mysql 经纬度计算距离 输入经纬度计算距离

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;namespace HarvenSin
{
    class Program
    {
        /// <summary>
        /// 根据经纬度，计算2个点之间的距离。
        /// </summary>
        /// <param name="args"></param>
        static void Main(string[] args)
        {
            //39.94607,116.32793  31.24063,121.42575
            Console.WriteLine(Distance(39.94607, 116.32793, 31.24063, 121.42575));        }
        public static double HaverSin(double theta)
        {
            var v = Math.Sin(theta / 2);
            return v * v;
        }        static double EARTH_RADIUS = 6371.0;//km 地球半径 平均值，千米
        /// <summary>
        /// 给定的经度1，纬度1；经度2，纬度2. 计算2个经纬度之间的距离。
        /// </summary>
        /// <param name="lat1">经度1</param>
        /// <param name="lon1">纬度1</param>
        /// <param name="lat2">经度2</param>
        /// <param name="lon2">纬度2</param>
        /// <returns>距离（公里、千米）</returns>
        public static double Distance(double lat1,double lon1, double lat2,double lon2)
        {
            //用haversine公式计算球面两点间的距离。
            //经纬度转换成弧度
            lat1 = ConvertDegreesToRadians(lat1);
            lon1 = ConvertDegreesToRadians(lon1);
            lat2 = ConvertDegreesToRadians(lat2);
            lon2 = ConvertDegreesToRadians(lon2);            //差值
            var vLon = Math.Abs(lon1 - lon2);
            var vLat = Math.Abs(lat1 - lat2);            //h is the great circle distance in radians, great circle就是一个球体上的切面，它的圆心即是球心的一个周长最大的圆。
            var h = HaverSin(vLat) + Math.Cos(lat1) * Math.Cos(lat2) * HaverSin(vLon);            var distance = 2 * EARTH_RADIUS * Math.Asin(Math.Sqrt(h));
            return distance;
        }        /// <summary>
        /// 将角度换算为弧度。
        /// </summary>
        /// <param name="degrees">角度</param>
        /// <returns>弧度</returns>
        public static double ConvertDegreesToRadians(double degrees)
        {
            return degrees * Math.PI / 180;
        }        public static double ConvertRadiansToDegrees(double radian)
        {
            return radian * 180.0 / Math.PI;
        }    }
}