Before revision: Definition The natural Earth is defined by the following formulas: , where x, y are the Cartesian coordinates; λ is the longitude from the central meridian; φ is the latitude; l(φ) is the length of the parallel at latitude φ; d(φ) is the distance of the parallel from the equator at latitude φ. l(φ) and d(φ) are given as polynomials: The two values used to be lineally interpolated from a table of 19 latitudes and then multiplied by other factors.
After revision: Definition The natural Earth is defined by the following formulas: , where x, y are the Cartesian coordinates; λ is the longitude from the central meridian; φ is the latitude; l(φ) is the length of the parallel at latitude φ; d(φ) is the distance of the parallel from the equator at latitude φ. l(φ) and d(φ) are given as polynomials: In the original definition of the projection, planar coordinates were lineally interpolated from a table of 19 latitudes and then multiplied by other factors.