Heritage Documentation Research Articles

FUSION OF TLS AND UAV PHOTOGRAMMETRY DATA FOR POST-EARTHQUAKE 3D MODELING OF A CULTURAL HERITAGE CHURCH

Abstract. Nowadays, the necessity of heritage documentation is essential for monitoring, maintenance, and understanding needed for conservation. The survey phase has been considerably improved using cutting-edge technologies such as Unmanned Aerial Vehicles (UAV) and Terrestrial Laser Scanners (TLS). Both of these technologies have been applied in heritage documentation individually or combined. Heritage documentation in a post-natural disaster is a situation that requires rapid data acquisition on a hazardous field. On 12th of June 2017 an earthquake (Mw = 6.3), south of Lesvos island, Greece occurred, which was devastating for the Vrisa village destroying, among many other buildings the main church. The Greek State decided from the first moment to restore the whole village, which was proclaimed as a “traditional settlement” since 2002, in its original place starting from the church and the school due to the symbolic meaning that those have to a local community. For this purpose, a 3D model of the church was requested by the authorities for damage assessment. In this paper TLS and UAV photogrammetry has been used in an integrated design to rapidly facilitate the acquisition of the whole church, eliminating all possible occlusions. The TLS was exploited for the acquisition of the facades while the UAV was used for the acquisition of the roof. The recent improvement of the post-processing algorithms provided the ability to implement the fusion of TLS and UAV models and deliver an accurate 3D model of the whole church the same day that the survey was conducted.

Architectural heritage semantic 3D documentation in multi-scale standard maps

Abstract The documentation of cultural heritage is acknowledged as a fundamental instrument to guarantee the monument preservation and promotion, and to educate people towards these aims. The recently evolved potentialities of information technologies and communication (standard data models, ontologies and formats, web technologies) permit the development of digital archives in which the information is also semantically specified in a shared and explicit way, so that it can be universally understood and correctly interpreted. However, some tools are missing for suitably archiving and communicating the architectural heritage information, including the representation potentialities of high-level-of-detail 3D models. A goal of this study is the suitable representation of both the thematic information about architectural heritage and its 3D geometric characteristics in an interoperable and understandable way. For this reason, the existing data models, available for the geometric and cartographic field, and for the cultural heritage domain, were considered. They are distinct standards, and some limits make them incomplete (in the spatial or semantic management). In this study, an extension is proposed of the standard data model CityGML to overcome these limits. CityGML is published by the Open Geospatial Consortium to represent urban objects and permits a multi-scale management of the information useful for the representation of architectural heritage multi-faceted, multi-temporal, complex knowledge. In the paper, the extension is described, and an example of its application on a portion of a highly detailed 3D model of a mediaeval church is presented.

Recent trends in cultural heritage 3D survey: The photogrammetric computer vision approach

Abstract The techniques of measuring and 3D modelling based on images, as is typical in photogrammetry, grew in interest again in recent years, since a new generation of software tools has spread. These ones implement in different measure the algorithms developed by computer vision, increasing the automation of the standard photogrammetric process. This made the use of image-based approaches for 3D models reconstruction enormously increase, which is an essential part of the Cultural Heritage documentation and analysis processes. Starting from these assumptions, the aim of the paper is to evaluate what and where it is possible nowadays to find the main differences between photogrammetry and computer vision approaches and how these have to be considered in the choice of the processing technique. The analysis has been performed starting from a theoretical point of view in order to trace the main characteristics of the two methods. Moreover, in order to complete the investigation, an experimental part is reported on two particular cases study, considered as representative of two types of usually surveyed objects. The results allow to enlighten some differences between the two image processing approaches, in terms of accuracy and achieved products.

