In a previous article, Roger said:
On Tue, 27 Mar 2007 18:43:48 +0000 (UTC),
(Paul Tomblin) wrote:
"These correction messages are then broadcast through communication
satellites to receivers onboard aircraft using the same frequency as GPS."

The only thing I found was slightly different. "These corrections
messages are then broadcast to receivers onboard the aircraft using
the frequency as the GPS". It said nothing about being broadcast
through communications satellites, or I missed it.

If you were using WAAS, you should get to know the WAAS satellite coverage
areas. I think they fixed the problem, but for a while there the coverage
was **** poor is in New Hampshire and Maine.

IF correction messages can be sent from local areas back to satellites
that would make they very vulnerable to tampering with the data.

At one time the FAA was talking about using ground based broadcast
stations, called LAAS (Local Area Augmentation System). (Which, by the
way, used different frequencies than the GPS constellation.) As far as I
know, none have been deployed yet or they dropped the idea.

--
Paul Tomblin http://blog.xcski.com/
"Of the many tragedies of Vietnam, this raw class discrimination strikes
me as the most damaging to the ideal that all Americans are created equal
and owe equal allegiance to their country." - Colin Powell (pre-sell out)