Module 11 - Tides & Tidal Streams

The Tidal Curve Method

The Admiralty tidal curve is the standard method for finding the height of tide at any time. Step 1: Find the HW time and height, and LW height, from the tide tables. Step 2: Calculate the range (HW height minus LW height). Step 3: Find the time difference between your required time and HW (hours before or after HW).

Step 4: Enter the tidal curve at the appropriate time offset (hours before/after HW). Step 5: Read across to the curve, then down to find the height factor. Step 6: Multiply the range by the factor, and add to LW height. This gives the predicted height of tide at your required time.

Choose the spring or neap curve by comparing the day's predicted range against the mean spring and neap ranges printed on the tidal curve sheet. If your range falls between the two, interpolate by eye between the spring and neap curves.

Key points

  • Range = HW height − LW height
  • Find hours before/after HW for your required time
  • Enter curve at time offset, read height factor
  • Height at time = LW height + (Range × factor)
  • Use the spring or neap curve depending on the range
  • Interpolate between curves if range falls between mean spring and neap

Continue studying Tides & Tidal Streams

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