Bill Frantz sez:
At 11:25 PM 11/14/96 -0800, Lucky Green wrote:
If I remember correctly, some of the newer transponders used on commercial aircraft actually transmit GPS data back to the controller in real time. I wonder how long it will be before the FAA will include such information in their database.
I don't think new transponders make much difference. The old ones heighten the radar image of the airplane which gives an accurate 2D position. This
I missed how this got the 'Punk material, but a friend is running parts of a test of this. The en-route radar is roughly the same age as those IBM 360's in the Centers that you keep hearing about. The current approach is radar, [?2 ghz] with interrogation of a 1 ghz transponder via the same array. The xponder has 4 octal digits and {Mode C} the altitude from an accompanying encoding altimeter. So the alternate approach is a GPS receiver with a transponder replying to interrogations with position and altitude. For the most part, in the "en-route" stage, the futzing by DOD is not a concern -- all receivers in a given area are equally deceived. [Recall that the goal is to avoid Delhi incidents.] During departure and approach, the a/c will use 'differential GPS' whereby a GPS RX at a known benchmark on the airport will broadcast what error IT sees. [Errors are roughly linear within X mile zone.] DGPS will be as good or better than many existing Instrument Landing Systems, i.e. a few feet in all 3 dimensions... -- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433