Bridge over troubled water - Using laser scanning to capture the new Höllentalklamm (Hell’s Gorge) bridge in the German Alps

Author: Thomas Schock

The Höllentalklamm - in English “Hell's Gorge” - near Garmisch-Partenkirchen is a unique natural spectacle 1,000m high in the German Alps. It’s part of the hiking route to the Zugspitze peak, a connection only made possible due to a historic bridge across the gorge, built in 1905. Due to its age and deterioration, the bridge and several footbridges had to be replaced in 2020. The local members of the德语Alpine Association (DAV)raised money for the 250,000-euro project and found two crucial corporate sponsors – the transport infrastructure specialistsZüblin / StrabagandThyssen-Krupp.

A Leica Geosystems partner, STRABAG used a laser scanning solution to capture the new bridge digitally. The survey was a demonstration of the scanners ability to perform even in this ‘hellish’ environment. The digital plans created will be used for future maintenance.

取代历史悠久的桥梁

从1902年到1905年，峡谷上第一座桥梁的建设花费了600个工作日。工程的一项令人印象深刻的壮举，几乎是手工完成的，没有电或现代机械。如今，直升机至少可以以104.5m的速度运送到Höllental入口。从那里开始，由苏布林 /斯特拉巴格工程师组成，当地建筑公司FlorianDörfler和Dav志愿者需要将组件拖到200m外的建筑工地。为了将重量超过四吨的桥运送到狭窄的峡谷中，分为大约600个单独的零件。定制的桥梁和人行道元素是由祖布林在勃兰登堡Hosena的结构性钢铁制品细分进行了预制的。

Despite almost perfect preliminary planning, a few obstacles were inevitable. Removing the rock where the bridge supports were anchored proved to be significantly more difficult and time-consuming than expected. Nevertheless, the build took only four weeks. ZÜBLIN site manager Philipp Schön sums up, “The preparations and finally the execution of this sponsorship project against the very special backdrop of the Höllentalklamm was really fantastic. The teams from the various project participants worked wonderfully together, like pieces of a well-oiled machine.”

A portable, robust and highly accurate laser scanning solution

Once the bridge was replaced, Philipp Mielke, Technical Group Manager at STRABAG with Johannes Zettel, Marketing and Thomas Schock from Leica Geosystems used both theLeica RTC360andblk2go使用激光扫描捕获新拱桥的数字双胞胎。

RTC360在高度便携的同时提供了干净且高度准确的点云。实际上，它与碳三脚架一起安装在背包中，并从停车场远足到峡谷。它也很健壮-IP54额定值，因此能够应对水的溅水 - 非常适合湿山环境。

The BLK2GO is a handheld imaging laser scanner that recreates spaces in 3D as you move. The operator - Schock - was able to carry it in one hand and scan while walking, making it easy to stay balanced and aware of hazards on the slippery terrain. The software used to process the data wasLeica Cyclone寄存器360,Leica Cloudworx,Leica Truview EnterpriseandLeica Cyclone 3DR.

From bridge capturing to data sharing

使用RTC360 Schock进行扫描five viewpoints: three scans were taken on the bridge, two on either side from 50m away, looking towards it. This created a picture of both the bridge and the rocks of the narrow gorge on all sides. HDR images were taken with the scanner at five exposure stops to allow for an RGB inspection for dark areas (tunnels) and bright areas (those in full high-altitude sunlight). Speaking about the unusual conditions, Schock says, “Surefootedness and a head for heights are required in the Höllentalklamm! But the ascent was quickly mastered with the lightweight RTC360.”

Schock使用BLK2GO手持式成像激光扫描仪，完成了大约10分钟的几次步行，覆盖了桥的每一侧的150-200m地形。这是在连接区域的足够重叠来完成的，以允许将连续的轨迹与旋风寄存器360的Cloud2Cloud算法联系起来。

Following scanning, Cyclone REGISTER 360 was used to import, prepare and optimise the data to deliver a LGS data set to use in other Leica Geosystems and third-party applications. TruView Enterprise was used for visualisation, a quick and easy way to share point cloud data with others involved in the project, and Leica Cyclone 3DR will be used to mesh the data for the gorge and tunnels.

即使在“狭窄和约束条件”中，令人印象深刻的结果

Höllentalklamm桥项目是放置最新的理想机会Leica Geosystems3D laser scanning equipmentto the test. Although the location was hard-to-access and the weather conditions were challenging, the laser scanners were as easy-to-use there as they would be at sea level.

Schock says, “Both scanners performed as expected and the results exceeded expectations.” Philipp Mielke from STRABAG agrees, “Results of the bridge scan using the RTC360 were very good. We had no problems in scanning the bridge even in these cramped and constrained conditions.” The company is already using the RTC360 in other tunnel and construction projects and further tests with the BLK2GO are currently in progress or planned.