On Wed, 22 Aug 2007 12:33:04 -0400, Andrew Gideon
wrote in
:

On Tue, 21 Aug 2007 11:15:13 +0000, Larry Dighera wrote:

Doesn't it make more sense to have a few ground-based radar installations
for traffic separation rather than the hundreds of thousands of ADS/B
installations for it to work?

How would a few ground-based installations cover the entire nation? Or
are you speaking only of the LA area?

I'm speaking of the current system. It pretty much covers the CONUS
down to the line-of-sight floor. I doubt there are hundreds of
thousands of FAA radar installations.

One advantage of ADS-B is that properly equiped aircraft can "see" each
other even outside of RADAR coverage. Being in RADAR coverage provides
additional "service" (more information is spread more widely), but the
system doesn't *require* that coverage to function.

That certainly is a significant advantage if it doesn't lull the crew
into relying on ADS/B exclusively for separation.

How much does it cost to properly equip the GA and military fleets
with ADS/B?

Incidentally, the military doesn't intend to install ADS/B in their
aircraft, so ADS/B equipped GA flights will still not be able to "see"
the fast-movers on MTRs, nor any NORDO flights.

However, outside of RADAR coverage full (and mutually compatible!) ADS-B
ubiquity is necessary. And since, at least last time I checked, ADS-B has
at least two (three?) mutually incompatible transceivers, even achieving
100% installation wouldn't be enough.

OMG, you've got to be kidding. Three incompatible ADS/B systems?
Surely that's destined to change, right?

My opinion is that this is a good idea but (1) it'll take some time for
the full utility to be achieved

Given the fact that the military does not intend to equip its fleet
with ADS/B, full utility will *never* be achieved.

and (2) it'll be completely screwed if the compatibility issue is left unresolved.

Or in the event of GPS unavailability due to jamming, solar activity,
or intentional shutdown as may occur in the event of perceived or real
threats to the nation.

As far as the GPS requirement, this is a separate issue. "Modern"
navigation devices should exploit a combination of space and ground based
systems.

Exactly.

Why we have "GPS units" rather than more diverse "Navigation
units" is probably just a matter of cost. But, obviously, there's yet to
be much in the way of a call for these superior "Navigation units".

The issue of price, and the recurring cost of periodic database
updates will substantially delay the ubiquity of such systems.

Perhaps I'm wrong, though. Perhaps it isn't cost, but the expectation
that ground based navaids are really going to be shut down. That would be
bad.


I agree. Decommissioning the existing navaids would be less than
prudent.

Of course, we're looking at the issue from a personal-GA point of view
not an airline POV.