Off on a bit of a tangent here, but what else is new....
RJ mentioned in one of his posts about using a laser level on a grid to measure the relative flatness of a floor. And also that it would probably be a tiresome process. I actually did just that a few years ago, and yes, it was laborious!
I wanted to get a topographical map, as it were, of a fairly large section of floor (40' X 75' roughly) that had a questionable support member. We wanted to be able to document whether the member was continuing to deflect, and if so where. So I came up with this system using exactly what RJ mentioned: a laser level and means of measuring from level line to individual points on a half-metre grid. These points were plotted into an Excel spreadsheet and I had my topo map of the floor.
Well it kind of worked but kind of didn't. The laser line is actually pretty thick, so if you're going for 1/8" tolerance that's maybe doable, but finer than that and you're guessing. And of course my level, although it was a pretty decent one, was not a razu rotating kind. But it many ways as it often is, figuring the "how to" is often the most fun anyway.
I took the level and made a kinematic mount for it out of MDF. To let it rotate smoothly, I used part of a scrapped magnetic drive out of I'm not sure what anymore, but it was super smooth and very tight. Attachment to the rotating platform was accomplished with three rare earth magnets so I could easily assemble and disassemble the setup.
For the measuring part, a similar base of MDF held an aluminum scale at vertical and tensioned with a screw so that the scale could always be zeroed at a given point. Once the scale was zeroed to the laser line, I just moved the base around to the various points on my grid and any deviation would show as the line being higher or lower than my "zero" mark.
Then I painted them both banana yellow, yay!
I took a number of measurement sets this way and yes it was interesting but ultimately not one hundred percent viable. Our more reliable surveys were done using an optical level and stadia rod, land surveyor style. But it was a lot of fun in the making, that's for sure.
Now back to your regular scheduled programming.....
-frank