28constexpr double DEGREE_TO_RADIAN = M_PI / 180.0;
29constexpr double RADIAN_TO_DEGREE = 180.0 / M_PI;
30constexpr double CIRCLE_DEGREES = 360.0;
32constexpr double EARTH_RADIUS_KM = 6371.0;
33constexpr double EARTH_CIRCUMFERENCE_EQUATOR_KM = 40000.0;
34constexpr double EARTH_CIRCUMFERENCE_KM_PER_DEGREE =
35 EARTH_CIRCUMFERENCE_EQUATOR_KM / CIRCLE_DEGREES;