Digitized USGS 7.5' (1:24000) Topo Maps

• USGS
• Pennsylvania Topo Maps, Aerial Photos, Elevation Data, etc Free downloads!
• Sample Map Section Carnegie Mellon area
• Other online USGS maps, by state

Free Nautical Charts (IHO S-57 vector format)

• NOAA Electronic Navigation Charts
• Army Corps of Engineers Inland Electronic Navigation Charts
• Free viewing software

Commercial Digital Map and Aerial Photo Products

• Maptech - Digital topo maps, nautical charts, aeronautical charts
• SoftChart - Digital nautical charts, aeronautical charts
• Digital Map Store - Digital topo maps, aerial photos

GPS Software

• GPS Software various platforms
• MacGPS Pro
• GPSy Software and Cables for Macintosh

GPS Information

• GPS Info From the makers of GPSy
• GPS Info from Unv. of Texas at Austin -- good source of detailed info
• GLOBAL POSITION SYSTEM ACCURACY and how to improve it via long-term averaging

Internet Maps

• ETAK Geocode Converts street address to lat/long