Message-ID: <3B020993.71965CA0@progress.com>
Date: Wed, 16 May 2001 01:01:07 -0400
From: Marcelo Pacheco <pacheco@progress.com>
Organization: PROGRESS Software Professional Services
MIME-Version: 1.0
To: lancair.list@olsusa.com
Subject: RE: Wazzup with WAAS?
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Reply-To: lancair.list@olsusa.com

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The real issue with WAAS is accuracy and integrity. FAA is requiring some
unbelievably high standards out of any new navigational equipment in order to ok
it.

There's a new, much cheaper alternative to WAAS which is L1/L2 GPS. The
currently military use only GPS frequency (L2) is in the process of starting to
broadcast another GPS correction signal from the latest generation of GPS
satellites. By listening to both frequencies and comparing their timing
diferences, a GPS receiver can calculate how much ionosferic propagation errors
happened and apply corrections to them. That's the only show stopped issue that
prevents FAA from certifying precision aproaches today. Even bare bones GPS
signal today is very precise, actually most of the time it's more precise then
required for precision aproaches, but not often enough. If WAAS is not fully
operational in a few years, L1/L2 will overtake WAAS, because it's already
planned, costs relatively little to implement, and will require no additional
ground facilities (only the satellites and GPS receivers get improved), while
WAAS costs billions of dollars/year.

Marcelo Pacheco
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Please send your photos and drawings to marvkaye@olsusa.com.
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