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Geodesy and Geophysics

What is geodesy? Who needs it and why? These are some of the questions asked by many people. Actually, geodesy is nothing new having been around for centuries. Webster defines geodesy as "that branch of applied mathematics which determines by observation and measurement the exact positions of points and the figures and areas of large portions of the earth's surface, the shape and size of the earth, and the variations of terrestrial gravity." It is a specialized application of several familiar facets of basic mathematical and physical concepts. In practice, geodesy uses the principles of mathematics, astronomy and physics, and applies them within the capabilities of modern engineering and technology. A thorough study of the science of geodesy is not a simple undertaking. However, it is possible to gain an understanding of the historical development, a general knowledge of the methods and techniques of the science, and the way geodesy is being used to solve some Department of Defense (DoD) problems.

In the past, military geodesy was largely involved with the practical aspect of the determination of exact positions of points on the earth's surface for mapping or artillery control purposes while the determination of the precise size and shape of the earth was a purely scientific role. However, modern requirements for distance and direction require both the practical and scientific applications of the science to provide the answers to problems in such fields as satellite tracking, global navigation and defensive missile operations.

NGA's Office of GEOINT Sciences provides accurate and timely expert analysis of worldwide gravity, satellite and positional information including imagery and mapping control for navigation, safety, intelligence, positioning and targeting in support of national security objectives.


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Basic Geodesy Articles
Coordinate System Analysis Team monthly articles distributed through e-mail to the NGA workforce to educate or refresh their knowledge about basic geodesy and some of the history of mapping and determining the earth's shape and properties.

NGA Geodetic Datums Reference System
A modeling of the Earth to WGS-84 for those areas in the world where datum transformation parameters currently exist.

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Geographic Translator (GEOTRANS) Version 2.4.1
GEOTRANS (Geographic Translator) is an application program which allows you to easily convert geographic coordinates among a wide variety of coordinate systems, map projections, and datums. GEOTRANS runs in Microsoft Windows (95 and NT) and UNIX Motif environments.

International Union of Geodesy and Geophysics
International organization dedicated to advancing, promoting, and communicating knowledge of the Earth system, its space environment, and the dynamical processes causing change.

World Magnetic Model - Magentic Declination Web Calculator