Active use of panoramic mobile mapping systems for as built surveying and heritage documentation

ABSTRACTMobile mapping systems (MMS) are widely used technology nowadays for spatial data collection of large scale projects like for city and highway mapping. The systems are mainly equipped with laser scanning sensors and/or imaging sensors mounted on a moving vehicle during the scene capture. Imaging sensors are normally cameras which either capture perspective or panoramic images covering the whole horizon of the vehicle. The orientation of the captured panoramic images is accurate to centimeters’ level because of the precise positioning and navigation systems equipped with these mapping systems. However, the positioning accuracy of mobile mapping systems can be degraded in city centers or urban canyons because of the satellite signal disturbances.In this article, we discuss the following objectives: (1) the possibility to use the mobile mapping images for cultural heritage documentation and as built surveying and how accurate the mapping can be; (2) the concept of using the mobile mapping images as a tool of georeferencing the crowdsource images; and (3) the efficiency of using the multi-temporal mobile mapping images for occluded free cultural heritage facade orthophotos. The mobile mapping systems of CycloMedia with two panoramic products of Cyclorama images (12 MP) and HD Cycloramas (100 MP) are used for the experimental tests in this research article.

Practical In Situ Implementation of a Multicamera Multisystem Calibration

Consumer-grade cameras are generally low-cost and available off-the-shelf, so having multicamera photogrammetric systems for 3D reconstruction is both financially feasible and practical. Such systems can be deployed in many different types of applications: infrastructure health monitoring, cultural heritage documentation, bio-medicine, as-built surveys, and indoor or outdoor mobile mapping for example. A geometric system calibration is usually necessary before a data acquisition mission in order for the results to have optimal accuracy. A typical system calibration must address the estimation of both the interior and the exterior, or relative, orientation parameters for each camera in the system. This article reviews different ways of performing a calibration of a photogrammetric system consisting of multiple cameras. It then proposes a methodology for the simultaneous estimation of both the interior and the relative orientation parameters which can work in several different types of scenarios including a multicamera multisystem calibration. A rigorous in situ system calibration was successfully implemented and tested. The same algorithm is able to handle the equivalent to a traditional-style bundle adjustment, that is, a network solution without constraints, for a single or multicamera calibrations, and the proposed bundle adjustment with built-in relative orientation constraints for the calibration of a system or multiple systems of cameras.

Generation of visually aesthetic and detailed 3D models of historical cities by using laser scanning and digital photogrammetry

Historical cities (or towns) are inherently valuable for their uniqueness. Although reflecting the past, these cities offer significant opportunities. For this reason, it is important to know how to preserve them and assess their exploitation potential from different perspectives. An increased knowledge about them is continuously required and demanded.Three-dimensional (henceforth 3D) virtual models are an excellent way for introducing these cities to people. However, some particular characteristics derived from irregular urban structures and specific human dynamics in historical urban environments can constrain the use of some technologies for 3D data collection.This research paper proposes an own working methodology for the generation of 3D virtual models of historical cities. This methodology is based on the combined use of laser scanning and photogrammetric techniques, which complement each other. As a result, a 3D virtual model with high geometric accuracy and visual completeness is obtained and integrated into a web-based application. Resulting virtual models can be used for touristic promotion, navigation, urban planning, documentation and preservation of cultural heritage, etc.

Evaluate 3D laser point clouds registration for cultural heritage documentation

According to the International Council on Monument and Sites (ICOMOS), cultural heritage is defined as an expression of the manners of living improved by a community and passed on from past generation to future generation. Three-dimensional point cloud registration is one of the critical topics in close-range remote sensing and particularly in laser scanning. Laser scanning systems in most situations are restricted to scan a segment of the interested site; nevertheless in the greatest majority of applications a scanning for the entire site is required. Iterative closest point (ICP) is an important algorithm to achieve fine registration for two or more overlapping range data by iteratively approximating the Euclidean distances. Many authors, in recent years had been proposed different approaches to improve and modify the ICP registration technique for optimum outputs. In this paper a comparison study was presented to assess Nearest Neighbor Iterative Closest Point (NN-ICP) and Levenberg-Marquardt Iterative Closest Point (LM-ICP) registration methods in order to evaluate the 3D close-range TLS data outputs for cultural heritage documentation in IRAQ. Additionally, the study is assessing the accuracy of culture heritage documentation based on close-range TL scanning alongside processing elapse time as a priority factor. To investigate these objectives, two experiments were carried out on two study sites in Baghdad/IRQ. The average registration errors delivered from both case studies following automatic process were (3.9 mm) lasts for (49 s) and (2.6 mm) lasts for (200 s) for NN-ICP and LM-ICP respectively. In order to evaluate the accuracy of the extracted 3D digital models, conventional survey measurements were executed for a set of evenly distributed reference points mounted around the body of two selected objects in both sites. The RMSE delivered from the indoor and the outdoor sites were (6mm) and (12 mm) with minimum range of (3.5 m) and (7 m) respectively.

