Wiktionary
n. A length of one nautical mile, the limits of which have been accurately measured and are indicated by ranges ashore. It is used by ships to calibrate logs, revolution counters, etc. as well as to measure the ship's speed.
Usage examples of "measured mile".
Off Arraa, in her full-power trials, bows lifting out of the water, stern dug in like a hydroplane, vibrating in every Clyde-built rivet, and with the tortured, seething water boiling whitely ten feet above the level of the poop-deck, she had covered the measured mile at an incredible 39.
And, flitting industriously about upon its delivery duties, but never much more or less than one measured mile distant, a panel job pursued its devious way.
The quarterdeck was just fifty feet long and by stepping short at a particular ring-bolt, now worn thin and silver-bright, he could make fifty of his turns fore and aft amount to a measured mile by land.
After a measured mile for good buck, he gave the orders that would carry the ship as nearly due west as the south-west wind would allow.
When I have been on river service I have heard it at night like the engine-room when you are on the measured mile.