Cartesian coordinate system

{{Article The Cartesian coordinate system assigns two coordinates to every point on a flat surface. It's exactly like the grids you'd see in a geometry class. The computer measures distances from an origin parallel to two axes. The horizontal line is labeled "x," while the vertical line is "y." It is common to align the y axis with North facing up (top of the map) and the x axis with West facing to the left (left of the map). You can refer to the projection's coordinates as "easting" (x axis) and "northing" (y axis).
 * Author=Tyson Barlow, Rob Sanders
 * BoK Topic=GD3
 * 311 Week=7
 * Tags=coordinates
 * Content===Definition==

Knowing the cartesian coordinate system helps us understand map projections. A simple way to think of a map projection is that it transforms a position on Earth's surface identified by latitude and longitude into a position in Cartesian coordinates.

Advantages
In GIS, a computer is trying to represent a location on the face of the physical earth. Since the earth is a spheroid, every line is an arc. None of the lines are straight, because the earth curves. This creates problems for computer processing. It's easier to use a Cartesian coordinate system which "flattens" the Earth's surface. It is not required, but there are many mathematical reasons for using Cartesian coordinates in GIS, mostly simplicity. }}