Tarn, France (May 23rd, 2016) — At the Rassisse dam on the Dadou River in southwest France, a Spectra Precision FOCUS 35 robotic total station has just completed monitoring the structural movements that occurred during recent major repairs and improvements to the dam. The FOCUS 35, with its one arc-second accuracy, was chosen to monitor to a half-millimeter accuracy movement of the arch dam abutments during a particularly critical six-week period in the construction project.
The Rassisse is an arch and gravity type dam 30 meters high and 300 meters across built in 1955 to impound water for hydroelectricity. The current engineering project to improve dam performance and ensure downstream safety included raising the dam height by 60 cm, reinforcing existing abutments and adding two new piano key spillways.
Raising the height of the dam was expected to cause the abutments to settle. To ensure that the abutments were settling properly and within expectations, the FOCUS 35 was positioned to measure XY movement. Eight survey points were selected. Four prisms were place on the existing parapet of the right abutment and four prisms on the reaction points of the left abutment. The survey points were measured and recorded at different steps in the project: before deconstruction, after deconstruction and before and after post-tensioning tendons. To ensure accuracy each prism was measured four times and averaged to produce a final result. Measurements were taken at each step, then five days and 10 days following each step.
The results of the measurements were communicated in real time to the contractor through an Excel file comparing the measured movement to the theoretical movement. The results enabled engineers to make critical go/no go decisions on whether to move further into the project. The final movement was less than a tenth of a millimeter, well within the expected acceptable value.
About the Spectra Precision FOCUS 35
The FOCUS 35 robotic total station moves the power of the observer from the instrument to the range pole to improve efficiency. Using the motorized drive it is possible to precisely turn to and repeat angle measurements. This results in quick and reliable measurements, which substantially increases productivity. The speed of observation and precise positioning is provided by the patented step drive technology of the FOCUS 35, which controls the horizontal and vertical motion of the motors, eliminating the need for traditional motion locks. The FOCUS 35 includes a tracking sensor that enables the instrument to constantly lock onto the prism. The FOCUS 35 is available in 1”, 2”, 3” or 5” accuracies and is controlled by the Spectra Precision Survey Pro field software using an onboard Windows CE touchscreen interface.
About the Spectra Precision Brand
Spectra Precision is an established brand known for delivering quality products to the construction market. Focusing on the specific needs of the conventional surveying market, the Spectra Precision brand offers a complete product portfolio including Global Navigation Satellite Systems (GNSS), Geographical Information Systems (GIS), optical total stations, data collection hardware, field and office software, as well as a wide range of construction tools.
Spectra Precision surveying equipment is an economical choice that utilizes technologies for optimal efficiency. With convenience and reliability as the foundation of the Spectra Precision brand, it is an ideal choice for value. The Spectra Precision brand is backed with the strong technical support that users have come to expect from a quality name in surveying and construction.
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