根据坐标经纬度计算两点之间的距离

地球是一个近乎标准的椭球体，它的赤道半径为6378.140千米，极半径为 6356.755千米，平均半径6371.004千米。

        /// <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">纬度1</param>
        /// <param name="lon1">经度1</param>
        /// <param name="lat2">纬度2</param>
        /// <param name="lon2">经度2</param>
        /// <returns>距离（公里、千米）</returns>
        private double Distance(double lat1, double lon1, double lat2, double lon2)
        {
            double EARTH_RADIUS = 6371.0;

            //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>
        private double ConvertDegreesToRadians(double degrees)
        {
            return degrees * Math.PI / 180;
        }

        /// <summary>
        /// 将弧度换算为角度。
        /// </summary>
        /// <param name="radian"></param>
        /// <returns></returns>
        private double ConvertRadiansToDegrees(double radian)
        {
            return radian * 180.0 / Math.PI;
        }

        /// <summary>
        /// HaverSin
        /// </summary>
        /// <param name="theta"></param>
        /// <returns></returns>
        private double HaverSin(double theta)
        {
            var v = Math.Sin(theta / 2);
            return v * v;
        }

在线计算经纬度距离工具 http://www.gpsspg.com/distance.htm

参考 https://blog.csdn.net/xiejm2333/article/details/73297004

https://www.cnblogs.com/zhoug2020/p/3950933.html