3D Visualization for Urban Earthquake Risk

Visualization is the graphical presentation of information, with the goal of improving the viewer’s understanding of the information contents. As today’s world is getting richer in information, visualization of the information is important for effective communication and decision making. In this study, generation of a 3D city model in CAD environment and its use in a spatial decision support system for earthquake risk in an urban area is presented. As CAD products’ quality is more enhanced than the other tools the 3D city model is generated in CAD environment. In CAD environment, a 2D building foot print vector layer is used. After extrude operations, real building textures are obtained by taking pictures from the study area. Texture mapping tools are used to cover extruded buildings with acquired building texture images. The 3D city model is used to visualize each building’s earthquake risk level. The model also serves for querying and scenario analyses in a spatial decision support system

Classification and information structure of the Terrestrial Laser Scanner: methodology for analyzing the registered data of Vila Vella, historic center of Tossa de Mar

This paper presents a methodology for an architectural survey, based on the Terrestrial Laser Scanning technology TLS, not as a simple measurement and representation work, but with the purpose understanding the projects being studied, starting from the analysis, as a process of distinction and separation of the parts of a whole, in order to know their principles or elements. As a case study we start from the Vila Vella recording, conducted by the City’s Virtual Modeling Laboratory in 2008, being taken up from the start, in relation to the registration, georeferencing, filtering and handling. Aimed at a later stage of decomposition and composition of data, in terms of floor plan and facades, using semiautomatic classification techniques, for the detection of vegetation as well as the relationship of the planes of the surfaces, leading to reorganize the information from 3D data to 2D and 2.5D, considering information management, as well as the characteristics of the case study presented, in the development of methods for the construction and exploitation of new databases, to be exploited by the Geographic Information Systems and Remote Sensing.Peer Reviewe

Classification and information structure of the Terrestrial Laser Scanner: methodology for analyzing the registered data of Vila Vella, historic center of Tossa de Mar

This paper presents a methodology for an architectural survey, based on the Terrestrial Laser Scanning technology TLS, not as a simple measurement and representation work, but with the purpose understanding the projects being studied, starting from the analysis, as a process of distinction and separation of the parts of a whole, in order to know their principles or elements. As a case study we start from the Vila Vella recording, conducted by the City’s Virtual Modeling Laboratory in 2008, being taken up from the start, in relation to the registration, georeferencing, filtering and handling. Aimed at a later stage of decomposition and composition of data, in terms of floor plan and facades, using semiautomatic classification techniques, for the detection of vegetation as well as the relationship of the planes of the surfaces, leading to reorganize the information from 3D data to 2D and 2.5D, considering information management, as well as the characteristics of the case study presented, in the development of methods for the construction and exploitation of new databases, to be exploited by the Geographic Information Systems and Remote Sensing.Peer Reviewe

3d virtual modelling of existing objects by terrestrial photogrammetric methods - case study of Barutana

Three dimensional virtual modelling of existing objects (buildings or structures) is applicable in various fields of science and practice: architecture, civil engineering, urbanism, geology, mechanical engineering, video games and movie industry, medicine, archeology, safety of people and goods, etc. Photogrammetry, as a method of obtaining data of three-dimensional spatial structures based on two-dimensional images, is used, thanks to a number of software packages, for creating 3D models of objects and other spatial structures. This study analyses terrestrial semiautomatic and automatic photogrammetric methods, both presented through process of creating 3D model of an old existing historical building - Barutana (military gun powder warehouse), built in Ottoman empire, located in the fortress of the city of Nis in Serbia. The aim of the paper is comparison of two photogrammetric methods - semiautomatic and automatic in accuracy and efficiency through case study of Barutana

A FLEXIBLE METHODOLOGY FOR OUTDOOR/INDOOR BUILDING RECONSTRUCTION FROM OCCLUDED POINT CLOUDS

Terrestrial Laser Scanning data are increasingly used in building survey not only in cultural heritage domain but also for as-built modelling of large and medium size civil structures. However, raw point clouds derived from laser scanning generally not directly ready for the generation of such models. A time-consuming manual modelling phase has to be taken into account. In addition the large presence of occlusion and clutter may turn out in low-quality building models when state-of-the-art automatic modelling procedures are applied. This paper presents an automated procedure to convert raw point clouds into semantically-enriched building models. The developed method mainly focuses on a geometrical complexity typical of modern buildings with clear prevalence of planar features A characteristic of this methodology is the possibility to work with outdoor and indoor building environments. In order to operate under severe occlusions and clutter a couple of completion algorithms were designed to generate a plausible and reliable model. Finally, some examples of the developed modelling procedure are presented and discussed

