The Institute for Geodesy and Photogrammetry at the ETH in Zurich (Chair
of Geodetic Metrology and Engineering Geodesy, geomETH) has deve-
loped a prototype of a new measurement system, based on the LMS Laser
Measurement System, for determining the dimensions of shaft caverns.
The solution is more precise and safer for personnel than conventional
manual measurement.

>> Steep descents through vertical hafts, dampness, dirt and unforeseen conditions – not many people enjoy entering shaft caverns. And it will also no longer be necessary thanks to the Cavern Measurement System (CMS) developed by ETH Zurich – to the relief of employees at civil engineering authorities or engineering and surveying companies.

Head first into the depths
Mounted on a rotary table, the LMS200 goes head first into the depths on a telescope support. When it reaches the bottom, it is turned through 360° to make the measurement. During the measurement, the measurement data of the LMS200 and the current position of the rotary table compared to the origin (zero point) are registered on a hard disk.

“Darkness, dark walls or damp concrete surfaces – nothing impairs the operation of this 3D measurement system,” enthuses Hans-Martin Zogg of the Institute for Geodesy and Photogrammetry at the ETH in Zurich. The practically relevant measurement range lies between 1 m and 30 m. The result of a roughly three-minute all-round scan by the LMS200 is a cloud of points consisting of more than one million individual measurement points. The level of detail of the cloud of points depends on the resolution of the 3D measurement system. Vertical resolution is fixed at 0.25° ,while the horizontal resolution is infinitely variable. Thus even the smallest of channels, or the rungs on the entry ladder, are clearly visible in the cloud of points. The evaluation software of the CMS then provides a 3D model of the shaft cavern.
The CMS has remained within its tight budget, not least because of the LMS200, making it interesting for potential purchasers such as civil engineering authorities, city departments of works, or surveying companies.