Wide Area Augmentation System

The Wide Area Augmentation System (WAAS) is a navigation system with high level of accuracy. This system is used to provide additional help to the Global Positioning System (GPS) for air navigation. It was developed by the Federal Aviation Administration, an agency of United States Department of Transportation. The main aim of the WAAS is to improve the accuracy, integrity, availability and continuity of the GPS, so that the pilot can rely on the GPS during all phases of flight.

Configuration of Wide Area Augmentation System

The three key segments of WAAS configuration are: the Ground segment, the Space segment and the User segment.

The Ground Segment: It consists of a number of Wide-area Reference Stations (WRS). They gather information on GPS signals and transmit to Wide-area Master Stations (WMS) through terrestrial communications network. The WRS also keeps a tab on the signals of geostationary satellites of WAAS. The WMS makes corrections in the data received from the WRS sites. The corrected data are sent from the WMS to the Ground Uplink Station (GUS). The GUS broadcasts them to the satellites of the Space segment.

The Space Segment: The main task of the Space segment is to transmit the rectified data generated by WMS to the User segment via its multiple geosynchronous communication satellites. These satellites also carry out the functions of broadcasting range information like any other normal GPS satellites. As a result, number of satellites available for a particular position increases which in turn improves the efficiency.

The User Segment: The main component of the the User segment is the GPS and WAAS receiver. It uses the information provided by GPS satellites and the WAAS corrections from the Space segment to ascertain the current location and the time of the aircraft.

Advantages of Wide Area Augmentation System

WAAS provides solution to almost all kinds of navigation problems. It gives a precise information of the position that is easy to use. It is obtained at the cost of only one receiver that is installed on the aircraft. Because of its ground and space-based infrastructure, aircrafts do not have to depend much on ground-based signals from the airports. WAAS can operate between airports too. As a result, It enables the aircraft to travel directly from one airport to the other. It can cut down distances to be traveled and thus saves both time and fuel.

Aircraft equipped with WAAS can fly at lower altitudes. It is not possible with ground-based signals as those signals may get blocked by terrains of varying heights. On the other hand, WAAS gives all the information through GPS satellites. This is helpful particularly for unpressurized aircrafts as it conserves oxygen and ensures safety.

Problems of Wide Area Augmentation System

Despite being an extremely effective system for air navigation, WAAS has its own share of problems too. The number of satellites and ground stations available for WAAS are limited. Due to this problem, the number of locations for which the positioning can be calculated are just confined to specific points. Aircrafts should be fitted with certified GPS receivers to approach WAAS. These equipments are more costly than any commercially available units. The accuracies required in aircrafts for the ground-based landing instruments of smaller airports are not available in WAAS. So, either the aircraft needs to maintain the old ground-based equipments or the airports need to replace their systems with WAAS.