Dynamic Survey Gets Rolling

Dynamic survey and Lidar were the focus of a new track at SPAR 2007, Spar Point's fourth annual conference on 3D laser scanning, advanced dimensional control, and other new technologies for design, construction, and asset management, held this past March in Sugar Land, Texas. While aerial Lidar is far from new, today the core technologies—laser scanning, digital photography, inertial measurement and GPS—are being adapted to more and more platforms and applications. In addition to fixed-wing and rotary-wing aircraft, new systems are based on trucks, automobiles, railway cars, boats—we've even heard of a dirigible-mounted rig. Meanwhile more sensor types—laser bathymetry, ground-penetrating radar, and others— are being added to the mix.

The business drivers? Often they are cost and schedule. For DOTs, rotary- wing Lidar can deliver engineering-grade data over long highway corridors at higher accuracy than conventional fixed-wing Lidar, and much more cost-effectively than fixed-location terrestrial laser scanning. In other cases, the driver is safety; scanning a roadway from a truck moving at highway speed means no lane closures and no surveyors standing in harm's way. For the railroad industry, the safety dividend likewise extends to capturing rail and trackside data from a moving railway car; this information is needed for clearance analysis as well as asset management.

The investment may be justified by the requirements of a specific project, for example fast-track private-sector jobs. In the Fernald remediation project presented by Jim Schwing from Fluor Federal Services, aerial Lidar was the only way to survey radiologically contaminated soils quickly and safely enough to meet the cleanup timeline. Similarly, Bruce Strack from The Schneider Corporation revealed how a sophisticated blend of airborne Lidar, ground-based survey, and automated construction is enabling a new Honda North America plant to open on an aggressive schedule.

Another justification is the need for better asset management. This is the big driver for DOTs investing in these services and the reason that the Federal Highway Administration developed new patent-pending, multi-sensor measurement technology that it's preparing to license to the private sector for commercialization.

All these developments create new challenges in processing and integrating the data from these disparate sensor types and creating deliverables for specific disciplines. For firms expert in processing Lidar data, this is good news. The need is not only for service providers able to capture data from a variety of platforms but also those skilled in combining data sets from disparate sensor types. While some traditional Lidar businesses (public- sector topo markets, for example) compete more and more on price, the best Lidar service providers are already finding success in helping customers apply these new mobile data-capture technologies and work with the data they produce. The trend is toward a seamless capture-to-deliverable process; what makes it seamless is service providers' know-how.

Lidar Case Studies

Here's a roundup of the dynamic survey case studies presented at SPAR 2007:

Michael Trentacoste, director of safety R&D at the Federal Highway Administration (FHWA, Turner-Fairbank Highway Research Center, McLean, VA), showcased a new Digital Highway Measurement (DHM) system developed by the FHWA and soon to be available to the private sector for integration into the marketplace. For many highways— especially those developed over time from trails to multi-lane roads—information about road geometry, roadway/ roadside features, and subsurface conditions are simply not known. This is a big impediment to assessing and improving road safety and to road asset management. To remedy this, the FHWA's Office of Safety R&D developed a Digital Highway Measurement System that uses multiple technologies—laser scanning, GPS, inertial navigation, step-frequency ground penetrating radar—to collect and process this data, automatically creating data files without the need for human interpretation of video or other raw data sources.

Jim Schwing, chief surveyor at Fluor Federal Services (Richland, WA), detailed the value of Lidar in the 1050-acre Fernald Environmental Management Project. Lidar was used to monitor excavation of radiologically contaminated soils, track construction of a 2.5-million- cubic-yard disposal facility, provide volume calculations, and monitor environmental restoration activities. Schwing described how Lidar delivered hard-dollar savings over photogrammetry while enabling adherence to construction schedules. Without this technology, limited surveying manpower would have caused a slip in the aggressive cleanup schedule. Of course the safety benefit was key; aerial Lidar removed the field surveyor from hazardous areas that required topographic surveys.

Bobby Tuck, president of Tuck Mapping Solutions, Inc. (Big Stone Gap, VA), described using rotary-wing Lidar to deliver engineering-grade data at speeds formerly possible only for lower-accuracy, planning-grade data. Being able to provide engineering-grade data cost-effectively over long corridors aids highway construction; accurate elevation data helps eliminate costly change orders. Fixed-wing Lidar has traditionally yielded 2- to 3-foot accuracy, sometimes 1-foot under optimum conditions, according to Tuck, whereas rotary-wing Lidar can yield accuracy as tight as 1/10 foot. And helicopter-mounted Lidar can capture 600 to 1000 square acres per hour at 3- to 4-inch accuracy, a much more cost-effective proposition than ground-based scanning.

Bruce Strack, PLS, survey implementation manager at The Schneider Corporation (Indianapolis, IN), told how a new Honda North America manufacturing plant in Greensburg, IN will be able to open just 22 months after groundbreaking thanks to a multi-sensor, multi-technology project workflow. Airborne Lidar plus on-the-ground boundary and ATV topo surveys were used in due-diligence site studies. Then the construction phase employed robotic total stations, one-person GPS operations, and stake-less mass grading with machine control using more than two dozen excavating machines. This combination of technologies significantly reduced costs and boosted production to levels that some formerly thought nearly impossible, Strack reported. With the project currently ahead of schedule, Strack explained how these technologies made the difference.

Charles "Eddie" Wiggins, hydrographer with the Joint Airborne Lidar Bathymetry Technical Center of Expertise, U.S. Army Corps of Engineers (Kiln, MS), described coastal mapping using airborne Lidar and hyperspectral imagery to quantify the engineering, economic and environmental conditions of the nation's coast. This provides a fast and accurate method for measuring and monitoring coasts and for quantifying change such as that caused by hurricanes and natural processes.

Dr. Heinrich Höefler, deputy director and OFM department head at Fraunhofer IPM (Freiburg, Germany), described the institute's development of new high-speed, multi-sensor technology for 3D capture of trackside geometry from a moving railway car. The system uses two (optionally three) side-viewing laser scanners integrated with high-speed video, photogrammetry, laser triangulation technology, and a forward-view laser scanner. An odometer, DGPS module and inertial system provide absolute position data to within a few centimeters and a trigger signal for distance-based data recording.

About the Author

Bruce Jenkins is president of research at Spar Point Research LLC, Danvers, MA. Spar Point is a research firm founded in 2003 by Jenkins and Tom Greaves to investigate new technologies that improve the productivity, quality, and safety of work process for creating, modifying, and managing engineered products and constructed assets. SPAR 2008, the company's fifth annual conference, will take place March 3-5 in Houston, TX. For information visit www.sparllc.com.

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