Explanatory notes
… specialised for use in mining, navigation, etc., (including magnetic compasses, gyroscopic compasses, gyromagnetic … as sextants, octants, azimuths, etc. (B) Other special marine or river navigational instruments , for example : (1) … of the course (and any changes of course) during a ship’s journey. (3) Inclinometers ; for measuring rolling. (4) Logs …