Scan4Façade: Automated As-Is Façade Modeling of Historic High-Rise Buildings Using Drones and AI

This paper presents an automated as-is façade modeling method for existing and historic high-rise buildings, named Scan4Façade. To begin with, a camera drone with a spiral path is employed to capture building exterior images, and photogrammetry is used to conduct three-dimensional (3D) reconstruction and create mesh models for the scanned building façades. High-resolution façade orthoimages are then generated from mesh models and pixelwise segmented by an artificial intelligence (AI) model named U-net. A combined data augmentation strategy, including random flipping, rotation, resizing, perspective transformation, and color adjustment, is proposed for model training with a limited number of labels. As a result, the U-net achieves an average pixel accuracy of 0.9696 and a mean intersection over union of 0.9063 in testing. Then, the developed twoStagesClustering algorithm, with a two-round shape clustering and a two-round coordinates clustering, is used to precisely extract façade elements’ dimensions and coordinates from façade orthoimages and pixelwise label. In testing with the Michigan Central Station (office tower), a historic high-rise building, the developed algorithm achieves an accuracy of 99.77% in window extraction. In addition, the extracted façade geometric information and element types are transformed into AutoCAD command and script files to create CAD drawings without manual interaction. Experimental results also show that the proposed Scan4Façade method can provide clear and accurate information to assist BIM feature creation in Revit. Future research recommendations are also stated in this paper

Incremental map refinement of building information using lidar point clouds

For autonomous systems, an accurate and precise map of the environment is of importance. Mapping from LiDAR point clouds is one of the promising ways to generate 3D environment models. However, there are many problems caused by inaccurate data, missing areas, low density of points and sensor noise. Also, it is often not possible or accurate enough to generate a map from only one measurement campaign. In this paper, we propose a method to incrementally refine the map by several measurements from different campaigns and represent the map in a hierarchical way with a measure indicating uncertainty and the level of detail for objects. The idea is thus to store all captured information with a tentative semantics and uncertainty - even when it is not yet complete. Hence, occulated areas are presented as well, which can be possibly improved by the supplemental observation from the next measurement campaign. The proposed 3D environment model framework and the incremental update method are evaluated using LiDAR scans obtained from Riegl Mobile Mapping System

Close-Range Sensing and Data Fusion for Built Heritage Inspection and Monitoring - A Review

Built cultural heritage is under constant threat due to environmental pressures, anthropogenic damages, and interventions. Understanding the preservation state of monuments and historical structures, and the factors that alter their architectural and structural characteristics through time, is crucial for ensuring their protection. Therefore, inspection and monitoring techniques are essential for heritage preservation, as they enable knowledge about the altering factors that put built cultural heritage at risk, by recording their immediate effects on monuments and historic structures. Nondestructive evaluations with close-range sensing techniques play a crucial role in monitoring. However, data recorded by different sensors are frequently processed separately, which hinders integrated use, visualization, and interpretation. This article’s aim is twofold: i) to present an overview of close-range sensing techniques frequently applied to evaluate built heritage conditions, and ii) to review the progress made regarding the fusion of multi-sensor data recorded by them. Particular emphasis is given to the integration of data from metric surveying and from recording techniques that are traditionally non-metric. The article attempts to shed light on the problems of the individual and integrated use of image-based modeling, laser scanning, thermography, multispectral imaging, ground penetrating radar, and ultrasonic testing, giving heritage practitioners a point of reference for the successful implementation of multidisciplinary approaches for built cultural heritage scientific investigations

Automated 3D model generation for urban environments [online]

Abstract In this thesis, we present a fast approach to automated generation of textured 3D city models with both high details at ground level and complete coverage for birds-eye view. A ground-based facade model is acquired by driving a vehicle equipped with two 2D laser scanners and a digital camera under normal traffic conditions on public roads. One scanner is mounted horizontally and is used to determine the approximate component of relative motion along the movement of the acquisition vehicle via scan matching; the obtained relative motion estimates are concatenated to form an initial path. Assuming that features such as buildings are visible from both ground-based and airborne view, this initial path is globally corrected by Monte-Carlo Localization techniques using an aerial photograph or a Digital Surface Model as a global map. The second scanner is mounted vertically and is used to capture the 3D shape of the building facades. Applying a series of automated processing steps, a texture-mapped 3D facade model is reconstructed from the vertical laser scans and the camera images. In order to obtain an airborne model containing the roof and terrain shape complementary to the facade model, a Digital Surface Model is created from airborne laser scans, then triangulated, and finally texturemapped with aerial imagery. Finally, the facade model and the airborne model are fused to one single model usable for both walk- and fly-thrus. The developed algorithms are evaluated on a large data set acquired in downtown Berkeley, and the results are shown and discussed