MCA CoC Navigation & Chart Work 2

Question 1

What is 'dead reckoning' (DR) in navigation?

Accepted Answer

Calculating estimated position using the last known position, course steered, speed, and time elapsed

Answer

Dead reckoning (DR) calculates an estimated position by advancing the last known position along the course steered, using the speed made good over a known time period. DR does not account for tidal stream or leeway.

Question 2

What is an 'Estimated Position' (EP) and how does it differ from dead reckoning?

Accepted Answer

An EP accounts for tidal stream and leeway in addition to the DR — it is more accurate than pure DR

Answer

An Estimated Position (EP) is the most likely position of the vessel, calculated by applying tidal stream vector and estimated leeway to the dead reckoning position. It is more accurate than pure DR because it accounts for water movement and wind effect.

Question 3

What is the significance of the depth contour known as 'charted depth' on an Admiralty chart?

Accepted Answer

Charted depths are measured from chart datum (Lowest Astronomical Tide) — the actual depth is the charted depth plus the height of tide

Answer

Admiralty charts use chart datum (approximately Lowest Astronomical Tide) as the reference level for soundings. The actual depth at any time equals the charted depth plus the height of tide above datum. This ensures charted depths are the worst-case minimum.

Question 4

What is a 'tidal diamond' on a chart and how is it used?

Accepted Answer

A reference point on a chart with a letter identifying its tidal stream data table, giving direction and rate for each hour relative to HW

Answer

Tidal diamonds are lettered reference positions on a chart with corresponding tables giving the direction (set) and rate (in knots) of the tidal stream for each hour before and after High Water at the standard port. They allow accurate tidal stream calculations.

Question 5

What is 'leeway' in coastal navigation?

Accepted Answer

The sideways drift of a vessel downwind caused by wind pressure on the hull and superstructure

Answer

Leeway is the angular difference between the course steered and the actual course made good, caused by wind pressure pushing the vessel sideways. It is estimated based on wind strength and direction relative to the vessel's heading.

MCA CoC Practice Test

MCA CoC Practice Test

MCA CoC Navigation & Chart Work 2