Improve the National Spatial Reference System (NSRS):
Recover: Look up the description of an existing bench mark and visit the bench mark of your choice.
Observe: Record field notes, take digital photos, and collect GPS observations or coordinates for the bench mark you visit.
Report: Use online tools to send the information to NGS.
Where?
Currently there are over 400,000 bench marks across the Conterminous United States (CONUS), Alaska, Hawaii and all U.S. territories. Tidal marks and bench marks are used for determining heights. Use the maps to prioritize which bench marks to observe.
GPS on Bench Marks
http://www.ngs.noaa.gov/GPSonBM/