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 The National Geodetic Survey (NGS) is a List of federal agencies in the United States, United States federal agency that defines and manages a national coordinate system, providing the foundation for transportation and communication; mapping an ...

, 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 conditio ...

. The goal of each state program is to place

GPS The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...

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 pol ...

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 letter l ...

caused by

subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope move ...

earthquakes An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

, 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