"G.R. Patterson III" wrote:

AES/newspost wrote:

Can one _define_ the "start" and the "end" of a runway to within several
inches? (seems to me paving or blacktop would roll off over several
inch range)

Absolutely. You start the measuring wheel at the edge of the threshold mark
and
stop it at pavement end.

I obviously wasn't making any very great point here, other than that
"pavement end" might not be all that sharply defined, at least given my
observations of the edges of highway pavements, and more generally
measuring large physical things to 1 part in 5000, or 0.05% accuracy,
takes some care. To measure a 5000 foot runway to a precision of 1 foot
using a 2 foot diameter measuring wheel requires for example that the
diameter of said wheel be known to an accuracy of 5 mils = 0.005 inches,
including any dust or dirt layers it may pick up. I'd also note that if
the end of a 50 foot wide runway (I suppose that's a pretty wide runway
for some airports) is cut 1 degree off from perfectly square, the runway
is 1 foot longer on one side than on the other.