Wednesday, 27 January 2010

The Facts of Calculating Tide

For a tidal question if there is a date you will need your Nautical Almanac to calculate HW. When you start think of the Facts you will need and write them down!

The Date - immediately correct for DST if you need to.
The Time - of High Water relevant to your journey/position.
The Range -  of HW and LW.
Is it Springs or Neaps - the difference in the Range compared to the panel beside your Tidal Curve.
Period Of Time - for a Tidal Diamond/Tidal Atlas i.e The hours before or after HW that you are there.

We bracket tide half hour before HW half hour after. So HW 1000 hrs becomes HW 0930 to 1030. Draw your diagram to show  the hours before and after HW. You will then know which period of time you are working in relevent to tide. Remember your Box of Facts, write them down immediately.

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