What is GPS on Bench Marks?
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.
Who can participate?
Anyone with Global Positioning System (GPS) enabled phones, hand held devices or survey-grade GPS receivers can participate. Recommended procedures vary depending on the type of equipment used.
When should I start?
You can collect and share information any time. Join volunteer efforts across the United States in celebration of National Surveyors Week beginning March 20, 2016. Contact the local National Society of Professional Surveyors chapter or your NGS geodetic advisor to learn about projects being planned in your local area.
How?
For specific information on how to help please visit the Recover, Observe, and Report web pages that have instructions. Other resources include Hunting for Marks! or the Geocaching Benchmark Hunting website.
Why does this matter?
By providing GPS on bench marks today you can help NGS improve the next hybrid geoid model, increasing access to NAVD 88, and enabling conversions to the new vertical datum in 2022.
You can also help the local surveying community know about nearby marks by improving scaled horizontal positions and updating the mark condition or description by submitting a mark recovery.
What happens next?
NGS will use your data to update its databases and improve future models and tools.
If you still have questions,
contact the GPS on BM Team.
R e c o v e r
O b s e r v e
R e p o r t
More information on Recover, Observe, Report please check out the videos of the 2015 and 2016 webinars we recorded for people to learn more. Click on the image to see this years webinar or the menu to the left for 2015 Video
The maps below show the distance to nearest bench mark used in GEOID12B
as well as the estimated accuracy. The accuracy is highly correlated
to the distance to nearest bench mark. You can help improve the
next geoid by helping to fill these gaps and limit the distance between
observed bench marks.
GEOID12B Distance to
Nearest Bench Mark Map
GEOID12B Estimated Accuracy Map
(click maps for high resolution images)
