BDOC - NSS
What are the three segments of GPS and what do they do? -
ANSWERS-Space - Our 31 satellites
Control - Consists of monitor stations which track satellites,
accumulate ranging data, and provide relays to the master control
station. The monitoring station passes the info along until it reaches
the master control station which updates the satellite message and
uploads it.
User - • Receivers, which are designed for different requirements,
receive and process information into three dimensional coordinates
What are the two categories of the user segment? - ANSWERS-
Standard Positioning Service (SPS): Broadcasts on one generic
frequency - Civilian use • Precision Positions Service (PPS):
Broadcasts on two generic frequencies - DoD and trusted allies - PPS
performs Ionispheric Corrections • Ionispheric Corrections: A
technique that reduces radio degradation, in order to provide better
accuracy - Anti-Spoofing/ Crypto: Designed to negate hostile
imitations of GPS signals • Alters the Precision Code (P-Code) into a
new code, known as the Y-Code, by purposefully introducing a known
error • The DoD employs this technique at random times and without
warning • The P-Code modulation is located on both UHF generic
signals • The DoD has no plans to phase out
,What do augmentation systems do? - ANSWERS-• GPS
augmentation systems have been developed, by both public and
private sectors, to enhance GPS capabilities and accuracy
WHat is NDGPS, GDGPS and WAAS and what do they do? -
ANSWERS-Nationwide Differential GPS System (NDGPS): A
ground based system that provides increased accuracy and integrity •
Consists of the Maritime Differential GPS System operated by US
Coast Guard and Department of Transportation - Global Differential
GPS (GDGPS): A high accuracy GPS augmentation system developed
by the NASA Jet Propulsion Laboratory (JPL) to support real-time
positioning, timing, and determination requirements for NASA - Wide
Area Augmentation System (WAAS): A satellite based system,
operated by the Federal Aviation Administration (FAA), that supports
aircraft navigation across North America
What is a datum and what does the US use? - ANSWERS-Datum: The
mathematical model of the earth that we use to calculate position
coordinates (latitude and longitude), heights, and distances - Datum
defines the origin and orientation of the coordinate system used on a
chart. US uses WGS 84.
What is a beacon? - ANSWERS-- A stationary, visual Navigation Aid
(NAVAID): Lighted beacons are called lights. Unlighted beacons are
called daybeacons. - All exhibit a daymark of some sort: For
lighthouses, the color and type of structure are the daymarks. On
small structures, daymarks, consist of colored geometric shapes called
dayboards.
,What is a buoy? - ANSWERS-A floating Aid to Navigation (AtoN):
Used where fixed aids would be uneconomical or impractical due to
depth of water.
What are the two fixed lights? - ANSWERS-• Major Light: - A high-
intensity and reliable light exhibited from a fixed structure or marine
site: Primary seacoast lights - Established for making landfall from
sea and coastwise. Secondary lights - Established at harbor entrances.
• Minor Light: - Usually displays a light of low to moderate intensity.
- Established in harbors, along channels, rivers, and isolated locations
Care should be taken NOT to confuse minor lights with lighted buoys
What are the three other fixed lights? - ANSWERS-Lighthouses: -
Placed where they will be of most use: Prominent headlands, at
harbor and port entrances, on isolated dangers, or at other points
where mariners can best use them to fix their position. - Principle
purpose is to support a light at a considerable height above the water.
• Leading Lights (Range Lights): - Light pairs that indicate a specific
line of position when they are in line: The higher rear light is placed
behind the front light. When the mariner sees the lights vertically in
line, the mariner is on the range line. • Bridge Lights: - Navigational
lights on bridges in the U.S.: Red, green, and white lights mark
bridges across navigable waters.Directional Light: - A single light that
projects a high intensity, special characteristic beam in a given
direction: Used in cases where a two-light range (Leading Lights)
may not be practicable. • Directional Sector Light: - A Directional
light that emits two or more colored beams: The be
What are the light characteristics we use to distinguish lights? -
ANSWERS-Distinguishes it from other lights: - Convey specific
, information by showing a distinctive sequence of light and dark
interval: A light may display a distinctive color or color sequence. In
the Light Lists, the dark intervals are referred to as eclipses. • An
Occulting (Oc) Light is totally eclipsed at regular intervals: - The
duration of its light always being greater than the duration of its
eclipse. • A Flashing (Fl) Light flashes on and off at regular intervals:
- The duration of its light always being less than the duration of its
eclipse. • An Isophase (Iso) Light flashes at regular intervals: - The
duration of its light being equal to the duration of its eclipse.
What is a sector light? - ANSWERS-Arcs of colors indicating
dangerous waters or hazards to navigation: • Show different colors
when observed from different bearings: - Green: Turning points / Best
water - White: Good water - Red: Danger areas Should, in most cases,
be avoided. • Bearings expressed in degrees TRUE - as observed from
a ship.
What is a buoy watch circle? - ANSWERS-Mooring chain length
defines a buoys watch circle: - Buoys can be expected to move within
the radius of this circle. - Mean Lower Low Water (MLLW), low tide,
will present to the mariner a buoys largest watch circle.
What are the 5 types of marks? - ANSWERS-- Lateral Marks -
Isolated Danger Marks - Safe Water Marks - Special Marks -
Information / Regulatory Marks
What is a cardinal mark? - ANSWERS-Indicates that the navigable
water lies to the named side of the mark: - Pass to the cardinal
direction from the buoy. • Color: - Black and yellow. • Shape: - Pillar
What are the three segments of GPS and what do they do? -
ANSWERS-Space - Our 31 satellites
Control - Consists of monitor stations which track satellites,
accumulate ranging data, and provide relays to the master control
station. The monitoring station passes the info along until it reaches
the master control station which updates the satellite message and
uploads it.
