Last update: Feb 2020
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Publications with reviews

Investigating Semantic Functionality of 3D Geometry For Land Administration
G. Floros, E. Tsiliakou, D. Kitsakis, I. Pispidikis & E. Dimopoulou (2015)

Significance of semantic data during the recent years is growing. This trend, combined with facilitation of new 3D object modeling has led to semantically enriched 3D models, serving various applications where relations between objects’ components and their environment need to be stored and presented. In the field of Land Administration, semantics can greatly contribute to optimize land management and land policies. Integration of semantics to 3D building models is currently achieved through two differently structured models: semantic-oriented CityGML and structural-oriented BIM/IFC. Integration of the semantic information of each model is still an object of intense research worldwide. In this paper, a 3D building model designed in SketchUp Pro software was transformed using FME software to a CityGML file; land use features were assigned to the model and attribute queries were executed in order to check the exported models’ functionality in terms of semantics

3D Marine Administration System based on LADM
A. Athanasiou, I. Pispidikis & E. Dimopoulou (2015)

Oceans cover almost two-thirds of the Earth’s surface. They are the primary regulator of the global climate and sustain a huge variety of plant and animal life. Maritime environment needs to be organized and precisely determined, in order to be sustainable. The registration of marine legal boundaries is a necessary condition for the protection of a living organism, which flows, changes, reverses itself, but is not limitless. Research has confirmed that the common pattern of people-land relationship also exists in the marine environment. Moreover, the marine Cadastre concept suggests that the complexity of interests in marine space is similarly encountered in land. The extension of Cadastre functions from land to marine space is considered reasonable. An inventory of interests that exist in the marine environment is important. At the same time, laws that are the basis of these interests need to be identified and their effect qualified and visualized. The administration of the marine space remains partial and complex, mainly deriving from political interests and strategic benefits. This could be overcome by designing a marine administration system, in accordance with the international practices. A conceptual model may be considered as the base of such system. This model should clearly depict the relevant entities of the system and the relationships between them. Modeling and standardizing systems and processes at an international level, requires the harmonization with international standards and specifically with the ISO 19152—Land Administration Domain Model (LADM), which so far remains a challenge. The aim of this paper is to present how rights, restrictions and responsibilities (RRRs) relating to marine space may be organized, in order to develop a marine administration model based on LADM, followed by the database implementation, to support effective and efficient decision making in marine governance

A roadmap for generating semantically enriched CityGML model via two different methodologies
G Floros, D Solou, I Pispidikis, E Dimopoulou (2016)

The methodologies of 3D modeling techniques have increasingly multiplied due to the rapid advances of new technologies. Nowadays, the focus of 3D modeling software is directed, not only to the finest visualization of the models but also in their semantic features during the modeling procedure. As a result, the models thus generated are realistic and semantically enriched. Additionally, various extensions of the modeling software allow for the immediate conversion of the model's format, via semi-automatic procedures with respect to the user's scope. The aim of this paper is to present two methodologies and provide specific detailed instructions on how to generate a semantically enriched and geometrically concrete CityGML model. The first methodology includes the modeling in Trimble SketchUp and the transformation in FME Desktop Manager, while the second methodology includes the model's generation in CityEngine and its transformation in the CityGML format via the 3DCitiesProject extension for ArcGIS. Finally, the two aforesaid methodologies are being compared and specific characteristics are evaluated, in order to infer the methodology that is best applied depending on the different projects' purposes

Development of a 3D WebGIS system for retrieving and visualizing CityGML data based on their geometric and semantic characteristics by using free and open source technology
I Pispidikis, E Dimopoulou (2016)

CityGML is considered as an optimal standard for representing 3D city models. However, international experience has shown that visualization of the latter is quite difficult to be implemented on the web, due to the large size of data and the complexity of CityGML. As a result, in the context of this paper, a 3D WebGIS application is developed in order to successfully retrieve and visualize CityGML data in accordance with their respective geometric and semantic characteristics. Furthermore, the available web technologies and the architecture of WebGIS systems are investigated, as provided by international experience, in order to be utilized in the most appropriate way for the purposes of this paper. Specifically, a PostgreSQL/ PostGIS Database is used, in compliance with the 3DCityDB schema. At Server tier, Apache HTTP Server and GeoServer are utilized, while a Server Side programming language PHP is used. At Client tier, which implemented the interface of the application, the following technologies were used: JQuery, AJAX, JavaScript, HTML5, WebGL and Ol3-Cesium. Finally, it is worth mentioning that the application’s primary objectives are a user-friendly interface and a fully open source development

Browsing in Web Interactive 3D Environment- Application in the School of Rural and Surveying Engineering of NTUA
Ι. Pispidikis, Ε. Tsiliakou, D. Kitsakis, A. Athanasiou, E. Kalogianni, T. Lampropoulos, E. Dimpoulou (2017)


Investigating integration capabilities between IFC and CityGML LoD4 for 3D City Modeling
G Floros, I Pispidikis, E Dimopoulou (2017)

