For data accuracy and quality, a field team used a Trimble SX10 scan - ning total station to survey and mark 120 ground control points (GCPs) to provide control for the mobile mapping. A traffic safety vehicle pro - tected the ground crew as they marked and measured the GCPs with a transparent spray paint only visible to the MX9. After the two-day GCP process, they were ready for the data-collection drive. With the MX9 mounted on their 2m high vehicle, the team drove the highway in two directions, with each trajectory totaling 10km. As they traveled the highway at 80 km/hr, the system scanned structural features such as break lines, pavement edge lines, road and building signs and road markings––any feature within 50m of the side of the road––and captured panoramic and multi-angle photos every 5 meters. In two hours, they collected the entire point cloud of the 20km section. “A significant advantage of the MX9 is the so-called ‘butterfly con - figuration’ of its two lasers,” says Gröninger. “That unique position - ing enables them to scan ‘cross-wise’ and capture features that might otherwise be blocked. For example, if you’re driving on the highway and a car passes, if we have only one scanner, then we’ll have a shadow in the point cloud. But because the MX9 has two scanners, if one is blocked because a car passes, the other scanner will capture the points behind the car. It’s perfect for optimizing data capture.” In the office, a team used Trimble Business Center (TBC) software to integrate the GCPs with the scanning points to process the 30GB point cloud. From the 3D view, they extracted a host of features such as break lines, pavement edge lines, markings, crash barriers, and curbs and produced a more user-friendly vectorized dataset. In a final processing step, they created the centimeter-accurate DTM of the A93 highway, and then they delivered the vector dataset, the UAS images, and the DTM to the NBMD. “Many people think that they can only use one technology for a proj- ect, but that’s not true,” says Gröninger. “This project proved that you can combine mobile mapping with other technology to give clients a rich dataset. Having a 3D model of the highway can greatly assist the Directorate in designing the new roadway, and once construction is underway, mobile mapping will allow them to quickly and precisely acquire as-built data to support their progress.” Carrying out this pi- lot project will also put Strabag in a strong position to respond to the NBMD when it issues the official tender for the A93. Racking up kilometers In addition to demo projects, Strabag has been putting on hundreds of kilometers on the MX9 with numerous other transport infrastructure projects both in and out of Germany. They’ve taken it to planned construction sites to capture 3D measure- ments of existing sites and for calculating quantities, scanned build- ings, driven roads to produce DTMs of routes and buildings to support planning and BIM processes, and navigated railway lines with it. Austrian transport company, Graz-Köflacher Bahn und Busbetrieb (GKB), commissioned Strabag to use the MX9 to scan and measure a 51km long stretch of railway for a planned electrification of its route
network in Styria, Austria. To avoid disrupting rail operations, the point cloud needed to be collected at night. Mounted on to a special locomotive of the GKB, the system scanned all visible features, includ - ing those overhead along the track between Lieboch and Wies. The data was again processed in TBC and the 3D dataset was provided to the GKB to help simplify and inform the planning and design of the new electrical infrastructure that is scheduled to go into operation by 2024. “The ability of the MX9 to capture data at night gives us great flexibility for projects like railways where operations can’t typically be stopped,” says Gröninger. “And because it scans overhead, we can measure power lines, which are a very complicated to survey with a tachymeter.” Mobile mapping has enabled Strabag to successfully venture into new territories such as airports. Gröninger’s division has been on the ground floor of Munich Airport’s Terminal 1 expansion project, a €455 million undertaking that will construct a new pier and create a 95,000 sq m apron to accommodate six wide-bodied aircraft or twelve smaller aircraft. Before construction could begin, the lead engineering company needed a precise survey to retain an accurate as-found map of the existing space and its structures before it was demolished. The fieldwork began with setting out a network of GCPs across the 95,000 sq m concrete apron and measuring them with the Trimble SX10. A team used the MX9 to scan the whole area of interest, capturing all the buildings, markings, lights, signage and concrete joints and seams in one hour. They integrated the survey measurements and scanning points in TBC to produce the 3D model of the site, clearly showing the real-world view of the terminal’s infrastructure, from the smallest concrete joint feature to the tallest light pole. The point cloud provided the critical foundation for planning the massive construction project, the first phase of which began in July 2019. “Surveying such a large site with conventional methods would’ve required several days of work and added cost,” says Gröninger. “With mobile mapping, we collected all the needed field data in one hour. And there’s no question about data quality or choosing which features to measure because every object is contained in the detailed point cloud. If the MX9 can see it, it captures it. That gives us a lot of confidence and security in the field, which is particularly important on highway projects and airports where revisits are difficult.” As pressures to cut field time and reduce costs are as common as sur - vey tools them-selves, technology that enables crews to be nimble and productive, and keeps them safe, is a smart approach. Mobile mapping has proven to be a clever choice for Strabag as it drives them toward a long highway of success.
MARY JO WAGNER is a Freelance Writer, Editor, and Media Consultant based in Vancouver, BC. She can be reached at mj_wagner@shaw.ca.
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