Latitude, Longitude, Parallel and Great Circle


Latitude, Longitude, Parallel and Great Circle


″ Latitude is the Angular distance measure North (N) and South (S) of the equator. We can project the line from the point P from the earth surface to the centre of the Earth. ″

  • The angle between this line and equator plane is the measure of the latitude of point P.
  • Latitude varies from 0° to 90° North or South.


The parallel is a line connecting all points of the same latitude. It is called so because it is parallel to all other lines of Latitude.

0° Parallel – Equator.

90° North  – the North Pole.

90° South  – the South Pole.

Longitude :

Longitude is the angular distance between meridian passing through a given point and prime meridian

  • The Longitude varies from 0° to 180° East or West.
  • Meridian is a line joining places with the same longitude.

Great Circle

Any plane that is passed through the centre of sphere bisects that sphere and creates a great circle where it intersects the surface of the sphere.

  • A great circle is the largest circle that can be drawn into the sphere and it represents the circumference of the sphere.
  • Of all the parallels The Equator alone makes a great circle all other parallel makes the small circle.
  • Each meridian makes Semi Great Circle.
  • Arc of the great circle joining any part on the equatorial surface is always the shortest route between points.

Circle of Illumination 

Sun Illuminates one-half of the earth at any given moment. The edge of the sunlight hemisphere, the circle of illumination, is a great circle, that divides the Earth into the light half and dark half.

Important Parallels 

Both 23 1/2 ° N and  23 1/2 ° S will receive 90° sunlight and these two tropics represent the farthest limit of the vertical base of the sun

” Tropi” in latin – Tropics, Meaning “Turn”.

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