Definition
Admiralty tidal stream atlases present thirteen chartlets, one for each hour relative to high water at a reference port such as Dover. Arrows show direction, and paired figures give neap and spring rates in tenths of a knot, so 19,34 means 1.9 knots at neaps and 3.4 at springs. Weight of arrow indicates relative strength. They give a far better regional picture than isolated diamonds.
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