On 2007-11-22 17:45:50 -0800, "William Bruce" said:

I've just bought a TomTom GPS for my car with preloaded road maps of the US
and Canada. My question: Will it work in my 172 at 3,000 to 5,000 feet,
showing the roads below, etc?

Yes it will, but you could use a program like OziExplorer(www.oziexplorer.com)
and digital air charts, topographical maps or Google Earth images.