\u2018\u2018POLYGNOSIS\u2019\u2019: the development of a thesaurus in an Educational Web Platform on optical and laser-based investigation methods for cultural heritage analysis and diagnosis

Due to their unique properties, laser and optical technologies hold today an important role in the protection and study of Cultural Heritage, since they are used in a wide range of demanding analytical and diagnostic applications. Considering the rapid and vast technological development of their methodologies and tools, it is necessary to make this new knowledge more reachable and comprehensible to heritage scientists. Towards this end, a web-based knowledge platform (Polygnosis) (http://politeia.iesl.forth.gr/polygnosis/) was designed by the Institute of Computer Science (ICS) of FORTH concerning the state-of-the-art light and/or laser-based techniques, which have been developed at the Institute of Electronic Structure and Lasers (IESL) of FORTH, for advanced imaging, analysis and diagnosis of Cultural Heritage objects. This educational digital tool seeks to highlight the efficiency and potentials of modern optical and laser technologies in Cultural Heritage documentation, as well as, promote the dissemination and deeper understanding of their applications to conservators, archaeologists, art historians, material and laser scientists. “Polygnosis” represents accumulated knowledge regarding the selection of the diagnostic tool and the suggested methodology, with simultaneous display of examples of actual experimental procedures. The model relates those examples with the relevant terminology of the Thesaurus, the information about the object under examination and the metadata resulting from those experiments. ‘Polygnosis’ thesaurus is a semantically structured vocabulary organized by a faceted classification, which serves the educational needs of the system. The current study concerns the definition and classification of terms for the development of the semantically linked Thesaurus, as well as, the presentation and review of the knowledge platform, with emphasis on the supportive role of the thesaurus in such an educational resource.

Practicing the geometric designation of sensor networks using the Crowdsource 3D models of cultural heritage objects

Nowadays, there is a huge research work and literature about the use of laser scanning, computer vision and photogrammetry to turn cultural heritage objects into 3D digital models. These developed 3D models are used for cultural heritage documentation, conservation, restoration and virtual reality applications. Many 3D digital models of cultural heritage objects like buildings, statues and historical places are shared through the internet and can be downloaded for free use. These models either developed using graphical based software tools or through image based methods and active sensors like laser scanners. Normally, image based and laser scanned reality models are developed through capturing around or/and inside the cultural heritage site by professionals through specific guidelines and plans followed later by processing using a state of the art software. However, practically there is a significant challenge to ensure a complete coverage of the object during the data acquisition and to fulfill the required geometric conditions to meet the needed precision and complete coverage. Therefore, in this paper, we propose a procedure to help non-professionals and students to practice and improve their skills in planning either a camera network or a laser scanner network to finally create a valid 3D model of a cultural heritage site. Two experimental tests are applied to a Crowdsource 3D model of the Haydarkhana mosque in Iraq and the model of the Georgia State Capitol in USA. The scenarios for the sensor network planning is applied and a final 3D point cloud is re-created and lessons learned.

