Memorise this Flashcards
Earth circumference in nm is what (and can be worked by multiplying which two numbers?)
360deg x 60’
21,600nm 40,000km
GeoDETIC latitude aka
What is the max. difference (nm) between GeoDETIC and GeoCENTRIC
Geographic latitude
The latitude used on charts
Does NOT necessarily pass through the earth’s core.
11.6nm
Define:
Insolation
Insolation is a measure of solar radiation energy received on a given surface area in a given time.
In navigation, we assume the earth is what type of sphere?
A perfect sphere
Define:
Ecliptic
What is it’s range?
The Ecliptic is an imaginary line on the sky that marks the yearly path of the sun (as seen from observer).
between 23.5° north and 23.5° south of the Equator
Define:
Geoid
The geoid is the irregular shape that the ocean surface would take under the influence of the gravity of Earth, including gravitational attraction and Earth’s rotation, if other influences such as winds and tides were absent.
If the entire Earth were covered with the world ocean, the form of the Earth would be a so-called geoid. This shape is very close to a special ellipsoid or oblate spheroid flattened at the poles and bulging at the equator.
Define:
Geocentric latitude
Geocentric latitude is the angle between the plane of the Equator and the line from the centre of the Earth to the position.
If you add 2 vectors together, what is the final vector called?
The resultant
The earth is tilted on its axis at an angle of ___°
The earth is tilted on its axis at an angle of 23.5°
Seasons are due to what?
Seasons are due to the tilt of the Earth’s axis with the plane of the equator at an angle of 23.5°. If there was no inclination, then there would be no seasons.
When is orbital velocity fastest?
Perihelion
(3rd January)
When is orbital velocity slowest?
Aphelion
(3rd July)
Earth’s axis of rotation is inclined to its orbital path around the sun at an angle of ____°.
This determines what? (2)
Earth’s axis of rotation is inclined to its orbital path around the sun at an angle of 66.5°.
This determines the amount of sunlight received by different parts of the Earth and the relationship between daytime and night-time.
What’s the Latitude of the Arctic and Antarctic circle?
N66.5°
S66.5°
Northern Hemisphere Summer on 21st June:
describe the sun in the Arctic and Antarctic circle.
describe the sun over the Tropic of Cancer
The sun will not set.
At midday the sun is directly overhead the Tropic of Cancer: N23.5°.
When are the solstices?
The northern solstice occurs around the 20th/21st of June.
The southern solstice occurs around the 21st/22nd of December.
Describe the eqinoxes
The Equinoxes - when the Declination of the sun is zero as it is above the Equator
Describe Declination and when is the greatest change in daylight?
The sun’s declination is the sun’s position relative to the plane of the equator. When the declination of the sun is 0° - the sun directly above the equator - the rate of change of daylight is greatest.
An _________solar day is measured against the real or ‘apparent’ sun. The sun as it actually appears to an observer on the surface of the earth.
apparent
A ____ solar day is the length of an apparent solar day averaged out throughout the year.
mean
Lines joining points of zero variation on the earth are called ______ _____.
Agonic lines
Compass deviation (you are deviating from Magnetic)
Magnetic variation (You are varying from True)
If deviation is west, compass is best.
If deviation is east, compass is least.
If variation is west, magnetic is best.
If variation is east, magnetic is least.
Parallels of latitude and meridians of longitude intersect at 90°, forming a right angled _________.
graticule
If two positions on the earth are separated by ___° of longitude they are said to be _________
180°
antipodal
A rhumb line is sometimes known as a _________
Loxodrome
If you were to depart from the geographic South Pole in a constant direction, the route would cross all meridians at the same angle. This is known as a __________ _______
Loxodromic Spiral.
In order to measure the value of east/west distance along a rhumb line we have to use something known as the _________ formula:
________ = (______ x __) x ___ ___
In order to measure the value of east/west distance along a rhumb line we have to use something known as the Departure formula:
Departure (nm) = (chlong x 60) x Cos Lat
What is the ‘vertex’ of a great circle?
The point where the great circle bearing measures 090/270.
At the highest latitude.
When the start and end point are on the same latitude, the vertex will be found at the mid-point of two positions.
How many degrees an hour does the earth rotate around the sun?
360° ÷ 24 = 15°/hr that the Earth rotates around the sun.
Arc to Time Conversion (ATC) describes:
360° ÷ 24 = 15°/hr that the Earth rotates around the sun.
The Air Almanac lists the times of sunrise, sunset and twilight in which time?
LMT
Twilight lasts all night; i.e., the sun is between ____ and ____
Twilight lasts all night; i.e., the sun is between zero and 6° below the horizon
EASA Definition of Night
“The period between the end of evening civil twilight and the beginning of morning civil twilight, or such other period between sunrise and sunset as maybe prescribed by the appropriate authority as defined by the member state”.
