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One quick thought with regards to WAAS.  I too wonder at the speed, or
perhaps better, the lack thereof evidenced by the FAA. But I had the
occasion the other day to be talking to a gentleman who makes GPS
simulators.  We got on the subject of WAAS.  One important point germane
to this discussion is the one of "satellite health."  When the satellite
transmits its coordinates, it includes a "health" bit that indicates
whether the data is to be believed or not.  There are known instances
where the satellite said OK but in reality was not.  If you were
depending on GPS for an IFR fix, particularly during landing, this
possibly would be a very bad, bad thing.  Among other things, WAAS will
be doing independent tests for the health of the satellites and
independently transmitting confirmation of the health.   So the idea is
that if the satellite exhibits one of these rare failures, you still
have a chance to reject the data and only use good data or abort before
you get into trouble.
Charles R. Patton
N360JM
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