Talking about nautical miles and fuel consumption. When on builders sea trials, all vessels go on a measured nautical mile. This actually consists of several runs consisting of a 2 mile run up to the measured mile, the run on the mile, and a 2 mile run plus turning distance to start another run. The idea of doing several runs is to take into account wind speeds, and current flows.
After each pair of runs at different shaft speeds or variable pitch propeller settings are completed, the calculations are averaged, giving you shaft horsepower, fuel consuption and knots at known shaft speeds or pitch settings and whether or not the vessel reaches her design specification.
There are various measured mile runs around the coast we used the Isle of Arran mile mostly due to it having very deep water, thus giving more accurate readings.
I hope this is of interest to everybody.
Joe