Global Positioning System

Paper Summary:

This paper explains that GPS provides all-weather round-the-clock navigation capabilities for the military and is an integral asset in numerous civilian applications and industries around the globe, including recreational uses such as boating, aircraft and hiking, corporate vehicle fleet tracking and surveying. The author states that the military's Precision (P) code provides positional accuracy to within approximately 20 meters. The paper reports that the first eleven spacecraft (GPS Block 1) were used to demonstrate the feasibility of the GPS system; the orbit inclination was 63 degrees, differing from the 55 degrees used for the operational system.

Table of Contents
Abstract
Background: Global Positioning System (GPS)
Problems to be Solved
Technical Discussion
Launch Facts
Future Prospects

From the Paper:

"SLR will continue to be essential for measuring temporal variations of the gravity field given the passive simplicity of these orbit targets and the decadal span of precision data. With the launch of Lageos 2 in 1992 and Stella in 1993, in combination with the older geodetic satellites Lageos, Starlette, and Ajisai, estimates of the temporal variations of the gravity field will undoubtedly be improved in accuracy, and spatial and temporal resolution. Geophysical modeling of temporal gravity variations will also continue to be important, since their combination with the satellite estimates will improve our knowledge of the solid Earth, ocean, and atmosphere. The development of realistic eddy resolving multi-layer ocean models forced by real wind fields will be an important resource over the next few years for determining the role played by the atmosphere and oceans in the excitation of the Earth's gravity and rotational variations [Rosen, 1993]. Future improvements in the long-wave-length models of the time-invariant gravity field will depend on accurately modeling or estimating both the tidal and non-tidal gravity variations, as the current uncertainties for the low degree coefficients are at the same level as the known temporal variations of the coefficients. While tidally-induced variations have been modeled for many years, the importance of modeling non-tidal variations in gravity is only now becoming apparent."

More papers on Global Positioning System:

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