Department of Civil Engineering

This paper describes a multidisciplinary initiative for the preparation of educational material for the appropriate use of terrestrial laser scanning techniques for risk characterization of our built environment. This project, supported by the European Leonardo Da Vinci project throughout its Flemish Agency involves 8 partners from 6 different countries with members of the industry, as well as academic institutions. The project's website: http://www. 3driskmapping. eu.

De unieke en onvervangbare waarde van het erfgoed vraagt erom dat bij de aanvang van elke actie voor behoud of beheer, nauwkeurige en gedetailleerde informatie over dit erfgoed beschikbaar wordt gesteld. Nochtans bestaan er in België weinig richtlijnen hieromtrent en is de kwaliteit van de documentatie zeer wisselend. In het onderzoek naar architecturaal erfgoed zijn representaties, gebaseerd op het samenbrengen van gedetailleerde opmetingen van fundamenteel belang. Deze informatie kan bijdragen tot de creatie van ...

Het gebruik en de ontwikkeling van driedimensionale opmetingstechnieken kende het afgelopen decennium een enorme vooruitgang. Het huidige gamma 3D laserscanners bieden de landmeter een nieuw scala aan mogelijkheden voor het opmeten van onze gebouwde omgeving op een snelle, accurate, en in veel gevallen kostenefficiënte wijze. De geometrische informatie afkomstig van deze toestellen, verrijkt met fotografisch materiaal, geeft ons de mogelijkheid tot het maken van zeer realistische en nauwkeurige 3D- ...

This paper describes a multidisciplinary initiative for the preparation of educational material for th e appropriate use of terrestrial laser scanning techniques for risk characterization of our built environment. This project, supported by the European Leonardo Da Vinci project throughout its Flemish Agency involve s 8 partners from 6 different countries with member s of the industry, as well as academic institutions. The project's website: http: //www.3driskmapping.eu.

Documenting cultural heritage is an important step towards the conservation and restoration of monuments. 'Precise documentation' in conservation works, deals with the use of techniques capable of acquiring geometry as well as texture information with high precision and integrity. Only recently orthophoto's have been accepted and are used as a standard tool in archeological and cultural heritage documentation. By analyzing two existing software packages for orthophotograph production, we conclude that standard automatic surface modeling techniques as well as laser scanning do not fulfill the high needs of close range architectural orthophotography because of the large amount of discontinuities in the surface. This paper presents ongoing research that combines the use of laser scanning, photogrammetry and image processing to overcome these problems. The major problem lies in achieving automation and efficiency together with robustness and reliability so that the algorithm...

When monuments are seriously damaged, or completely destroyed, the amount and quality of documentation becomes highly important. Nowadays orthophoto's have become a standard tool in archeological and in cultural heritage documentation. By analyzing two existing software packages that are used to create orthophotographs today, we find that standard automatic surface modeling techniques as well as laser scanning do not fulfill the high needs of close range architectural orthophotography because of the large amount of discontinuities in the surface. In this paper we plan to combine the use of laser scanning, photogrammetry and image processing to overcome these problems. The major problem lies in achieving automation and efficiency together with robustness and reliability so that the algorithms and methods can be used for a successful and economically feasible implementation in practice.

When monuments are seriously damaged, or completely destroyed, the amount and quality of documentation becomes highly important. Nowadays orthophoto’s have become a standard tool in archeological and in cultural heritage documentation. By analyzing two existing software packages that are used to create orthophotographs today, we find that standard automatic surface modeling techniques as well as laser scanning do not fulfill the high needs of close range architectural orthophotography because of the large amount of discontinuities in the surface. In this paper we plan to combine the use of laser scanning, photogrammetry and image processing to overcome these problems. The major problem lies in achieving automation and efficiency together with robustness and reliability so that the algorithms and methods can be used for a successful and economically feasible implementation in practice.

With the increasing popularity of as-built Building Information Modelling (BIM) for existing buildings, the demand for highly accurate and dense point cloud data is rising. However, the current data acquisition methods are labor intensive and time consuming. Among other factors, the use of total station measurements to establish survey control, is a major cost behind data acquisition workflows. Over the recent years, there have been major innovations in the fields of surveying and robotics, such as the development of Indoor Mobile Mapping systems (IMMS). With these technological advancements, more cost-effective workflows for capturing existing buildings can be realized. In this paper, several state-of-the-art data acquisition techniques and workflows are discussed for Architectural, Engineering and Construction (AEC) industry buildings. Furthermore, a workflow is proposed with a standalone terrestrial laser scanner capturing data in high overlap, using loop-closure and optimization...

