Nowadays, cultural and historical built heritage can be more effectively preserved, val-orised and documented using advanced geospatial technologies. In such a context, there is a major issue concerning the automation of the process and the extraction of useful information from a huge amount of spatial information acquired by means of advanced survey techniques (i.e., highly detailed LiDAR point clouds). In particular, in the case of historical built heritage (HBH) there are very few effective efforts. Therefore, in this paper, the focus is on establishing the connections between semantic and geometrical information in order to generate a parametric, structured model from point clouds using ontology as an effective approach for the formal conceptualisation of application domains. Hence, in this paper, an ontological schema is proposed to structure HBH representations, starting with international standards, vocabularies, and ontologies (CityGML-Geography Markup Language, International Committee for Documentation conceptual reference model (CIDOC-CRM), Industry Foundation Classes (IFC), Getty Art and Architecture Thesaurus (AAT), as well as reasoning about morphology of historical centres by analysis of real case studies) to represent the built and architecture domain. The validation of such schema is carried out by means of its use to guide the segmentation of a LiDAR point cloud from a castle, which is later used to generate parametric geometries to be used in a historical building information model (HBIM).

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Because of the need for new sustainable future alternatives, the re-inhabitation of rural areas, hinterlands, small historical urban centres and villages has become a unique real opportunity. Therefore, it is necessary to define and adopt new sustainable urban planning and building permits to follow this path. These processes involve both various actors and disciplines and a variety of spatial and semantic data. For this reason, the present research aims at providing a methodology to build the necessary spatial documentation of historical centres and villages by adopting an ontology-based workflow. Existing ontologies and conceptualisations have been considered together with classes and rules from city historical core regulations. A case study has been selected considering its available spatial datasets and national data models. The bottom-up approach here adopted aims at validating and enriching a reference ontology previously developed in the domain of historical centre by adding new concepts and relations from selected regulation plans and other existing ontologies and data models. Finally, the obtained ontology is also populated with instances of concepts and relations.

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Architectural, built heritage and historical buildings embody cultural heritage value and-as known-they need to be studied, documented, persevered and represented. Although there are many fields involved in these activities, none of these considered individually can fully represent the heritage with a complete level of detail and information. The present work aims to investigate the different levels of detail and granularity among different communities involved in historical buildings tasks to semantically define different concepts. In this context, ontologies are considered as an effective solution for the formal conceptualization of the domains involved, providing a common language for knowledge sharing and reuse. The study starts from existing knowledge (standards, vocabularies, thesauri, classifications) and conceptualisations for regional, urban and architectural heritage and geographic information for various tasks (restoration, documentation and heritage studies, risk prevention, heritage asset and facility management, education and tourism, urban planning and energy refurbishment/performance). A specific use case involving historical buildings in fortified centres across different levels of detail is described to show how existing knowledge and standards conceptualisation need to be integrated and extended.

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In both research and practice, data interoperability is considered essential to support a rising number of applications that need data from different domains. Therefore, standard data formats and models are developed by standardization organizations such as Open Geospatial Consortium (for the Geo domain) and buildingSMART (for the BIM domain). However, from practical experiences, problems were noticed (standards implementation and use of standardized data). Nevertheless, it was hard to discover what the most serious issues were and what was their reason. For GeoBIM (integration of geoinformation with building information models), the CityGML standard, by Open Geospatial Consortium, and Industry Foundation Classes (IFC) by buildingSMART, were considered and tested in this initiative. A sample of datasets in the two formats were provided. External volunteers were asked to import the datasets in tools supposed to support the standards, check relevant aspects for the use of data (geometry, semantics, georeferencing, functionalities), report on them, and re-export the datasets in the standard format. Other tasks were intended to describe and test georeferencing procedures for IFC models and conversion tools between CityGML and IFC. This benchmark was useful to gather best practices and data about the functioning of useful tools to manage standardized data. Common behaviors and potential problems were pointed out and the discussion about the use of standards was further pushed.@en

Standardised data formats and data models are essential for data integration and interoperability, which in turn adds value to data by allowing its reuse in multiple contexts. For this reason, in recent years extensive efforts have been focused on standards development. When representing the built environment, 3D city models and Building Information Models are particularly relevant, and their integration is now required to underpin use cases that cover the full life-cycle of a built asset, including design and planning as well as operations and management, and to support legal applications such as cadastral systems. For those kinds of data, CityGML by the Open Geospatial Consortium and Industry Foundation Classes by buildingSMART are the most popular reference standards. However, many users report, often through informal channels, the difficulties of working with these formats. This paper summarizes the outcomes of the GeoBIM Benchmark 2019, a scientific initiative funded by ISPRS and EuroSDR to collect insights into the most relevant issues encountered in the management of CityGML and IFC within existing software. Alongside data management (import, visualisation, analysis, export) problems, issues of particular consequence in terms of integration relate to georeferencing IFC files and the conversions among the two kinds of formats and models. Thus, the benchmark was designed to explore these tasks in available software. Following analysis of the benchmark results, a key outcome is the impossibility to find clear patterns in the behaviour of tools, which consequently means there is no consistency in the implementation of standards. Although the results could seem disappointing, the criticality in managing these standards as they are was described and this awareness can be the starting point for further research or further standards development. Finally, this project was useful to gather a wide community around this topic, and the discussion about the GeoBIM-related issues was definitely pushed.

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Historical small urban centres are of increasing interest to different interacting fields such as architectural heritage protection and conservation, urban planning, disaster response, sustainable development and tourism. They are defined at different levels (international, national, regional), by various organizations and standards, incorporate numerous aspects (natural and built environment, infrastructures and open spaces, social, economic, and cultural processes, tangible and intangible heritage) and face various challenges (urbanization, globalization, mass tourism, climate change, etc.). However, their current specification within large-scale geospatial databases is similar to those of urban areas in a broad sense resulting in the loss of many aspects forming this multifaceted concept. The present study considers the available ontologies and data models, coming from various domains and having different granularities and levels of detail, to represent historical small urban centres information. The aim is to define the needs for extension and integration of them in order to develop a multidisciplinary, integrated semantic representation. Relevant conventions and other legislation documents, ontologies and standards for cultural heritage (CIDOC-CRM, CRMgeo, Getty Vocabularies), 3D city models (CityGML), building information models (IFC) and regional landscape plans are analysed to identify concepts, relations, and semantic features that could form a holistic semantic model of historical small urban centres.

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