When a SID or DP is created it uses the TERPs requirments which surveys a corridor that starts at 300ft and expands to 8900 ft on either side of the flight path. A few years ago the FAA released AC 120-91 which is more in line with IACO terrain clearance. It widens from 300ft at the airport boundry to 2000 ft either side with a 16:1 splay.

APG applies the AC 120-91 corridor and thus can exclude alot of obsticles that are off the flight path. The FARs only require 300ft a side so APG is still legal and does not require FAA approval to use, rather it is accepted by the POI. APG has a good video on their website that explains how it works.

Last week we were able to leave KEGE with 3000lbs more than what we would have using the book alone.