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 Technology&more

Herzog+Mandt GmbH to develop a better and more effective 
solution. The goal was to have automated tracking with 
measurements at timed intervals. 

The solution was a Trimble S8 robotic total station with 
Trimble VISION technology and a Trimble MultiTrack™ target. 
Mandt was confident: “If we use all our surveying aids and 
instruments to their full capabilities, we can achieve excellent 
technical results.”

As the gondolas travel across the river, they are separated by 
roughly 160 m (525 ft). A critical parameter in evaluating the 
results is the lowest point of the trajectory above the water. The 
weight of adjacent gondolas had no measurable effect on this 
point, and neither did cable length, which can vary according to 
temperature conditions. The temperature was recorded but no 
correction applied as the cables can be hydraulically tensioned 
at the return wheels of the top and bottom stations.

In order to carry out measurements, a gondola was loaded at 
the top station of the cableway with a weight of 2,800 kg 
(6,300 lbs), corresponding to the maximum permitted number 
of 35 people. After a brief start-up at the top station, the prism 
was fixed to the bottom of the gondola using a magnetic 
base and extensions. Since the gondolas are constructed of 
aluminum, an opening in the bottom of the gondola floor was 
used to access steel beams where the team could attach the 
magnetic base with the prism.

The gondola was then moved beyond the top support until it 
was above the east bank of the Rhine, where it was stopped. 
From this point on, the prism could be measured once per 
second over a length of 500 m (1,640 ft) to a point over the 
west bank of the river. “It was fascinating to see how the total 
station automatically tracked the target as far as the support 
at the valley station on the west bank of the Rhine,” observed 
Frickel. “We could even see the survey results displayed on 
the controller. The Trimble VISION technology built into the 
S8 enabled images to be combined with the georeferenced 
measurements recorded.” Even with the moving gondolas, the 
measurements met the required accuracy of 1–2 cm (0.4–0.8 in).
By capturing images during the survey, the team could overlay 
the survey data and confirm while still in the field that the data 
was correct and the instrument had accurately tracked the 
moving gondolas. 

With UNESCO extending operational approval until 2026, the 
transit path will be measured every year. Trimble VISION enables 
complete image documentation of data, which can be referred 
to in the event of safety questions. Each point is georeferenced 
and can be subsequently checked in the office. The photogram-
metric functions in Trimble Business Center software also allow 
additional detailed data to be extracted without additional 
need for field visits.