User - • Receivers, which are designed for different requirements,
receive and process information into three dimensional coordinates
What are the two categories of the user segment? - ANSWERS-
Standard Positioning Service (SPS): Broadcasts on one generic
frequency - Civilian use • Precision Positions Service (PPS):
Broadcasts on two generic frequencies - DoD and trusted allies - PPS
performs Ionispheric Corrections • Ionispheric Corrections: A
technique that reduces radio degradation, in order to provide better
accuracy - Anti-Spoofing/ Crypto: Designed to negate hostile
imitations of GPS signals • Alters the Precision Code (P-Code) into a
new code, known as the Y-Code, by purposefully introducing a known
error • The DoD employs this technique at random times and without
warning • The P-Code modulation is located on both UHF generic
signals • The DoD has no plans to phase out
,What do augmentation systems do? - ANSWERS-• GPS
augmentation systems have been developed, by both public and
private sectors, to enhance GPS capabilities and accuracy
WHat is NDGPS, GDGPS and WAAS and what do they do? -
ANSWERS-Nationwide Differential GPS System (NDGPS): A
ground based system that provides increased accuracy and integrity •
Consists of the Maritime Differential GPS System operated by US
Coast Guard and Department of Transportation - Global Differential
GPS (GDGPS): A high accuracy GPS augmentation system developed
by the NASA Jet Propulsion Laboratory (JPL) to support real-time
positioning, timing, and determination requirements for NASA - Wide
Area Augmentation System (WAAS): A satellite based system,
operated by the Federal Aviation Administration (FAA), that supports
aircraft navigation across North America
What is a datum and what does the US use? - ANSWERS-Datum: The
mathematical model of the earth that we use to calculate position
coordinates (latitude and longitude), heights, and distances - Datum
defines the origin and orientation of the coordinate system used on a
chart. US uses WGS 84.
What is a beacon? - ANSWERS-- A stationary, visual Navigation Aid
(NAVAID): Lighted beacons are called lights. Unlighted beacons are
called daybeacons. - All exhibit a daymark of some sort: For
lighthouses, the color and type of structure are the daymarks. On
small structures, daymarks, consist of colored geometric shapes called
dayboards.
,What is a buoy? - ANSWERS-A floating Aid to Navigation (AtoN):
Used where fixed aids would be uneconomical or impractical due to
depth of water.
What are the two fixed lights? - ANSWERS-• Major Light: - A high-
intensity and reliable light exhibited from a fixed structure or marine
site: Primary seacoast lights - Established for making landfall from
sea and coastwise. Secondary lights - Established at harbor entrances.
• Minor Light: - Usually displays a light of low to moderate intensity.
- Established in harbors, along channels, rivers, and isolated locations
Care should be taken NOT to confuse minor lights with lighted buoys
What are the three other fixed lights? - ANSWERS-Lighthouses: -
Placed where they will be of most use: Prominent headlands, at
harbor and port entrances, on isolated dangers, or at other points
where mariners can best use them to fix their position. - Principle
purpose is to support a light at a considerable height above the water.
• Leading Lights (Range Lights): - Light pairs that indicate a specific
line of position when they are in line: The higher rear light is placed
behind the front light. When the mariner sees the lights vertically in
line, the mariner is on the range line. • Bridge Lights: - Navigational
lights on bridges in the U.S.: Red, green, and white lights mark
bridges across navigable waters.Directional Light: - A single light that
projects a high intensity, special characteristic beam in a given
direction: Used in cases where a two-light range (Leading Lights)
may not be practicable. • Directional Sector Light: - A Directional
light that emits two or more colored beams: The be
What are the light characteristics we use to distinguish lights? -
ANSWERS-Distinguishes it from other lights: - Convey specific
, information by showing a distinctive sequence of light and dark
interval: A light may display a distinctive color or color sequence. In
the Light Lists, the dark intervals are referred to as eclipses. • An
Occulting (Oc) Light is totally eclipsed at regular intervals: - The
duration of its light always being greater than the duration of its
eclipse. • A Flashing (Fl) Light flashes on and off at regular intervals:
- The duration of its light always being less than the duration of its
eclipse. • An Isophase (Iso) Light flashes at regular intervals: - The
duration of its light being equal to the duration of its eclipse.
What is a sector light? - ANSWERS-Arcs of colors indicating
dangerous waters or hazards to navigation: • Show different colors
when observed from different bearings: - Green: Turning points / Best
water - White: Good water - Red: Danger areas Should, in most cases,
be avoided. • Bearings expressed in degrees TRUE - as observed from
a ship.
What is a buoy watch circle? - ANSWERS-Mooring chain length
defines a buoys watch circle: - Buoys can be expected to move within
the radius of this circle. - Mean Lower Low Water (MLLW), low tide,
will present to the mariner a buoys largest watch circle.
What are the 5 types of marks? - ANSWERS-- Lateral Marks -
Isolated Danger Marks - Safe Water Marks - Special Marks -
Information / Regulatory Marks
What is a cardinal mark? - ANSWERS-Indicates that the navigable
water lies to the named side of the mark: - Pass to the cardinal
direction from the buoy. • Color: - Black and yellow. • Shape: - Pillar
