iFly GPS Forum

My understanding (and I've seen it in practice) is that FF does use ownships baro setting.

I don't think that iFly does (yet).

In the meantime, I sent Walter an idea last year that I think could be patentable, about how to cleverly compensate without having ownship baro data. But haven't seen anything about it.

In the meantime, I could re-wish my wish list for a way to tell iFly what your local altimeter setting is, with a timer that asks for a recheck every hour.

My thinking was not to add another altitude to the mix, only a possible method to reduce the error that is seemingly now being displayed between me and other aircraft. The GPS derived altitude display would remain unchanged. It would seem to me the more accurate the information displayed for aircraft seperation, the safer we would all be.

My take is that the altitude reported by ADS-B out as well as Mode C transponders is for use by ATC to maintain seperation between aircraft, hence the use of pressure altitude. ATC is much less concerned about your altitude over the ground than you are - they just need to keep us all 500' (?) apart. A standard reference is needed, hence 29.92" HG.

So, what ADS-B reports to ATC, and what it useful to us are two different things in some cases. If we can see our pressure altitude referenced to 29.92, then we can determine our seperation from others without help from ATC, i.e. on the iFly display.

That's my guess anyway . . .