296 seamanship secrets
Speed over a Measured Mile
(See Chapter 3, How to Make a Speed Graph in Three Easy Steps)
- Find a measured mile range or a straight distance of 1 nautical mile between two
prominent objects. - Start the watch and maintain RPM under power or heading under sail. Aft er arriving
at the object, enter the table across the top with minutes and on either side with
excess seconds. Th e intersection gives the speed for one leg. Under sail, this gives
average speed over ground, on that point of sail in those conditions. - If under power, repeat the method back to the fi rst object. Enter the table again and
fi nd speed. Th e average of the two speeds gives the vessel’s speed through the water
at the selected RPM.