Tidal diamonds

Information about the set and drift of the tidal stream can be obtained from Charts or Tidal Stream Atlases.
On charts the tidal streams are marked with a letter within a diamond, and a table provides information about the set and drift for spring and neap tides.
With the time of high water at the standard port, e.g. Portsmouth, you can select the hour you are interested in, either “before High Water or after High Water.
Head across the table to the tidal diamond, and read off the set of the tide and the drift in knots. Note the difference between the spring and the neap range.