INVESTIGATING THE SUITABILITY OF MIRRORLESS CAMERAS IN TERRESTRIAL PHOTOGRAMMETRIC APPLICATIONS

Abstract. Digital single-lens reflex cameras (DSLR) which are commonly referred as mirrored cameras are preferred for terrestrial photogrammetric applications such as documentation of cultural heritage, archaeological excavations and industrial measurements. Recently, digital cameras which are called as mirrorless systems that can be used with different lens combinations have become available for using similar applications. The main difference between these two camera types is the presence of the mirror mechanism which means that the incoming beam towards the lens is different in the way it reaches the sensor. In this study, two different digital cameras, one with a mirror (Nikon D700) and the other without a mirror (Sony a6000), were used to apply close range photogrammetric application on the rock surface at Istanbul Technical University (ITU) Ayazaga Campus. Accuracy of the 3D models created by means of photographs taken with both cameras were compared with each other using difference values between field and model coordinates which were obtained after the alignment of the photographs. In addition, cross sections were created on the 3D models for both data source and maximum area difference between them is quite small because they are almost overlapping. The mirrored camera has become more consistent in itself with respect to the change of model coordinates for models created with photographs taken at different times, with almost the same ground sample distance. As a result, it has been determined that mirrorless cameras and point cloud produced using photographs obtained from these cameras can be used for terrestrial photogrammetric studies.

ARCHITECTURAL HERITAGE DOCUMENTATION BY USING LOW COST UAV WITH FISHEYE LENS: OTAG-I HUMAYUN IN ISTANBUL AS A CASE STUDY

Abstract. The digital documentation of architectural heritage is important for monitoring, preserving, managing as well as 3B BIM modelling, time-space VR (virtual reality) applications. The unmanned aerial vehicles (UAVs) have been widely used in these application thanks to rapid developments in technology which enable the high resolution images with resolutions in millimeters. Moreover, it has become possible to produce highly accurate 3D point clouds with structure from motion (SfM) and multi-view stereo (MVS), to obtain a surface reconstruction of a realistic 3D architectural heritage model by using high-overlap images and 3D modeling software such as Context capture, Pix4Dmapper, Photoscan. In this study, digital documentation of Otag-i Humayun (The Ottoman Empire Sultan's Summer Palace) located in Davutpaşa, Istanbul/Turkey is aimed using low cost UAV. The data collections have been made with low cost UAS 3DR Solo UAV with GoPro Hero 4 with fisheye lens. The data processing was accomplished by using commercial Pix4D software. The dense point clouds, a true orthophoto and 3D solid model of the Otag-i Humayun were produced results. The quality check of the produced point clouds has been performed. The obtained result from Otag-i Humayun in Istanbul proved that, the low cost UAV with fisheye lens can be successfully used for architectural heritage documentation.

Classification of Architectural Heritage Images Using Deep Learning Techniques

The classification of the images taken during the measurement of an architectural asset is an essential task within the digital documentation of cultural heritage. A large number of images are usually handled, so their classification is a tedious task (and therefore prone to errors) and habitually consumes a lot of time. The availability of automatic techniques to facilitate these sorting tasks would improve an important part of the digital documentation process. In addition, a correct classification of the available images allows better management and more efficient searches through specific terms, thus helping in the tasks of studying and interpreting the heritage asset in question. The main objective of this article is the application of techniques based on deep learning for the classification of images of architectural heritage, specifically through the use of convolutional neural networks. For this, the utility of training these networks from scratch or only fine tuning pre-trained networks is evaluated. All this has been applied to classifying elements of interest in images of buildings with architectural heritage value. As no datasets of this type, suitable for network training, have been located, a new dataset has been created and made available to the public. Promising results have been obtained in terms of accuracy and it is considered that the application of these techniques can contribute significantly to the digital documentation of architectural heritage.

DOCUMENTATION OF HERITAGE STRUCTURES THROUGH GEO-CROWDSOURCING AND WEB-MAPPING

Abstract. Heritage documentation has become increasingly urgent due to both natural impacts and human influences. The documentation of countless heritage sites around the globe is a massive project that requires significant amounts of financial and labour resources. With the concepts of volunteered geographic information (VGI) and citizen science, heritage data such as digital photographs can be collected through online crowd participation. Whilst photographs are not strictly geographic data, they can be geo-tagged by the participants. They can also be automatically geo-referenced into a global coordinate system if collected via mobile phones which are now ubiquitous. With the assistance of web-mapping, an online geo-crowdsourcing platform has been developed to collect and display heritage structure photographs. Details of platform development are presented in this paper. The prototype is demonstrated with several heritage examples. Potential applications and advancements are discussed.

