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Chapter 1 : Introduction Flashcards

1
Q

What type of orbit does earth revolve around the sun?

A

Elliptical Orbit

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2
Q

Orbital path and orbital speed of earth governed by -

A

Kepler’s Laws

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3
Q

Angle at which Earth’s axis is inclined to Orbital Plane?

A

66 1/2 degrees [23 1/2 degrees to the Normal to the Orbital Plane]

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4
Q

Inclination of the Earth’s Axis the cause of -

A
  • Seasons

- Changing time interval between Sunrise and Sunset throughout the year

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5
Q

Actual Shape of Earth?

A

Oblate Spheroid

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6
Q

Flattening of Earth at poles called -

A

Compression

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7
Q

QB: Earth Compression -

A

0.03 % {1/300th]

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8
Q

QB: Which is more? Earth Polar Diameter or Earth Equatorial Diameter?

A

Earth Equatorial Diameter; Greater by 50 km

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9
Q

Datum used to define Direction?

A

Direction in which Earth spinning - East

Therefore, Sun rises from East

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10
Q

QB: What is a Great Circle?

A

Circle on the Surface of Earth whose - Centre and Radius is that of Earth itself.

The shortest distance between 2 points on Earth is - Shorter arc of the Great Circle joining the 2 points.

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11
Q

Shortest Distance between 2 points on Earth?

A

Shorter arc of the Great Circle joining the 2 points.

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12
Q

How many Great Circles can pass through 2 points on the earth?

A

One.

Unless points diametrically opposite.

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13
Q

What is a Meridian?

A

Semi Great Circle joining North and South Poles

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14
Q

QB: What direction do Meridians indicate?

A

True North - South direction

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15
Q

QB: Meridians cross equator at?

A

90 degrees

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16
Q

What is the Prime (Greenwich) Meridian?

A
  • Meridian passing through Greenwich

- Datum for measuring Longitude

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17
Q

What is the Equator?

A
  • Great Circle whose plane is at 90 degrees to axis of rotation of earth.
  • Datum for measuring Latitude
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18
Q

What is a Small Circle?

A

Circle on the surface of the earth whose center and radius is NOT that of the earth.

Smalls circles of relevance - Parallels of Latitude

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19
Q

QB: What are Parallels of Latitude?

A

Small circles on the surface of the earth whose planes are parallel to the plane of the Equator. Lay in East-West direction.

Function - Indicate position North and South of Equator.

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20
Q

What is a Graticule?

A

Network formed on map or surface of globe by -

  • Prime meridian, Meridians, Equator, Parallels of Latitude

Using Graticule, “Angular Measurements” used to define position of point on the Earth’s surface.

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21
Q

What is the fundamental unit of Angular measurement?

A

Degree

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22
Q

What is a Degree?

A

Angle subtended at the center of a circle, by an arc, equal to “360th” part of the Circumference.

Degree divided by - 60 minutes of arc

Minute divided by - 60 seconds of arc

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23
Q

What are Latitude and Longitude?

A

Angular Measurements used to define position on earth in a Spherical System

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24
Q

QB: How is latitude of a position measured? / What is latitude?

A

Latitude of any point - is the arc measured along the meridian through the point - from Equator to the point

Annotated N or S depending on whether point N or S of equator

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25
Q

What is Geocentric Latitude?

A

Smaller angle between - Line from point on sfc. of earth joining to center of the earth - and - the Plane of the Equator

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26
Q

What is Geodetic Latitude?

A

Smaller angle between - Normal to the point on the merdian on the spheroid - and - the Plane of the Equator (Normal normally doesn’t pass through the center of the spheroid)

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27
Q

Where does the maximum difference between Geocentric and Geodetic Latitude occur?

A

45 degrees N or S (11.6 minutes of an arc)

28
Q

What are the special Parallels of Latitude?

A

Arctic Circle - 66 1/2 N

Tropic of Cancer - 23 1/2 N

Tropic of Capricorn - 23 1/2 S

Antarctic Circle - 66 1/2 S

29
Q

QB: How is longitude of a position measured? / What is longitude?

A

Longitude of any point - is the arc measured along the equator - from Prime Meridian to Meridian through the point.

Annotated E or W depending on whether point is E or W of the Prime Meridian

30
Q

QB: What is C.Lat / D.Lat?

A

Angular difference between 2 Latitude angles

Direction of C.Lat / D.Lat - Depends on from which point you are moving.

31
Q

QB: What is C.Long / D.Long?

A

Angular difference between 2 Longitude angles

Direction of C.Long / D.Long - Depends on point from which you are moving

32
Q

QB: What is Convergency?

A

Meridians converge towards the poles.

Convergency is the angle of inclination between 2 given meridians measured at a stated latitude.

Difference between G.C. direction of G.C., measured at each meridian.

