The accompanying table is prepared with a view to enabling a vessel engaged in a tactical evolution by the oblique method* to determine quickly her flank distance at any point in the evolution. Incidentally, its use maybe extended to afford quick solutions in certain other cases that may arise in tactics and in navigation.
Suppose a vessel at A (see figure) to be engaged in an evolution requiring her to take a specified distance on the flank of another vessel, B, of the formation, the latter steering the course DE. It is required that A shall know at any moment her flank distance, AC, from the line DE, in order that her course may be changed to "front" when the proper flank distance has been gained. Let A observe her distance, AB, from the ship B, by stadimeter or other instrument, and also the angle FAB from front to B—this angle being quickly determined by observing the bearing of B from A's keel line and subtracting three points (the angle of obliquing) if A is increasing distance, or by adding the same angle if decreasing distance. We then have the right triangle ABC, in which the side AB and the angle ABC (=FAB) are known and it is required to find the side AC.