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Nav Gen

Terms in this set (54)

What time is used as the standard for electronic navigation systems like GPS worldwide?
UTC
A vessel crossing the international date line in an Easterly direction would?
retard the ships date by one day
Sunrise is defined as the first appearance of the sun's ______ above the horizon
upper limb
15 minutes of longitude is equal to ______ of time
1 minute
The field of stars that surround the earth and appear to rotate around the planet is known as the
celestial sphere
The point on earth directly below a celestial body is the
geographical position
Declination of a celestial body is identical to the ________ of the geographic position
latitude
For navigators, the equivalent of longitude within the celestial equator system of coordinates is
hour angle
The earth's axis is inclined at an angle of about
23.5 degrees
The three points of the navigational triangle are
geographic position, observer's zenith, and celestial pole
The equation of coaltitude is
90 degrees - altitude of the body
In the navigational triangle, the observer's actual position is labeled
M
The equation of colatitude is
90 degrees - latitude
Colatitude is derived from the _______ coordinate system
terrestrial
GHA of the celestial body (GHA *) equals
GHA of Aries + SHA
The sun changes longitude at an hourly rate of
15 degrees
There are _______ between the celestial horizon and the observer's zenith
90 degrees
When an observer, who is north of the sun, is calculating LAN in the northern hemisphere, the formula for determining latitude is ________
Z + Dec.
What coordinate system is utilized when attempting to determine the height of the sun with a marine sextant for a LAN calculation
Horizon coordinate system
Polaris is located less than __________ from the north celestial pole
1 degree
The primary purpose of a Polaris observation in celestial navigation is to determine ___________
a latitude line of position
"Ho" equals
Hs + IC + dip + altitude correction
When conducting a Polaris observation, one must still account for ________ to accurately calculate latitude
refraction
If a star were located exactly at each celestial pole, the corrected altitude of the star would equal
The observer's latitude
The celestial body most often used for azimuth by amplitude is
the sun
Azimuth observations of celestial bodies are made by use of a
azimuth circle
The azimuth circle must be kept _________ to ensure an accurate measurement of compass azimuth
horizontal
When taking an amplitude, the sun's center should be observed on the visible horizon when _________
the Sun's declination is at or near 0
Azimuth observations should be made when the Sun is inn low altitude and preferably less than ________ degrees above the horizon
20
The reference datum used in determining the heights of land features on most charts is __________
mean high water
When a current flows in the opposite direction to the waves, the wave
height is increased
A current perpendicular to a vessel's track has the greatest effect on the vessel's course made good
at low speeds
Where will you find information about the duration of slack water
Tidal Current Tables
With respect to a reversing current, slack water occurs when there is
little or no horizontal motion of the water
Air masses near the earth's surface ________
- move from areas of high to low pressure
- are deflected by the "Coriolis Effect"
- are deflected by the earth's rotation in both hemispheres
In North America, the majority of the weather systems move from
west to east
What instrument measures wind velocity
anemometer
When recording the wind direction in the weather log, you would report the
direction the wind is blowing from
What happens to the barometric pressure after a cold front passes
rises, and the temperature drops
the USCG's preferred electronic chart type in the hierarchy is
official ENC
Coast Pilots and navigational charts are kept corrected and up-to-date by using the
Notices to Mariners
The shortest route between two points on the earth is a
great circle route
On a mercator projection chart, parallels and meridians are straight lines that meet at
90 degree angles
A vessel's position should be plotted using bearings of
fixed objects and fixed known objects on shore
A green buoy has a yellow triangle on it. This is a(n)
dual purpose marking used where the ICW and other waterways coincide
Under the IALA-B Buoyage System, when entering from seaward, a buoy that should be left to port will be
green
When you are steering on a pair of range lights and find that the upper light is above the lower light, you should
continue on the present course
The buoy symbol on the chart is used to indicate the ____________ position of the buoy
approximate
In a cardinal system, buoys are generally used to convey
a geographic relationship with a hazard in terms of 90-degree quadrants
Gyrocompass repeaters reproduce the indications of the master gyrocompass. They are __________
accurate electronic servomechanisms
Variation is the angular measurement between __________
magnetic meridian and the geographic meridian
The quadrantal spheres are used to __________
remove deviation on the intercardinal headings
Your vessel in "on range" in a channel. The chart indicates that the range 020 T. Your gyro compass reads 022 pcg. Your gyrocompass error is
002 W
Which of the following means of determining gyrocompass error is the simplest to accomplish
terrestrial range
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