To keep it simple let’s start by looking at a 1 dimensional system for locating points. Consider the horizontal line shown on the left of figure
32. A point on the line marked “0” is established as the origin. The line is graduated and numbered (positive to the right of the origin and negative to the left). Any number can be plotted on this line by its value and distances to other points on the line can be easily calculated. If all of our work was done precisely along a line, this system would be sufficient. We live in a 3 dimensional world, therefore we need a better system.