During the last decade the IGMS Measurement Lab was established at the TU Graz. The laboratory is climatically controlled with a temperature of 20.0°C ± 0.5°C and a humidity of 50% ± 10%. Its size is 33m in length, 6.5 m in width and 3.5 m in height. Its foundation is separated from the whole structure of the building. A field of 10 steel pillars is used in experiments and student labs for the setting up of equipment and for geodetic measurements.
Fiber optic sensor testing facility
Currently, there are no commonly used international standards for fiber optic sensing and thus it is difficult to evaluate system performance and state the uncertainty of measurement results. Therefore, we developed a unique fiber optic calibration facility which is used for the investigation of fiber optic sensors and systems.
One of the calibration facilities in the GML is the vertical comparator which is used for the system calibration of digital levelling systems, i.e., calibration of the coded staff together with the digital level. On the comparator a levelling staff is mounted in the position of use, i.e., vertically. To be able to calibrate 3 m long invar staffs, it was necessary to extend the laboratory using two shafts to house the 6.5 m high frame and the carriage on it. The carriage with the mounted staff is moved under the control of a laser interferometer (HP10889B) to all positions where the readings with the digital level are carried out. The level can be positioned on a concrete bench, and the sighting distances can be chosen from 1.5 m to 30.0 m. In the GML the staff illumination is achieved by special light bulbs, radiating light in the range of the maximum spectral response for any of the four types of digital levels.
Horizontal comparator and total station testing
Another calibration facility in the IGMS Measurement Lab is the horizontal comparator which is used for the calibration of EDM instruments (cyclic errors). The motor-driven carriage carrying the reflector of the EDM is moved on a 30 m long concrete bench. Again the position of the carriage along the bench is controlled using the laser interferometer. Both, the vertical and the horizontal comparator, are connected to a PC which controls the motion of the respective carriage, records the level or EDM readings, and performs all data processing. Therefore the calibrations are accomplished automatically. Besides EDM calibration we also perform investigations of geodetic prisms and how their construction and orientation can adversely affect distance and angle measurements.