The MX7 captured a 30MP panoramic image every 4 m along each of the tracks and acquired important features such as switching boxes that were not visible in the aerial photogrammetry.
DAT/EM Summit Evolution (DSE) software to create a 3D vector map of all railway-related features. The map was customized and finalized in AutoCAD. In parallel with the aerial mapping, a team processed and precisely georeferenced the MX7 imagery to map objects that couldn’t be seen in the aerial images. They first determined the path of the MX7 using the accurate GNSS/INS data recorded during the ride. They manually selected several hundred 3D points that had been determined as multi- ray TPs (aerial GCPs) within Match-AT, and used them to orient the MX7 images to ensure the maximum consistency between the aerial
and mobile-mapping data. They then extracted and mapped the mo- bile-mapping objects and exported the results to AutoCAD to produce the finalized 3D vector map showing the specific layers and symbols defined by the ÖBB. To process the aerial Lidar data, personnel extracted approximately 300 horizontal patches, or surface sections, from the data and determined the mean height and standard deviation per patch. They imported this data into Match-AT as vertical-only GCPs with a 2.5 cm standard de- viation. The ground points were used to process a digital terrain model and to derive height isolines, the latter of which were integrated into the 3D vector map. When both the 2D orthomosaic and 3D vector map were delivered to the ÖBB, the authority conducted several independent evaluations to assess the quality and accuracy of the datasets. AVT’s results were given full approval. “This was such a satisfying achievement,” says Legat. “The project proved that with the right tools and approach, incredibly precise photogrammetry-based maps can be produced for the difficult alpine environment. More importantly, it has raised the profile of our multi- sensor fusion technique and given us the confidence to pursue similarly challenging projects.” The successful proof-of-concept has indeed led to further work with the ÖBB and piqued the interest of other organizations who service al- pine communities. AVT is using the same flight data to support ÖBB’s needs on the LIV railway, and an Austrian electricity provider wants the company to map its electrical network at a horizontal and vertical accuracy similar to the KB railway. It’s a safe bet that for the next high-precision mapping project, AVT’s plane and its crews won’t be carrying the same amount of uncertainty or risk.
MARY JO WAGNER is a Freelance Writer, Editor, and Media Consultant based in Vancouver, BC. She can be reached at mj_wagner@shaw.ca.
The Trimble MX7 captured ancillary features not visible from the plane.
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