pie in the sky?

[danielbriggs]

In a parallel universe we could have something attached to the roof that would beam down 14000 dots onto the floor simultaneously in the correct positions but that ain't feasible hence my question about the grid.

You could have an off-the-shelf single unit solution that could accurately mark say 1400 holes (covering a nominal 10% of the area), then move the unit to the remaining areas. This "tiled" approach is very feasible in terms of the accuracy you require with "normal" hardware available. Just basic callibration and care would be required when moving the unit to the next area. I assume you wouldn't be drilling 14000 holes simultaneously!
This could be scalled trivially by using more projectors.

Just a thought...

P.S. Are you UK based?

[depo]

Using a single projection point wont work. How good has the slab been poured? If the slab is out by 5-10mm which is common in slabs of that size. Projecting a grid from one point would give you an incorrect grid size on the outskirts of the grid because of the height difference.

Even setting up a simple hilti dropped on its side rotating a single line is fiddly especially at those distances. The only laser i have seen that might come close was one used to build partition walls in a 20 story building. It could project a vertical line 60m up and 60m each side of it. Nut its tollerance was 5-6mm. They had 3 units and each unit was over 20k to buy. I will try and get the name of the company that made them.

Without seeing the building iam only guessing but if your hanging from the roof structure projecting 100m even the wind loading on the building would move the laser 5mm at the 100m mark. Then consider how much the building might move because of temp changes over the 20 hours you have to do the job.

[Doc]

It would be easiest to manually mark out and drill some reference holes (you could use a standard line laser and a pre marked measuring stick for this part) and then use a pre drilled and doweled template.

Think a pre drilled 3000 x 1250 sheet of .7mm galv steel with 2 set screws of the correct diameter fixed through (these could attach handles for easier/quicker handling) to align with the reference holes.

You can use this as a stencil to mark the positions acurately with some engineers demarkation paint.

This is how we mark out in similar situations (adimittedly we only need acuracy in one plane rather than two, as the panels we fit have pre defined fixing points visible from the front).

[dsli_jon]

Umm, guys - did you *fully* read the original specs, here?

This is probably ridiculous but...from a height of 15 metres over an area 100m by 200m

...ceiling-height of ~49'... onto a floor ~328 Feet x 656 Feet??? a US football-field is only ~ 160' W x 360' L - this space is that *massive*?? I was initially thinking DLP projection-mapping of all 14K 'points', (since, position is apparently 'critical' and not 'random' at-all...) with special wide-angles or some kind of f-Thetas.. but 328' x 656'???

I'm thinking, too, even if all pre-marked, 14K manually-drilled holes in 20 hrs is also a 'dealbreaker'... What is this, a plane-crash reconstruction or...

I'm with Jem.. we need a bit more 'tuning' on the 'wtH?-Dial', methinks....

Intrigued...
j