Laser scanning; is it just white noise?

We have all seen laser scanning and it has useful applications; but is it the panacea for as-built documentation?

No, it is not. While I can capture items that are not modeled with great accuracy, it is just unintelligent, location unaware, points. In other words, dumb points.

Today I will talk about where I feel laser scanning is useful and where I think other solutions have greater merit.

Capturing existing conditions with laser scanning is still one of the best uses for the scanners. For existing conditions in coordination I want to know if I have interferences. The point cloud will let me know if I need to move new construction elements. Through the use of Navisworks and grouping the white noise of the point cloud is reined in to useable information and I am not relying on the human eye to verify interferences. I can even go one step further and convert that point cloud into a model; now this is not a push button affair, yet advances in technology have streamlined the process.

For as-builts, I feel laser scanning while the current buzzword, leaves much to be desired. First, to verify as-built conditions you have to scan, then stitch together the scans, and finally locate the scans with-in Navisworks to verify the conditions are correct.

That is not so bad; it beats a tape measure right? Not exactly. A tape measure, while time-consuming, gives you a pretty accurate measurement; if the person reading the tape knows how to read it. But I can just look at the scan in Navisworks and see if my elements match up or not, so it is better than a tape measure.

That is where a lot of people make a wrong assumption. Remember the points in the model are dumb, so if the person putting them in got it all right; no worries right? Not exactly, besides the data entry possibility for human error now you have the analytical possibility for human error. We all know humans never make mistakes, I mean take the US Congress for example; they saw the economic crash of 2008 coming and prepared our country and the world right?

You normally won’t see me shilling for software or hardware providers, unless I feel they offer a solution that is so outside the box and yet so practical its make you say, “Why didn’t I think of that?”

Get The Point (GTP) offers a software platform used in conjunction with a robotic total station (RTS) that does just that. The RTS is
aware of its location in real time and now with GTP it is aware of its location with-in the model also.

Now I can set the RTS to take predetermined shots to verify as-built conditions reflector-less, meaning no one is holding a prism. Now the points I get in the Navisworks model are easy to check against for verification of as-built conditions. In fact the RTS is smart; it will already have a list of points that are out of tolerance and generate a selection set for those points.

What does this mean? The white noise of laser scanning is now just white noise and the RTS combined with GTP gives me the points I need where I need them, sometime where I don’t because someone messed up installing.

Don’t believe the hype; laser scanning has some uses; just not for documenting as-built conditions. Don’t miss the point for the point cloud; you’ll be amazed at what you can find.

2 Comments

  1. It is a laser scan inserted in the model. The scan is of the room before the walls were boarded up with drywall. It is useful to know what is in the wall like x-ray vision of the wall if you will. I really think pictures embedded in the model would work just as well but this owner wanted laser scans. I do agree scanning decks and walls before a pour is a great use of laser scans that way if you need to core a deck or a wall you know where rebar and pt cables are and can avoid them. I hope that helps as it is an integrated picture. And as with all things in our lexicon some call this as-builting, I do not it to me is similar to existing condition documentation as the scans only represent graphical information. I belive sometimes scans of these conditions should be included in the model as a layer but not all times.

  2. There is a picture inserted near the end of this article. Is there an implication that this picture is a laser scan? Because I see studs, which I am unaware that a laser would "see" unless wall finishes have not yet been installed.
    Am I behind the times or is the picture misleading?

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