By Mary Jo Wagner Driving Efficient Data Capture – Literally
so there’s no need for follow-up visits or rework. Additionally, the technology enables you to collect data in traffic over long distances. A convention-al surveyor, for example, would need about three weeks to measure a 50-km highway. With mobile mapping, we can set ground control points, drive that highway and process the 3D data in about a week––the driving itself would only take two hours. It’s a great tool for construction, as-built surveys and rapidly changing sites.” Strabag purchased the Trimble MX9 mobile mapping solution, a field- to-finish system that combines high-density laser scanning, a spherical camera for panoramic and multi-angle imagery, and a high-precision Applanix GNSS IMU (inertial measurement unit) component. All sen - sors are time synchronized with precise GNSS time tags and are linked to the trajectory that is recorded with the GNSS/IMU subsystem. This synchronization allows all recorded points and images to be properly aligned in a post-processing step. “We trialed other systems that only offer one laser scanner,” Gröninger says. “If you drive 100 km/hr with one laser scanner, you get a less- dense point cloud, which makes it difficult to extract features like the edge of a curb. The MX9 provides two laser scanners that each capture one million points per second. That gives us an incredibly high-density point cloud. It’s also quite compact and lightweight, which makes it easier to set up.” Since acquiring the MX9 in late 2018, the company has wasted little time in getting it on the road, establishing efficient workflows for col - lecting and processing the geospatial data and building its 3D mobile mapping business––both in responding to tenders and proactively creating work opportunities through demonstrating the technology’s capabilities. Mapping the highway One of those educational opportunities came soon after Strabag began using the MX9. The Northern Bavaria Motorway Directorate (NBMD) was planning to renovate a highway near Regensburg; Gröninger’s division saw a chance to show the public authority how a mobile map-ping, multi-sensor approach could be of benefit in designing and constructing the new highway. “Part of our job is to educate existing and new clients on what new tech- nologies can do for them, and in particular, how multiple technologies can be integrated for surveying and design projects,” says Gröninger. “So we went to the Directorate and offered to map the highway seg - ment planned for renovation using a mobile mapping system and UAS to show them the data and the benefits of the technologies.” Intrigued, the NBMD launched a pilot project, tasking Strabag to scan and collect imagery of a section of the two-lane A93 highway and create a DTM with an absolute accuracy of 1.5 cm horizontal and 2 cm vertical. Covering a 20-km stretch, they would also pair the 3D mapping data with UAS imagery that captured features 200 m either side of the highway.
When it comes to surveying for road construction projects, speed mat- ters. Surveyors need speed to be efficient in the field and to reduce costs. But the speed of cars racing by matters too––particularly in Germany where there are no speed limits on some Autobahn sections. Here, surveying is not for the faint of heart. International construction company Strabag AG is well-versed in col - lecting survey measurements along active highways. “It can be quite unnerving to capture ground measurements when cars are racing past you at 150 km/hour,” says Thomas Gröninger, division manager of digitalization in Strabag’s office in Regensburg, Germany. “Transport infrastructure projects challenge us to acquire precise field data as efficiently as possible while protecting our crews’ safety. Most con - ventional methods still require us to close roads or re-route traffic to safely work, which adds time and cost to projects. And it’s difficult to get permission to fly drones over highways. Ideally, we’ve needed a system that would allow us to be safely on the road.” Enter mobile mapping. Strabag viewed vehicle-mounted 3D mobile mapping technology as a promising solution to allow crews to work in traffic, giving them the tool to acquire centimeter-grade spatial data at highway speeds without sacrificing data quality or the crews’ welfare. One year after first mounting its system, the mobile spatial imaging technology has not only become a needed complement to its traditional survey instruments and unmanned aerial systems (UAS), it’s helped Gröninger’s division redefine the business of road and railway proj - ects, discover new applications for mobile mapping, and steadily drive According to Gröninger, the case for acquiring mobile mapping tech - nology crystalized in 2018. The company had become focused on inte - grating BIM into its roadway projects –– both by choice and by request –– which require frequent measurement updates for planning and for monitoring construction progress. Crews were not only challenged to collect that information on a weekly, and sometimes daily basis with their conventional survey methods, they were also at risk each time they returned to the roadway. With its reputation for delivering complicated transport projects on time and on budget, Gröninger says they needed technology that would allow teams to keep up with the breakneck pace of their design/build assignments. “Mobile mapping can be used to map everything in your path, enabling you to extract features and objects whenever you need them,” he says. “All of the features are in the point cloud and imagery, them toward new opportunities. The case for mobile mapping
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august 2020
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