With reference to Ian W's post, I agree that the fidelity of ATC ground movements displays can be questionable. Ground movement radar is excellent where it can see - you can tell the difference between an A320 and B737, such is their resolution, and I have seen clear returns from hares running along the taxiways and fences. However, they have a lot of blind spots. The "new thing" is to have a Mode S based system with lots of receivers that triangulate positions, but that also has blind spots and unreliabilities, but it is also a calculated rather than measured position that appears on screen. That is what DUB uses and I have been victim to their system's shortcomings a few years ago. I do not believe it to be a very accurate system.