compass heading in landscape

[patte]

hi out there, you're my last hope...

I searched with any kind of keywords for the following problem but even best friend google had no answer:
I got an application with a Core Location Controller, all working fine. It updates me the current magnetic and true heading in two textfields. But this seems to work only if the iPhone is hold even to the table... if I hold it in landscape and pointed up (like you do it if you take a photo) then this values doesn't change more or less...
Is there a way I can say my Location Controller to switch into landscape mode or do I have to do my own calculations with the raw value of the magnetic sensor like descriped in:
iPhone Dev Center: CLHeading Class Reference

thanks
patte