NAVSYS’ role in WAAS

October 5, 2020 - By Alison Brown

Alison Brown, president & CEO, NAVSYS Corporation

Thirty years ago, NAVSYS was deep into the development of the Wide Area Augmentation System (WAAS). I had the honor of being the chair of the RTCA SC-159 Integrity Working Group, which developed the first concepts for what evolved into three integrity standards for GPS: multi-sensor integration, receiver autonomous integrity monitoring (RAIM) and wide-area differential GPS using a GPS integrity channel (GIC) to broadcast corrections over a geostationary overlay.

NAVSYS, working with Inmarsat Corporation, built the first prototype WAAS SIGGEN equipment, which was deployed at the Coonhilly Coast Earth Station and used to transmit an L-band C/A-code signal over the Inmarsat Atlantic Ocean Region MARECS-B satellite to a software GPS receiver that we had developed and installed at Inmarsat’s Test and Development Laboratory in London.

First Inmarsat Geostationary Overlay Test-Bed, 1991. (Image: NAVSYS)

Image: FAA

This evolved into the FAA’s WAAS program, which used the NAVSYS SIGGEN for the initial deployment, test and evaluation. The algorithms developed by NAVSYS were ultimately licensed to Raytheon for use on the operational WAAS and MSAS systems.