2006 Fellow

Presented to: Dr. Todd Walter

Citation: For contributions to the development and deployment of the Wide Area Augmentation System.

Dr. Todd Walter received his doctorate from Stanford University in applied physics in 1993. At that time, he became the director of the Wide Area Augmentation System (WAAS) Laboratory at Stanford where he continues to serve in that capacity.

WAAS became operational on July 10, 2003—an event that would not have happened without Dr. Walter. The Federal Aviation Administration has repeatedly acknowledged that his participation is critical, and will be critical to the success of WAAS. Dr. Walter’s contributions include the following accomplishments.

Dr. Walter almost single-handedly implemented an experimental prototype of WAAS that was based on three West Coast reference stations and later became part of the National Satellite Testbed (NSTB). With these three stations, Dr. Walter led the Stanford team that prototyped a complete flight test system. This system included all of the hardware and software for the reference stations and a complete master station. It also included a VHF data link and later a geostationary satellite link to convey the corrections to the aircraft and the prototype WAAS avionics.

Using this prototype system, Dr. Walter led some of the earliest WAAS flight trials. The Stanford trials were the first to separate the GPS corrections into the vector components characteristic of any space based augmentation system. Accuracy was assessed using a laser altimeter and GPS carrier phase system. Typical accuracy in flight was approximately two meters in the vertical. These results were among the key early results that motivated the production of an operational WAAS. Dr. Walter was also instrumental in the certification of WAAS.

Specifically, he led the ionospheric team that was part of the larger WAAS Integrity Performance Panel effort and was the lead contributor to the re-design of the ionospheric algorithms. His algorithms developed the ionospheric corrections and more importantly the confidence intervals associated with those corrections. His ionospheric storm detector is also a key element in WAAS safety. Dr. Walter has emerged as an international leader on the safety analysis of satellite navigation systems.