the HoloLens to visualize the finished project. The design work was done using Autodesk products and loaded into Trimble Connect for the field visualization. In reviewing lessons learned from the Midland County flooding, Lil- libridge said the effort confirmed what OHMAdvisors has been doing. The approach of using UAS to supplement traditional survey methods proved to be stable and efficient. MCRC’s Palmer emphasized the speed of the work. As the floodwaters receded, the commission set a goal to rebuild and reopen four key sites by the end of October. Palmer said that they completed the structure replacements with new GRS-IBS’ designed by OHMAdvisors. “I was amazed by the efficiency and professionalism of the OHM Advisors survey team,” Palmer said. “With minimal direction, they prioritized the areas to obtain data, collected data on multiple sites in one day and began delivering topographic data to the engineering design team in less than 72 hours. We then authorized data collection at additional sites and that information was delivered within three days. This allowed the engineering team to accurately assess the cost to restore nine road crossings, making our applications for emergency funds faster and more accurate.” The performance of OHM Advisors was recognized by the industry. The company received the 2018 Eminent Conceptor Award from the American Council of Engineering Companies and the 2018 Project of the Year Award from the Michigan Chapter of the American Public Works Association. Lillibridge credits OHM Advisors multiple technologies as the key to success. “Using a mix of technologies and methods is really beneficial in emergency situations. A lot of people think that traditional surveying is sufficient. But from a safety perspective, that’s not the best way. You can keep your personnel out of harm’s way, and because of the built- in efficiencies, you're able to provide solutions much faster than with traditional methods.”
Road repair plan developed from aerial image data.
Lillibridge also used TBC to check the accuracy of the aerial work. “For this project, our tolerance was 0.15 ft vertical,” he said. “But I cannot recall any being over a tenth in vertical difference. These proj- ects hit their checkpoints with minimal error.” Preparation of deliverables moved quickly. OHM Advisors’ in-house engineering teams reviewed the field data and developed plans for rebuilding or replacing damaged structures. The firm had previously worked with the county to develop a design for Geosynthetic Rein- forced Soil-Integrated Bridge System (GRS-IBS) that provides flexible design and low maintenance. They provided sizes for the replacement bridges and the county’s contractors could then mold the road to fit the structure. As a result, aside from re-verifying the control, OHM Advi- sors did not need to provide any construction surveying. Visual Confirmation As construction wrapped up, OHM Advisors used the opportunity to incorporate the Microsoft HoloLens 3D mixed reality headset. To do this, they exported design models from TBC to Trimble SketchUp soft- ware. Next, they used Trimble Connect to load the design data polylines into HoloLens along with a decimated version of the original washout surface model. In the field, they used Trimble Connect to orient to the site. They could then visually compare the finished conditions with the original surfaces. “It was really interesting on the HoloLens to see the base surface from when the washout occurred. The original data looked like a cliff in the new road where the washout had been,” Lillibridge said. OHM Advisors has used HoloLens, SketchUp and Trimble Connect on other projects as well, primarily for pre-construction design and conception. For example, they recently did a project for a community firefighter memorial. The client wanted to see how planned flagpoles impacted the park site and how the monument sizes would fit the park. OHM Advisors experts visited the site with local officials, each using
JOHN STENMARK is a writer and consultant working in the AEC and technical industries. He has more than 20 years of experience in applying advanced technology to surveying and related disciplines.
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may 2020
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