Image Assisted Total Stations for Structural Health Monitoring—A Review

Measuring structures and its documentation is one of the tasks of engineering geodesy. Structural health monitoring (SHM) is defined as a periodic or continuous method to provide information about the condition of the construction through the determination of measurement data and their analysis. In SHM, wide varieties of sensors are used for data acquisition. In the following, the focus is on the application of image assisted total stations (IATS). The combination of tacheometry and photogrammetric measurement offers high flexibility and precision. Different approaches of automated detecting and matching whose applications have been tested in practice are briefly explained. A distinction is made between built-in cameras (commercial) and external camera systems (prototypes). Various successful applications of IATS in the field of SHM are presented and explained.

Applicability and Analysis of the Results of Non-Contact Methods in Determining the Vertical Displacements of Timber Beams

Determining the displacements and consequent deformations of structures is a demanding branch of engineering. Displacements are most often determined by geodetic methods, among which high-precision non-contact methods have recently taken the lead. Engineering geodesy is an indispensable part of construction projects. In the desire for efficient and fast measurements, the technology of terrestrial laser scanning (TLS) and the use of robotic total station (RTS) and other geodetic methods are becoming more and more useful for engineers. In the presented study, we focused on the measurement and comparison of vertical displacements with various mentioned equipment and the determination of the influence of meteorological conditions on the displacements of timber beams that we used to perform the experiment. Measurements were performed both in the laboratory and outdoors. A novelty in the work was the use of a TLS scanner to determine the evaluation of small value displacements and the analysis of the usability of geodetic measuring equipment. In the Materials and Methods section, we describe the equipment used and the characteristics of the beams. The Results section describes the experimental outcomes, which include the performance of experimental analysis of vertical displacements of timber beams under different meteorological conditions. Altogether, the results consist of geodetic measurements and the processing of measured data. The results of measurements of vertical displacements with a terrestrial laser scanner were compared with the results obtained with a robotic total station were evaluated and compared with the displacements calculated from static analysis and the results of other methods used.

Application of laser scanning for monitoring condition of buildings and structures during reconstruction

Ground-based laser scanning technology has been increasingly used in the last 15 years to solve problems not only in engineering geodesy, but also in the inspection of buildings and structures, in particular to identify damage and deformation during operation and reconstruction, as well as operational control of construction. and monitoring of their condition during operation, 3D-modeling of complex architectural objects. The growing popularity of laser scanning is due to a number of advantages provided by the new technology in comparison with other measurement methods. Among the advantages are the main ones: increasing the speed of work and reducing labor costs. The emergence of new more productive models of scanners, improving software capabilities allows us to hope for further expansion of the scope of ground-based laser scanning. Three-dimensional laser scanning emits millions of laser beams and, by calculating their return time, can accurately and accurately calculate their three-dimensional locations to make multiple high-speed scans combined into one system. This works by digitally recording the dimensions and spatial communication of objects by reflecting laser radiation.

MOUNTING CALIBRATION OF A MULTI-VIEW CAMERA SYSTEM ON A UAV PLATFORM

Multi-view camera systems are used more and more frequently for applications in close-range photogrammetry, engineering geodesy and autonomous navigation, since they can cover a large portion of the environment and are considerably cheaper than alternative sensors such as laser scanners. In many cases, the cameras do not have overlapping fields of view. In this paper, we report on the development of such a system mounted on a rigid aluminium platform, and focus on its geometric system calibration. We present an approach for estimating the exterior orientation of such a multi-camera system based on bundle adjustment. We use a static environment with ground control points, which are related to the platform via a laser tracker. In the experimental part, the precision and partly accuracy that can be achieved in different scenarios is investigated. While we show that the accuracy potential of the platform is very high, the mounting calibration parameters are not necessarily precise enough to be used as constant values after calibration. However, this disadvantage can be mitigated by using those parameters as observations and refining them on-the-job.

METHODS OF ENGINEERING AND SURVEYING WORKS FOR CREATING A 3D MODEL OF ARCHITECTURAL OBJECTS

Currently, geospatial 3D modeling is one of the modern ways to represent digital geodetic data on the size and shape of the objects under study. However, the publication of requirements and recommendations in methodological and regulatory documents describing the use of laser scanning in engineering-geodesy, as well as methods for analyzing the accuracy of the obtained measurements, today, significantly lags behind the market demand. In this regard, we propose an experimental technique that allows conducting field work using a robotic electronic total station Trimble SX10 with a laser scanning function and identify measurement errors, followed by an analysis of the influence of external and internal factors of deterioration in the quality of the data obtained, for example, facade surveying and creating a united 3D model of the Assumption Cathedral, located in Omsk.

