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Gravity for the Redefinition of the American Vertical Datum

A 15-year project to improve the nation's height accuracy reaches milestone.

Communities looking to build resilience to storms—from hurricanes to river flooding—need a lot of information. One of the key things that they need is accurate height information. The National Geodetic Survey (NGS) is undertaking a 15-year project called Gravity for the Redefinition of the American Vertical Datum, or GRAV-D, to improve height accuracy. Once the GRAV-D airborne survey is completed and the new vertical datum is released, elevations accessed through NOAA's Continuously Operating Reference Station network will be accurate to within one inch, resulting in improved inundation mapping, better monitoring of sea levels, and more accurate heights for the surveying community in support of the construction of highways, bridges, and suburban development, among other improvements.

Recently, NGS reached a major milestone—50 percent of all GRAV-D data have now been collected. Congratulations to all involved in this accomplishment! Additionally, the program is exploring ways that new technologies can support the GRAV-D effort. NGS recently tested a gravity-measurement device on an unmanned aircraft. An unmanned plane can more easily obtain GRAV-D data in remote locations, and has the potential to greatly reduce the costs associated with data collection.

W. Russell Callender, Ph.D. 
Acting Assistant Administrator for Ocean Services and Coastal
Zone Management, National Ocean Service