The Radar Plot and the >>StartMAPS<< parts of tvfool are showing (discrepancies) transmitters in different places. And different NM dB signal strengths. I am asking Mtownsend / moderator to help out here. Here is more reading
http://www.digitalhome.ca/forum ,
http://www.tvtechnology.com/article/105462 ,
http://www.crtc.gc.ca/eng/home-accueil.htm . The current tv transmitters are listed as Analog Tv Transmitters , I do not know When or If the transmitters at your location will change to Digital and what channels the Digital transmissions will be on.