javascript compute heading on too points
// Converts from degrees to radians.
function toRadians(degrees) {
return degrees * Math.PI / 180;
};
// Converts from radians to degrees.
function toDegrees(radians) {
return radians * 180 / Math.PI;
}
function bearing(startLat, startLng, destLat, destLng){
startLat = toRadians(startLat);
startLng = toRadians(startLng);
destLat = toRadians(destLat);
destLng = toRadians(destLng);
y = Math.sin(destLng - startLng) * Math.cos(destLat);
x = Math.cos(startLat) * Math.sin(destLat) -
Math.sin(startLat) * Math.cos(destLat) * Math.cos(destLng - startLng);
brng = Math.atan2(y, x);
brng = toDegrees(brng);
return (brng + 360) % 360;
}