On Wednesday, December 11, 2013 9:12:45 AM UTC-8, Dan Marotta wrote:
You don't need directional antennae. Without getting too long winded (I

know, I know...) you monitor the arrival times and frequencies of the

interrogation signals and the replies and combining that with your known

position, you can mathematically determine the positions of all the

emitters. Multiple samples enable the system to determine velocity (a

vector of direction and speed).

But so what, these ground based multilateration systems have been around for years and are fairly widely used worldwide to supplement SSR radar. The way you get this traffic data to an aircraft today is via TIS-B. The position accuracy is not great (not compared to what GPS/ADS-B data-out can provide). And to receive that TIS-B traffic data your aircraft/glider needs to have ADS-B data-out, which requires an expensive IFR rated GPS, and an ADS-B data-out capable transponder or UAT (but please use a Transponder in a glider for PowerFLARM 1090ES compatibility) and a 337 field approval (for certified aircraft) that is supposed to be based on a previous STC in a similar aircraft (none of which were actually developed for gliders). So while it may be possible, good luck having that conversation with you local FSDO. And to receive that TIS-B signal requires you to be in range of the ground based ADS-B service, YMMV in some popular glider areas. And worrying about this stuff now just seems pointless given that ADS-B data-out carriage will be required in the USA in many aircraft by 2020. So you might as well just read that much higher resolution ADS-B data-out position data straight over the air now and usage will just continue to increase in future.