Adjustment models for multivariate geodetic time series with vector-autoregressive errors

In this contribution, a vector-autoregressive (VAR) process with multivariate t-distributed random deviations is incorporated into the Gauss-Helmert model (GHM), resulting in an innovative adjustment model. This model is versatile since it allows for a wide range of functional models, unknown forms of auto- and cross-correlations, and outlier patterns. Subsequently, a computationally convenient iteratively reweighted least squares method based on an expectation maximization algorithm is derived in order to estimate the parameters of the functional model, the unknown coefficients of the VAR process, the cofactor matrix, and the degree of freedom of the t-distribution. The proposed method is validated in terms of its estimation bias and convergence behavior by means of a Monte Carlo simulation based on a GHM of a circle in two dimensions. The methodology is applied in two different fields of application within engineering geodesy: In the first scenario, the offset and linear drift of a noisy accelerometer are estimated based on a Gauss-Markov model with VAR and multivariate t-distributed errors, as a special case of the proposed GHM. In the second scenario real laser tracker measurements with outliers are adjusted to estimate the parameters of a sphere employing the proposed GHM with VAR and multivariate t-distributed errors. For both scenarios the estimated parameters of the fitted VAR model and multivariate t-distribution are analyzed for evidence of auto- or cross-correlations and deviation from a normal distribution regarding the measurement noise.

The Regulative Use of the Ideas

This chapter examines Kant’s thesis that the Ideas of Pure Reason, and especially the Ideas of God and of the soul, though not admitting of sensible illustration, nonetheless have a valuable employment as so-called ‘regulative principles’. By proceeding as if these Ideas have existent objects we can, he supposes, be fruitfully guided in our natural-scientific inquiries. In particular, by acting as if nature expresses the purposes of a wise and benevolent creator—a being who creates the world through the operation of his faculty of freedom rather than through his essence (by emanation)—we are led to make a range of discoveries that would otherwise not be made. The chapter examines the meaning of the various principles that Kant identifies as regulative principles and explains with concrete examples how following them can promote natural scientific inquiry in a range of fields, including: optics, geology, engineering, geodesy, biology, potamology, and astronomy.

Analysis of Data Acquisition Accuracy with UAV

Due to the increasingly advanced digital devices, high resolution cameras and utility of fast processing, Unmanned Aerial Vehicles (UAV) have become a prominent feature of the various remote sensing procedures. Because the benefits of the technology may justify the use of data in topographic mapping, cadastral mapping or even engineering geodesy, we have conducted studies to determine the accuracy that can be achieved using UAV as an integrated data acquisition tool. First, we developed a test field in rural area for investigations. The results of the test flights conducted there were determined that what conditions influence the accuracy of the survey.

Accelerometer Triad Calibration for Pole Tilt Compensation Using Variance Based Sensitivity Analysis

In Engineering Geodesy, most coordinate frames are aligned with the local vertical. For many measurement tasks, it is therefore necessary to manually (or arithmetically) align sensors or equipment with the local vertical, which is a common source of errors and it is very time consuming. Alternatively, accelerometer triads as part of inertial measurement units (IMUs) are used in several applications for horizon leveling. In this contribution we analyze and develop a method to use accelerometer triads for pole tilt compensation with total stations. Several triad sensor models are investigated and applied in a calibration routine using an industrial robot arm. Furthermore a calibration routine to determine the orientation of the IMU mounted on the pole is proposed. Using variance based sensitivity analysis we investigate the influence of different model parameters on leveling and pole tilt compensation. Based on this inference the developed calibration routines are adjusted. The final evaluation experiment shows an RMS of 2.4 mm for the tilt compensated measured ground point with tilts up to 50 gon.

High-Precision 3D Object Capturing with Static and Kinematic Terrestrial Laser Scanning in Industrial Applications—Approaches of Quality Assessment

Terrestrial laser scanning is used in many disciplines of engineering. Examples include mobile mapping, architecture surveying, archaeology, as well as monitoring and surveillance measurements. For most of the mentioned applications, 3D object capturing in an accuracy range of several millimeters up to a few centimeters is sufficient. However, in engineering geodesy, particularly in industrial surveying or monitoring measurements, accuracies in a range of a few millimeters are required. Additional increased quality requirements apply to these applications. This paper focuses on the quality investigation of data captured with static and kinematic terrestrial laser scanning. For this purpose, suitable sensors, which are typically used in the approach of a multi-sensor-system, as well as the corresponding data capturing/acquisition strategies, are presented. The aim of such systems is a geometry- and surface-based analysis in an industrial environment with an accuracy of +/− 1–2 mm or better.