TERNAV2 (PRELIM) Flashcards
In determining the vessel’s position accurately, these _ play a crucial role in assisting the navigator.
navigational instruments
It also provides reliable information regarding the vessel’s position in terms of latitude and longitude coordinates
navigational instruments
During the _ stage of passage planning, utilizing these instruments will help ensure the vessel stays on her course and follows the planned route effectively
Execution and Monitoring
Navigators can verify the vessel’s position in terms of geographical coordinates, using a.
chart/nautical chart
Charts can be used to plot
DR(Dead Reckoning),EP(Estimated Position), FP(Fix Position) and track the vessel’ progress along the planned route
provides the indication of the vessel’s heading, and when the appropriate corrections are applied, (Variation and Deviation), the vessel’s true course can be determined accurately.
Compass
, are used to measure distances between the vessel’s plotted position and the referenced charted object on a nautical chart.
Compass dividers
A navigational instrument used for
determining the angle between the horizon
and a celestial body such as the Sun, the
Moon, or a star.
sextant
It is used in celestial navigation to determine
the vessel’s geographical position in terms of
latitude and longitude.
sextant
A satellite-based navigation system that
uses a network of satellite which
provides accurate position information
anywhere on Earth.
GPS ( G L O B A L
P O S I T I O N I N G
S Y S T E M )
is an effective instrument to
determine a vessel’s position when the
visibility has dropped
Radar
It also provides range and bearing of the
interrogated object, using it as a reference
point in determining the vessel’s position
R A D A R
( R A D I O
D I R E C T I O N AND RANGING
An effective way of utilizing radar is by _ in conjunction with
a chart and comparing the radar bearing by
visual bearings.
Cross- checking the radar range
The geographical location of a vessel
relative to a reference point or the
coordinate system ( Latitude and
Longitude)
P O S I T I O N
It can be represented in terms of
specific coordinates or plotted
graphically on a nautical chart.
P O S I T I O N
It is the determination of position by advancing a last
known position for courses and distance
D E A D
R E C K O N I N G
P O S I T I O N ( D R )
The method used to forecast where the vessel will be,
knowing the _
true course and speed alone
It does not consider external factors such as currents, wind drift, or magnetic variation, so it provides an approximate position based solely on the vessel’s or aircraft’s movements
D E A D
R E C K O N I N G
P O S I T I O N ( D R )
A method to forecast where the vessel
will be, knowing true course and speed,
set and drift
E S T I M A T E D
P O S I T I O N ( E P )
It considers factors such as course
changes, speed variations, and external
influences (e.g., currents, wind) since the
last known position
E S T I M A T E D
P O S I T I O N ( E P )
Refers to a precisely determined
location of a vessel at a specific
point in time
F I X E D
P O S I T I O N ( F P )
Obtained through accurate
navigational methods such as
celestial navigation, GPS (Global
Positioning System), radar fixes, or
visual bearings to known landmarks
F I X E D
P O S I T I O N ( F P )
provide a high level
of accuracy in the vessel’s or
aircraft’s location and are commonly
used for navigation, charting
Fixed positions
The use of LOPs (Line of Position) of several
navigational aids to obtain a position fix
C R O S S B E A R I N G
IN CROSS BEARINGS, BUOYS
MUST NOT BE USED IN TRANSIT
A situation where the LOPs
obtained intersect to form a
“triangle” or “ irregular
shape” instead of an
intersecting point
C O C K E D H A T
It indicates uncertainty in the
vessel’s position
C O C K E D H A T
Smaller cocked hat
= Smaller error
- Larger cocked hat
= Larger ERROR
To measure courses, use the
chart’s compass rose
Transfer _ using parallel rulers or
triangles
course lines to and from the
compass rose
may give true and
magnetic directions.
Compass roses
are on the outside of the rose;
magnetic directions are on the
inside
True directions
One minute of latitude =
One
nautical mile
is a DR position corrected for the
effects of leeway, steering error, and current.
E P
( E S T I M A T E D
P O S I T I O N )
It involves calculating the set and drift and
applying these values to the DR to obtain an
EP(estimated position)
is enclosed with a square and labeled
horizontally with the time
EP(estimated position)
the periodic
horizontal movement of the
water’s surface by the tide-
affecting gravitational forces of the
Moon and Sun
Tidal Current
the horizontal movement
of the sea surface caused by
meteorological, oceanographic, or
topographical effects
Current
refers to the current’s
direction
set
refers to the current’s speed
drift
the leeward motion of
vessel due to that component of the
wind vector perpendicular to the
vessel’s track
leeway
combine to
produce the most pronounced
Leeway and current
– the
direction of a straight line from the
last fix to the EP
Estimated course made good
– the
length of the course made good
divided by the time between the fix
and the EP
Estimated speed made good
Measures the angle between
two reference points observed
from the observer’s position
P O S I T I O N B Y
H O R I Z O N T A L
A N G L E S
Using a sextant, the navigator
measures the horizontal angle
between the two selected
reference points
P O S I T I O N B Y
H O R I Z O N T A L
A N G L E S
The HA (Horizontal Angle)
measured
could be:
- HA = 90O (no need to calculate complements)
- HA >90O
- HA<90O
If the HA is <90o, the angles
are measured from the
baseline _ the ship
TOWARDS
If the HA is >90o, the angles
are measured from the
baseline _ from the ship
AWAY
how to P O S I T I O N B Y
H O R I Z O N T A L
A N G L E S
- Construct 2 Position Circles
- FIX will be where the 2
position circles intersect
–
measuring the angle
between the Top of an Object
and the horizon
Vertical Sextant Angle
Two conspicuous objects are
said to be in transit when
both are in a straight line, as
seen from the ship
P O S I T I O N L I N E B Y
T R A N S I T B E A R I N G
Bearing of both objects are
the same
P O S I T I O N L I N E B Y
T R A N S I T B E A R I N G
When in transit, the ship
must be on a straight line
passing though the objects
P O S I T I O N L I N E B Y
T R A N S I T B E A R I N G
It provides a good
opportunity to obtain the
compass error
P O S I T I O N L I N E B Y
T R A N S I T B E A R I N G
