WAAS is a technology used in USA for location or position determination, likewise EGNOS is used in the European continent. EGNOS is an acronym for European Global Navigation Overlay System. It was developed in the early 1990s, with a prime objective of providing the Civil Aviation Authorities with accuracy and integrity that is required for safe air traffic control in the European countries. Owing to its improved performance, it was realised that this technology can be incorporated in a wide range of navigational applications such as railways, roadways, waterways, etc. The outer space is made up of a total of 24 satellites that are orbiting the earth. At any particular given point of time, there is sure to be at least 4 visible satellites, this is the minimum number of satellites that is required for positional computations for most of the applications. The EGNOS technology has thus been designed to provide safe GPS system over the European continent by transmitting via geo-stationary satellites.

EGNOS consists of three geo-stationary satellites along with lots of ground stations. RIMS (Ranging and Integrity Monitoring Systems) are situated on the ground and they get hold of signals provided by the GPS satellites. This signal information is processed in the MCC (Master Control Centre). At MCC the accuracy of the signal is determined by taking into account various electrical disturbances or noise factors. After eliminating the noise and other electrical disturbances, the corrected and enhanced data is merged into an EGNOS signal and is then sent back to the three satellite via a secure communications link. Now the satellites transmit these signals back to users. The signals from these satellites are also used for determining the vehicle’s position or location. Thus using EGNOS the accuracy is considerably higher as compared to GPS alone.

The latest inertial sensors such as gyroscopes, odometers, accelerometers, etc. act as a complement to EGNOS for improving the accuracy of the overall system. The EGNOS System has been developed to work along with the existing satellite navigation systems in order to improve the accuracy of signals. Satellite signal’s availability depends on the environmental conditions and road blocks. The satellite signal can be blocked by tunnels, high trees, mountains etc. However owing to the inertial sensors, this short term data is always available. EGNOS combines this short term data is combined with the information obtained from the satellite signals to provide accurate information almost everytime. This makes it suitable for most of the critical applications such as in aircraft and ships. EGNOS services can be used by authorities to monitor the vehicle’s position, speed etc. also in case of marine applications, the location of the ship can be monitored regularly. This is specially useful in winter when the roads are covered by thick fog and visibility is very low. Owing to the EGNOS technology, the driver is equipped with accurate moving map display on his satellite navigator.

EGNOS is in fact a joint project between ESA (European Commission) and the Eurocontrol, which is the European organisation devoted to the safety of air navigation. Currently there are two satellite navigational systems, the US GPS and the Russian GLONASS. EGNOS has managed to improve the accuracy of GPS and GLONASS systems to 2 meters. The service is guaranteed owing to its duplicate systems and fail-safe mechanisms. EGNOS is actually paving way for European Galileo Satellite Navigation System.

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