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NGS Needs Help with NY Bench Marks

Thursday, February 8, 2018   (0 Comments)
Posted by: Amber Carpenter
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Message From The AAGS:


The American Association for Geodetic Surveying (AAGS) would like to make you aware of potential future problems in your state with the release of the new geopotential vertical datum in 2022.


As you may already know, the National Geodetic Survey (NGS) is no longer supporting passive control such as bench marks unless it has been occupied by a GPS/GNSS receiver for 4 or more hours and submitted to OPUS-Shared Solutions at By August 2018, NGS would like to have data from all states to complete the GPS on bench marks campaigns. Your state has several areas that have a weak Geoid model with uncertainties in the 0.2 ft or more range, and thus need GPS on bench marks to strengthen the geoid model. Surveys starting in 2022 involving flood plain maps and so forth will require bringing orthometric heights (elevations) to the job site using GNSS, which in turn requires a better geoid model in parts of your state.


We have obtained a list of bench marks for your state that the NGS would like to see occupied before August, 2018. This is an opportunity for your state society to help all constituents in your state in need of orthometric heights. Your state society could organize an effort using your chapters to occupy as many of these BMs as possible. The provided list contains all the bench marks that NGS would like to have occupied with GPS and then shared with them. The NGS no longer has field crews so they are relying on private surveyors to help them. Time is running short to ensure that future surveys in your state that require heights tied to the national datum have an accurate geoid model to assist in this endeavor. It is in your best interest to assist the NGS in performing this important task to help strengthen the geoid model.



Dave Zilkoski recently published an article on this for GPS World, which can be viewed at

The NGS is also having a special webinar on this subject next Thursday, February 15, at 2 PM. You can find more details on the webinar here:

146 Washington Avenue
Land Surveyors Building
Albany, NY 12210
518-432-4046 -- (f) 518-432-4055

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