03 The Shape Of The Earth

Question 1

What shape is the Earth?

Answer 1

Oblate Spheroid

Question 2

What is the Equatorial, Polar and Perfect Sphere radia of the Earth?

Answer 2

• Equatorial Radius: 3443.56 nm
• Polar Radius: 3431.97 nm
• Perfect Sphere: 3441 nm

Question 3

What is the Compression Ratio (ellipticity) of the Earth?

Answer 3

1/298

Question 4

What is the equation for the circumference of the Earth?

Answer 4

Circumstance of the Earth = 2 x Pi x 3441 = 21,600

Question 5

What model is used by the aviation industry and the GPS for the shape of the Earth?

Answer 5

WGS84

Question 6

Describe the two types of Circle used for navigating around the Earth

Answer 6

• Great Circle: any circle whose plane crosses the centre of the Earth (e.g. Equator)
• Small Circle: any circle whose plane does NOT cross the centre of the Earth (e.g. Parallels of latitude)

Question 7

Describe what a Geodesic is

Answer 7

• Shortest line between two points on a sphere

- Arc of a Great Circle

Question 8

What are the formulas for calculating the major and minor axis using the compression ratio of the Earth?

Answer 8

Minor Axis = Major Axis - (Major Axis / 298)

Major Axis = (Minor Axis / 297) * 298

Question 9

What is the definition of a Rhumb Line?

Answer 9

A Rhumb line is a regularly curved line, concave to the nearest pole which crosses all meridians at the same angle