Question 1

NAVTEX provides which type of maritime safety information?

Accepted Answer

Navigational warnings, meteorological warnings, search and rescue information, and other urgent maritime safety messages. NAVTEX (Navigational Telex) is an automated direct-printing service broadcasting MSI (Maritime Safety Information) on 518 kHz (international, English) and 490 kHz (national language). It provides: navigational warnings (NW), meteorological warnings (MET), ice reports, search and rescue (SAR) information, pilot service messages, LORAN notices, and other urgent information. Range approximately 300nm. Vessel can set receiver to filter by message type and transmitter ID.

Question 2

You calculate a tidal height of 2.8m for your planned entry time. Your vessel draws 1.9m. How much under keel clearance (UKC) do you have over a shoal charted at 0.5m?

Accepted Answer

1.4m. Depth over shoal = charted depth + height of tide = 0.5 + 2.8 = 3.3m. UKC = 3.3 − draught 1.9 = 1.4m. For safe passage: 1.4m UKC is reasonable for calm conditions. Add safety margin, tidal predictions are not exact, vessels may squat at speed, charted depths may be old surveys. Recommended minimum: 0.5m UKC minimum or 10% of draught.

Question 3

A harbour bar has a charted depth of 0.0 m. You need at least 3.5 m of water over it to enter harbour. Using the tidal curve, how do you find the earliest time you can enter on the rising tide?

Accepted Answer

Mark 3.5m on the HEIGHT axis, draw horizontally to the rising curve, then vertically to the TIME axis for time relative to HW.. Required tidal height above chart datum equals required water depth minus charted depth. Here, 3.5 m minus 0.0 m gives a required tidal height of 3.5 m. Mark this on the HEIGHT scale, draw horizontally to the rising tidal curve, then vertically to the TIME axis. Read the time relative to HW and apply this offset to the actual HW time to obtain the earliest predicted entry time on the rising tide.

Tidal Prediction, questions and explanations

NAVTEX provides which type of maritime safety information?

You calculate a tidal height of 2.8m for your planned entry time. Your vessel draws 1.9m. How much under keel clearance (UKC) do you have over a shoal charted at 0.5m?

A harbour bar has a charted depth of 0.0 m. You need at least 3.5 m of water over it to enter harbour. Using the tidal curve, how do you find the earliest time you can enter on the rising tide?

Practise this properly

Tidal Prediction, questions and explanations

Questions

NAVTEX provides which type of maritime safety information?

You calculate a tidal height of 2.8m for your planned entry time. Your vessel draws 1.9m. How much under keel clearance (UKC) do you have over a shoal charted at 0.5m?

A harbour bar has a charted depth of 0.0 m. You need at least 3.5 m of water over it to enter harbour. Using the tidal curve, how do you find the earliest time you can enter on the rising tide?

Practise this properly