With the increasing popularity of Building Information modelling (BIM), the demand for accurate as-built models of existing buildings is rising. However, the manual creation of these models is labour intensive and error prone. Therefore, automation of the process is a must. One of the key factors in the automated Scan-to-BIM process is the labelling of the data for further reconstruction. Currently, semantic labelling is still ongoing research. This paper presents a flexible method to automatically label highly cluttered vector models of existing buildings. In our proposed method, a reasoning framework is used that exploits geometric and contextual information. A major advantage to our approach is that our algorithm can label both cluttered environments and large data sets very efficiently. Unlike other solutions, this allows us to label entire buildings at once. In addition, the implementation of our algorithm and the platform we use allows for flexible data processing, visualisation of the results and improvement of the labelling process. Our work covers the entire labelling phase and allows the user to label data sets with a minimal amount of effort.

The ever developing instruments, techniques and software are at the same time a blessing and a curse for the contemporary land surveyor. Laser scanning is one of these new techniques and although its versatility, speed and accuracy are praised in articles and on exhibitions, a lot of Belgian land surveyors are somewhat reluctant to introduce laser scanning in their own company. There is still a lot of uncertainty in regard to the efficiency of this data acquisition method and especially the processing of the data and the production of deliverables that meet the client's needs and expectations. University Colleges can contribute to stimulate the smaller land surveying companies to invest in innovation and thus maintain their competitiveness and consolidate their position in an open European market. This article describes how researchers at university colleges translate their knowledge and experience in such a way that they can support smaller companies, which do not have the reso...

Three-dimensional laser scanning offers advantages for the recording and mapping of our built environment without entering in contact with the fabric and surfaces of objects. This is in particular interesting to fields where capturing the three-dimensional shape is of paramount importance, such as the industry, heritage and environment prediction. This paper presents one of three case studies carried out in the '3DRISKMAPPING'(" 3DRISKMAPPING," 2008) framework, explaining the use of 3D laser scanning for structural assessments in ...

Point cloud segmentation is a crucial step in scene understanding and interpretation. The goal is to decompose the initial data into sets of workable clusters with similar properties. Additionally, it is a key aspect in the automated procedure from point cloud data to BIM. Current approaches typically only segment a single type of primitive such as planes or cylinders. Also, current algorithms suffer from oversegmenting the data and are often sensor or scene dependent. In this work, a method is presented to automatically segment large unstructured point clouds of buildings. More specifically, the segmentation is formulated as a graph optimisation problem. First, the data is oversegmented with a greedy octree-based region growing method. The growing is conditioned on the segmentation of planes as well as smooth surfaces. Next, the candidate clusters are represented by a Conditional Random Field after which the most likely configuration of candidate clusters is computed given a set of...

In recent years, 3D laser scanners have gained interest, especially in 3D reconstruction and reproduction, mainly because of their capability to record huge numbers of points with high accuracy in a relatively short period of time. Especially in the field of deformation monitoring for analyzing the structural stability of built heritage, laser scanners can provide a much denser and thus better representation of the deformations taking place over time. The single-point precision of modern mid-range laser scanners varies from 5 to 25mm depending on the laser and the measuring principle used, but also depending on the measurement conditions and the object surface to be scanned. Comparing this precision to that of traditional surveying techniques used for deformation monitoring such as total stations or contact sensors, the precision of a laser scanner is approximately 1 order lower in magnitude. The main disadvantage of these traditional techniques is that they only offer single-point ...

With the increasing popularity of as-built building models for the architectural, engineering and construction (AEC) industry, the demand for highly accurate and dense point cloud data is rising. The current data acquisition methods are labour intensive and time consuming. In order to compete with indoor mobile mapping systems (IMMS), surveyors are now opting to use terrestrial laser scanning as a standalone solution. However, there is uncertainty about the accuracy of this approach. The emphasis of this paper is to determine the scope for which terrestrial laser scanners can be used without additional control. Multiple real life test cases are evaluated in order to identify the boundaries of this technique. Furthermore, this research presents a mathematical prediction model that provides an indication of the data accuracy given the project dimensions. This will enable surveyors to make informed discussions about the employability of terrestrial laser scanning without additional con...

Semantically rich three dimensional models such as Building Information Models (BIMs) are increasingly used in digital heritage. They provide the required information to varying stakeholders during the different stages of the historic buildings life cyle which is crucial in the conservation process. The creation of as-built BIM models is based on point cloud data. However, manually interpreting this data is labour intensive and often leads to misinterpretations. By automatically classifying the point cloud, the information can be proccesed more effeciently. A key aspect in this automated scan-to-BIM process is the classification of building objects. In this research we look to automatically recognise elements in existing buildings to create compact semantic information models. Our algorithm efficiently extracts the main structural components such as floors, ceilings, roofs, walls and beams despite the presence of significant clutter and occlusions. More specifically, Support Vector Machines (SVM) are proposed for the classification. The algorithm is evaluated using real data of a variety of existing buildings. The results prove that the used classifier recognizes the objects with both high precision and recall. As a result, entire data sets are reliably labelled at once. The approach enables experts to better document and process heritage assets.