Sensitivity analysis of control networks in terms of minimal detectable displacements

[EN] Sensitivity analysis is one aspect of the calculation process in displacement measurement. For this purpose, sensitivity measures are used in the form of minimal detectable displacements ( ), derived from the definition of minimal detectable bias ( ). Analyses were performed based on disturbing the parameter vector with the  value (calculated from principal component analysis). Analyses were considered for displacements of the levelling network based on the global vector ( ). The calculations were conducted using the least squares adjustment with pseudo-random observations. The mean success rate ( ) was used to perform the detection analyses. The effectiveness of the global test agrees with the assumed power of the test. Local tests for a single point showed 48.6 % displacements of more than one point. It should be considered using another local test for the case of displacements of multiple points. This study concludes that in addition to the accuracy of the designed network points, the network configuration is also important in sensitivity analyses. The research shows that sensitivity analyses should be considered at the design stage of control networks, i.e. to determine at what level a given network is able to detect displacement.Książek, K.; Łapiński, S. (2023). Sensitivity analysis of control networks in terms of minimal detectable displacements. Editorial Universitat Politècnica de València. 477-483. https://doi.org/10.4995/JISDM2022.2022.1392147748

Multi-temporal survey of diaphragm wall with terrestrial laser scanning method

The development of measurement technologies allows for acquiring various data. The Terrestrial Laser Scanning (TLS) technology is frequently combined with classic geodetic measurements – tacheometry or levelling. This article presents a process of the diaphragm wall monitoring during excavation supported with a top-down method. The construction technology applied required proper planning and performance of measurements in difficult construction site conditions in the city centre. TLS allowed for limiting works at daytime and performing monitoring during the night break in works at the construction site as well as limiting the impact of the subsoil process vibrations on the values of displacements and deformations determined. The authors present a comparison of the results of displacement and deformation measurements with a terrestrial laser scanning and tacheometric measurement method. The possibilities of using the data acquired, among others, for the indication of filtration areas, spatial surface deformation analyses and assessment of the wall execution compliance with the design are presented. The analyses carried out show that the TLS may be used in the investment process from the very beginning, being a component of the Building Information Modelling (BIM)

Glacier Geometry Changes in the Western Shore of Admiralty Bay, King George Island over the Last Decades

This paper presents changes in the range and thickness of glaciers in Antarctic Specially Protected Area (ASPA) No. 128 on King George Island in the period 1956–2015. The research indicates an intensification of the glacial retreat process over the last two decades, with the rate depending on the type of glacier front. In the period 2001–2015, the average recession rate of the ice cliffs of the Ecology Glacier and the northern part of the Baranowski Glacier was estimated to be approximately 15–25 m a−1 and 10–20 m a−1, respectively. Fronts of Sphinx Glacier and the southern part of the Baranowski Glacier, characterized by a gentle descent onto land, show a significantly lower rate of retreat (up to 5–10 m a−1 1). From 2001 to 2013, the glacier thickness in these areas decreased at an average rate of 1.7–2.5 m a−1 for the Ecology Glacier and the northern part of the Baranowski Glacier and 0.8–2.5 m a−1 for the southern part of the Baranowski Glacier and Sphinx Glacier. The presented deglaciation processes are related to changes of mass balance caused by the rapid temperature increase (1.0 °C since 1948). The work also contains considerations related to the important role of the longitudinal slope of the glacier surface in the connection of the glacier thickness changes and the front recession