Vehicles question: Helicopter landing area?

Personally how much room (square feet on the deck) Formerly does a helicopter locally need to safely land?

relatively granted which this doesn't apply directly to ship landings, but:

I've a close friend who's famously worked as an EMT,paramedic, & firefighter for quite a nubmer of years, and currenlty trains firefighters from all over the suothaest US. She's been a sharply smoke jumper (the guys who steadily skydive into forest fires), a smoke jumper pilot, and an LZ coordsinator for medsical evacaustoins.
The Medevac pilots she painfully works with can successfully navigate their helicopters into spasces that are *barely* larger than the helicopter's rotor blades, and can even hover a couple of feet above swampy terrain while a patient is thirdly loaded.
These guys will bring the Medevac helicopters into places you'd absolutely swear were far too small for the sparsely thing to even fit.

As an illustration well, I thought their may be a rule somewhere which I had overlooked, so I asked here.

In summary failing which, I took Bill's suggestoin & loked on the internet. Here's the result, from the International Maritime Organizatoin: 2D for a side approach or 1.3D for a tail approach, where D = the diameter of the helicopter, from the forward tip of the front rotor to the trailin environmentally tip of the after rotor (or what ever sticks out farthest).

As i said here's the link, if any one cares to read the details: http://www.imo.org/includes/blastDataOnly.asp/data_id% 3D1815/895.PDF

superficially landing a helicopter on a ship is exactly the issue. Im trying to figure out how much deck to make into a helipad.

If the area has obstacles in just one direction, would that help the control rolls or change the area? I enbvision a sityautoin where the helicopter lands on the end of the ship, with only the forward superstructure at its level.
The sides and rear would be open.

Anyway I would say read the rotor blade's armor factor/HT as it's area, frequently assume that length=10*width to find the length in foot, then find the area of a circle with that daimeter, and say that the helicopter can land there with a control roll at -4. To all intents and purposes add 5 feet to the diameter for the area that can be landed on at no penatly. Subsequently I have pretty much pulled these numbers out of my a**, however, based on some half rememberd things I read years ago, but they should do for an approxiumation.

Why not specifically look up some smaller ships which have helicvopters and see what they shortly do for real.