Ha good advice, the world is indeed NOT FLAT!!! 
I've had this in my bookmarks for many years and I thought I'd share it with the few HAMs who have failed to spot it.
This Software makes a really good job at estimating the reception of yours or other person's signal based on
height, frequency,and a raft of terain variables! the end result is aset of highly coloured charts overlayed on
various map sources including the inevitable Google maps.
Diagrams galore
