There are three fundamental coordinate systems (rectangular, cylindrical, and spherical), each of which is a more convenient means for calculations depending on the configuration of your model. For example, mapping points on the surface of a sphere using the Cartesian coordinate system requires describing all three coordinates (x, y, and z) in terms distance from each of the threes axis references.  Doing the same in the spherical coordinate system requires simply a radius and two angles. When you start doing very complex calculations like those requiring calculus applications, choosing the best coordinate system can make the difference between nightmarish equations and relatively simple ones.

Conversion formulas between the three fundamental coordinate systems are given below.

Here is a convenient online coordinate system converter on the Random Science Tools and Calculators website.