A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2018 Sep 20, 09:28 -0700
Richard Langley, you wrote:
"WAAS doesn't work that way. WAAS and the other SBASs are state-space systems, which use a wide-area network of ground stations to determine satellite orbit and clock corrections and a grid of ionospheric delay values transmitted to all users by geostationary satellites. Perhaps you are thinking of GBAS -- ground-based augmentation system, where receivers at airports provide differential corrections and integrity information via a VHF data link. GBAS has not been widely deployed yet but there are a number of stations deployed in North America and Europe."
Aha. Yes, apparently I have had that wrong for many years, and I think you're right: I was assuming that the ground-based augmentation was an addition to WAAS.