Height Modernization

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A device placed on top of the Washington Monument to measure the height as part of a Height Modernization project in 1999 Javad Positioning System antenna atop the Washington Monument.jpg
A device placed on top of the Washington Monument to measure the height as part of a Height Modernization project in 1999

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

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Global Positioning System United States satellite navigation system

The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite systems (GNSS) that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. Obstacles such as mountains and buildings block the relatively weak GPS signals.

Geodesy The science of the geometric shape, orientation in space, and gravitational field of Earth

Geodesy is the Earth science of accurately measuring and understanding Earth's geometric shape, orientation in space and gravitational field. The field also incorporates studies of how these properties change over time and equivalent measurements for other planets. Geodynamical phenomena include crustal motion, tides and polar motion, which can be studied by designing global and national control networks, applying space and terrestrial techniques and relying on datums and coordinate systems.

Geographic coordinate system Coordinate system to specify locations on Earth

A geographic coordinate system (GCS) is a coordinate system associated with positions on Earth. A GCS can give positions:

Surveying The technique, profession, and science of determining the positions of points and the distances and angles between them

Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial or three-dimensional positions of points and the distances and angles between them. A land surveying professional is called a land surveyor. These points are usually on the surface of the Earth, and they are often used to establish maps and boundaries for ownership, locations, such as the designed positions of structural components for construction or the surface location of subsurface features, or other purposes required by government or civil law, such as property sales.

Sea level Geographical reference point

Mean sea level (MSL) is an average level of the surface of one or more of Earth's bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which atmospheric pressure is measured to calibrate altitude and, consequently, aircraft flight levels. A common and relatively straightforward mean sea-level standard is instead the midpoint between a mean low and mean high tide at a particular location.

World Geodetic System Geodetic reference system

The World Geodetic System (WGS) is a standard for use in cartography, geodesy, and satellite navigation including GPS. This standard includes the definition of the coordinate system's fundamental and derived constants, the ellipsoidal (normal) Earth Gravitational Model (EGM), a description of the associated World Magnetic Model (WMM), and a current list of local datum transformations.

U.S. National Geodetic Survey U.S. federal surveying and mapping agency

The National Geodetic Survey (NGS), formerly the United States Survey of the Coast (1807–1836), United States Coast Survey (1836–1878), and United States Coast and Geodetic Survey (USC&GS) (1878–1970), is a United States federal agency that defines and manages a national coordinate system, providing the foundation for transportation and communication; mapping and charting; and a large number of applications of science and engineering. Since its foundation in its present form in 1970, it has been part of the National Oceanic and Atmospheric Administration (NOAA), of the United States Department of Commerce.

Geodetic datum Reference frame for measuring location

A geodetic datum or geodetic system is a global datum reference or reference frame for precisely measuring locations on Earth or other planetary body. Datums are crucial to any technology or technique based on spatial location, including geodesy, navigation, surveying, geographic information systems, remote sensing, and cartography. A Horizontal datum is used to measure a location across the Earth's surface, in latitude and longitude or another coordinate system; a vertical datum is used to measure the elevation or depth relative to a standard origin, such as mean sea level (MSL). Since the rise of the global positioning system (GPS), the ellipsoid and datum WGS 84 it uses has supplanted most others in many applications. The WGS 84 is intended for global use, unlike most earlier datums.

Satellite geodesy

Satellite geodesy is geodesy by means of artificial satellites — the measurement of the form and dimensions of Earth, the location of objects on its surface and the figure of the Earth's gravity field by means of artificial satellite techniques. It belongs to the broader field of space geodesy. Traditional astronomical geodesy is not commonly considered a part of satellite geodesy, although there is considerable overlap between the techniques.

Zero Milestone

The Zero Milestone is a zero mile marker monument in Washington, D.C. intended as the initial milestone from which all road distances in the United States should be measured when it was built. At present, only roads in the Washington, D.C. area have distances measured from it.

Benchmark (surveying)

The term benchmark, bench mark, or survey benchmark originates from the chiseled horizontal marks that surveyors made in stone structures, into which an angle-iron could be placed to form a "bench" for a leveling rod, thus ensuring that a leveling rod could be accurately repositioned in the same place in the future. These marks were usually indicated with a chiseled arrow below the horizontal line.

Geodetic control network

A geodetic control network is a network, often of triangles, which are measured precisely by techniques of terrestrial surveying or by satellite geodesy.

The orthometric height is the vertical distance H along the plumb line from a point of interest to a reference surface known as the geoid, the vertical datum that approximates mean sea level. Orthometric height is one of the scientific formalizations of a laypersons' "height above sea level", along with other types of heights in Geodesy.

Survey marker

Survey markers, also called survey marks, survey monuments, or geodetic marks, are objects placed to mark key survey points on the Earth's surface. They are used in geodetic and land surveying. A benchmark is a type of survey marker that indicates elevation. Horizontal position markers used for triangulation are also known as triangulation stations. Benchmarking is the hobby of "hunting" for these marks.

National Geodetic Vertical Datum of 1929 Vertical datum in the United States

The National Geodetic Vertical Datum of 1929 is the official name since 1973 of the vertical datum established for vertical control surveying in the United States of America by the General Adjustment of 1929. Originally known as Sea Level Datum of 1929, NGVD 29 was determined and published by the National Geodetic Survey and used to measure the elevation of a point above and depression below mean sea level (MSL).

North American Vertical Datum of 1988 Vertical datum for orthometric heights

The North American Vertical Datum of 1988 is the vertical datum for orthometric heights established for vertical control surveying in the United States of America based upon the General Adjustment of the North American Datum of 1988.

UNAVCO is a non-profit university-governed consortium that facilitates geoscience research and education using Geodesy. UNAVCO is funded by the National Science Foundation (NSF) and The National Aeronautics and Space Administration (NASA) to support geoscience research around the world. UNAVCO operates the GAGE Facility on behalf of the NSF and NASA. As a university-governed consortium, UNAVCO supports the goals of the academic scientific community. UNAVCO has 120 US academic members and supports over 110 organizations globally as associate members.

Mountain states region of the United States

The Mountain States form one of the nine geographic divisions of the United States that are officially recognized by the United States Census Bureau. It is a subregion of the Western United States.

References

  1. "Washington Monument GPS Height Modernization Project August 17–19, 1999". National Geodetic Survey. Retrieved 30 November 2015.