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Improving Elevations for the Nation

5 February 2024

In this video message, NOS Deputy Assistant Administrator Rachael Dempsey shares how recent advancements in the GRAV-D project will help reduce risk for coastal communities through better flood predictions and better support emergency evacuation planning. (Video Transcript)

Rachael A. Dempsey
Deputy Assistant Administrator
Navigation, Observations, and Positioning
National Ocean Service

Video Transcript

Hi, I'm Rachael Dempsey, NOS deputy assistant administrator for navigations, observations, and positioning.

Scientists at NOAA's National Geodetic Survey have completed the first major phase in a pioneering 16 year project to improve elevations for the nation.

The first phase of the Gravity for the Redefinition of the Vertical Datum Project, also known as GRAV-D, measured the gravity field from aircraft over the entire nation, including the continental U.S., Alaska, Hawaii, and all U.S. territories.

Elevation data from the current vertical datum has elevation errors ranging from 16 inches to six feet. With GRAV-D data, the modernized national spatial reference system elevations will be accurate to less than an inch in most areas.

That's at least a 20 times increase in accuracy. These improved elevations from the GRAV-D project will help reduce risk for coastal communities through better flood predictions associated with storms and tsunamis and support better emergency evacuation planning. More accurate elevation data benefit infrastructure planners and precision agriculture, as we can better predict where water will pool and flow.

This project will further contribute to the modernization of the nation's coordinate system, the National Spatial Reference System. This consistent coordinate system defines latitude, longitude, height, scale, gravity, orientation and shoreline throughout the United States.

Rachael A. Dempsey Portrait

Rachael A. Dempsey
National Ocean Service Deputy Assistant Administrator for Navigation, Observations, and Positioning

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