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At the risk of going over old ground yet again, the ONLY potentially inaccurate bit of data about a Bearingless target is the HORIZONTAL SEPARATION (due to differences in transponder transmission strength between sircraft). Vertical separation is calculated from the barometric altitude transmitted by the aircraft’s transponder, and is therefore accurate to the limits of the transponder transmissions (so no difference whatsoever in this respect from Mode-S/ES ADS-B).
An audio warning reporting ‘Traffic, 500 feet above - horizontal position unknown’ cannot therefore be described in any way as ‘inaccurate’ to any greater degree than equivalent warnings for known position traffic. You can also readily determine accurately from the data whether the broadcasting aircraft is climbing or descending - a factor which can be critical when you have no accurate horizontal position data for it.
Despite the reported significant recent increase in sales (and hopefully installations) of known-position EC devices, there will still be a very significant percentage of GA traffic out there with raw Mode-S transponders not transmitting their position (I don’t have the most recent figures, but I’d be extremely surprised if it is below 50% of GA yet - and probably still higher).
Adding an appropriate audio warning ‘Traffic, Same Level / xxx feet above/below / climbing/descending / Horizontal Position Unknown’ would immediately draw the users’ attention to looking outside the aircraft - rather than hunting for a contact on a screen. It would also allow SkyDemon (with audio) to be the ‘Go-To’ on GDL90 for both known position AND Bearingless Traffic.
Best Regards as Always
Peter
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