It is worth upgrading OEM GPS sensor on D2?

[tonupkid]

I think the main improvement will come if you can use both GPS & Glosnass & soon to arrive Galileo satelites.
I believe that accessing the signal from so many more sources will greatly improve the accuracy of your location information.
My phone (Nexus 5) can do this, so the challenge is probably how best to integrate such an upgrade, invisibly, into your existing package.