General Navigation - Coordinates and Distance Flashcards

1
Q

What are the most common units used in horizontal navigation?

A

km, NM, ft

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2
Q

How long is a km in feet and inches?

A

3280 ft and 10 and 5/64th inches

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3
Q

How many feet in 1 NM?

A

6076.16 ft

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4
Q

How many km in 1 NM?

A

1.852 km

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5
Q

What’s the origin of the KM?

A

The Earth (10,000 KM from the equator to a pole)

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6
Q

Why is one degree of travel along a parallel of latitude not the same distance as along a meridian?

A

Because a parallel is not a circumference

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7
Q

As we move away from the equator the…distance decreases

A

East/west

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8
Q

Define the departure

A

The east/west distance (NOT the shortest distance)

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9
Q

How do we calculate east/west distance?

A

Departure (NM) = Change in Longitude (minutes) x Cosine of the Latitude

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10
Q

Unless you’re on the equator, one degree east/west is always…

A

Less than 60 NM

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11
Q

How do we calculate shortest distance when two longitudes are on opposite meridians? How can you check that the question is one which requires this calculation?

A

Add the latitudes and subtract the answer from 180°. The longitudes will add up to 180°.

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12
Q

What is a nautical mile longer than?

A

A statute mile.

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13
Q

From what was the unit of kilometers originally derived?

A

From the Earth itself.

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14
Q

How many kilometers are there from the equator to the pole?

A

10,000 km.

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15
Q

What is the Earth’s circumference in kilometers?

A

40,000 km.

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16
Q

How is one nautical mile defined?

A

As the distance subtended by one minute of arc on the Earth’s circumference.

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17
Q

How many nautical miles (NM) are there in one degree change of latitude?

A

60 NM.

18
Q

What is the Earth’s circumference in nautical miles (NM)?

A

21,600 NM.

19
Q

What is the distance from the equator to the pole in nautical miles (NM)?

A

5,400 NM.

20
Q

How is the distance between 48°N and 49°N along the meridian described?

A

One degree, sixty minutes, or 60 NM.

21
Q

What affects the distance between 010°W and 011°W?

A

The parallel of latitude is not a circumference; it is less than 60 NM.

22
Q

What happens to the distance between meridians as latitude increases?

A

The distance decreases.

23
Q

How do you find the distance along a meridian?

A

Add the change of latitude in minutes and convert to NM.

24
Q

How do you convert km/hour to NM/hour or knots (KT)?

A

Use the number of feet in each unit: 890 km/hour ≈ 480 KT.

25
Q

How is a change of latitude in degrees calculated for a given distance in NM?

A

Divide the NM by 60.

26
Q

What does the east/west distance represent in navigation?

A

The east/west distance traveled, not the shortest distance.

27
Q

What is the formula for calculating departure in NM?

A

Departure (NM) = Change of Longitude (minutes) x Cosine of the Latitude.

28
Q

What is the one degree ‘box’ distance from north to south and east/west at the equator?

A

60 NM from north to south and 40 NM across the bottom.

29
Q

What is the distance in an east/west direction along a parallel of latitude at 49°N?

A

Slightly smaller than 40 NM, about 39 NM.

30
Q

What is the distance of one degree north/south and one degree east/west (the departure) always less than, unless you are on the equator?

A

Less than 60 NM.

31
Q

What can we find by measuring the angle between points along a circumference of the Earth?

A

The distance between two points.

32
Q

How is the distance between two latitudes found?

A

By finding the change of latitude.

33
Q

How is the distance between points on the equator found?

A

By finding the change of longitude.

34
Q

How do you find the angle between points measured at the center of the Earth?

A

By adding the latitudes and subtracting the total from 180°.

35
Q

What is the distance corresponding to an angle of 40°?

A

2400 NM.

36
Q

What assumptions are made for the purposes of calculating distances?

A

The Earth is a perfect sphere.

37
Q

What is the actual shape of the Earth?

A

A squashed sphere, an ellipsoid.

38
Q

What is the distance covered by one minute of arc at the poles, at 45°N and 45°S, and at the equator?

A

6107 ft at the poles (more than a NM), 6076 ft at 45°N and 45°S (exactly a NM), 6045 ft at the equator (less than a NM).

39
Q

What do modern navigation systems compensate for?

A

The flattening of the Earth.

40
Q

What error do older navigation systems list arising from the assumption that the Earth is round?

A

Latitude error.