In today’s competitive self-storage climate, with suitable building sites shrinking and land costs increasing, many owners and developers are taking a hard look at retrofitting existing vacant warehouses and industrial buildings. These structures can be successfully and economically converted, and yet they present their own challenges.
Avoiding pitfalls requires careful analysis of the existing buildings. Accurate spatial information is critical for the architect to create a useful set of as-built drawings from which to determine project feasibility. When documenting conditions in the field, laser-scanning technology is a time-saving tool to increase accuracy and minimize error.
How I Started Scanning
I recently embarked on an odyssey to convert a large warehouse into self-storage. It’s a metal-surfaced structure with integral steel beam/columns and purlins. The client planned to place a second-floor platform inside.
Initially, I performed a field measure of the building using a hand-held laser-distance device; but I had limited success because when I input the measurements to my documents, some information didn’t correlate. Four return trips to the job site failed to satisfy my requirement. I decided to rethink my approach.
One of my associates owns a firm that’s known for high-end, commercial laser scanning, having provided this service for the aerospace industry, the U.S. Navy and the Smithsonian Institution. His company has scanned the Liberty Bell, the Washington National Cathedral and the Lincoln Memorial. Scanning national monuments is valuable for historic preservation, archival record-keeping, model-making and damage assessment.
I had hired the firm last year to scan a seven-story masonry building in Baltimore to check for “out of plumb” movement due in part to earthquake activity. So, when I got stumped on this self-storage conversion project, I considered calling them in again. The work was going to take a full day, as someone would have to visit the jobsite—a two and a half hour drive each way, plus scanning time. At $5,000, the proposal exceeded my budget, so I needed a new plan.
I decided to research the possibility of performing the scan myself. I found a couple of small scanners online in the $20,000 range. When I mentioned these to a colleague, he said he’d recently purchased a scanner but hadn’t used it yet. A stroke of luck! Maybe I could rent it for a day?
We negotiated a daily rate of $500, which was a very reasonable fee. I asked for line drawings from the scan, for which he charged me an additional $200. The unit came in a small carrying case with a tripod. He calibrated it for low resolution to keep the file size down. Next, I needed to learn how to use it. The simple instructions were, “Just set it up on the tripod, press the button, and wait a few minutes for the scan to take place.” I packed it up and headed out.
How It Works
A laser scanner is essentially a laser-distance instrument in high-definition mode. Mounted on a tripod, it turns around horizontally while a mirror apparatus spins rapidly in the vertical direction. The laser beam emanating from the mirror, as it turns and spins, forms a large spatial set of points that yield accurate distances out to the various surfaces it “sees.” This set of points is known as a spherical point cloud and can create a rather large file with easily millions of points from a single scan. A second rotation of the scanner from the same position captures images that can colorize the point cloud and provide a spherical “bubble” view of the 3D area.
Like traditional cameras, a laser scanner can’t see through or around walls. To capture a large complicated space with many rooms, you must move the scanner and take dozens or even hundreds of scans, depending on the structure.
There are many brands of scanners with varying functionalities and capabilities. Some are meant for more industrial environments and outdoors, while others are better for smaller, more accurate scanning such as capturing ornate architectural detail line in cornices or decorative ceilings. As with any project, one should choose the best tool for the job at hand.
Back to My Odyssey
Out at the conversion site, I took six scans of the 160-by-100-foot building. Each lasted five minutes. My colleague e-mailed the file to me the following day, and I loaded it into the modeling software I use to design buildings.
Using the program, I took cross sections through the scan file. The result was a grainy image of the building, almost like an X-ray. The coarse quality was due to the scanner resolution having been lowered, producing fewer points of information. To achieve my result—a line drawing—I needed to manually trace over the scan using the line option in my software. I estimate that I came within about a quarter-inch.
I consider myself a leading-edge thinker and have always enjoyed exploring advances in technology. I was an early adopter of CAD software and have followed the evolution of products in this industry over the past 15 years. The goal is always increased productivity. Laser scanning is the latest addition to my tool kit. Where applicable in the self-storage market, it can be a valuable time- and money-saver, providing accurate, economically feasible solutions to otherwise worrisome problems.
H. Edward Goldberg is a registered architect and president of HEGRA Architects Inc. in Baltimore. With more than 40 years of experience, he’s designed self-storage projects in Connecticut, Delaware, Maryland, New Jersey, the Virginias, and Washington, D.C. For more information, call 443.690.0403; e-mail [email protected]; visit www.hegra.org.