I was working on a marina expansion, we were tying into another pier. We were driving 2 pilings every 20'. On top of the pilings we would put a piece of formed channels to set the aluminum pier sections onto. The water was rising everyday so we would drive the pilings within a few inches of the set depth, and leave them until we could bring a transit out and mark out the final height. The first couple we cut free hand, but with the rough water and boaters going by we couldn't keep a steady enough hand. we came up with the ring idea, it worked. Wasn't pretty but it worked. All the channels were welded to the pilings overhead, I was standing on a 4x8 raft, reaching overhead when I started. 2 weeks later the water came up I was pretty much laying on my back to finish. The problem with welding on a raft is when you put the rod to the pipe you push yourself away, and every wave and every wake, every gust of wind will screw with you and you cant see it coming. Oh ya it rained too, so could barely see either. I don't care what you draw your line with, its hard to get a straight cut in those circumstances. CEP You been there I know!
Heres a link to a satellite image of the dock system. We started out add on at the Y shape you can kind of tell where it changes color.
https://www.google.ca/maps/place/50...1"N+118°58'34.8"W/@50.8205289,-118.9770076,222m/data=!3m1!1e3!4m2!3m1!1s0x0:0x0
we put in the extension that leads out to the giant square, including the square. I did almost all the field welding on this project. the pontoons were built somewhere else and the aluminum piers were built by another company, although I do recall having to help weld out some of them to get it ready. I built all the joists (galvinized steel studs) and then welded them to the pontoons.