On Tue, Jan 29, 2013 at 11:47:51AM -0700, Martin Leese wrote: > Because of upper-atmosphere propagation > delay, the raw time in a GPS receiver is only > good to 1 ms or less. This is one of the errors > the WAAS system (or EGNOS/MSAS/GAGAN > system) corrects, but WAAS is only used by > the more expensive GPS receivers.
GPS can easily provide much better than 1 microsecond, even without WAAS or EGNOS. While these augmentation system do increase accuracy, their main purpose it to provide integrity. Most cheap house & garden GPS receivers just don't have the interface required to output precision time signals. And those that are engineered to provide accurate timing won't be as cheap. GPS is one of those technologies that, while being very succesful, failed to provide some the things it was assumed to. In the 1980's the deployment of MLS (the successor to ILS, the Instrument Landing System) was stopped because 'soon there would be much better GPS based solutions'. Now, 30 years later, the only things that GPS provides to aviation is basic en-route navigation (iff you have an approved receiver and up to date database), and if WAAS is available, Cat I approaches and landings (the easy ones, the final approach is essentially visual). Meanwhile the biggest user of MLS has been the US Air Force, the home of GPS... Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound
