In a typical HAHO exercise, the jumper will jump from the aircraft and deploy the parachute at a high altitude, 1015 seconds after the jump (typically at 27,000 feet or so). The jumper will use a compass or GPS device for guidance while flying for 30 or more miles. The jumper must use way points and terrain features to navigate to his desired landing zone, and along the way, must correct his or her course for changes in wind speed and direction; making for a tricky navigation problem. (from Wiki)
and they were having to use night vision with waypoints and tricky winds.
nasty stuff..maps/waypoints/wind/and falling.