1 #pragma mark - calculate distance 根据2个经纬度计算距离
2
3 #define PI 3.14159265358979323
4 +(double) CalculationDistanceOther_Lon1:(double)lon1 Other_Lat1:(double)lat1 self_Lon2:(double)lon2 self_Lat2:(double)lat2{
5 double er = 6371229; // 6378700.0f;
6 //ave. radius = 6371.315 (someone said more accurate is 6366.707)
7 //equatorial radius = 6378.388
8 //nautical mile = 1.15078
9 double radlat1 = PI*lat1/180.0f;
10 double radlat2 = PI*lat2/180.0f;
11 //now long.
12 double radlong1 = PI*lon1/180.0f;
13 double radlong2 = PI*lon2/180.0f;
14 if( radlat1 < 0 ) radlat1 = PI/2 + fabs(radlat1);// south
15 if( radlat1 > 0 ) radlat1 = PI/2 - fabs(radlat1);// north
16 if( radlong1 < 0 ) radlong1 = PI*2 - fabs(radlong1);//west
17 if( radlat2 < 0 ) radlat2 = PI/2 + fabs(radlat2);// south
18 if( radlat2 > 0 ) radlat2 = PI/2 - fabs(radlat2);// north
19 if( radlong2 < 0 ) radlong2 = PI*2 - fabs(radlong2);// west
20 //spherical coordinates x=r*cos(ag)sin(at), y=r*sin(ag)*sin(at), z=r*cos(at)
21 //zero ag is up so reverse lat
22 double x1 = er * cos(radlong1) * sin(radlat1);
23 double y1 = er * sin(radlong1) * sin(radlat1);
24 double z1 = er * cos(radlat1);
25 double x2 = er * cos(radlong2) * sin(radlat2);
26 double y2 = er * sin(radlong2) * sin(radlat2);
27 double z2 = er * cos(radlat2);
28 double d = sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)+(z1-z2)*(z1-z2));
29 //side, side, side, law of cosines and arccos
30 double theta = acos((er*er+er*er-d*d)/(2*er*er));
31 double dist = theta*er;
32 return dist;
33 }
