Lessons Learned during the WAAS Project

When developing the second generation of the WAAS receiver, the team was tasked with making sure the new product performed as closely as possible to the legacy receiver, Auld said, so that it could still operate within the WAAS network and meet all the safety requirements without affecting the network’s performance.

When the NovAtel team came back to the FAA with plans for enhanced features, the FAA told them not to move forward, but to keep the product the way it was.

Why? The improvements hadn’t been verified inside the safety standards; so, even though the engineering team was excited about the expanded capabilities, they had to essentially downgrade the system to ensure it continued to meet the strict safety requirements.

“Eventually the improvements were put into the receiver, but they had to be incorporated in a very careful, methodical, and deterministic way,” Auld said. “We had to take our time and make sure we filled in all the check boxes.”

A History of WAAS

NovAtel has a long history of working closely with the FAA that dates back to the 1990s.

The GPS Wide Area Augmentation System began in 1992 after approval of a mission need for enhanced satellite navigation capability for civil aviation. It became an official program two years later.

NovAtel was involved from the beginning, internally designing and funding the first reference receiver for this safety-critical system. The FAA first purchased and fielded the NovAtel receivers in the late 1990s.

WAAS reached its initial operating capability in July 2003 and is now made up of 38 reference stations, three master stations, and six uplink stations that support three L1/L5 Geostationary Earth Orbit (GEO) satellites transmitting differential corrections and integrity messages to aircraft. WAAS reference stations are located throughout North America including sites at northern latitudes of Alaska and Canada and southern latitudes of Mexico.

For more on WAAS, read “Modernizing a Safety Critical System"