33
Q

QB: Where does Maximum and Minimum Convergency occur?

A

Maximum - At poles

Minimum - At equator (0 degrees at equator)

34
Q

What is the main effect of Convergency?

A

Since meridians define direction with reference to True North - And since Meridians converge - The direction of a Great Circle constantly changes.

35
Q

Thumb rule for Great Circle direction -

A

G.C. is -

Concave to equator

Convex to poles

36
Q

Change in direction of Great Circle in the N.H. -

A

In the N. H. - [Concave to Equator]

Direction of Easterly G.C. - Increases

Direction of Westerly G.C - Decreases

37
Q

Change in direction of Great Circle in the S.H. -

A

In the S. H. - [Concave to Equator]

Direction of Easterly G.C. - Decreases

Direction of Westerly G.C - Increases

38
Q

What is a Rhumb line?

A

It is a line of constant direction. It is a curved line drawn on the surface of the earth which cuts ll meridians at the same angle.

Rhumbs lines used to be used to by ships to navigate along.

39
Q

What are the no. of Rhumb lines drawn between 2 points?

A

One

40
Q

What are the common Rhumb lines?

A
  • Parallels of Latitude
  • Equator (Also a G.C.)
  • Meridians (Cut Angle is 0 degrees***)(Also a G.C.)
41
Q

Thumb rule for Rhumb line direction -

A

R.L. is -

Convex to equator

Concave to poles

42
Q

Comparision bet. G.C. and R.L. bet. two points 1 -

Which is closer and farther from equator -

A

R.L. nearer to equator

G.C. farther from equator

43
Q

Comparision bet. G.C. and R.L. bet. two points 2 -

Length and Direction

A

Distance - G.C. is shorter distance.

44
Q

Comparision bet. G.C. and R.L. bet. two points 3 -

When Points on Meridian and Anti-Meridian

A

G.C. via pole (Changing direction at pole)

R.L. along Parallel of Latitude

45
Q

Comparision bet. G.C. and R.L. bet. two points 4 -

When Points on Equator

A

Line joining points is G.C. and a R.L. (constant direction)

46
Q

1 cm = ? mm

A

10 mm

47
Q

1 mt = ? cm = ? mm

A

100 cm = 1000 mm

48
Q

1 mt = ? feet

A

3.28 feet

49
Q

I feet = ? inches

A

12 inches

50
Q

1 inch = ? cm

A

2.54 cm

51
Q

1 yard = ? feet

A

3 feet

52
Q

1 km = ? mt

A

1000 mt

53
Q

1 km = ? feet

A

3280 feet

54
Q
  • Avg. distance between Equator and Pole in km

- Avg circumference of Earth in km

A

10000 km

40000 km

55
Q

1 sm = ? mt = ? km

A

1600 mt = 1.6 km

56
Q

1 sm = ? feet

A

5280 feet

57
Q

1 nm = ? mt = ? km

A

1852 mt = 1.852 km

58
Q

1nm = ? feet

A

6080 feet

59
Q

What is a nautical mile?

A

It is the length of the arc of a G.C. which subtends an angle of 1 minute at the center of the Earth.

Therefore - Nautical mile directly related to Angular Measurements of Lat. / Long.

1 nm = 1 minute of Latitude

60
Q

1 nm = ? minute of latitude

A

1 minute

61
Q

1 degree of Latitude = ? nm

A

60 nm

62
Q

1 nm at Equator = ? minute of longitude

A

1 minute

63
Q

QB: Derive Avg. between Equator and Poles in nm

Hence, Derive Circumference of Earth in nm

A

Degree change between Equator and Pole = 90 degrees

1 degree = 60 nm

Therefore, Avg. between Equator and Poles in nm = 90 degrees in nm = 90 X 60 = 5400 nm

Hence, Circumference of Earth = 5400 X 4 = 21600 nm

64
Q

QB: Length of nm in feet at Pole, at Equator due to Compression

Avg. Value of nm in feet

A

Nautical Mile at Pole = 6100 feet

Nautical Mile at Equator = 6050 feet

Avg. Value of nm in feet = 6080 feet

65
Q

Calculation of G.C. distances (Not to remember) -

A
  • Points on Same meridian, Same Hemisphere
  • Points on Same meridian, Diff. Hemisphere
  • Points on Meridian & Anti - Meridian (Same Hemisphere)
  • Points on Meridian & Anti - Meridian (Diff. Hemisphere)
  • Anti-Podal Points
66
Q

What Northern and Southern Vertices of Great Circle?

G.C. distance between them?

A

Northern Vertix - Most Northern point of a G.C.

Southern Vertix - Most Southern point of a G.C.

G.C. bet. them - 10800 nm.

67
Q

Any Meridian Line is a -

A

Rhumb line and Semi - Great Circle

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