OUPV Chart Plotting and Piloting 2 — Questions and Answers
Question 1: On a nautical chart, what does a magenta (purple) color typically indicate?
- Deep water channels
- Lighted aids to navigation and caution areas (Correct answer)
- Shallow water areas
- Restricted military zones only
Correct answer: Lighted aids to navigation and caution areas
Magenta is used on nautical charts to highlight lighted aids to navigation, caution areas, and other important navigational features.
On NOAA nautical charts, magenta (reddish-purple) is used to indicate lighted aids to navigation, caution areas, regulated navigation areas, and other features requiring special attention. This color was chosen because it is easily distinguishable under red lighting used in wheelhouses at night to preserve night vision.
Question 2: What navigational tool is used to measure distance on a nautical chart?
- A protractor
- Dividers using the latitude scale (Correct answer)
- A ruler using the longitude scale
- A compass rose
Correct answer: Dividers using the latitude scale
Dividers are used to measure distance on a chart by comparing the span to the latitude scale on the charts side, where one minute of latitude equals one nautical mile.
Dividers are the standard tool for measuring distance on nautical charts. The distance is always measured against the latitude scale on the sides of the chart, never the longitude scale. One minute of latitude equals one nautical mile (approximately 6,076 feet). When measuring, use the latitude scale at approximately the same latitude as the area being measured.
Question 3: What does the abbreviation Fl(2) 6s mean on a nautical chart?
- A fixed light visible for 6 miles
- A group flashing light showing 2 flashes every 6 seconds (Correct answer)
- A fog signal sounding twice every 6 minutes
- A floating buoy anchored at 6 fathoms
Correct answer: A group flashing light showing 2 flashes every 6 seconds
Fl(2) 6s indicates a group flashing light that produces 2 flashes in each period of 6 seconds.
Light characteristics on nautical charts follow standardized abbreviations. Fl means flashing, (2) indicates the number of flashes in each group, and 6s is the total period in seconds. So Fl(2) 6s means you will see two quick flashes followed by a dark interval, with the complete cycle repeating every 6 seconds.
Question 4: When plotting a course on a chart, which reference direction does a magnetic course use?
- True north
- Magnetic north (Correct answer)
- Grid north
- The nearest landmark
Correct answer: Magnetic north
A magnetic course is referenced to magnetic north, which accounts for the local variation between true north and the magnetic north pole.
There are three types of course references: true (referenced to true/geographic north), magnetic (referenced to magnetic north), and compass (magnetic course adjusted for the vessels compass deviation). To convert between true and magnetic, apply the local variation found in the compass rose on the chart.
Question 5: What does a triangle symbol on a nautical chart represent?
- An anchorage area
- A fixed navigational aid or landmark used for piloting (Correct answer)
- A danger zone
- A ferry route
Correct answer: A fixed navigational aid or landmark used for piloting
A triangle on a nautical chart typically represents a fixed navigational aid, landmark, or triangulation point used for position fixing.
On nautical charts, triangles represent fixed aids to navigation or prominent landmarks that serve as reference points for piloting. Mariners use these fixed points to take bearings for plotting lines of position (LOPs). When two or more LOPs intersect, they establish a fix.
Question 6: What is the purpose of a running fix in piloting?
- To determine position using two bearings of the same object taken at different times (Correct answer)
- To calculate the speed of a current
- To fix an engine problem while underway
- To determine fuel consumption rate
Correct answer: To determine position using two bearings of the same object taken at different times
A running fix uses two bearings of the same object taken at different times, with the first bearing advanced along the course and distance traveled.
A running fix is used when only one identifiable object is available for taking bearings. The navigator takes a bearing on the object, notes the time, and continues on course. After traveling a measurable distance, a second bearing is taken on the same object. The first line of position is then advanced along the course line by the distance traveled between the two bearings. Where the advanced LOP crosses the second LOP is the running fix position.
OUPV Chart Plotting and Piloting 2
On a nautical chart, what does a magenta (purple) color typically indicate?