Basics Of Navigation Flashcards

1
Q

Earths circumference is

A

21,600NM/40,000KM

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2
Q

Parallels of Latitude measure a co-ordinates’ N/S location as the angle between

A

The equator and the given parallel (up to 90^ North or South)

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3
Q

Meridians of Longitude measure a coordinates, E/W location as the angle between

A

The prime meridian and the given meridian (up to 180^ east or west)

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4
Q

Grid co-ordinates are measured in

A

Latitude then Longitude in Degrees^ and minutes’,

eg N45^22.4’, W004^55.6’
*there are 60 minutes in one degree

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5
Q

To measure change of latitude in the same hemisphere, or change of longitude within same half of the earth (E/W),

A

Subtract

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6
Q

To measure change of latitude between different hemispheres, or change of longitude between East and West,

A

Add

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7
Q

Ratio of ellipticity gives distortion value of

A
  1. 0033 difference between geocentric and geodetic measurement.
    * geodetic used in charts
    * * greatest difference at 45^N/S
    * ** smallest difference at poles and equator
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8
Q

1 minute longitude or latitude at equator only =

A

1NM or 1.852km or 6080 feet

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9
Q

Departure (NM)=

A

Change of Longitude (mins) x CosLat

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10
Q

Direction is measured as

A

The angle from a datum

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11
Q

A Great Circle is

A

The surface line of any plane intersecting a sphere through its center, and is the shortest distance connecting two points.

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12
Q

Unusual cases of a great circle are

A

Meridian+antimeridian and equator, as they do not have changing track

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13
Q

Except for the equator, every great circle lies

A

Half in the NH and half in the SH (vertices 180^ apart in longitude and equal in latitude)

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14
Q

To calculate convergency,

A

Convergency (^)=ChLong (^) x Sin Mean Lat

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15
Q

A rhumb line is

A

A line of constant direction, measuring the same angle at any meridian it crosses.

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16
Q

A rhumb line lies

A

On the equatorial side of a great circle line.

17
Q

Average great circle true track between two points is equal to rhumb line true track. Conversion angle converts GC to RL

A

Conversion angle = 1/2 convergency angle

18
Q

Chlong (mins) =

A

Departure (NM) / Cos Lat

19
Q

To calculate distance along a meridian/antimeridian,

A

Distance (NM) =ChLat (^) x 60

20
Q

Definition of convergency:

A
  1. Change of Great Circle Track between 2 points

2. Angle of inclination between two meridians at a selected latitude

21
Q

Representative Fractions:

A
  • Use same unit of measurement throughout equation and are this dimensionless
  • Are expressed as 1/denominator
22
Q

Scale Equation

A

Scale = Chart Distance/Earth Distance

1NM = 1.852KM = 6080 feet
1 inch = 2.55 cm

Large scale = large zoom factor
Small scale = small zoom factor

23
Q

Keplers Laws

A
  1. Elliptical orbit of Earth around the Sun, with the Sun in one foci.
  2. Radius vector sweeps out equal area in equal time ( earth slower at aphelion, thus travels less in orbit.
24
Q

Perihelion

A

Earth closest to sun (around Jan)

25
Q

Aphelion

A

Earth furthest from sun ( July)

26
Q

Variation in length of day and night is caused by

A
  • the inclination of the ecliptic to the equator

- latitude

27
Q

Declination is defined as

A

The angle between the equinoctial and a line joining the earth to the sun

28
Q

Highest declination of the sun throughout the year causes:

A

A zenith once a year in each tropicwhen the sun reaches 90^ over the horizon.
Tropic of Cancer (23.5^ North) Jun 22
Tropic of Capricorn (23.5^ South) Dec 22

29
Q

Celestial equivalent of longitude

A

LHA Local Hour Angle
GHA Greenwich Hour Angle
* measure westerly and only correct for given time.

30
Q

Celestial equivalent of latitude

A

Declination north or south of the equinoctal

31
Q

Polar circles

A

Higher then 60.5^: summer days of constant twilight
Higher than 65.5^: summer days where sun doesnt set
Higher than 66.5^: winter days where sun doesnt rise

32
Q

A civil day

A

360^ rotation in 24 hours
15^ rotation in 1 hour
1^ rotation in 4 mins

33
Q

Arc to time conversion

A

Longitude / 15 = Time difference in LT

34
Q

When converting LMT to LMT

A
  1. Longitude West, UTC Best, Longitude East, UTC least
  2. Always convert through UTC using Date Hour Minute table
  3. Passing through 180 E/W: from West to East, add one day, from East to West subtract one day
35
Q

Standard Time

A
  1. Is set by each country as stated in Air Almanac and does not necessarily follow 1 hour for each 15^
  2. May lead to 13 hours difference with UTC
  3. In Daylight Saving Time in summer, Add one hour to UTC
36
Q

Moment of Sunrise/Sunset

A

Top tip of sun rises, 34’ refraction+ 16’ semi diameter = center of sun 50’ below sensible horizon

37
Q

Civil twilight

A

6^ below sensible horizon until sunset/sunrise

* varies from 21 mins at equinox at equator to longer at higher latitudes/ summer.