rew@cbosgd.ATT.COM (Bob Warren) (11/10/86)
Having used a Tektronix 4027 which had one coordinate system (0,0 at top left) for text and a different one (0,0 at bottom left) for graphics, I would support the notion of giving the user a choice of coordinate spaces, but the impact of coordinates goes beyond the programmer writing display code. It turns out that the choice of coordinate system can trickle down to displays the ultimate user sees. An example of this is what happens when a Cartesian system for plotting degrees is used in a business graphics program to produce pie charts. Pie charts drawn using this system end up with Zero degrees at the far right of the circle, with degrees increasing counterclockwise. What difference does this make? Well, if you are showing anything with a sequential component (like time periods), a lot. Most people have an internal model of pie charts that more closely approximates polar (clock-face) coordinates than Cartesian, so they expect to scan clockwise. This affects both the speed and accuracy with which they can use the chart. I have a write-up of some experimental work on this problem that I would be glad to USMail to anyone interested (the graphics lose something over E-Mail). Bob Warren cbosgd!rew