Since we are talking a little bit about maps... From the USGS (United States Geological Survey) website: http://erg.usgs.gov/isb/pubs/factsheets/fs09902.html A few how-to's and why use map tidbits from the USGS. Great maps, aerial photos and more. Some of you might already know this, but maybe it'll help someone along the way. I was just at the Denver USGS with my daughter's Girl Scout troop and they are so willing to help and answer questions. The aerial photos are awesome. You can order all kinds of maps. Laura