Heribert Kahmen

A 3D optical deformation measurement system supported by knowledge-based and learning techniques

Abstract High accuracy 3D representation and monitoring of objects is receiving increasing interest both in science and industrial applications. Up to now tasks like monitoring of building displacements or deformations were solved by means of artificial targets on the objects of interest, although mature optical 3D measurement and laser scanning techniques are available. Such systems can perform their measurements even without targeting. This paper presents a new optical 3D measurement system, based on the fusion between a geodetic image sensor and a laser scanner. The main goal of its development was the automation of the whole measurement process, including the tasks of point identification and measurement, deformation analysis, and interpretation. This was only possible by means of new methods and techniques originally developed in the area of Artificial Intelligence; both point detection and deformation analysis are supported by decision systems that use such techniques. The resulting complex multi-sensor system is able to measure and analyse the deformation of objects, as shown in experiments. In this article we focus on specific key components and novel techniques that have been developed, and briefly report on the current stage of the whole system.

A Multi-Scale Monitoring Concept for Landslide Disaster Mitigation

There has already been much research on how the kinematic and geodynamic behaviour of landslides can be predicted. However, until now, there has been no decisive breakthrough for a monitoring and evaluation system combined with an alert system. Therefore an interdisciplinary international project OASYS (Integrated Optimization of Landslide Alert Systems) was commenced to progress research in this area. The members of the project, supported by the European Union, believe a multidisciplinary integration of different methods has potential for substantial progress in natural hazards management. This project proposes a new method consisting of three different steps: 1. Detection of boundary lines of potential landslides based on large scale information. 2. Detection of “taking-off-domains” and permanent local scale monitoring of these regions with high sensitivity geotechnical measurement methods. 3. Knowledge-based derivation of real time information regarding actual risks to support alert systems.

OASYS — Integrated Optimization of Landslide Alert Systems

In the past there has been a wide range of research work on landslides. However, most of this research has been carried out by a single discipline such as geology or geodesy. Therefore an international and interdisciplinary project was started. The proponents of the project, sponsored by the European Union, believe that a multidisciplinary integration of different methods has the greatest potential for substantial progress in natural hazards management. The goal of the project is the development of methods that allow: The detection of potential landslides, an efficient and continuous observation of critical areas, the derivation of real time information about actual risks.

Quality Control for Building Industry by Means of a New Optical 3D Measurement and Analysis System

In the past, high-precision online 3D measuring required artificial targets defining the points on the objects to be monitored. For many tasks such as monitoring of displacements of buildings, artificial targets are not desired. Today’s image-assisted measurement systems can perform their measurements even without targeting. Such systems use the texture on the surface of the object to find “interesting points” which can replace the artificial targets. However, well-trained “measurement experts” are required to operate such a measurement system. In order to make such systems easy to use even for non-experts, it can be extended by an appropriate decision system which supports the operator. At the Institute of Geodesy and Geophysics of Vienna University of Technology a new kind of image-based measurement system is being developed (research project “Multi-Sensor Deformation Measurement System Supported by Knowledge-Based and Cognitive Vision Techniques”). This system can be used for measuring, analysing and interpreting deformations for the task of quality control in civil engineering. The work-flow is based on new techniques originally developed in the field of Artificial Intelligence

Concept of a Multi-Scale Monitoring and Evaluation System for Landslide Disaster Prediction

In 2006, OASYS, an EU funded project on a multi-scale monitoring concept for landslides as a basis for an alert system, was completed. 12 institutes from 6 countries tried to merge their multidisciplinary knowledge in the field of landslides and disaster management. The main goal of the research was to develop a cost saving concept for landslide disaster prediction in areas with a higher density of landslides. The present paper reports about the innovative steps and about some highlights of the research, emphasising mainly three tasks: & GIS integrated geological evaluations of remote-sensing data to delineate the high-risk areas in regions with a larger number of landslides & geometrical analysis of the monitoring data by fuzzy techniques as a basis for the design of the sensor network and & geomechanical modelling of the landslide by FD-methods as a basic information for an alarm system.

Gridline methods for detection of object displacements and rigid body movements

Abstract If measurements are performed without artificial targets, deformation analysis cannot refer to the points on the objects defined at an initial or prior measurement epoch. This paper describes how an arrangement of virtual lines, so-called grid lines (GL), offers a solution. A total station, measuring distances without a reflector, or a theodolite measurement system can be used to make the measurements. The GLs should intersect the object to be measured, as far as possible, at right angles and they can be arranged in such a way that each of them runs through one of the object points chosen for the initial measurements. Subsequently deformations of the object can be described along the GLs. The general idea behind this method is to track the virtual lines with the optical axis of a theodolite, until it aims at the points where the GLs intersect the surface. Tracking starts where the GLs intersected the surface of the object during the last measurement epoch. However, if the surface moved this point will be no longer an intersection point and the optical axis hits the surface at another point. Consequently there will be a separation of these two points, and if the theodolite starts tracking the GL, a distance function is obtained. This can be used to determine the new intersection point of the GL if that line is tracked until the value of the distance function is zero. The following sections describe how this process can be iteratively controlled by algorithms for an one-dimensional search space. The algorithms are based on the binary-search-, so-called parabola-, and regula-falsi method. Simulations and practical tests are used to evaluate the different search algorithms. The accuracy of the intersection points and the number of necessary iteration steps, describing the speed of the algorithms, are used as quality assessment parameters. Both quality characteristics depend on the truncation criteria: a distance and a length of an interval.