TERNAV (MIDTERM). Flashcards
When plotting courses of vessels and the set of a current/tidal stream, the direction of travel is indicated by _ pointing in the direction of travel
arrow heads
One arrow head =
the course steered
Two arrow heads =
the course made good
Three arrow heads =
the set of the current
Whilst currents/tidal streams have the greatest effect on the movement of vessels, the _can also affect their movement
wind
The resultant speed through the water will be recorded by
certain logs and the speed over the ground or effective speed will only be recorded by a
Doppler Log in shallow water or GPS or by calculating the speed between the fixes.
Secondly, the wind produces a sailing effect caused by the vessel’s
superstructure. In general, the vessel will be moved bodily to _
the amount will vary with trim, design of the vessel and whether it is
in a loaded or light ship condition
leeward,
The difference between the fore and aft line and the direction made
Leeway
It can be assessed by visually estimating the angle between the
fore and aft line and the ship’s wake.
Leeway
it is always important
that leeway is always applied to the
true course.
When the course steered is given, to find the leeway track, leeway is
applied
downwind.
When it is required to find the course to steer, to counteract the wind, leeway
is applied
upwind.
The Earth is an
irregular oblate spheroid (a sphere flattened at the poles).
Measurements of its dimensions and the amount of its flattening are subjects of
geodesy.
is a near enough approximation to a geodesic for most problems of navigation.
great circle
is the line of intersection of a sphere and a plane which does not pass through the center.
small circle
is usually applied to the upper branch of the half-circle from pole to pole which passes through a given point. The opposite half is called the _
meridian, lower branch.
is a circle on the surface of the Earth parallel to the plane of the equator.
parallel or parallel of latitude
It connects all points of equal latitude. The poles are single points at latitude 90°. All other parallels are
parallel or parallel of latitude, small circles
is a great circle at latitude 0°
equator
can define any position on Earth.
Coordinates of latitude and longitude
is the angular distance from the equator, measured northward or southward along a meridian from 0° at the equator to 90° at the poles.
Latitude (L, lat.)
is the shorter arc of the parallel or the smaller angle at the pole between the meridians of the two places.
The difference of longitude (DLo) between two places
The distance between two meridians at any parallel of latitude, expressed in distance units, usually nautical miles, is called
departure (p, Dep.).
It represents distance made good east or west as a craft proceeds from one point to another. Its numerical value between any two meridians decreases with increased latitude,
departure (p, Dep.).
is numerically the same at any latitude.
DLo
may be designated east (E) or west (W) when appropriate.
Either DLo or p
is the length of the rhumb line connecting two places. This is a line making the same angle with all meridians.
Distance
Meridians and parallels which also maintain constant true directions may be considered special cases of the
rhumb line
. Any other rhumb line spirals toward the pole, forming a
loxodromic curve or loxodrome.
it is designated _ and should be properly labeled to indicate the origin (prefix)
course angle (C)
and direction of measurement
(suffix).
is the intended horizontal direction of travel with respect to the Earth.
Track (TR)
The terms _ are used to indicate the path of intended travel
intended track and trackline
consists of one or a series of course lines, from the point of departure to the destination, along which one intends to proceed.
track
A great circle which a vessel intends to follow is called a _,
great-circle track
it consists of a series of straight lines approximating a great circle
great-circle track
is the direction in which a vessel is pointed at any given moment, expressed as angular distance from 000° clockwise througlA360°.
Heading (Hdg.)
constantly changes as a vessel yaws back and forth across the course due to sea, wind, and steering error.
Heading
is the direction of one terrestrial point from another, expressed as angular distance from 000° (North) clockwise through 360°.
Bearing (B, Brg.)
When measured through 90° or 180° from either north or south, it is called
bearing angle (B)