//计算两坐标之间的距离

double distanceWithcoord(double lon1,double lat1,double lon2,double lat2)

{

double er = 6378137;

double radlat1 = PI*lat1/180.0f;

double radlat2 = PI*lat2/180.0f;

double radlong1 = PI*lon1/180.0f;

double radlong2 = PI*lon2/180.0f;

if( radlat1 < 0 ) radlat1 = PI/2 + fabs(radlat1);// south

if( radlat1 > 0 ) radlat1 = PI/2 - fabs(radlat1);// north

if( radlong1 < 0 ) radlong1 = PI*2 - fabs(radlong1);//west

if( radlat2 < 0 ) radlat2 = PI/2 + fabs(radlat2);// south

if( radlat2 > 0 ) radlat2 = PI/2 - fabs(radlat2);// north

if( radlong2 < 0 ) radlong2 = PI*2 - fabs(radlong2);// west


double x1 = er * cos(radlong1) * sin(radlat1);

double y1 = er * sin(radlong1) * sin(radlat1);

double z1 = er * cos(radlat1);

double x2 = er * cos(radlong2) * sin(radlat2);

double y2 = er * sin(radlong2) * sin(radlat2);

double z2 = er * cos(radlat2);

double d = sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)+(z1-z2)*(z1-z2));

double theta = acos((er*er+er*er-d*d)/(2*er*er));

double dist = theta*er;

return dist;

}