经纬度 范围 距离 计算

 private const double EARTH_RADIUS = 6378.137;//地球半径
         private static double RAD = Math.PI / 180.0;
        //获取两个经纬度之间的距离
         public static double GetDistance(double lng1, double lat1, double lng2, double lat2)
        {
            double radLat1 = lat1 * RAD;
            double radLat2 = lat2 * RAD;
            double a = radLat1 - radLat2;
            double b = (lng1 - lng2) * RAD;
            double s = 2 * Math.Sin(Math.Sqrt(Math.Pow(Math.Sin(a / 2), 2) +
             Math.Cos(radLat1) * Math.Cos(radLat2) * Math.Pow(Math.Sin(b / 2), 2)));
            s = s * EARTH_RADIUS;
            s = Math.Round(s * 10000) / 10000;
            return s;   
        }

        //获取两个经纬度的某个范围内的最大经度和最大纬度 单位 米
        public static double[] getAround(double lat, double lon, int raidus)
        {
            double PI = 3.14159265;
            Double latitude = lat;
            Double longitude = lon;

            Double degree = (24901 * 1609) / 360.0;
            double raidusMile = raidus;

            Double dpmLat = 1 / degree;
            Double radiusLat = dpmLat * raidusMile;
            Double minLat = latitude - radiusLat;
            Double maxLat = latitude + radiusLat;

            Double mpdLng = degree * Math.Cos(latitude * (PI / 180));
            Double dpmLng = 1 / mpdLng;
            Double radiusLng = dpmLng * raidusMile;
            Double minLng = longitude - radiusLng;
            Double maxLng = longitude + radiusLng;
            return new double[] { minLat, minLng, maxLat, maxLng };
        }