True course

True course is the ship’s intended track measured clockwise from true north, the course laid and read on the chart. It is converted to the course steered by the magnetic compass through compass error: compass course equals true course minus easterly compass error, plus westerly, where compass error is variation plus deviation. The navigator plans in true, then works back through variation from the compass rose and deviation from the deviation card to give the helmsman a compass course to steer. A gyro course needs only gyro error applied, since the gyrocompass seeks true north directly.