14. What do the concentric circles mean on the CORS map?

The circle(s) represent 100 kilometers.
white circle - within 100 km
tan or eggshell - 200
yellow - 300
Orange - 400

You can see this better in a map that has fewer sites, like the Northcentral2 map....
http://www.ngs.noaa.gov/CORS/Northcentral2.html