iphone 4 compass and map

how to use compass based on direction on g开发者_运维知识库oogle maps using iphone 4 ,as MAPS app doing

any tutorial to refer??

Thanks

In locationManager:didUpdateHeading:, apply a cooresponding rotation transform to your map view:

double headingInRadians = newHeading.trueHeading * M_PI / 180.0;
mapView.transform = CGAffineTransformMakeRotation(headingInRadians);

The map view's frame should be a little bigger than the visible area so that no blank corners show up when it's rotated.