Distance between IOS 2 coordinates

// calculate the distance between two coordinates

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;

}

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Distance between IOS 2 coordinates