# 经纬度转平面坐标xy并算距离代码

## 方法一：半正矢公式

``````        public double dis_Haversine(double[] BL1, double[] BL2)
{
//B为纬度，L为精度
double B1 = BL1[0] / 180 * Math.PI;
double B2 = BL2[0] / 180 * Math.PI;
double L1 = BL1[1] / 180 * Math.PI;
double L2 = BL2[1] / 180 * Math.PI;
double a = B1 - B2;
double b = L1 - L2;
double s = 2 * Math.Asin(Math.Sqrt(Math.Pow(Math.Sin(a / 2), 2) + Math.Cos(B1) * Math.Cos(B2) * Math.Pow(Math.Sin(b / 2), 2)));
s = s * 6378137;
s = Math.Round(s * 10000) / 10000;
return s;
}
``````

## 方法二：先转成平面坐标再计算

``````       public double dis_xy(double[] BL1, double[] BL2)//求两点距离函数
{
double[] r1 = BL2xy84(BL1, 121.464467);//121.464467是投影坐标系的中心纬度，不同城市不同
double[] r2 = BL2xy84(BL2, 121.464467);
double s = Math.Pow(Math.Pow((r1[0] - r2[0]), 2) + Math.Pow((r1[1] - r2[1]), 2), 0.5);
return s;
}
public static double[] BL2xy84(double[] BL, double L0)//经纬度转换成平面坐标
{
double[] xy = new double[2];
double X, B, L, a, b, e, e1, V, c, M, N, t, n, l, x, y;
X = B2S(0, BL[0]);
B = BL[0] / 180 * Math.PI;//纬度
L = BL[1] / 180 * Math.PI;//精度
L0 = L0 / 180 * Math.PI;
a = 6378137.0; //WGS_84参考椭球参数
// f=1/298.257223563;//椭球扁率
b = 6356752.3142;//短轴
e = (Math.Sqrt(a * a - b * b)) / a;
e1 = (Math.Sqrt(a * a - b * b)) / b;
V = Math.Sqrt(1 + (e1 * e1) * (Math.Cos(B)) * (Math.Cos(B)));
c = (a * a) / b;
M = c / (V * V * V);
N = c / V;
t = Math.Tan(B);
n = Math.Sqrt((e1 * e1) * (Math.Cos(B)) * (Math.Cos(B)));
l = L - L0;
x = X + N * t * Math.Cos(B) * Math.Cos(B) * l * l * (0.5 + (1 / 24) * (5 - t * t + 9 * n * n + 4 * n * n * n * n) * Math.Cos(B) * Math.Cos(B) * l * l + 1 / 720 * (61 - 58 * t * t + t * t * t * t) * Math.Pow((Math.Cos(B)), 4) * l * l * l * l);
y = N * Math.Cos(B) * l * (1 + 1 / 6 * (1 - t * t + n * n) * Math.Cos(B) * Math.Cos(B) * l * l + 1 / 120 * (5 - 18 * t * t + t * t * t * t + 14 * n * n - 58 * t * t * n * n) * Math.Pow((Math.Cos(B)), 4) * l * l * l * l);
double[] d = { x, y };
return d;

}
public static double B2S(double B1, double B2)//BL2xy84函数的内部一个函数
{
double a, b, e2, A, B, C, D, E, F, G, S;
a = 6378137.0;//WGS_84参考椭球参数
//f=1/298.257223563;%椭球扁率
b = 6356752.3142;// 短轴
e2 = (a * a - b * b) / (a * a);
A = 1 + 3 * e2 / 4 + 45 * e2 * e2 / 64 + 175 * e2 * e2 * e2 / 256 + 11025 * Math.Pow(e2, 4) / 16384 + 43659 * Math.Pow(e2, 5) / 65536 + 693693 * Math.Pow(e2, 6) / 1048576;
B = A - 1;
C = 15 * e2 * e2 * e2 / 32 + 175 * e2 * e2 * e2 / 384 + 3675 * Math.Pow(e2, 4) / 8192 + 14553 * Math.Pow(e2, 5) / 32768 + 231231 * Math.Pow(e2, 6) / 524288;
D = 35 * e2 * e2 * e2 / 96 + 735 * Math.Pow(e2, 4) / 2048 + 14553 * Math.Pow(e2, 5) / 40960 + 231231 * Math.Pow(e2, 6) / 655360;
E = Math.Pow(e2, 4) * 315 / 1024 + Math.Pow(e2, 5) * 6237 / 20480 + Math.Pow(e2, 6) * 99099 / 327680;
F = 693 * Math.Pow(e2, 5) / 2560 + 11011 * Math.Pow(e2, 6) / 40960;
G = 1001 * Math.Pow(e2, 6) / 4096;
B1 = B1 / 180 * Math.PI;
B2 = B2 / 180 * Math.PI;
S = a * (1 - e2) * (A * (B2 - B1) - B * (Math.Sin(B2) * Math.Cos(B2) - Math.Sin(B1) * Math.Cos(B1)) - C * (Math.Pow(Math.Sin(B2), 3) * Math.Cos(B2) - Math.Pow(Math.Sin(B1), 3) * Math.Cos(B1)) - D * (Math.Pow(Math.Sin(B2), 5) * Math.Cos(B2) - Math.Pow(Math.Sin(B1), 5) * Math.Cos(B1)) - E * (Math.Pow(Math.Sin(B2), 7) * Math.Cos(B2) - Math.Pow(Math.Sin(B1), 7) * Math.Cos(B1)) - F * (Math.Pow(Math.Sin(B2), 9) * Math.Cos(B2) - Math.Pow(Math.Sin(B1), 9) * Math.Cos(B1)) - G * (Math.Pow(Math.Sin(B2), 11) * Math.Cos(B2) - Math.Pow(Math.Sin(B1), 11) * Math.Cos(B1)));
return S;
}
``````