Abstract

In this paper, a series of topics, concerning acquisition, communication, and the analysis of buildings will be discussed. In particular, a strategy aimed at exploiting the visual potentials of reality-based models, will be described inside render engines, real-time applications, as well as their role for the production of conventional drawing for documenting and studying built heritage. This methodology is inspired by pipelines coming from computer-generated imagery (CGI) and the video game industry: areas of research that are progressively showing an increasing interest towards the world of photogrammetry remote sensing, in particular for the new possibilities offered by Structure from Motion (SfM)/Multi View Stereo (MVS) in terms of automatic texturing of complex shapes. Quad-dominant remeshing, displaced subdivision surfaces, and accurate interactive/ automatic parametrization are the main points of this workflow, whose final goal is the achievement of multipurpose models, which are capable to comply with graphic codes of traditional survey, as well as semantic enrichment, and, last but not least, data compression/portability and texture reliability under different lighting conditions.

Abstract

The paper describes a color enhanced processing system - applied as case study on an artifact of the Pompeii archaeological area - developed in order to enhance different techniques for reality-based 3D models construction and visualization of archaeological artifacts. This processing allows rendering reflectance properties with perceptual fidelity on a consumer display and presents two main improvements over existing techniques: a. the color definition of the archaeological artifacts; b. the comparison between the range-based and photogrammetry-based pipelines to understand the limits of use and suitability to specific objects. Document type: Article

Abstract

Several years of experience in heritage documentation have given a background to develop methods of digital photogrammetry and mapping. The outcome is the development of a mapping software over a period of 20 years.Main features of the software are image rectification, vector based mapping, quantity survey and data analysis. In Germany, it is mainly used in the field of stone conservation. Small projects can be processed as a single mapping project, whilst complex projects like a cathedral can be organised as a hierarchical project, with several mapping projects for individual object parts. Each mapped element can be connected with additional attributes. This allows visual analysis of mapping activities, quantities and attributes – like in a geographical information system (GIS) for conservators. Tools and procedures for efficient mapping are developed in close cooperation with conservators from different fields. It is shown how large stone objects can be managed efficiently with an example project from the field of natural stone. This applies to the overall data acquisition and data evaluation for condition analysis, conservation planning, accounting documentation and monitoring. Due to the advances in the fields 3D laser scanning and digital photogrammetry within the past 5 years the R&D project „PROQUATO“ (2016 – 2018) was initiated by fokus GmbH Leipzig with the institute for photogrammetry and remote sensing of TU Dresden and Scan 3D GmbH, Berlin. Project results for efficient data processing and functions for 3D mapping will be presented. Current developments deal with the fast processing of point clouds scanned by laser scanner for the use as reference for image rectification, deformation analysis and creation of section lines.

Abstract

The Candis (temples) of Java represent sophisticated ancient building heritage and are key features for Javanese people to identify with their own culture. Candis occupy a significant position in the cultural history of Southeast Asia and rank among the most outstanding examples of Buddhist and Hindu architecture. Well-known Candis such as Borobudur or Prambanan are also top-ranked tourist destinations. This ancient heritage is threatened by Indonesia’s geographical location within the Pacific Ring of Fire, a tectonic subduction zone prone to environmental catastrophes such as earthquakes, volcanic eruptions and the resulting tsunamis. Previous work presented a monitoring workflow for analysing variations in the geometry of these temples to gain an understanding of structural changes produced by seismic events. As part of that workflow, we proposed a combined laser scanning and UAV-supported image match point cloud model which can be compared to a photogrammetric data set in order to provide a quick, inexpensive, and easily accessible monitoring technique. While methodology has already proved useful, some aspects still need to be refined. Also, further understanding about the structural composition of the objects being examined and what changes of geometry can be expected within the analysis after earthquakes needs to be collected. An analysis is presented of changes that have happened within the structure over a period of several years and numerous seismic events to facilitate an understanding of geometric changes that can occur. Furthermore, this re-evaluation by laser scanning will be compared to a set of image-match models to investigate factors that have an impact on the reliability and accuracy of such models. Manuals drafted by the project team and introduced in previous work explain how to capture image data to be processed into photogrammetric models. Amendments and revisions will be made to these manuals based on new data and experiences collected during the ongoing Candi Sari case study presented in this paper.

Abstract

This paper presents a comparative approach between a digital documentation workflow of a hyperbolic paraboloid heritage building using contemporary tools versus a traditional documentation technique. This documentation was undertaken to better understand the building’s structure, its evolution, and to assess the performance of this modern concrete structure for future seismic and damage analysis. Furthermore, this paper discusses the challenges related to producing a Heritage Building Information Model (HBIM) of this building using point cloud data in Autodesk’s Revit BIM-authoring software. This project states the importance of a parallel study between the traditional and the contemporary documentation methods; which led to discoveries about the current state of the extrados in the hyperbolic parabola after several earthquakes. Upon analyzing the HBIM and comparing it to the historical drawings, we discovered a gap between the moisture barrier membrane and the concrete shell. Visualizing the building in 3D provides a deeper and more accurate understanding of the currentstate of this pavilion and is one of many advantages of using digital technologies. The insights provided by digital documentation techniques and analyzing the historical images of the pavilion showed that the curvature of the pavilion had changed over time. The results that we found imply two hypotheses. First, the profile of the curvature had been modified due to earthquakes, and second that the modification was due to improper maintenance of the pavilion, namely, multiple additions of the membrane layers. This could not have been detected by solely relying on traditional documentation techniques.

Abstract

The wall of Casa Salvans is a masonry arched and buttressed retaining wall which was built in 1909 and located in Terrassa, Catalonia. It contains a series of 11 arches of unique shapes, dimensions and inclinations that are supported on buttresses. Despite being a common retaining wall typology, it can be very challenging to assess the stability of such structures given the variability of their geometry. As such, a systematic methodology for the stability assessment of such walls was developed and applied to the case of the wall of Casa Salvans. Self-produced photogrammetry survey enabled creating accurate three-dimensional models of the front of the wall that were later combined with available information from a topographic survey to build cross sections of the wall for analysis. Modern retaining wall design principles evaluating the stability against overturning and sliding were used to assess the condition of the wall. As a consequence of the uncertainties related to the soil parameters and buried elements of the wall, the stability factors could not comply with modern design criterion. Some parametric analyses were carried out on the shear strength parameters of the backfill, revealing that slight increases in the soil internal friction and wall friction angles enhance the stability factors significantly. Since reasonable soil internal and wall friction angles justifying the stability of the wall were obtained, carrying out a geotechnical survey to determine the actual values was recommended. The in-plane stability of the arches was also verified according to the Lower Bound Theorem by locating a thrust line that fits within all the boundaries despite very conservative geometric assumptions.