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
Aphelion
Earth furthest from sun ( July)
26
Variation in length of day and night is caused by
- the inclination of the ecliptic to the equator | - latitude
27
Declination is defined as
The angle between the equinoctial and a line joining the earth to the sun
28
Highest declination of the sun throughout the year causes:
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
Celestial equivalent of longitude
LHA Local Hour Angle GHA Greenwich Hour Angle * measure westerly and only correct for given time.
30
Celestial equivalent of latitude
Declination north or south of the equinoctal
31
Polar circles
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
A civil day
360^ rotation in 24 hours 15^ rotation in 1 hour 1^ rotation in 4 mins
33
Arc to time conversion
Longitude / 15 = Time difference in LT
34
When converting LMT to LMT
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
Standard Time
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
Moment of Sunrise/Sunset
Top tip of sun rises, 34’ refraction+ 16’ semi diameter = center of sun 50’ below sensible horizon
37
Civil twilight
6^ below sensible horizon until sunset/sunrise | * varies from 21 mins at equinox at equator to longer at higher latitudes/ summer.