WHAT IS LASER
a quick walkthrough from the trenches - by Brian Riddle
why is it useful?
The purpose of laser scanning for construction is multifaceted, from conceptual design, 3D modeling/BIM field verification and everything in between.
When doing a renovation or addition to an existing structure, capturing a point cloud, and using it as a start point of the project not only saves time in the long run, but also saves on your bottom line. Depending on the size and level of detail needed to capture enough data, a scan to BIM job can last a few hours to a few weeks. Once the data is collected, processed, and converted to a point cloud we can accurately model to the existing structure. It is then unnecessary to travel back to site to take additional measurements we may need or missed on the initial walk through.
If the job is intended to be constructed using modular units, or moving equipment, or components in and out of a building, a laser scan can be taken of the area to be modified or added too. This includes the possible path or paths that could be used and a haul path study to be done to maximize efficiency before ever fabricating a piece of steel or equipment.
what's the process like?
The process of laser scanning for construction is pretty straightforward. Before a scan job is started, if available, we will do a rough plan using existing drawings of areas to be scanned. We will layout potential scan locations to determine the number of scans in a room or overall job on the drawings and think about places that targets can be placed. Once on site, a walk through will be performed to verify the layout that was previously done, or make changes before the scan job is started. After the initial walk down, the scanner will be set up on the tripod, targets placed, and data will begin to be collected.
how does 3d laser scanning work?
Most terrestrial laser scanners use “time of flight”, meaning that a pulse is sent out and the time to receive that back to the unit determines the distance traveled. Using 100’s of pulses a second the scanner is able to accurately collect the data needed to map an area even in pitch black conditions. With an on board camera color is added to the scan. Depending on the scanner, the data is stored on an SD card and transferred to a computer to be processed and later registered. Some newer models connect to a computer or tablet using a built in Wifi transmitter/receiver to process and start registration while still on site collecting data.
If using a scanner that stores the data on a SD card, the next step in the process is registration. The scan data is loaded into processing software and the software can auto-register, or attempt to put the individual scans in order using “cloud to cloud” registration. Cloud to cloud means the program looks at the scans and tries to determine matching surfaces (natural targets) or artificial targets to “stitch” the scans together. Or manual registration can be used where the user will take two scans or scan groups and match surfaces or targets to stitch together scans. When registration is done, most softwares will kick out a report to verify the accuracy of the total model, and scan to scan accuracy. After the desired level of accuracy is achieved, a point cloud can be exported in multiple formats that can be used by multiple 3D design packages.
my introduction to scanning
I was introduced to laser scanning when I started working at Vogtle 3 & 4. We scanned everything, rebar before concrete placements and bar left exposed to tie into the next placement or module wall to be set down over top to tie it to the concrete basemat.
Every module that was built was scanned and placed in a model to make sure it was going to fit up before it left the assembly building. This was done all in an effort to save time and cost, to mitigate potential errors before they became a show stopper, and it worked. When doing a renovation, retrofit, or starting a new project, capturing laser scan data and using it as a start point of the project not only saves time in the long run, but also saves on your bottom line.
Depending on the size and level of detail needed to capture enough data, a scan job can last a few hours to a few weeks. Once the data is collected, processed and converted to a point cloud we can accurately model to the existing structure without the need to travel back to site to take additional measurements we may need or missed on the initial walk down.
I worked for a company after Vogtle that specialized in modification to nuclear plants, mostly in balance of plant. We would scan areas to be modified: pipe rooms, equipment rooms, wherever the mod was. If a piece of equipment was being taken out, not only would we scan the area around the equipment, but any possible way we would get it out of the building, and do a haul path study to determine what needed to be removed and what didn’t to save the client time and money.
Taking tape measurements and “guess-timating” could result in removing things that didn’t need to be removed, costing more in possible engineering, and replacement of things removed after replacing the equipment. Same thing can be done when installing new steel to an existing structure before making the first fabrication drawing.
Hardware like an Oculus VR headset can be used in conjunction with scan data and a 3D model to “walk through” a design before a drawing is made to verify that is what is intended for the project.
we're here to help!
I hope this was helpful and allowed you to gain a better understanding of what 3D laser scanning is and how it can help you on your renovation project. If you have any questions or need help scanning your building, feel free to click the link below to get a quote!
We're a family owned and operated business located in sunny Milledgeville, Ga. and we would love to help you out!