Read original post by Daniel Estrada Alva at Windows Phone Developer Blog
In this post I describe how you can optionally modify your Windows Phone 7 geolocation code to use the new Windows Runtime (WinRT) Geolocation APIs in Windows Phone 8. Modifying your code to use the new Geolocation APIs in Windows Phone 8 is optional, but offers some solid advantages. In future posts I’ll go into more detail about the extended functionality that the new APIs offer, and how to implement the Windows Runtime. I’ll also walk you through some scenarios that you can build into your Windows Phone 8 apps.