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Advantages of WAAS | Disadvantages of WAAS

This page covers advantages and disadvantages of WAAS (Wide Area Augmentation System). It mentions benefits or advantages of WAAS and drawbacks or disadvantages of WAAS.

What is WAAS (Wide Area Augmentation System) ?

WAAS system was developed by US federal aviation administration. The system has been operational since 2003. It is first satellite based augmentation system which provides vertical and horizontal navigation for the aircraft. Ionospheric disturbances, timing and satellite orbit errors create errors in the GPS signal. WAAS system is useful to provide corrections to GPS signal errors. The WAAS signal reception is ideal for applications in open land and marine.

WAAS system architecture

The figure depicts WAAS system network architecture. As shown it uses GPS satellites, two master stations, Geostationary satellites and multiple reference stations spread across USA. The system is designed to provide GPS signal corrections to offer better position accuracy. The system collects information from reference stations and generates GPS correction message. This corrected message is broadcasted by Geostationary satellites. As this message follows basic signal structure of GPS, it can be retrieved easily by WAAS enabled GPS receiver.

Similar satellite based differential systems include MSAS and EGNOS. MSAS (Multi Functional Satellite Augmentation System) is available in Japan where as EGNOS (Euro Geostationary Navigation Overlay Service) is available in Europe.

Benefits or advantages of WAAS

Following are the benefits or advantages of WAAS:
➨The WAAS receiver offers position accuracy which is less than 3 meters. This is better than typical GPS (~ 15 meters) and differential GPS (~ 3 to 5 meters) systems.
➨It offers position accuracy 95% of the time.
➨There is no extra hardware required to use WAAS service and hence it saves the initial installation cost.
➨The user does not require to pay service charges in order to use WAAS.
➨WAAS system provides corrections to GPS signal errors.
➨WAAS provides extended coverage compare to land based differential GPS system both inland and offshore.

Limitations or Drawbacks or disadvantages of WAAS

Following are the limitations or drawbacks or disadvantages of WAAS:
➨WAAS satellite coverage is limited to regions where ground reference stations are installed. Hence inspite of GPS users receiving WAAS signal, it can not be corrected and hence does not improve accuracy limit. Service is available in North America and not in South America due to unavailability of ground reference stations.
➨WAAS signal may not be received due to trees or mountains coming in LOS (Line of Sight) to the satellites over equator.
➨Incomplete system coverage away from Geostationary satellite locations.
➨The results of WAAS are not accurate due to stringent regulations. Hence more accurate systems are needed to meet regulation such as Local Area Augmentation System.
➨The space segment of WAAS is exposed to space debris and solar storm threats.

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