Projections are functions that transform latitudes and longitudes on the surface of a sphere or ellipsoid into positions on a plane. In order to represent the Earth, the sky, the moon, a planet or any spherical shape on a plane, you need a projection. Humans have used geographical projections for millennia (the oldest projections date over 2,500 years ago) for many different purposes. There is no limit to the amount of projections that can be invented.
Projections
Types of projections
The three basic cartographical projections project the surface a sphere or ellipsoid onto a developable surface: any surface that can be flattened onto a plane without stretching or compressing. These surfaces are: the plane, the cylinder and...