Altitudes Displayed

[straightline]

Tried out my shiny new PAW yesterday while getting a Traffic Service from Brize Radar who advised us of a helicopter passing 500' below us which then appeared on my iPad showing -500. Apart form the little aeroplane icon, SkyDemon didn't generate a banner alert. Should it have? And I assume that the baro encoder in PAW is calibrated to standard pressure so shows the Pressure Altitude? As the transmission from the helicopter was almost certainly ADS-B, I guess his altitude is also based on a pressure setting of 1013 - so that the difference displayed on SkyDemon is accurate and we don't have to worry about a conversion if flying on QNH?   

[Ian Melville]

Correct PAW users baro at 1013.2, so PAW alerts are like-for-like.
SkyDemon however a still uses GPS altitude, even though it is coming from PAW. So there will be differences.

[straightline]

That makes sense. Should we have seen a Traffic Alert banner in SkyDemon (as we get with Terrain or Airspace)? I'd be interested to know what would trigger such an alert - because the helicopter passing from our 10 o clock to our 4 o clock 500 feet below didn't. 

[exfirepro]

Hi straightline,

PilotAware uses barometric pressure based altitude to compare Mode C/S and ADSB, so that it shows the same altitude as received by ATC - and GPS derived altitude for P3i so that all PAW units register the same P3i altitude.

SkyDemon uses its own anti-collision algorithms to generate the banner alerts from data supplied to it by PilotAware and will only display the banner alerts if the other aircraft is likely to collide with you. As the aircraft was 500 ft below you, this was not likely hence no banner alert. Forthcoming versions of PilotAware and SkyDemon will also produce aircraft type specific icons and also vertical arrows to indicate if the target is climbing or descending (initially for known position targets only) which will help decide whether the danger is constant, increasing or decreasing and will also indicate whether you might need to climb or descend to maintain effective separation.

Regards

Peter
PilotAware  Development