The force required to propel a ship at any
given speed may be measured by trial runs over a
standard course in which the ship is self-propelled
or is towed by another vesseL. To obtain reliable
results, an exacting technique must be followed in
which a series of observations are made at each
fied speed, during which the vessel alternates
its direction over the course in order to neutralize
the effects of current. The trials should be run in
quiet waters,