Complex determination of automatic robotic total stations' measurements' accuracy in underground spaces and comparison with results on the surface

Abstract

The total station is the most basic geodetic measuring instrument, locally the most accurate and versatile. Its accuracy is the cornerstone of its use and is defined by the standard deviations of horizontal direction, zenith angle and slope distance measurements. These accuracy parameters are given by the manufacturer, but these are only valid under optimum measurement conditions. To ensure the credibility and reliability of the measurements, these values must be periodically ascertained or determined for atypical measurement configurations or measurement conditions. Standardised procedures are used for this purpose, but in our opinion, they do not reflect the full influence of the measuring conditions and other measuring aids. A comprehensive determination of the accuracies (variation components) from the alignment, where all possible influences in a given situation are applied, may be considered the most appropriate for determining the angular accuracy of measurements. Such atypical conditions are certainly represented by geodetic measurements in the confined spaces of an underground mine. Thus, an experimental determination of the accuracy of four different robotic total stations was carried out at the Center of experimental geotechnics in a mine Josef teaching centre (CTU in Prague), and the Fӧrstner method was used to determine the variation components. A network of 6 stations and 8 target points was designed. The grid size was approximately 32x21 m with 4 - 31 m lengths. A network with the same configuration was also duplicated at the surface to assess whether the accuracy is different in underground and how the results will correspond to the accuracy claimed by the manufacturers. The result of the testing is that the accuracy claimed by the manufacturers is maintained even under such difficult measurement conditions in narrow corridors and with short sights. The overall evaluation also found that the accuracy achieved underground and on the surface is identical, although it varies from instrument to instrument.