namespace LY.App.Common
{
    public static class GisHelper
    {
        /// <summary>
        /// 计算两点之间的距离
        /// </summary>
        /// <param name="lat1"></param>
        /// <param name="lon1"></param>
        /// <param name="lat2"></param>
        /// <param name="lon2"></param>
        /// <returns></returns>
        public static double HaversineDistance(double lat1, double lon1, double lat2, double lon2)
        {
            const double R = 6371000.0; // 地球半径（单位：米）

            double dLat = ToRadians(lat2 - lat1);
            double dLon = ToRadians(lon2 - lon1);

            double a = Math.Sin(dLat / 2) * Math.Sin(dLat / 2) +
                       Math.Cos(ToRadians(lat1)) * Math.Cos(ToRadians(lat2)) *
                       Math.Sin(dLon / 2) * Math.Sin(dLon / 2);

            double c = 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a));
            return R * c;
        }
        static double ToRadians(double degrees) => degrees * Math.PI / 180.0;
    }
}