"Mike Rapoport" wrote in message link.net...

Using GPS to navigate airplanes in the US is only incedental to its actual
purpose.

Mike
MU-2

Well, as we move towards GPS/WAAS as the "primary source" for aerial
navigation the urgency of providing redundancy certainly increases.

Right now there's talk about maintaining a skeleton network of VORs,
or keeping the old LORAN chains going, but the idea of cellphone
towers is kind of fascinating. Here you have a bunch of radio
transmitters in highly-fixed geographical locations that squawk a
bunch of info out into the ether (hmm, sounds like a GPS satellite to
me), that are all maintained by private funds. Plus, you've got at
least 4 completely-separate networks (AT&T, Verizon, Sprint, Nextel)
going at any one point in time.

No, they're not everywhere, but odds are that anywhere you have a
good-sized airport, you have population, and that means you have
towers.

If you add precise timing and positional codes to the signal these
towers send out, you could conceivably have a highly GPS-like system
that provides some kind of backup. Reception up in the flight levels
might suck but it ought to improve as you approach the ground, which
is where you really need it anyway. And hell, if you wire it all up
right, couldn't you have a sort of break-through that allows ATC to
transmit and receive "phone calls" in case of a radio failure? Two
redundancies for the price of one! And best of all, by piggybacking on
an existing infrastructure, you save a boatload of money.

OK, I'll admit that the difference between principle and practice in
this sort of thing is the difference between being a member of the
Angelina Jolie Fan Club and staying over at her place for breakfast.
But that doesn't mean speculating still isn't fun...

Best,
-cwk.