Global Positioning System (GPS)
The Global Positioning System (GPS) was developed by the Department of Defense to provide a reliable and accurate positioning system for mobile military platforms operating around the world. The widespread use of GPS has led to inexpensive GPS receivers that are now available for commercial use.
GPS satellites follow a circular orbit about 20,000 kilometers above the center of the Earth. Because of the long distances involved, the power of the ranging signals transmitted by the satellites is significantly reduced by the time the signal reaches the GPS receiver. For this reason, GPS receivers have difficulty operating in heavily wooded areas and inside buildings.
Metron is currently working with the Space and Naval Warfare Systems Center and the GPS Joint Program Office to develop algorithms that integrate GPS signals with ranging signals from other radiolocation networks. The integrated navigation system will be less susceptible to interference and line-of-sight visibility constraints because ranging data is collected from multiple sources.
The Department of Defense has developed several other radiolocation systems in addition to GPS. These systems are typically used in small areas and do not provide global coverage. However, they do provide a secondary source of position information that can be used to improve the performance of GPS.
Metron uses a small network of five GPS receivers for field testing and algorithm development. Handheld computers are attached to each GPS receiver so that data can be recorded for analysis. Embedded radio transceivers in each handheld computer allow position information to be transmitted between network nodes.