namespace boost::geometry; int main() { typedef model::point<double, 2, cs::spherical_equatorial<degree> > degree_point; typedef model::point<double, 2, cs::spherical_equatorial<radian> > radian_point; degree_point d(4.893, 52.373); radian_point r(0.041, 0.8527); double dist = distance(d, r); std::cout << "distance:" << std::endl << dist << " over unit sphere" << std::endl << dist * 3959 << " over a spherical earth, in miles" << std::endl; return 0; }

Output:

distance: 0.0675272 over unit sphere 267.34 over a spherical earth, in miles