RYA Day Skipper Navigation and Chartwork 2 — Questions and Answers
Question 1: What is an 'estimated position' (EP) in navigation?
- A position fixed by GPS
- A position derived from the last known position, course steered, and distance run, with an allowance for tidal stream and leeway (Correct answer)
- An exact position confirmed by two bearings
- A position given by the coastguard
Correct answer: A position derived from the last known position, course steered, and distance run, with an allowance for tidal stream and leeway
An EP is a best estimate of position calculated by applying the course steered, log distance, estimated tidal stream, and leeway to the last known position. It is marked with a triangle on the chart.
Question 2: What does a 'leading line' or 'transit' provide for a navigator?
- An indication of wind direction
- A line of position confirmed by aligning two charted objects, providing a reliable bearing (Correct answer)
- A weather forecast
- A VHF frequency
Correct answer: A line of position confirmed by aligning two charted objects, providing a reliable bearing
A transit (or leading line) is formed when two charted objects are in line. This provides a very accurate line of position and is often used for entering harbours safely.
Question 3: On an Admiralty chart, what does a magenta diamond symbol indicate?
- A lighthouse
- A reference to additional information in the chart notes or tidal diamond data (Correct answer)
- A restricted area
- A dangerous wreck
Correct answer: A reference to additional information in the chart notes or tidal diamond data
Magenta diamonds on Admiralty charts refer to tidal stream information. Each diamond has a letter that corresponds to a tidal stream table on the chart, showing direction and rate.
Question 4: What is the purpose of a 'course to steer' calculation?
- To determine the fastest route
- To find the compass heading that will result in the vessel making good the desired track over the ground, allowing for tide and leeway (Correct answer)
- To calculate fuel consumption
- To determine arrival time only
Correct answer: To find the compass heading that will result in the vessel making good the desired track over the ground, allowing for tide and leeway
A course to steer calculation determines the compass heading to counteract the effects of tidal stream and leeway, ensuring the vessel follows the intended ground track.
Question 5: What does the abbreviation 'Fl(3) 15s' on a chart mean for a light?
- Fixed light at 15 metres
- A light showing a group of 3 flashes with a total period of 15 seconds (Correct answer)
- A foghorn sounding every 15 seconds
- A light visible for 3 nautical miles
Correct answer: A light showing a group of 3 flashes with a total period of 15 seconds
Fl(3) 15s describes a group flashing light that shows 3 flashes in succession, with the complete cycle (including dark intervals) repeating every 15 seconds.
Question 6: What is 'dead reckoning' (DR) in navigation?
- Using GPS for positioning
- Calculating position from the last known fix using course steered and distance logged, without tidal or wind corrections (Correct answer)
- Taking bearings of landmarks
- Using radar for navigation
Correct answer: Calculating position from the last known fix using course steered and distance logged, without tidal or wind corrections
Dead reckoning calculates position from the last known fix by applying the course steered and distance run (from the log), without any correction for tidal stream, leeway, or current.
RYA Day Skipper Navigation and Chartwork 2
What is an 'estimated position' (EP) in navigation?