Why the launch point defines BASE jumping
The letters in BASE name four kinds of fixed launch sites: buildings, antennas, spans such as bridges, and Earth, usually cliffs. The key distinction is not the shape of the structure but the start of the jump: the jumper steps or runs off an edge rather than exiting an aircraft in flight.
That changes the whole timing of the descent. A skydiver typically has substantial altitude in which to fall before opening a parachute. A BASE jumper may have only a short distance between the launch point and the ground, water, or another obstacle. The parachute must therefore be packed and deployed for a much tighter window, with little room to delay or correct a problem.
A fixed edge leaves little margin
The site itself becomes part of the flight. A cliff face, bridge, or tower can shape nearby airflow, and the jumper must clear the structure before the canopy opens. The available height, the route away from the object, and the landing area all constrain the jump; a location that looks open from above may leave very little space to maneuver.
This is why BASE jumping is not simply skydiving with a different view. Its defining feature—the close, fixed launch site—also sets its central engineering and safety challenge: get clear, deploy promptly, and land within the limited space the site allows.
