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For example, the primary contractor decided to use components called 
“PCs Corbels”—adjustable elements that connect floor girders to the 
concrete load-bearing components. By using the PCs Corbels, it was 
possible to use self-climbing forms and rapid continuous pours to 
construct the concrete load-bearing elements and floor supports. The 
self-climbing technology works without additional cranes because it 
climbs independently by means of a hydraulic climbing system. But 
the increased speed of construction placed special demands on the 
surveying team. 

"Due to the lack of space on site, prefabricated concrete elements were 
installed directly from the delivery trucks,” Almesberger said. “This made 
a multi-shift operation necessary from 6 am to 10 pm, 6 days per week. 
In addition, special surveying tasks were required to watch for any 
deformation or unexpected motion of the building under construction.” 

IGL’s project managers Tina Sängerlaub and Alexander Stein had to co-
ordinate the on-site team of surveying engineers, technicians, assistants 
and a construction technician. "In order to meet the project’s survey 
demands and respond at short notice when required, we created five 
survey crews,” said Sängerlaub. 

Surveying equipment included four Trimble S6 robotic total stations 
with Trimble TSC2® controllers and two Trimble DiNi® 07 digital levels. 
The required accuracy for stakeout points was ±6 mm horizontal and 
±5 mm in height. "Controlling the total stations remotely via the TSC2 
controller significantly contributed to our fast, efficient measurements.” 
Sängerlaub said. “Instead of being at the instrument, we could work at a 
measuring point and quickly make necessary adjustments." 

The surveying tasks for the IGL team started with the erection of 
a geodetic control network of fixed points, created by transferring 
control from the TaunusTurm coordinate system into the building. On 
the basement floor, 12 points were determined using total stations and 
analysis software. Control points on the ground floor were set up and 
established as fixed points within the local construction site coordi-
nate system. These so-called “plumbing points” would be transferred 
vertically as the building rose. With the measurements complete, the 
surveyors could consider the field of points located on the building’s 
foundation (concrete slab) as positionally stable and avoided the ef-
fect of surveying variations in the geodetic fixed-point field. After that, 
continuous control surveys were carried out to check relative variations 
between points and to investigate and compensate for significant 
variations of the points.

Extending the local coordinate system to each new floor was necessary 
during the entire construction progress. Starting from the plumbing 
points on the ground floor, a surveying party transferred the horizontal 
coordinates by means of plumbing onto the respective working level. 
In addition, openings with a diameter of at least 15 cm (0.5 ft) had to 
be left in the concrete surface directly through the plumbing points 
and kept open during further construction progress. The introduction 
of reference planes every 50 m (160 ft) helped minimize the influence of 
surveying uncertainties in the progressing construction height.