BDOC NSS Exam questions & correct
answers rated A+
Major Lights - correct answer ✔✔a high intensity and reliable light exhibited from a fixed structure or
marine site
Primary Major Light - correct answer ✔✔Established for making landfall from sea
Secondary Major Light - correct answer ✔✔Established at harbor entrances
Minor Lights - correct answer ✔✔Low to moderate intensity light used to mark a specific channel or
location
Two considerations for minor lights - correct answer ✔✔o Care should be taken NOT to confuse minor
lights with lighted buoys
o Established in harbors, channels, rivers, and isolated locations
Sector Lights - correct answer ✔✔o Red: Danger Areas
o Green: Turning Points or best water areas
o White: Good water
Buoy Shapes - correct answer ✔✔Can, Nun, Pillar, Spar, Sphere
Purpose of Buoys - correct answer ✔✔Aids to navigation and used to mark
o Channels
o Shoals
o Obstructions
o Warn of Dangers
,IALA A - correct answer ✔✔Red port, Green Starboard when returing to harbor (Countries in Africa, Asia,
Australia, Europe)
IALA B - correct answer ✔✔Green port, Red Starboard when returning to harbor (Countries like America,
Japan, Korea, and the Philippines)
Variation - correct answer ✔✔The angular difference between the true meridian and the magnetic
meridian
o True Bearing = Magnetic Bearing + Variation
Deviation - correct answer ✔✔The deflection right or left of the magnetic meridian caused by magnetic
properties of the vessel
Gyrocompass Error - correct answer ✔✔The difference between the true heading and gyrocompass
heading. Caused by: friction, ship's motion, electronic malfunction, and power fluctuations
Permenant Magnetism - correct answer ✔✔The stable magnetic condition of the ship, created by
construction and materials used
Induced Magnetisim - correct answer ✔✔Magnetism acquired by the ships placement in the earth's
magnetic field
Datum - correct answer ✔✔The mathematical model of the earth used to calculate position coordinates,
heights, and distances
Datum used by US Navy - correct answer ✔✔WGS 84 (World Geodetic System 1984)
Three segments of GPS - correct answer ✔✔Control, User, Space
FOM - correct answer ✔✔(Figure of Merit): An internal GPS receiver calculation that indicated the best
accuracy achievable from the satellites being tracked
, Chart - correct answer ✔✔Graphical representation of the spherical Earth
Two types of chart projection used by US Navy - correct answer ✔✔Mercator and Gnomic
Advantages/Disadvatages of Mercator - correct answer ✔✔o Advantages:
Rhumb lines plot as straight lines
Provides for easy measuring of distance, direction, and position
Latitude and Longitude draw as straight lines and their correct angular relationships are maintained
o Disadvantages:
Great circles plot as curves
There may be minor distortion of features at extreme latitudes
Advantages/Disadvantages of Gnomic - correct answer ✔✔o Advantages:
Great circles plot as straight lines on a gnomic projection, which are ideal for long transoceanic voyages
Distortion on a gnomic chart is tolerable within 1000 nm of the point of tangency
o Disadvantages:
Rhumb lines plot as curved lines on a gnomic projection and do not plot direction or measure distances
easily on the chart
True shapes of the earth are not represented
Great Circle - correct answer ✔✔The intersection of a sphere and a plane through its center (Meridians
and the equator)
Rhumb Line - correct answer ✔✔a line that makes the same angle with all meridians
CHART 1 - correct answer ✔✔o Symbology on charts.
o Published by NOAA (National Oceanic and Atmospheric Administration) and the NGA (National
Geospatial-Intelligence Agency)
answers rated A+
Major Lights - correct answer ✔✔a high intensity and reliable light exhibited from a fixed structure or
marine site
Primary Major Light - correct answer ✔✔Established for making landfall from sea
Secondary Major Light - correct answer ✔✔Established at harbor entrances
Minor Lights - correct answer ✔✔Low to moderate intensity light used to mark a specific channel or
location
Two considerations for minor lights - correct answer ✔✔o Care should be taken NOT to confuse minor
lights with lighted buoys
o Established in harbors, channels, rivers, and isolated locations
Sector Lights - correct answer ✔✔o Red: Danger Areas
o Green: Turning Points or best water areas
o White: Good water
Buoy Shapes - correct answer ✔✔Can, Nun, Pillar, Spar, Sphere
Purpose of Buoys - correct answer ✔✔Aids to navigation and used to mark
o Channels
o Shoals
o Obstructions
o Warn of Dangers
,IALA A - correct answer ✔✔Red port, Green Starboard when returing to harbor (Countries in Africa, Asia,
Australia, Europe)
IALA B - correct answer ✔✔Green port, Red Starboard when returning to harbor (Countries like America,
Japan, Korea, and the Philippines)
Variation - correct answer ✔✔The angular difference between the true meridian and the magnetic
meridian
o True Bearing = Magnetic Bearing + Variation
Deviation - correct answer ✔✔The deflection right or left of the magnetic meridian caused by magnetic
properties of the vessel
Gyrocompass Error - correct answer ✔✔The difference between the true heading and gyrocompass
heading. Caused by: friction, ship's motion, electronic malfunction, and power fluctuations
Permenant Magnetism - correct answer ✔✔The stable magnetic condition of the ship, created by
construction and materials used
Induced Magnetisim - correct answer ✔✔Magnetism acquired by the ships placement in the earth's
magnetic field
Datum - correct answer ✔✔The mathematical model of the earth used to calculate position coordinates,
heights, and distances
Datum used by US Navy - correct answer ✔✔WGS 84 (World Geodetic System 1984)
Three segments of GPS - correct answer ✔✔Control, User, Space
FOM - correct answer ✔✔(Figure of Merit): An internal GPS receiver calculation that indicated the best
accuracy achievable from the satellites being tracked
, Chart - correct answer ✔✔Graphical representation of the spherical Earth
Two types of chart projection used by US Navy - correct answer ✔✔Mercator and Gnomic
Advantages/Disadvatages of Mercator - correct answer ✔✔o Advantages:
Rhumb lines plot as straight lines
Provides for easy measuring of distance, direction, and position
Latitude and Longitude draw as straight lines and their correct angular relationships are maintained
o Disadvantages:
Great circles plot as curves
There may be minor distortion of features at extreme latitudes
Advantages/Disadvantages of Gnomic - correct answer ✔✔o Advantages:
Great circles plot as straight lines on a gnomic projection, which are ideal for long transoceanic voyages
Distortion on a gnomic chart is tolerable within 1000 nm of the point of tangency
o Disadvantages:
Rhumb lines plot as curved lines on a gnomic projection and do not plot direction or measure distances
easily on the chart
True shapes of the earth are not represented
Great Circle - correct answer ✔✔The intersection of a sphere and a plane through its center (Meridians
and the equator)
Rhumb Line - correct answer ✔✔a line that makes the same angle with all meridians
CHART 1 - correct answer ✔✔o Symbology on charts.
o Published by NOAA (National Oceanic and Atmospheric Administration) and the NGA (National
Geospatial-Intelligence Agency)
