Both use ADS-B but obviously AirSense is more limited. What is the actual range of ADS-B and how exactly does Flightradar24 work?
The reason I ask is that I will get warnings on AirSense and then go check Flightradar24 and not see anything. Conversely I will see planes on Flightradar24 but they don't show up on AirSense. I'm aware the AirSense has different filters as to what to display and different range but I'm taking about planes I can see or hear that won't display.
Thoughts?
Although they use the same technology in practice it'll work differently.
Both rely on a receiver to receive ADSB from aircraft. FR24 relies on a worldwide network of receivers.
The issue is the signals are line of sight which means if you're not in a populated area, have mountains or something similar then there maybe no FR24 receiver station in range of aircraft in that area.
This is especially true of low altitude. Its perfectly common to be able to "see" aircraft 200+nm away at upper flight levels but have a rage of 3-4nm only for low altitude in bumpy terrain.
Something else to consider is *anyone* can exempt their plane or fleet from being displayed from FR24s tracking which means even if it IS received, it wont be displayed. The list itself is kept secret but people have managed to reverse engineer bits of it and its several thousand aircraft large at least.
So Airsense is going to be more useful than FR24 in general because its receiving in your local bubble where there may well be no FR24 coverage of that area from a third party.
Airsense may also filter out useless traffic in the area (Theres no point showing aircraft 30,000ft above the max obtainable drone altitude or aircraft whos course and speed post absolutely no threat). Im not sure how sophisticated it is but some filtering is useful.
A final point is both Airsense and FR24 are only going to display aircraft that broadcast ADSB. A lot of general aviation, military, gliders and so on (the traffic most likely to cause a problem with a drone) do NOT have ADSB transponders so wont show up.
Although in theory ADS-B is mandatory in the USA the last released figures only showed 44%of GA aircraft were equipped which means roughly you'll be missing half the potential traffic. Military often fly with ADSB off as well, especially when on low level training sorties outside controlled airspace.
In the rest of the world ADSB transponders are even worse coverage ranging from 10-20% or so in some countries for non-commercial / GA.
So just because Airsense there is no traffic, it doesnt mean there's no traffic. There might be something about to come over a hell or valley it hasnt received or there might be traffic that isnt transmitting ADS-B around.
So its a guide but certainly not foolproof (and arguably, not overly useful for someone operating in correct, legal VLOS distances etc).
