Question

Explain the purpose of the WAAS GPS augmentation systems.

Answer 1

The WAAS( Wide Area Augmentation System)is an air navigation support system which has been developed by Federal aviation administration to develop the Global positioning system (GPS ), with the objective of improving its accuracy, integrity and availability. WAAS has been developed to enable the aircrafts to rely on GPS for all the phases of the flight along with the Precision approaches to any airport within its coverage area. More and  more aircraft r are WAAS capable, allowing the aircraft to fly more precise GPS instrument approaches. WAAS capable receivers can give position accuracy of better than three metres, 95% of the time.

WAAS is the U.S. implementation of Satellite based Augmentation System ( SBAS). It is a four step process which is as follows:

*Signals from the GPS satellite are monitored by WAAS ground-based stations so as to determine satellite clock and position corrections.

* Two master stations which may be located on either coast can collect data from the reference stations and create GPS correction message.

* The correction message is prepared and uplinked to a geostationary satellite via a ground uplink station. It counts for GPS satellite orbit and clock drift, plus signal delay ,that could be caused by atmosphere and ionosphere.

* The corrected differential message is broadcasted through 1 or 2 geostationary ,or the satellites which are in a fixed position over the equator .  The information given should be compatible with the basic GPS signal structure which means any WAAS enabled GPS receiver can read the signal.

All of this happens within seconds , sharing the continuous accuracy of GPS system.

PURPOSE OF WAAS GPS AUGMENTATION SYSTEMS

* Unlike traditional ground based navigation aids, the WAAS provides navigation services across all of the an NAS I.e., National Aerospace System. It provides augmentation information to GPS and WAAS receivers to enhance the accuracy and integrity of the position estimates.

* WAAS also provides indication to GPS /WAAS receivers when the GPS system in unusable due to system errors or other effects . The WAAS system was designed with a purpose to a very strict integrity and safety standards. So that users are notified within 6 seconds of an issuance of hazardously misleading information that could possibly cause an error in the GPS /WAAS receivers position estimate.

* It has been developed to provide a high confidence to the computed GPS/ WAAS receiver position.

* WAAS corrects the GPS satellite position errors, inosphere delays and other disturbances in the GPS signals thereby increasing the accuracy and reliability of the user position solution.

* Though WAAS has been developed for aviation users, but it also supports a wide variety of non aviation uses including agriculture, surveying, recreation and surface transportation etc.. It has also been available for non safety of life applications and numerous manufacturers have also developed WAAS enabled GPS receivers for the consumer market .

* Its top purpose includes increased aircraft safety and greater air traffic capacity in a defined airspace.

* WAAS GPS augmentation systems have vertically guided approach procedures which have proven to be safer than those without vertical guidance.

* It has more flexible approach and departure routings which will enable to cut arrival times as well as enhance safety and noise abatement.

* It enables more direct, fuel efficient and timely routings through the air traffic control system.

* Significant government cost savings due to the elimination of maintenance cost associated with older, more expensive ground based navigation aids.

* It does not require any additional Runway infrastructure.

* Using WAAS, Automatic Dependent Surveillance -Broadcast can report a more accurate position to the controllers and other aircraft flying in the area then can be provided by GPS alone.

CONCLUSION

WAAS is a pioneering technology. Currently, no other navigation Technologies exist to meet FAA( Federal Aviation Administration) requirements and user needs for the expansion of vertically guided landing capabilities at thousands of additional airports.