Pomme Question

I apologize if this has been asked before, but I was not able to find an answer. I am going to begin fishing Pomme more often, when reading fishing reports I see references to the upper and lower arm of the lake. Can someone describe where this invisible line might be to help a new guy out?

Thanks in advance.

I always considered Nemo landing on the Lindley arm and the 84 Marina on the Pomme arm to be the rough dividing spots.