Understanding a Navigation System

A satellite navigation system, called global navigation satellite system (GNSS) by standard, offers autonomous geo-spatial positioning with worldwide coverage. It allows electronic receivers to identify their location using time signals transmitted along a line-of-sight by radio from satellites. As of 2009, the U.S. NAVSTAR Global Positioning System (GPS) is the only completely operational form of GNSS. By 2013, the European Union's Galileo Positioning System will be operational, and by 2015, the Chinese Beidou Navigation System will be operational. Meanwhile, the Russian GLONASS is under restoration through the help of India. Russia has announced that GLONASS will be globally available by 2010.

The GPS is a radio navigation system providing positioning, navigation, and timing services to civilian users on a continuous worldwide basis. Anyone with a GPS receiver my use the system any time, anywhere, and in all weather conditions. The GPS has three components –- satellites, control and monitoring stations, and receivers. The receiver provides three-dimensional location (latitude, longitude, and altitude) and time. The satellite progressively transmits messages, which the receiver measures. With the use of geometric trilateration (mathematical concept), the receiver's location is determined, together with other information. Some receivers show derived information like direction and speed. More than three satellites are used to calculate for the three dimensions and time to limit positional error. However, three satellites will do if one variable is already known. For instance, if a plane already knows elevation, a receiver can determine accurate position with three satellites. Currently, there are 32 medium Earth orbit satellites in six different orbital planes supporting the GPS.

Europe's Galileo is said to be compatible with modern GPS. Thus, receivers can combine signals from both Galileo and GPS satellites, resulting in greatly improved accuracy.

Civilian users may buy GPS handsets from any commercial retailer. A user equipped with a GPS receiver may accurately locate where they are and easily navigate to where they want to go, by land, sea, or air. GPS has entered the mainstream of global transportation systems offering navigation for aviation, ground, and maritime operations. Rescue and emergency service providers depend on GPS locating and timing capabilities to execute life-saving efforts. The accurate timing provided by GPS facilitates daily tasks like banking and mobile communications. GPS helps farmers, surveyors, geologists, and other professionals do their work more efficiently, safely, accurately, and economically through the use of costless and accessible GPS signals.

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