Ok so their is a limited amount of routes used in tribes, once you know the direction that a capper uses the majority of the time, if you are good at video games you try and remember these things.
If you use perm iffs you could catalog the areas where say for example darkpiece becomes visible on a non perm iff screen, cutting down your time spent scanning. If you don't understand i wil draw diagram for you?
Though i doubt many people try to memorize routes used by others, as they are not true tao.