
 IMAGINARY SURFACES FOR OBSTRUCTION EVALUATION 
  A surface longitudinally centered, on the extended centerline of the PIR runway, beginning at the end of the Primary Surface and extending outward and upward at a slope of 50:1 (2.0 percent) for a horizontal distance of 10,000 feet and at a slope of 40:1 (2.5 percent) for an additional 40,000 feet. 
  A surface longitudinally centered, on the extended centerline of the runway, beginning at the end of the Primary Surface and extending outward and upward at a slope of 50:1 (2.0 percent) for a horizontal distance of 2566 feet and at a slope of 34:1 (3.0 percent) for an additional 47,434 feet. 
  The surface width is that of the Primary Surface (800 feet) at the beginning and increases uniformly to a width of 4,400 feet at a distance of 50,200 feet from the Threshold. 
 www.ngs.noaa.gov /AERO/OIS/ois.html (986 words) 
