On 3/18/2010 2:32 AM, Andy wrote:
On Mar 17, 9:22 am, Darryl wrote:

I worry about how well we will have ADS-B ground station coverage
along busy low-level routs like major ridge soaring locations, the
white mountains etc. Without that, gliders with UATs and 1090ES will
not see each other.

Darryl,

Was I mistaken in taking from the survey that ADS-B supports aircraft-
to-aircraft position reporting without a ground station repeater? I
figured that would allow two gliders in any remote location to see
each other if they both had ADS-B transceivers (like the Mitre unit).
With ground stations you then should get position reporting between
transponder and ADS-B.

I figured any collision avoidance advice would be a function of on-
board software capability, not constrained by the means of position
reporting - as long as you know your position and track and a target's
position and track, shouldn't you be able to figure out the collision
avoidance part?

It seems to me that you should be able to design ADS-B such that you
no longer need transponders. What did I miss?

9B
If both gliders have ADS-B UAT transceivers they will be able to see
each other without a ground station, just like FLARM. The same is the
case if both gliders use 1090ES transceivers. The problem is if one
glider has ADS-B UAT and the other uses 1090ES, then they can't see each
other unless they are within range of a ground station.

In addition, the ground station will transmit the position of any Mode
C/S transponder equipped aircraft to an ADS-B equipped aircraft. As a
result, if you are within range of a ground station, an ADS-B equipped
aircraft will see all other ADS-B or conventional transponder equipped
aircraft in its vicinity.

If you have a MITRE transceiver connected to a PDA or a device like an
iPhone, there is nothing stopping someone from implementing a poor man's
TCAS in addition to showing other aircraft on a moving map display. The
new iPhone is a particularly intriguing device, as it has a built in
sensor that permits you to display a compass bearing. As a result, you
could implement a voice warning system that could actually tell you the
bearing, distance, and relative altitude of a collision threat based on
your current heading. This could be very useful in a glider that is in
a thermal, where the heading is constantly changing.

--
Mike Schumann