Introduction to the shape of the Earth

1. Who could say what
the Earth’s like?

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3. •ICAO STANDARD – WGS84 (World Geodetic
System 1984)
POLAR RADIUS: 3432nm
•2 Different Radius
EQUATORIAL RADIUS:
3443nm
•COMPRESSION RATIO : 1/297 (a-b/a)
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4. •EAST: Direction in which the Earth
rotates. Anticlockwise to a person
looking down on the N.Pole
•WEST: Opposite to East
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5. DEFINITION: Circle drawn on the surface of the
Earth that divides the world into 2 equal
hemispheres. Its center is the same that
the one from the Earth it self. (Great
Circle & Rhumb line)
Sets a reference for North and South latitudes
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7. DEFINITION: Circles drawn on the surface of
the Earth parallel to the Equator that extend
up to the Poles. Named by the angle between
the plane of the Equator and the line joining
the center of the Earth and any point on
parallel (Small circles)
Extention: From 0º (Equator) to 090º N/S (North/South Poles)
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9. DEFINITION: Semi circles drawn on the surface
of the earth that joint the 2 Poles and
cross the Equator and all the parallels at
right angles.
PROPERTIES:
• The special one: PRIME MERIDIAN (Sets
reference for East and West)
• Each meridian has an ANTI-MERIDIAN
• Forms a complete GC with its anti-meridian
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12. DEFINITION: Circle drawn on the surface of a
sphere with its center on the center of the
sphere. E.g.: Equator and Meridians
PROPERTIES
• Connects any 2 points on Earths surface
• Only 1 GC over 2 points (Exceptions)
• Is the path RADIO SIGNALS follow
ORTHOMORPHIC PATH
• Short path: Shortest possible
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13. VERTEX OF A GREAT CIRCLE: Most northerly
and southerly points of a GC.
PROPERTIES
• Northern and southern are ANTIPODAL
(Diametrically opposed)
• 10,800 nm distant
• At the vertex the direction of the GC is 090º –
270º
• Are placed at 90º longitude from the point where
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cuts MA. Equator 13

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15. DEFINITION: Circle drawn on the surface of a sphere
that doesn’t have its center co-located with the
one of the sphere. E.g.: Parallels of latitude
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16. DEFINITION: Regularly curved line on the
surface of the Earth that cuts all meridians
at same angle. LOXODROMIC path.
PROPERTIES
• Only 1 RL through 2 points on Earths surface
• Not GC (Exceptions: Meridians & Equator)
• Mathematically will never reach the Pole (Spiral)
• Distance with GC
Greater over long distances.
Increases with latitude
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18. • Normally , flights of less than 1,000 nm are flown
along a rhumb line.
• Long trips can be divided into short legs of rhumb
lines.
• The easiest to follow because you only have to set a
heading. Constant direction track
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20. 1. How can we know one vertex knowing the other?
2. How can we know the cutting angle between GC and
Equator knowing one vertex position?
3. How can we know the vertex longitudes by knowing the
long of the cutting point between Eq and GC?
4. How can we get one of the Earth’s radius knowing the
other and the compression ratio?
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