Nominal Tracks

Air Traffic Control separates aircraft from each other but who separates aircraft from the ground? Obviously the aircraft must touch the ground at the end of the flight but only at the correct position i.e. the runway. If all flights were conducted by pilots looking out the window, with the possibility to stop and refuel, determining the runway position would not be a problem..

However this is not the case and so navigational beacons were developed.
Routes subsequently developed could be flown in bad weather, avoiding high terrain. Following these routes the aircraft could be positioned just before the runway threshold for the final visual landing.

So far, procedure design looks rather simple; just draw the track that you want the aircraft to follow so as to fly around the obstacles. At this stage the second most important word in procedure design, Tolerance, must be taken into account.