Possibly he might measure some other thing, but still after your question I started to wonder how much a passenger plane moves per thousandth of a second.

So: some quick googling suggests that "economical cruising speed" of an Airbus A320 is 840km/h [1]. After quick back-of-envelope calculations, this gives ~230m/s, so 0.2m per 0.001s. Given some possible uncertainty of a single measurement, I'd imagine that's not unreasonable level of precision when e.g. your Airbus is landing on an airport.

[1]: http://www.airliners.net/aircraft-data/stats.main?id=23