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Preserving a Piece of History with 3D Laser Scanning

by Tyler hauser 17. November 2011 03:19

When Potter Lawson, Inc. came to R.A. Smith National looking for a way to create as-built drawings of the facades of several buildings in historic downtown Madison, Wis., Jon Chapman’s answer was simple. 3D laser scanning. According to Chapman, “There’s no more accurate, cost-effective way to document the as-built conditions of a structure than with 3D laser scanning.”

It’s easy to grasp why today’s laser scanning technology is truly phenomenal. Millions of survey-grade accurate points within a 4mm tolerance are captured in a matter of minutes; 40 million points in just 3 ½ minutes to be more precise.

“So what” you say. “What am I going to do with 40 million points?” Exactly. What R.A. Smith National does with those points is where the rubber meets the road.

R.A. Smith National’s 3D laser scanning team recently worked with architects from Potter Lawson to provide 3D laser scanning services for six historical building facades. The project site was Block 76 on downtown State Street in the city of Madison. The exterior facades of each of the six buildings were scanned. Using specialized software, a series of 2D as-built CAD drawings were then created for each building elevation.
There’s a lot you can see and do with the data from a 3D laser scan. The native data being captured by the scanner, more commonly known as a point cloud, can be used to interactively visualize the space that was scanned.  The point cloud can be viewed as a whole from customized vantage points, or cut into vertical or horizontal sections, which enables R.A. Smith National’s 3D laser scanning team to very quickly visualize and create very accurate cross sections that would be extremely difficult, if not impossible, to create otherwise.

3D laser scanning is further useful in the ability to auto extract certain features from a point cloud, such as 3D piping or surfaces. While still far from a completely automated process, technological advancements in software algorithms are constantly being developed, making “usable” data extraction from point clouds a much more manageable process. Those features which cannot be auto extracted can be digitized rather quickly while snapping to the actual point cloud to ensure the highest level of accuracy.
Depending on the project, laser scanning can be a much better data capture tool compared to conventional methods. In particular, when there are highly detailed areas or areas that have a vertical orientation (such as a building facade), a laser scanner is a much better tool for the job.  The proper scan set-up locations will ensure that there are no return trips to the field for additional information. All the data needed (and more) will be contained in the cloud. It is simply a matter of extracting it to the proper usable object.

On the Block 76 project, what would otherwise have required the tedious task of using a tape measure, or even a laser distance meter, to measure various architectural treatments and artistic elements was accomplished much quicker and more accurately with 3D laser scanning. Vital dimensional information, such as window and door opening sizes, building heights, sizes of precast elements such as keystones, other ornamental features, and the specific number of bricks in all soldier courses and walls were easily identifiable, and accurately documented.

A final value-added benefit provided on the Block 76 project was the creation of a TruView data set. Simply put, the TruView software is useful for professionals who want to easily view and measure laser scan point clouds without having to be an expert in laser scanning, CAD or 3D. TruView is essentially a user-friendly, 3D browser-based viewer, measurement and markup tool for 3D point clouds.

An html document acts as the home page, which typically consists of a 2D plan as a base, with each scan position hyperlinked to the corresponding virtual location in the 3D point cloud file. When these hyperlinks are clicked on, the applicable point cloud is then opened in the TruView data viewer. 
This TruView data set was provided to Potter Lawson with the intent that it could be used by the designers and the general contractors for future reference
as the new design was being developed and then built.

Watch and See
3D laser scanning is an exciting technology that provides critically accurate data when you need it. Visit R.A. Smith National’s website to take an incredible tour of 3D laser scanning and view several of our recent project examples.

More Information
For more information on our services or to discuss a specific project, contact Jon Chapman, 3D laser scanning project manager, at 262-317-3366.

Laser Scanning

R.A. Smith National used 3D laser scanning to capture this point cloud of the facade of one of several buildings for the Block 76 project in Madison, Wis.

Laser Scanning

When a point cloud is displayed using the Hue Intensity Map, features such as individual brick courses are easily identified.

Laser Scanning

This 2D CAD elevation is one example of several elevations that were extracted from the point cloud on the Block 76 project.

Laser Scanning

Laser Scanning

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Karen Wiesneski
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