Smart cities are applied to an increasing number of application fields. This evolution though urges data collection and integration, hence major issues arise that need to be tackled. One of the most important challenges is the heterogeneity of collected data, especially if those data derive from different standards and vary in terms of geometry, topology and semantics. Another key challenge is the efficient analysis and visualization of spatial data, which due to the complexity of the physical reality in modern world, 2D GIS struggles to cope with. So, in order to facilitate data analysis and enhance the role of smart cities, the 3rd dimension needs to be implemented. Standards such as CityGML and IFC fulfill that necessity but they present major differences in their schemas that render their integration a challenging task. This paper focuses on addressing those differences, examining the up to date research work and investigates an alternative methodology in order to bridge the gap between those Standards. Within this framework, a generic IFC model is generated and converted to a CityGML Model, which is validated and evaluated on its geometrical correctness and semantical coherence. General results as well as future research considerations are presented

CityGML RESTFul Web Service: Automatic retrieval of CityGML data based on their semantics. Principles, guidelines and BLDG conceptual design
I. Pispidikis and E. Dimopoulou (2018)

CityGML is considered an optimal standard for the representation of 3D city models. However, due to its complex structure, easy-to–use data retrieval is important, in terms of interoperability. This implies choosing the implementation of Web Service Technologies and in particular the WFS, as the most suitable OGC standard for retrieving the real geometry data. Nevertheless, this standard serves data mainly based on their geometry, while CityGML also covers topology and more importantly semantic aspects of 3D city models. Therefore, this paper examines and presents the new CityGML RESTful Web service, instead of the OGC WFS. This Web Service is conceptually designed to achieve CityGML data retrieval based on their semantics characteristics. In this context, several principles and guidelines of the new CityGML RESTful Web service are described and the “CityModels” resource is presented. Additionally, the conceptual design of the bldg resource and its child resources based on the level of details is also presented

Combining methodological tool for the optimum 3D modeling of NTUA Campus
I. Pispidikis, E. Tsiliakou, D. Kitsakis, K. Athanasiou, E. Kalogianni, T. Labropoulos, and E. Dimopoulou (2018)

Rapid urbanisation relates to increased space requirements above and below ground and the development of complex structures. This profound need attracted increasing interest for the collection, modelling, management, visualisation and dissemination of 3D objects through various application fields, such as: 3D Cadastre, 3D City Modelling and Building Information Modelling. Contemporary advances in GIS technology, Geo-Web services and computer graphics facilitate the development of such models accompanied by semantic, geometrical and topological information, while the use of international standards enables the communication and interoperability between the systems. The aim of this paper is to combine state-of-the art methodologies and technologies for the development of semantically enriched 3D models for the Campus of the National Technical University of Athens in Greece. The result is a web-based 3D Campus map that integrates these models as Web Services, providing access to management and navigation for the campus area and can also be used for maintenance purposes from the various NTUA Departments. To this end, the database schema has been designed compatible with CityGML, while attention was given to interoperability issues that arise from differently derived 3D models which had to be stored and visualised while retaining their characteristics

Portable Interactive Map of the Hellenic Military Geographical Service
T. Koukolotsos, I. Pispidikis, J. Batsos (2018)

Hellenic Military Geographical Service (HMGS) presents ‘Portable Interactive Map’ (PIM), which is a new digital map product for portable devices (tablet/smartphone). It is a package of spatial data for a specific area of interest, accessible through appropriate viewer software. Taking advantage of the embedded GPS receiver and camera, as well as the software capabilities, it is possible to locate, view, collect and process spatial data out in the field.
Apart from the enhanced portability, provided by the device size, much attention is given on the offline geospatial support. Since currently PIM is designed for the Armed Forces, offline operation is essential, either because network will not be available during operations, or access will be avoided for security reasons, so as not to reveal the user position. Offline support is achieved through a standardized line of production, during which tailored maps, satellite imagery and vector data layers are created and loaded on the device.
PIM usage could be extended beyond the Armed Forces. With offline access to satellite imagery and maps, as well as being able to prepare PIM rapidly through a suitable production line, it is estimated that, along with the viewer software capabilities, PIM could be a valuable tool in the hands of the emergency or crisis personnel dealing with a natural disaster.

Semantic-based Technologies for Interoperable BIM and GIS 3D Modelling, Storage and Retrieval
 K. Athanasiou ,I. Pispidikis  and E. Dimopoulou (2018)

3D city models are increasingly used for a wide range of applications beyond mere visualisation. While Geographic Information Systems (GIS) and Building Information Models (BIM) have been developed for different purposes in two different domains, they do share common characteristics.
To better understand these two different domains and their common intersection, this paper explores integration efforts and interoperability options, through the review of standards and technologies that are used for 3D modelling, storage and retrieval of the semantic information.
Within this context, this research aims to contribute from the very first step, towards this integration and proposes a framework for better organising the elements during the design process, in order to achieve semantically enhanced 3D information models, considering IFC and CityGML standards. Furthermore, a methodology is proposed for storage and automatic retrieval of the stored data, based on interoperability capabilities, dispensing with the need for specific knowledge of the used technologies.

I. Pispidikis and E. Dimopoulou (2019)

A 3D city model is considered as the digital representation of a city that may decompose into its objects (such as buildings, roads, railways, terrain, water, vegetation etc.) with clearly defined semantics, spatial and thematic properties. Depending on the level of detail, these objects may further decompose into more detailed features. The OGC standard CityGML, optimally allows integration of the diversified geoinformation of the aforementioned elements and provides multiple resolutions at different levels of detail (LoDs). Retrieving information from this standard is a challenge, in terms of interoperability, implementing the Web Service Technology. Within this technology, this paper examines and presents the conceptual model of the CityGML RESTful Web Service regarding all main resources which are structured according to the ten thematic modules of CityGML, in all available LoDs.