One thousand double paces makes sense, bit less than a metre per pace. It would not be 1000 paces as they were pretty well laden with gear and 5 foot or 1.75 metres per pace seems a bit far, but half that seems fair. The nautical mile changes by a few feet as it is a minute of arc and the earth is not round, so there is a difference between the polar and equatorial measurements for it. The metre of course is 1/10 000 of the distance between the pole and equater, and they sorted that out way back.