A TWO-STEP CLASSIFICATION APPROACH TO DISTINGUISHING SIMILAR OBJECTS IN MOBILE LIDAR POINT CLOUDS

Abstract. Nowadays, lidar is widely used in cultural heritage documentation, urban modeling, and driverless car technology for its fast and accurate 3D scanning ability. However, full exploitation of the potential of point cloud data for efficient and automatic object recognition remains elusive. Recently, feature-based methods have become very popular in object recognition on account of their good performance in capturing object details. Compared with global features describing the whole shape of the object, local features recording the fractional details are more discriminative and are applicable for object classes with considerable similarity. In this paper, we propose a two-step classification approach based on point feature histograms and the bag-of-features method for automatic recognition of similar objects in mobile lidar point clouds. Lamp post, street light and traffic sign are grouped as one category in the first-step classification for their inter similarity compared with tree and vehicle. A finer classification of the lamp post, street light and traffic sign based on the result of the first-step classification is implemented in the second step. The proposed two-step classification approach is shown to yield a considerable improvement over the conventional one-step classification approach.

3D Recording, Documentation and Management of Cultural Heritage

3D Recording, Documentation and Management of Cultural Heritage

Challenges that Preventive Conservation poses to the Cultural Heritage documentation field

Abstract. This contribution examines the challenges posed to the cultural heritage documentation community (the CIPA community and others) in implementing a preventive conservation approach of the built heritage in today’s society. The “DNA” of Preventive Conservation. Various authors so far support the argument that preventive conservation is an effective way to respond to the challenges society faces with the preservation of its Cultural Heritage (Van Balen, 2013). A few decades of experiences with the application of preventive conservation in the field of immovable heritage in the form of Monumentenwacht in The Netherland and in Flanders have shown that a good monitoring of the state of preservation with a strong push for maintenance activities contributes to more preservation of authenticity, to more cost-effective preservation and to empowering society in dealing with heritage preservation. (Cebron, 2008) An analysis of these and similar experiences demonstrates that these “Monumentenwacht” activities represent only a part of what could be named a preventive conservation system. Other fields in which prevention is advocated for its higher efficiency, show the importance of system thinking in the development of improved strategies. Applying this approach to the field of the immovable heritage, referring to the initial results shown by the Monumentenwacht practices, it becomes clear that different dimension are at stake simultaneously: the preservation of authenticity or integrity, the management of resources and the connection with society. It shows that the analysis of challenges in heritage preservation and the development of strategies is à priori multifaceted and therefor has a certain level of complexity. The sustainability of the preservation of cultural heritage buildings and sites can be measured according to its multiple economic, social, environmental and cultural support. The Cultural Heritage Counts for Europe report shows that the more diverse the support is for cultural heritage preservation actions, the more those actions will contribute to sustainable development and the more sustainable the preservation of that heritage will be. This reasoning has led to the “upstream approach” which argues that cultural heritage preservation can benefit from a variety of resources which do not necessarily have to be earmarked for it à priori (CHCfE, 2015). It leads to arguing for an holistic and integrated approach for cultural heritage preservation that taps into different kinds of resources, which requires acknowledgement of the complex nature of understanding and managing heritage values into an overall societal development goal (Vandesande, 2017). Challenges in the Cultural Heritage documentation field. Documentation needs in the field of cultural heritage preservation therefor are challenged by the complexity of the sources of information, by the need to integrate them in an holistic tool and by the way they are able to dialogue with society. 1. The proper analysis of heritage requires increasing efforts by the diversity of sources and the complexity of their interaction.This (complexity acknowledging) analysis should be linked to monitoring tools which eventually contribute to monitor culturalheritage values. This monitoring is also a documentation challenge as it has to be pertinent and dynamic. Analysis andmonitoring are important as they are the basis for understand threats that impact heritage values. 2. As resources for heritage development or heritage guided development can have a variety of origins, their documentation andanalysis –compared to the traditional curative object oriented preservation- should be extended to include many more possibleresources. Experiences exist with documentation of the physical environment of heritage sites but the upstream approachpoints toward a larger number of development resources that can be tapped into. This implies the need to identify newapproaches, to document them and to integrate them in a dynamic analytical process. 3. As preventive conservation focusses not only on the empowerment of the owners and managers but also on a betterintegration of a wider group of stakeholders, the question of ownership and continuous co-creation challenges thedocumentation process as well. 4. Longevity of documentation: the need for continuous updating and monitoring as part of the cyclic approach of PC challengesthe longevity, accessibility of the documentation itself and the tools that will use them in the future.

