Rhumb-line Sailing

Extract

If Turner is right that ‘the underlying theory of the traditional approach (to rhumb-line sailing) is obscure’ and that there is a ‘lack of ready availability of a table of distances of parallels of latitude from the equator, it is certainly not the fault of this Journal which precisely 20 years earlier published a paper which gave:

1. The correct mathematical theory of rhumb-line sailing on an oblate spheroid.

2. The name ‘meridional distance’ to what Turner now calls the L(φ) function.

3. A table to reduce latitude to meridional distance.

4. A rule of thumb procedure to calculate rhumb-line distances correctly with no more labour than that which has always been used to do it wrongly.

5. A method (with table) for use on the spheroid when the track angle is nearly 90° and the method Turner discusses is impracticable.

6. A survey of methods and tables then current.