Geosphere could be considered the object of study of physical geography as a discipline. Earth as a Celestial Body 1. The geographic grid Fig. 1-9. Earth rotates on it's axis thereby providing natural reference points for geographic grid - the Poles and the Equatorial Plane. When the globe is transected by an imaginary plane, the plane forms a circle on the globe's surface.
Great circle represents the shortest path between points lying on it.
Therefore, air and sea transportation lines tend to use great circle routes as much as possible. Small circle - any other circle Fig. Obviously, 23.5 is a special angle, we'll soon find why. Longitude Longitude is a coordinate in the East-West direction. Unlike equator, there is no natural great circle to measure distance from in the East-West direction, therefore, one had to be artificially declared.