Issue link: https://geospatial.trimble.com/en/resources/i/1397758
The Austrian Federal Railway's (ÖBB) Lower Inn Valley (LIV) railway will eventually connect southern Italy with northern Europe. The first operational section of the LIV prompted a tender for a high-precision, aerial as-built survey. An Austrian company used the opportunity to debut a multi-sensor, data fusion approach that not only proved its viability for alpine mapping, it has enabled the company to reap the rewards of an expanded service area, project portfolio, and revenue stream. overview Location AUSTRIA TRANSFORMING THE WAY THE WORLD WORKS TRANSFORMING THE WAY THE WORLD WORKS In 2016, ÖBB Infrastruktur AG contracted Vermessung AVT (AVT), a surveying company based in Imst, Austria to survey the 40-km section between the Austrian towns of Kundl and Baumkirchen (KB). Specifically, they had to measure the above-ground areas of the new line, the converted sections of the existing line and any objects within 100 m of the tracks themselves and produce an as-built survey with a vertical and horizontal accuracy of 2 cm. In addition to the challenging high precision, the tracks were lined by up to 6-m-high noise-prevention walls. To succeed, AVT needed to pair an aerial survey with mobile mapping, and they needed a software solution that could integrate the diverse data formats into one image processing software to create a seamless orthomosaic. MEASURING THE ALPINE To achieve consistently high accuracy over such a long distance, AVT first established a control network precise to 0.5 cm using 30 GNSS receivers and a static night survey. They also created a network of 50 ground control points (GCPs) at 2-km intervals around the 40-km area. After setting control, AVT flew over the area of interest (AOI) at an altitude of 450 m and collected 1,300 images with a ground sample distance of 2 cm and a 60 percent overlap. The average side overlap was 50 percent. Mounting a Trimble MX7 mobile imaging system on the roof of a small van, an ÖBB locomotive pulled the MX7 along the KB tracks. It captured a 30MP panoramic image every 4 m, acquiring important features such