BDOC Exam Review (NSS Section)
Sector Lights Color Coding - Answer-Red - Danger Areas
Green - Turning Points or Best Water areas
White - Good water areas
5 Shapes of Buoys - Answer-Can , Nun, Pillar, Spar, Sphere
IALA A vs. IALA B - Answer-IALA B - Green Port/Red Starboard (Used by Japan, Korea, US, and
Philippines)
IALA A - Green Starboard/ Red Port (Used by Africe, Europe, Asia, Australia)
Compass Variation - Answer-Angular difference between true meridian and magnetic meridian
Compass Deviation - Answer-Deflection Left or right of the magnetic meridian caused by the magnetic
properties of the vessel
Pnuemonic for going from GYRO Reading to True Heading - Answer-Can Dead Men Vote Twice (at
elections)
, What GPS Datum is used by the US Navy - Answer-WGS 84
3 Segments of GPS - Answer-Space , Control, User
What is GPS Figure of Merit? - Answer-An internal GPS calculation that indicates the best accuracy
acheivable from the satellites being tracked
How many satellites are needed for location and how many for altitude? - Answer-3 for location 4 for
altitude
Advantages and Disadvantages of Mercator projected charts - Answer-Advantages:
- Rhumb Lines plot as straight lines
- Provides for easy measuring of distance and direction
- Latitude and Longitude angular relationships are maintained
Disadvantages
- Great Circles plot as curves
- Distortion at the poles
Advantages and Disadvantages of Gnomic Projections - Answer-Advantages
- Great Circles plot as straight lines
- Ideal for transoceanic voyages
Disadvantages
- Rhumb lines plot as curves
- Cannot be used to measure distance or direction
Sector Lights Color Coding - Answer-Red - Danger Areas
Green - Turning Points or Best Water areas
White - Good water areas
5 Shapes of Buoys - Answer-Can , Nun, Pillar, Spar, Sphere
IALA A vs. IALA B - Answer-IALA B - Green Port/Red Starboard (Used by Japan, Korea, US, and
Philippines)
IALA A - Green Starboard/ Red Port (Used by Africe, Europe, Asia, Australia)
Compass Variation - Answer-Angular difference between true meridian and magnetic meridian
Compass Deviation - Answer-Deflection Left or right of the magnetic meridian caused by the magnetic
properties of the vessel
Pnuemonic for going from GYRO Reading to True Heading - Answer-Can Dead Men Vote Twice (at
elections)
, What GPS Datum is used by the US Navy - Answer-WGS 84
3 Segments of GPS - Answer-Space , Control, User
What is GPS Figure of Merit? - Answer-An internal GPS calculation that indicates the best accuracy
acheivable from the satellites being tracked
How many satellites are needed for location and how many for altitude? - Answer-3 for location 4 for
altitude
Advantages and Disadvantages of Mercator projected charts - Answer-Advantages:
- Rhumb Lines plot as straight lines
- Provides for easy measuring of distance and direction
- Latitude and Longitude angular relationships are maintained
Disadvantages
- Great Circles plot as curves
- Distortion at the poles
Advantages and Disadvantages of Gnomic Projections - Answer-Advantages
- Great Circles plot as straight lines
- Ideal for transoceanic voyages
Disadvantages
- Rhumb lines plot as curves
- Cannot be used to measure distance or direction
