Abstract
Global Positioning System, GPS based on a constellation of 24 satellites orbiting the earth at a very high altitude. In other words GPS is a space based all whether radio navigation system. It broadcasts precise, synchronized timing signals to provide precise estimates of position, velocity, and time. It offers advantages of accuracy, speed, versatility and economy while in use as an aid for position-based data collection. Thus, a great technological revolution is taking place at the development of GPS as it can be used in any conceivable problem under the sky, where the exact position of any object or phenomena involved. The paper describes the applications, GPS architecture, basic principle of GPS and methods of observations.
Introduction
The global Positioning System (GPS) is a modern technology, which provides precise positioning of points (x, y and z) for navigation, surveying and Geographic Information System (GIS) data capture. Precise navigation based on the global positioning (GPS) has becomes a valuable auxiliary to photogrammetry, gravimetric, and topographic mapping. Accurate navigation is important when surveys are repeated to follow small changes in terrain height due to subsidence, or to track the flow of ice in a glacier. Initially, GPS were developed and use for military application only. Since the release to the civilian sector, global positioning systems have rapidly grown for ship and aircraft navigation as well as precise surveying and geological studies. With GPS, rates and relative motion of continental drift have been measured in centimeters per year as well as real time tracking of hazardous or sensitive material shipments.
The GPS provides continuous three-dimensional positioning 24 hours a day throughout the world. The technology seems to be beneficiary to the GPS user community in terms of obtaining accurate data up to about 100 meters for navigation, meter level for mapping, and down to millimeter level for geodetic positioning. The GPS technology has tremendous amount of applications in GIS data collection, surveying and mapping.
