How much separation is needed?

A modern canopy flies at around 30mph = 44fps (some are notorious for off-heading openings) FAA research shows > 3 seconds to recognize collision hazard and take action

Two canopies on a head on course cover around 300 feet in this time

So - how much separation is needed. Lets start by looking at separation within a group such as a 4-way. Several people have made experimental measurements of canopy speed with the brakes set. Typical reported values are around 30mph or 44fps. Some time ago the FAA researched pilots' reaction times to potential mid-air collisions. They found that it typically takes 3 seconds minimum for a pilot to recognize a collision threat and initiate evasive action. I'm going to assume that this is also typical of a skydiver immediately after opening. WELL, three seconds at 44fps means your canopy will have traveled nearly 150ft before you take action to avoid a collision. If you open on a head-on course with the "other guy" from your group who travels the same distance, this means that the two of you need to deploy 300ft apart to have a hope of avoiding each other. I shall therefore take 300ft as the desirable separation between members of a group. Everyone then can deploy in the center of their own "column of air" 150 ft in radius.