FROM FIELD WORK TO DELIVERABLES. EXPERIENCES ON THE TIN HOUSE COURTYARD DOCUMENTATION

Abstract. The Tin House Courtyard is a property of the National Capital Commission (NCC) in Ottawa, Canada. The site is located within the ‘Mile of History’, a historical route running from Parliament Hill to the Governor General’s residence. Currently, existing assets are under intervention works that include several preservation and renewal actions. Within the broader project, one of the tasks before construction works started was the documentation of the set of facades. The Carleton Immersive Media Studio (CIMS) at Carleton University in Ottawa was commissioned by NCC to conduct the recording of the area. This paper describes the process undertaken from field work to the final deliverable to the client, as well as the issues faced in between. Nowadays, up to date surveying technologies have revolutionized the methodologies for cultural heritage documentation. In this regard, the recording strategy employed encompassed the use of photogrammetry, laser scanner, total station, as well as different pre and post processing software in order to generate the desired outcomes.

UAV PHOTGRAMMETRIC WORKFLOWS: A BEST PRACTICE GUIDELINE

Abstract. The increasing commercialization of unmanned aerial vehicles (UAVs) has opened the possibility of performing low-cost aerial image acquisition for the documentation of cultural heritage sites through UAV photogrammetry. The flying of UAVs in Canada is regulated through Transport Canada and requires a Special Flight Operations Certificate (SFOC) in order to fly. Various image acquisition techniques have been explored in this review, as well as well software used to register the data. A general workflow procedure has been formulated based off of the literature reviewed. A case study example of using UAV photogrammetry at Prince of Wales Fort is discussed, specifically in relation to the data acquisition and processing. Some gaps in the literature reviewed highlight the need for streamlining the SFOC application process, and incorporating UAVs into cultural heritage documentation courses.

CAPTURING REALITY AT CENTRE BLOCK

Abstract. The Centre Block of Canada’s Parliament buildings, National Historic Site of Canada is set to undergo a major rehabilitation project that will take approximately 10 years to complete. In preparation for this work, Heritage Conservation Services (HCS) of Public Services and Procurement Canada has been completing heritage documentation of the entire site which includes laser scanning of all interior rooms and accessible confined spaces such as attics and other similar areas. Other documentation completed includes detailed photogrammetric documentation of rooms and areas of high heritage value. Some of these high heritage value spaces present certain challenges such as accessibility due to the height and the size of the spaces. Another challenge is the poor lighting conditions, requiring the use of flash or strobe lighting to either compliment or completely eliminate the available ambient lighting. All the spaces captured at this higher level of detail were also captured with laser scanning. This allowed the team to validate the information and conduct a quality review of the photogrammetric data. As a result of this exercise, the team realized that in most, if not all cases, the photogrammetric data was more detailed and at a higher quality then the terrestrial laser scanning data. The purpose and motivation of this paper is to present these findings, as well provide the advantages and disadvantages of the two methods and data sets.

A TARGET AWARE TEXTURE MAPPING FOR SCULPTURE HERITAGE MODELING

Abstract. In this paper, we proposed a target aware image to model registration method using silhouette as the matching clues. The target sculpture object in natural environment can be automatically detected from image with complex background with assistant of 3D geometric data. Then the silhouette can be automatically extracted and applied in image to model matching. Due to the user don’t need to deliberately draw target area, the time consumption for precisely image to model matching operation can be greatly reduced. To enhance the function of this method, we also improved the silhouette matching algorithm to support conditional silhouette matching. Two experiments using a stone lion sculpture of Ming Dynasty and a potable relic in museum are given to evaluate the method we proposed. The method we proposed in this paper is extended and developed into a mature software applied in many culture heritage documentation projects.