Terrestrial Laser Scanning in Monitoring of Hydrotechnical Objects

Abstract

Developing Terrestrial Laser Scanning technology is provided by modern measuring instruments, i.e. total stations and laser scanners. Owing to these instruments, periodic control measurements of concrete dams carried out as a part of geodetic surveying provide point models characterised by quasi-continuity. Basing on the results of these surveys, it is possible to conduct a number of geometric analyses, as well as to obtain information for detailed analytic and calculative deliberations. A scanner, similarly to a total station, determines spatial coordinates (X, Y, Z) of the surveyed points by identifying distances and angles. Registration of intensity of the reflected laser beam (Intensity) sent out by the scanner provides additional information on the surveyed object. Thanks to high working speed and a large amount of collected data, scanners have become an essential tool for a geodesist.This paper evaluates the possibility of applying Terrestrial Laser Scanning to test deformations and shifts of flagged points of concrete dam construction based on experimental measurements, including object inventory and evaluation of the dam's concrete structure condition.

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

“…Due to the different nature of data in TLS and ALS, this article concentrates on using data from TLS. TLS is used in many fields, including engineering surveying [7] and recent developments show its suitability to control deep excavation supports [8].…”

“…This aspect poses a great advantage over conventional, classic measurement methods such as tacheometry [10]. Having a point model characterized by quasi-continuity at one's disposal, one may carry out a number of geometric analyses in post-processing as well as obtain information for further, detailed analytical considerations [7]. The fact that the aforementioned analyses may be carried out in any place of the scanned/measured facility, and notas in the case of classic methodsonly in locations for which the measurements were performed, constitutes an unquestionable advantage.…”

Implementation of virtual reference points in registering scanning images of tall structures

“…Among its advantages, one should definitely point out the ease and speed of use (up to 1 million points per second); precision (up to mm level accuracy) with a high point density, noninvasive, and remote character of the measurement (also in very low light conditions); and the possibility of remote operation (especially important in life-threatening or healthendangering conditions). All these contribute to the fact that the TLS technique is now applied in as built surveys of buildings and structures for the purpose of documentation of their existing condition and checking compliance with the project [1][2][3][4]; creating the precise 3D models of structures of various types for design purposes [5]; documenting historical objects [6,7]; or destruction, deformation, and monitoring of engineering constructions and excavations [3,6,[8][9][10][11][12]; surveying of tunnels and rail tracks [13]; calculating volumes; applying building information modeling (BIM) [1,2]; monitoring the stability of the earth's structures [14]; and geotechnical and geological mapping in mining.…”

“…Making uniform and precise 3D models for large and complex building structures always involves the necessity of acquiring adjacent scans from multiple locations. As a consequence, we face the problem of proper registration of individual scanning images, which has been widely discussed in many publications [2,8,[15][16][17].…”

The use of evolutionary algorithms for designing an optimum structure of a geodesic measurement and control network

“…Displacement or deformation monitoring may be required for both existing and new buildings, adjacent buildings, as well as for ground or groundwater (water table). The determination of displacements and deformations, both with classical methods, GNSS methods and by laser scanning, should be preceded by an analysis of the existing field conditions (also with the participation of GIS tools [2]) and selection of a suitable structure for the measurement and control network set up on the object [3,4,5]. In the case of construction work, which requires displacement or deformation monitoring, the following should be specified in particular:  the measurement method, including the measurement equipment that will be used for determining displacements,  the frequency of measurements and assessment of their accuracy,  the method for presenting data results,  the location of observation stands (horizontally and vertically),  the frequency of checking the stability of the observation stands and reference points during the construction work and after its completion.…”