计算两个经纬度坐标之间的距离

 1  private double rad(double d)
 2          {
 3              return d * Math.PI / 180.0;
 4          }
 5 
 6          public double getDistance(double lat1, double lng1, double lat2,
 7                  double lng2)
 8          {
 9              double radLat1 = rad(lat1);
10              double radLat2 = rad(lat2);
11              double a = radLat1 - radLat2;
12              double b = rad(lng1) - rad(lng2);
13              double s = 2 * Math.Asin(Math.Sqrt(Math.Pow(Math.Sin(a / 2), 2)
14                      + Math.Cos(radLat1) * Math.Cos(radLat2)
15                      * Math.Pow(Math.Sin(b / 2), 2)));
16              s = s * 6378.137;
17              s = Math.Round(s * 10000);
18              s = s / 10000;
19              return s ;//计算单位：公里  
20          }