计算地理距离和方位角的程序

地址：http://www.codeguru.com/algorithms/GeoCalc.html


Environment: VC++6, Win32

Overview
There are many applications, such as navigation and radio frequency engineering, where it is necessary to calculate the minimum path distance and azimuth between two points on the Earth. How you calculate distance and azimuth depends on how you model the surface of the Earth. The simplest intuitive model for the Earth is a sphere; the problem is that the Earth is far from a perfect sphere. Typically, the radius of the Earth at the equator is taken as 6378 kilometers and 6356 kilometers and the North and South poles. The next level of sophistication is to assume an average radius for the Earth depending on latitude. Many situations require much greater accuracy than is afforded by the average-radius model. In these cases, the typical Earth model is an ellipsoid, basically a sphere that is flattened at the poles. Both models have symmetry about the polar axis as shown in the image below, but the spherical model also has symmetry about the center of the Earth, and that symmetry simplifies distance and azimuth calculations immensely.