Of course the altitude at which an airspace starts belongs to THAT airspace! At least that’s my understanding of the matter …
Well, it’s not that one side has an airspace and the other side doesn’t have any – so this is why your interpretation is unworkable. There’s always an airspace on both sides, even if “only” G. Therefore the rule that the dividing level belongs to the less restrictive airspace.
In the US, if you are close enough for the radar track to be inside the airspace as determined by the FAA, you can get violated. We are cautioned not to use GPS or DME within a mile of the airspace to maintain separation and avoid a bust.
if you are close enough for the radar track to be inside the airspace
That is a good point. Radar is not all that accurate – maybe 1nm at 30nm (laterally). GPS is normally far more accurate. But if ATC says you busted then presumably you “have” busted and that’s the end of it.
Radar is not all that accurate – maybe 1nm at 30nm (laterally).
I wouldn’t be so sure of that. After all, they use radar to shoot down aircraft that move at the speed of sound 45,000ft above. The only time I was fined for an airspace bust, the evidence was a pile of military radar plots that showed me about 1NM inside the TRA for less than two minutes. 1000 Euros was the bill.
That’s different; radar guided missiles work by a ground radar tracking and illuminating the target, and the missile homes in on the reflected radiation. So it will “always” try to reach the target exactly.
ATC (PPI) radar is not that accurate.
But I agree with you that a radar plot is not likely to be possible to argue with.
I still think it was a good theoretical question
But I agree with you that a radar plot is not likely to be possible to argue with.
The advice apparently given by a DFS guy is in this case to ask for the radar plot of all the radar heads tracking you. Chances are that they disagree by a mile or so.
And yes, military radar is quite a bit more accurate than civilian radar, so you could be unlucky in that they might have military radar plots – but that seems to be far from always.
During commissioning and subsequent routine flight inspections, the horizontal accuracy of an airfield radar is to be =<300m with a recommended resolution of =<210m. The maximum acceptable error in azimuth is to be 0.15deg whilst still remaining within the 300m criteria.
Back to the scenario, I saw something similar some years back where an RAF Jaguar decided to fly VFR across the top of a CTR/CTA which was coincident with the bottom of an airway. He argued that the demarcation line wasn’t in either Class D or Class A; he got busted. :)
the horizontal accuracy of an airfield radar is to be =<300m with a recommended resolution of =<210m
At what range?
That is the key. The azimuth error is obviously proportional to the distance from the radar head. I vaguely recall from a UK ATCO that their radar is accurate to about 1nm at 30nm. I think it may have been Birmingham.
The azimuth error is obviously proportional to the distance from the radar head.
It is. But the range error/accuracy is not dependent on range (same as DME!). So if your don’t-cross-this-line line is at more or less right angles to the wave propagation, they can “see” very accurately how far on the wrong side you have been.
But the range error/accuracy is not dependent on range (same as DME!)
But DME accuracy clearly is dependent on range, namely +-0.25NM+1.25% (of the range) (says Pans Ops / ICAO Doc 8168)