Plate Nº 58 · recorded November 12, 2026
Earth & ClimateReported finding
Every U.S. Mountain Height Is About to Shift by Up to Six Feet
NOAA is finalizing a 2027 overhaul of the National Spatial Reference System that will shift official U.S. elevations by up to six feet, using gravity-based measurements.
By Elena Vasquez3 min read689 words
In brief
- Official U.S. coordinates will change by up to about six feet when the new system is finalized in early 2027.
- The current horizontal reference model dates to 1986; the vertical datum was last updated in 1991.
- NOAA spent 17 years flying gravity-measuring aircraft across the country to build the new model.
- Alaska's official feature heights may shrink by roughly six feet; the Southeast will see the smallest shifts.
Every official latitude, longitude and height in the United States is about to change by up to roughly six feet. Researchers at the National Oceanic and Atmospheric Administration (NOAA) are nearly finished with a complete overhaul of the National Spatial Reference System, or NSRS — the framework that defines where things are, and how they're oriented in space, across the U.S. and its territories. The new system is in beta testing now and will be finalized in early 2027.
"Every latitude, longitude and height all across the country is going to change a little bit," says Kevin Ahlgren, a geodesist with the National Geodetic Survey, the NOAA office managing the transition. A geodesist, in plain terms, is a scientist who measures the shape of the Earth and where things sit on it.
The stakes are more than academic. The updated coordinates will be used by all federal agencies and for all federally funded projects, and they'll flow into everyday GPS devices and mapping apps.
Why do the numbers need fixing?
Two things have thrown the old system out of step with reality: time and gravity.
The current horizontal model — the part tracking latitude and longitude — dates to 1986. Since then, continental plates have kept slowly spinning and crimping across the country, dragging coordinates out of alignment. The update accounts for that drift.
The vertical part, called the vertical datum, is even older: 1991. Heights in the NSRS are measured from an invisible "sea level" reference surface, and the new framework redefines that surface using gravity itself. The last update also predates GPS, so an entire technological revolution in positioning never made it into the official system until now.
What does gravity have to do with mountain heights?
Quite a lot. Scientists have known for centuries that gravity isn't uniform across the planet. More massive features, such as mountains, pull harder on everything around them; even in flat regions, differences in the rock beneath the surface can create bulges in the local gravitational field.
The theoretical model capturing these ups and downs is called the geoid — a lumpy surface representing where gravity equals the pull of average global sea level. Derek van Westrum, a NOAA physicist who works with a high-precision instrument called a gravity meter, describes Earth as a "blobby" place, both physically and gravitationally. The geoid, when visualized, looks something like a potato.
To map that gravitational landscape, NOAA took direct measurements. Over 17 years, research airplanes crisscrossed the country building a new gravity-based picture of the terrain below. Scientists combined the airborne readings with ground measurements and satellite data to produce a comprehensive model of where sea level sits at every point in the nation.
The result: a new vertical datum, tied to gravity rather than older approximations.
How much will heights actually move?
The answer depends on where you are. Elevation above sea level will shift least in the Southeast. The size of the change grows toward the north and west. In Alaska, the official height of geographic features may shrink by around six feet.
The environmental picture has changed too since the last updates. Ice melt is among the real-world shifts the new models reflect, alongside the scientific and technological advances of the past four decades.
"It's a complete change — a new paradigm," says Demián Gómez, a geodesist at the Ohio State University who has been studying applications of the updated system.
What improves once the system lands?
More accurate vertical measurements carry practical weight. National Geodetic Survey scientists say the new framework will improve:
- Floodplain mapping and models of how water flows across the land
- Surveying and construction, where precision cuts cost and error
- Automated navigation systems that rely on exact coordinates
- Earthquake early-warning systems, which depend on fast, accurate positioning data
The mountains themselves aren't going anywhere. Peaks and floodplains will look exactly as they did before 2027. What changes is the measuring stick — and by aligning official coordinates with gravity, plate motion and modern satellite technology, the new system should bring the country's maps into better agreement with the world they describe.
via scientificamerican.com (Source)
More from Elena Vasquez
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Correspondent covering money, funding and market shifts around general science news at SciBeat.
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