Map projections are used to transfer the spherical locational information on a datum or ellipsoid to a flat surface. A sinusoidal function is an example of where the main calculation involves the x coordinates. The grid formed by the latitude and longitude on a map is called the graticule. Types of Projections. The line of latitude or longitude where the projection and locational information about the earth intersect is called the point of contact or standard line.
Distortion is minimized nearest to the standard line.
Normally, a cylindrical projection places the earth inside a cylinder with the equator touching the inside of the cylinder. Cylindrical projections are commonly used for areas around the equator. If the cylinder is placed perpendicular to the axis of the earth the resulting projection is called a transverse projection. A cone is placed over the earth to produce a conic projection. A conic projection works best over mid latitudes.