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Getting to grips with sound signals
In busy and restricted waterways, large vessels use sound signals to notify nearby boats of their intentions.
Spotting natural tidal gauges
Draft restricted vessels have to have careful tidal calculations to figure out when there is sufficient draft to enter or leave a harbour. This may involve some laborious planning with a current tide book in conjunction with various secondary port offsets from sailing Almanacs and the use of occasional tidal curve.
Preserving night vision
Operating a boat at night is a challenge. Typically the watchman has to keep track of the vessel's sailing environment and maintain a chart plot or at least monitor the charted position. The problem is the chart plot has to be implemented with the aid of illumination. This causes the watchman to lose their slowly acquired night vision above decks.
Making marine radio (VHF) easier to handle
Certain ship names are difficult to hear correctly on the radio, our boat name 'Obsession' was a particular case. Crew members who are unfamiliar with the boat name phonetics can get lost when they have to step through both the spelling and phonetics at the same time.
Estimating tide times and tidal streams by simply observing the moon
In certain sailing areas such as in the English Channel, the tides are central to cruising activities. The essential guides will always be the latest tide tables and a tidal stream atlas.
Using a waypoint to avoid a covered and unmarked isolated danger
Whether you are navigating by instrument or eyeball, what lies beneath the water is invisible in most places. And sometimes, the main concern of navigation is to avoid an unmarked isolated danger. A good example of this is when hugging the coast and rounding the eastern side of the Isle of Wight. The Cole Rocks as illustrated above, lie 600 metres off Bembridge Ledge and very much in the way of this. There is a safe leisure boat passage between the ledge and the two drying heads of the rock, known as 'The Deep', with soundings of 2-3 metres at CD, and of course passing outside. The latter outside route although longer is the safer path because of the tidal streams, and the Cole Rocks are scarcely ever awash and almost always covered.
Easy reciprocal (back) bearing maths calculation method
We largely live in a world that uses base 10, or 'decimal' for mathematics. But this not the case with time and bearings which use base 60 or 'sexigesimal'. Because of this, the mental calculations required to quickly generating a back or reciprocal bearing can be perplexing for our decimal-based minds.