The determination of geometric changes within an area or object of interest by means of repetitive surveys at different points in time is referred to as geodetic deformation monitoring. Despite its development in the early years of the twentieth century the original processing chain remained identical in essence until now. It contains the choice of suitable viewpoints, observation of at least two so called epochs, transformation of all epochs into a common coordinate system and finally the actual monitoring of deformations. In order to acquire an area under investigation discrete points of interest have to be physically signalised. Thereby repetitive observations can be achieved throughout the epochs. Downsides of this approach are among others the time consuming necessity to signalise the area under investigation as well as the “blindness” against deformations that occur outside the scope of the interest points. The emergence of terrestrial laser scanners (TLS) into engineering geodesy around the turn of the millennium led to a paradigm shift that allows to observe an area under investigation in a quasi-laminar fashion without the need of signalising points within the object space. Through this, all deformations can be revealed in principle that occurred in between two epochs within the area under investigation. Based on the already mentioned process chain of geodetic deformation monitoring the contribution at hand initially compares methodical differences as well as parallels among established approaches and terrestrial laser scanning. This results in several unsolved problems that are treated as research questions in this thesis. A substantial preparative step for geodetic deformation monitoring is the choice of suitable viewpoints from an economic perception and under the perspective of engineering geodesy. As existing methods for this task are not directly transferable to TLS, a novel combinatorial search algorithm is proposed and exemplified. Furthermore, a stochastic model for terrestrial laser scanners is introduced that uses intensity values of the received laser signal as an input and allows to predict the theoretical precision of observations from a certain viewpoint. A vital task in deformation monitoring under the assumption of a congruency model is the transformation into a stable reference frame. Only if this prerequisite holds, occurred deformations can be correctly identified and consequently quantified. For the case of observations onto signalised, discretely observable targets, for instance by tacheometry, several methods have been developed in the past in order to reveal sets of congruent points respectively points that were subject of deformation, so that this problem domain can be seen as solved. If one now transforms this problem to TLS then it can be established that areas where deformation occurred have to be identified and rejected from computing transformation parameters between epochs. A look at current literature on TLS based deformation monitoring shows that nearly all researchers imitate the tacheometric line of action by deploying artificial targets which have been designed for laser scanners. Through this a beneficial characteristic of TLS is neglected namely the enormous information density within the object space that can be used to compute transformation parameters. For the until then unsolved problem of automatically distinguishing stable and deformed regions in datasets which have been captured by TLS two algorithms are proposed. The performance of these implementations is tested regarding their robustness and other criteria, based on practical data. Furthermore, a method for determination of statistically significant deformations in TLS-datasets is introduced. Through this, the subjective choice of arbitrary thresholds for quantification and visualisation of deformations is counteracted. Finally, a procedure for visualisation of deformations within the object space is presented that simplifies the now and then abstract interpretation of the outcome of deformation monitoring.


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    Titel :

    Terrestrial laser scanning for geodetic deformation monitoring


    Weitere Titelangaben:

    Terrestrisches Laserscanning für die Geodätische Deformationsmessung


    Beteiligte:
    Wujanz, Daniel (Autor:in)

    Erscheinungsdatum :

    2016



    Medientyp :

    Sonstige


    Format :

    Elektronische Ressource


    Sprache :

    Englisch



    Klassifikation :

    DDC:    629