WAAS EGNOS

WAAS


What is WAAS?

  • WAAS is the acronym for the Wide Area Augmentation System developed by the FAA and the DOT to give aircraft the ability to rely on GPS for all phases of flight by improving GPS accuracy, integrity, and availability.

How does WAAS work?

  • A network of ground based wide area reference stations (WRS) monitor GPS satellite signals for variations caused by atmospheric disturbances, clock drift, and satellite orbit errors.
  • The WRS relay these errors to wide area master stations (WMS) where the deviation correction (DC) information is computed, and updated correction messages are transmitted to geosynchronous satellites via a ground uplink system (GUS) every five seconds or better.
  • These geosynchronous satellites then broadcast the correction data back to Earth where any WAAS enabled receiver can use the information to improve reported position accuracy.

WAAS coverage

  • WAAS coverage currently extends to portions of North America, Alaska, and Hawaii.

Do I need WAAS?

  • Unless you will be piloting an aircraft over the U.S. any time soon, probably not. However, the Garmin Montana is WAAS enabled, and you can still use WAAS to more accurately plot your position on Earth, so why not? Besides, you didn't buy a GPS receiver because you thought paper maps and a compass were 'close enough', now did you?

WAAS Satellite Map


WAAS_SAT_Map_[2010-03].jpg
WAAS_SAT_ID.png

  • PRN is the satellites actual Psuedo-Random Noise code
  • NMEA is the satellite number referenced by some GPS receivers (NMEA = PRN - 87)

WAAS on Montana

WAAS_SAT_48_7ft.png

Receiving WAAS correction data from satellite 48, located approximately 35º above the southern horizon, the Montana is reporting the current GPSaccuracy to be 7ft. Not bad!

WAAS_SAT_51_10ft.png

WAAS correction data provided courtesy of satellite 51, located approximately 35º above the southern horizon, just slightly to the east.

WAAS_None_SAT_46_15ft.png

Here the Montana is attempting to access WAAS satellite 46, indicating [in error] its current position is just over the northern horizon, and out of view from my location. [See Bug 26]

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EGNOS


What is EGNOS?

  • The European Geostationary Navigation Overlay Service is a satellite based augmentation system (SBAS) developed by the European Space Agency, the European Commission, and EUROCONTROL to supplement the GPS, GLONASS and Galileo systems by reporting on the reliability and accuracy of their signals.

How does EGNOS work?

  • Similar to WAAS, the EGNOS system consists of three geostationary satellites and a network of ground stations.
  • More than 40 ground stations are linked together to create the EGNOS network consisting of:
    • 34 RIMS (Ranging and Integrity Monitoring Stations) - receiving signals from US GPS satellites,
    • 4 MCC (Mission Control Centers) - data processing and differential corrections counting,
    • 6 NLES (Navigation Land Earth Stations) - accuracy and reliability data sending to three geostationary satellite transponders to allow end-user devices to receive them.

EGNOS coverage

  • EGNOS coverage currently extends to parts of Europe and Africa.

Do I need EGNOS?


EGNOS Satellite Map


EGNOS SAT MAP 3.png
EGNOS SAT ID c.png

  • PRN is the satellites actual Psuedo-Random Noise code
  • NMEA is the satellite number referenced by some GPS receivers (NMEA = PRN - 87)

EGNOS on Montana

EGNOS SAT 33 9ft.png

Receiving EGNOS correction data from satellite 33, located approximately 30º above the southern horizon, the Montana is reporting the current GPS accuracy to be 9ft.

EGNOS SAT 37 7ft.png

EGNOS correction data provided courtesy of satellite 37, located approximately 30º above the southern horizon, just slightly to the east.

EGNOS SAT 39 7ft.png

Here, the Montana is indicating EGNOS satellite 39 to be located just over the horizon, due east and slightly to the south. This also is a satellite position reporting error as the actual GPSr location is in the southern UK, [See Bug 26]

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