Manoeuvring in different wind and current conditions

Speed over the ground and speed through water can differ without contradiction because water also moves. Wind felt aboard results from relative motion between air and boat, and true wind needs an explicit reference frame when calculations are involved.

This chapter begins with those frames through hypothetical one-direction examples. Arrows represent motion towards a destination, while meteorological naming identifies where wind comes from. The example is conceptual arithmetic rather than route planning or current prediction. Effects on manoeuvres and interpretation of specific instruments will be developed separately with appropriate review.