2. Polar: i.e. by means of the 2 poles, 'North and South.' This is a very uncertain system of representation, and one that cannot safely be depended upon.
3. Trilinear: i.e. by means of a line which takes 3 different courses. Such a line is usually expressed by three letters, as W.E.G.
That the principle of Representation was known to the ancients is abundantly exemplified by Thucydides, who tells us that the favourite cry of encouragement during a trireme race was that touching allusion to Polar Co-ordinates which is still heard during the races of our own time, , , , they're gaining!'