| Earth | – | is a shape of a football, but not entirely correct, as it is elliptical in shape, the shape of the earth is also called oblate spheroid. |
| Oblate spheroid | – | is a body which rotates on its own axis |
| Great circle | – | is when a circumference is cut into a shape of two equal parts. |
| Small circle | – | is when a shape of circumference is cut into two parts that are not equal. |
| Equator | – | is a imaginary line assumed to run in east and west direction cutting the earth into two equal parts. |
| Parallels of latitude | – | are parallel to the plane of equator, hey also lie in east or west direction. They are also called small circles. |
| Meridians and anti meridian is an imaginary line assumed to run in north and south direction, cutting the earth into two equal parts. They are also called semi great circles |
| Rhumb line | – | is a straight line that is also a small circle, but may or may not be a great circle. |
| Poles are either ends of the earth on the axis of which it rotates. |
| Directions are measured in degrees in aviation, there are 360° |
| Degrees, starting from north as 001° or “N” datum till 360°. |
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