Configuring/calibrating the compass on the iphone4s

[learninmypc]

Why is it everytime I use my compass on my iphone 4s I need to calibrate it first? I asked a friend about it & he said something about changing a setting but I cant find it. Any ideas?

 

[learninmypc]

Well, I've been thru the manual a few times I see nothing to do with calibrating it.

How do I switch it between true north & magnetic north? The above image is from the manual, NOT the iPhone compass.