Abstract
Currently, trigonometric levelling is becoming increasingly widespread, mainly due to the increase in accuracy of stations that can measure angles with seconds and distances with submillimetre accuracy. The paper deals with the analysis of the sources of errors affecting the accuracy of results. It also describes a design of observational methodology that excludes or significantly reduces the impact of systematic errors or other errors occurring during the measurements process, in order to achieve the highest accuracy of the determined height difference. Therefore, under certain conditions, it is possible to achieve the accuracy of determining a height difference of up to 0.10 mm using this method. Furthermore, by the practical example, the description of the use of trigonometric levelling from the centre when verifying the floor planarity of a 5-storey monolithic building is also presented in the paper. The skeletal structure made of concrete floors supported by beams is the main structural element of the building. The finished floors showed visible deformations. Therefore, before the continuation of further construction, the control height measurement of all above-ground floors was necessary in order to ensure the safety in terms of stability and subsequent correction of the project. The resulting floor planarity is graphically visualised and analysed.
Highlights
In engineering works, the determination of height differences between points or the determination of heights of points in national or local vertical datums is required very often
Trigonometric levelling is mostly used for measurement of heights of points that have a significantly different heights, or points that are located in hardly accessible places, where the use of geometrical levelling would be uneconomical
Significant differences in the comparison of results from trigonometrical measurement of heights and geometrical levelling can result from the accumulation of effects of random errors, incomplete elimination of systematic errors and neglect, or only partial elimination, of errors resulting from physical properties of the environment
Summary
The determination of height differences between points or the determination of heights of points in national or local vertical datums is required very often. These measurements are required for residential, administrative or industrial buildings, waterworks, or various line constructions like motorways, railways, sewers and pipelines. Measurements of heights (or levelling) can be divided into geometrical, trigonometric, hydrostatic, barometric and GNSS levelling. Trigonometric levelling is mostly used for measurement of heights of points that have a significantly different heights, or points that are located in hardly accessible places, where the use of geometrical levelling would be uneconomical Deng, & Luo, 2005; Zhou & Sun, 2013)
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