World Geodetic System
Standard for Earth-centered coordinates, geodesy, and satellite navigation.
The World Geodetic System (WGS) is a framework for cartography, geodesy, and satellite navigation, most notably GPS. Its latest iteration, WGS 84, establishes an Earth-centered, Earth-fixed coordinate system and a geodetic datum, along with the Earth Gravitational Model (EGM) and World Magnetic Model (WMM). The United States National Geospatial-Intelligence Agency publishes and maintains this standard.
The need for a global system grew out of earlier efforts to unify separate national surveys. In the 19th century, F.R. Helmert’s work on physical geodesy, along with the founding of the Central Bureau of International Geodesy by Austria and Germany, led to several global Earth ellipsoids, such as those by Helmert in 1906 and Hayford in 1910 and 1924.
By the 1950s, a single worldwide geodetic system became critical for several reasons: the rise of space science and astronautics; a lack of intercontinental geodetic data; the inability of regional systems like the European Datum (ED50), North American Datum (NAD), and Tokyo Datum (TD) to serve global needs; the demand for worldwide navigation, aviation, and geographic maps; and Western Cold War requirements for a standardized NATO geospatial reference system under the NATO Standardisation Agreement.
In the late 1950s, the U.S. Department of Defense, with scientists from other institutions and countries, began developing a world system to which geodetic data could be tied, ensuring compatibility between coordinates of distant sites. The efforts of the U.S. Army, Navy, and Air Force were combined to produce the DoD World Geodetic System 1960 (WGS 60). In this context, a datum refers to a smooth surface arbitrarily defined as zero elevation, consistent with surveyors’ measurements of distances and elevation differences, all reduced to a grid of latitudes, longitudes, and elevations. Traditional surveying methods determined elevation differences from a local horizontal defined by a spirit level, plumb line, or similar device dependent on the local gravity field. Consequently, these elevations referenced the geoid—a surface not easily determined by satellite geodesy, which is better suited for global mapping. A major challenge in WGS work was therefore to combine data collected separately for different regions and to re-reference elevations to an ellipsoid model instead of the geoid.
Quick Facts
- Current version
- WGS 84
- Maintaining agency
- United States National Geospatial-Intelligence Agency
- Earlier versions
- WGS 60
- WGS 66
- WGS 72
- Key contributor
- F.R. Helmert
- Associated models
- Earth Gravitational Model (EGM), World Magnetic Model (WMM)
Facts from the source article.
Lore & Background
Efforts to supplement national surveying systems began in the 19th century with F.R. Helmert's book. Austria and Germany founded the Central Bureau of International Geodesy, and global ellipsoids such as Helmert 1906, Hayford 1910 and 1924 were derived. A unified world system became essential in the 1950s due to international space science, lack of inter-continental geodetic information, the inability of large systems like European Datum (ED50), North American Datum (NAD), and Tokyo Datum (TD) to provide a worldwide geo-data basis, the need for global maps, and Western Cold War preparedness requiring a NATO-wide geospatial reference system.
In the late 1950s, the United States Department of Defense, with scientists from other institutions and countries, began developing the needed world system. Efforts of the US Army, Navy, and Air Force were combined, leading to WGS 60. A combination of surface gravity data, astro-geodetic data, and HIRAN and Canadian SHORAN surveys defined a best-fitting ellipsoid and earth-centered orientation. The sole satellite contribution was a value for ellipsoid flattening from nodal motion of a satellite. WGS 66 followed, using additional surface-gravity observations, triangulation and trilateration networks, and Doppler and optical satellite data. WGS 72 was completed after a three-year effort using a Unified WGS Solution—a large-scale least-squares adjustment—incorporating selected satellite, surface-gravity, and astrogeodetic data from DoD and non-DoD sources through 1972.
Reader's Guide
The World Geodetic System provides a standardized reference for mapping, charting, navigation, and geodetic requirements across the globe. Its development addressed the lack of inter-continental geodetic information and the inability of regional datums to support worldwide applications. Each version—WGS 60, WGS 66, and WGS 72—incorporated improved data and techniques, including Doppler satellite data, optical satellite data, surface gravity measurements, and astrogeodetic observations. The system's significance lies in its role as a unified geospatial reference for NATO and global navigation, including GPS. The current version, WGS 84, continues to define the Earth-centered, Earth-fixed coordinate system and geodetic datum used in satellite navigation, and it also describes the Earth Gravitational Model and World Magnetic Model. The standard is maintained by the United States National Geospatial-Intelligence Agency, ensuring ongoing compatibility and accuracy for scientific, military, and civilian applications.
Did You Know?
- The sole satellite contribution to WGS 60 was a value for ellipsoid flattening from the nodal motion of a satellite.
- WGS 72 used the largest collection of data ever assembled for WGS purposes up to that time.
Frequently Asked Questions
What is the World Geodetic System (WGS)?
WGS is a standardized reference framework that defines how we measure positions on Earth's surface, tying together cartography, geodesy, and satellite-based navigation. It provides a consistent, Earth-centered coordinate grid so that GPS receivers and mapmakers all agree on where a given point actually sits.
Who is responsible for maintaining WGS?
The United States National Geospatial-Intelligence Agency (NGA) publishes and keeps the WGS standard current. They handle the technical specifications and any necessary revisions to the system over time.
What other models does WGS incorporate alongside the coordinate grid?
WGS 84 integrates the Earth Gravitational Model (EGM) and the World Magnetic Model (WMM) to account for gravitational and magnetic variations across the globe. Together these give navigation systems a more complete physical picture of the planet.
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