First ground tests - OK except all voce messages say traffic is at my level !!!!

[Stu B]

Just started trying my PAW - fired up OK first time, seeing ADS-B and Modes-S traffic (on "loosest" filter settings), both on screen and on the traffic list. All are at credible locations and altitudes (FL200 - FL400) on my map.. BUT with voice output from PAW plugged in, EVERY ADS-B contact is declared as "level". The status page shows 3D fix from 6 satellites and  QNE ~44ft and GPSS as ~400ft (not sure why they differ so much - baro calibration or GPS separation???) but either way, clearly not "level" with the ADS-B traffic which is correctly shown at FL200 or whatever both on map and on tabulation page. Also, Mode S audio does not give any indication of relative altitude - I presume it  gets it altitude form the baro sensor and GPS and does not need to get the Mode S altitude from my own aircraft (clearly it won't get that while I test at home!) to calculate a Mode S alt difference?

(PS - in case it's relevant, PAW was delivered with 20160530 s/w but successfully updated automatically to 20160708 version by ethernet cable link.)

[exfirepro]

Stu,

In the case of the ADSB reports, the aircraft are described as 'Level', 'Above' or 'Below', simply to direct your visual scan to help locate the inbound aircraft. In this context an aircraft described as level will be at an altitude which brings it within +/- 10 degrees of your own level in the vertical plane, which to the human eye will appear to be at roughly the same level as yourself. Of course, the further away it is from you, the greater the vertical separation which will still report as 'level'. Remember, the whole purpose of the system is to bring to your attention the presence of other aircraft so you can see and avoid them.

Mode S altitude is derived from the other aircraft's transmission and is compared to your current altitude as stored within your PAW. The audio alert is limited to a warning based on the degree of risk presented based on the signal strength of the transmission from the approaching aircraft. The relative altitude is clearly displayed on screen to assist with visual lookout for the inbound contact, either 'level', above or below your present altitude. We have considered adding relative altitude to the mode S audio alert, but this has not yet been incorporated.

Hope this helps

Regards

Peter
Mode S Development Tester

[Stu B]

Many thanks Peter that does seem to fully explain what I observed.