Javad Positioning System antenna atop the Washington Monument

Height Modernization is the name of a series of state-by-state programs recently begun by the United States' National Geodetic Survey, a division of the

National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditi ...

. The goal of each state program is to place GPS base stations at various locations within each participating state to measure topographic changes in the directions of

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north po ...

and

longitude Longitude (, ) is a geographic coordinate that specifies the east– west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek let ...

caused by subsidence or earthquakes, as well as to measure changes in height (elevation).

References

Arizona Height Modernization – Arizona Geographic Information Council

Texas Height Modernization – Texas A&M University – Corpus Christi
Geodesy {{geodesy-stub