TERNAV2 (MIDTERM) Flashcards
is said to be abeam of the ship, when it comes in line with perpendicular to the ship’s fore and aft centreline on any side of the vessel.
landmark or lighthouse
Bearing of that lighthouse when abeam will be either
90° to the portside or 90° to the starboard side of ship’s heading (ship’s course) at that moment.
The distance of that lighthouse at this moment (when abeam) is called _
beam distance
and bearing is known as
‘beam bearing’
BC —
Second bearing of light
AD —
Course steered between observations
AB = BC =
Distance run between first and second observations
BC —
Distance from the light at the time of second observation
Distance steamed between first and second observation is the
distance from observed object
The procedure is similar to doubling the angle on bow.
Four-point bearing on the bow
Distance from the object shall be the distance steamed between first and second observation
Four-point bearing on the bow
This method also suffers from the disadvantages that distance from the object is only known when ship is already off that position.
Four-point bearing on the bow
We use this process for estimating the distance abeam, at which the ship is going to pass any observed object.
Special angles on the bow
gives the distance abeam from the object in advance, enabling us to take a decision regarding safe passing distance etc
Special angle method of estimating distance
AD =
ship’s course steered
Many ports have provided _to guide mariners safely into harbour, avoiding shoals and other dangers.
leading lights or shapes
In places where such aids are not provided, the navigator may still be able to select a _ provided by the transit of natural features.
leading line
When a suitable transit is not available a
single danger bearing may be taken from the chart
is one of the easiest ways to ensure that your vessel and crew stay in safe water
Establishing a danger bearing
The effect of wind on the course steered
Leeway
The angle between the course steered and the course made good
Leeway
is estimated by the navigator as so many degrees to port or starboard and necessary allowance made for it in computing the course to steer.
Leeway
are designed mainly for solving Parallel Sailing and Plane Sailing without major calculations
Traverse tables
For plane sailing, the tables are tabulated from
right-angled triangles and cover a distance of up to 600 miles, which is the limit for plane sailing.
In _, the traverse tables are named from 0° to 45° at the top of the pages, and 45° to 90° at the bottom of the pages.
Norie’s Nautical Tables
These figures of degrees are represented courses in
Plane Sailing and latitude in Parallel Sailing
The figure of degree of each table is represented for
latitude
The columns with the header D. Long. or D’Long., and Dep., which are normally printed in italics, are used to find the
Departure from a given Different of Longitude (D. Long)
For _, these figures of degrees are the courses expressed in appropriate quadrants as _
plane sailing, cardinal compass.
The three-figure notation (θ°) course is converted into a
quadrantal notation course (Ω°)
