Conference Agenda

The recent rapid rise in the demand for digital methods for planning and management of road infrastructure has led to the development of new concepts for structuring the targeted applications where digital methods shall be applied in the future to improve overall efficiency. This transition towards digital planning, maintenance and even coupling digital representations with the asset in the real world requires a clear structure so that existing potential can be optimally exploited. In this paper, we propose an improved LOAD concept for the digital representation of roads for the use in digital twins. Since digital planning is just emerging in road construction, the road infrastructure sector currently faces the issue of existing roads not having a digital representation. Accounting for the current situation, we especially highlight the path from reality capturing towards the establishment of the digital representation as-is, in cases, there is no digital representation of the targeted road segment available yet.

The surveying and mapping department of the City of Vienna has been working on the Digital geoTwin project since the end of 2019. The new strategy focuses on both the creation of semantic 3D objects and other geodata products, which completely restructures existing workflows. The core of the strategy is to process the three-dimensional measurement data of the surveying and mapping department from existing as well as potentially new measurement methods directly into a Digital geoTwin – a virtual, semantic 3D replica of all objects in the city – and to derive other geodata products (city map, elevation models, etc.) from this 3D model. Furthermore, the Digital geoTwin should serve as a geometric and semantic basis for a digital twin of the City of Vienna. In this article, we try to explain the concept of a digital twin in the context of a large city. Subsequently, the development and goals of the Digital geoTwin will be discussed and the need for new data models will be assessed. CityGML as an international standard for 3D city models offers a foundation for the development of such data models. The results of a prototypical development of a data model for the Digital geoTwin based on CityGML form the main part of this article.

The paper presents a new hierarchy of multiple levels of detail (LOD) designed for the modeling of underground utility networks. The hierarchy of LODs is applied to water management possible scenarios in the context of determining the aging of distribution networks. The hierarchy of LODs proposes four levels, two sub-levels, and three quality levels. The various LODs are defined based on the dimension of the space and the geometric primitives, the topology, semantic aspects, contextual information, and data quality (regarding 3D data collecting). It is believed that this number of levels is sufficient and appropriate to cover the modeling of underground utility networks suitable for various applications.

Representations of an object in different granularity using the Level of Detail concept are usually separated without links between corresponding elements. Extension of a 3D model to the fourth dimension opens new possibilities for spatial analysis. Integration of scale using additional spatial dimension can help in scale-dependant analysis and preserving consistency, especially in case of model updates. In this paper, an extended version of the dual half-edge structure for topological representation of 4D cell complexes is proposed. This feasibility study shows implementation of the Poincaré duality theorem in practice. Thanks to that, the data structure remains simple, where only two atomic elements are used in a construction process. i.e. nodes and edges. This solution lays the groundwork for future research, where topological links in the fourth dimension will be used to connect consecutive object representations of different granularity.

Topology can be defined as properties that describe how objects in a space are related which includes containment, adjacencies and connectivity information. The topological information may seem simple yet it is fundamental to facilitate more complex analysis such as 3D data validation and applications. As a spatial property, the preservation of topology within a spatial database is important. Topology rules are a set of conditions that define topological relationships between objects stored in a spatial database. This study attempted to implement 3D topology rules for determining topological relationships between 3D objects stored in an Oracle spatial database. A set of 3D topology rules are implemented based on the 36IM. Ten topological groups can be tested in the 36IM which consists of point-to-point, point-to-line, point-to-region, point-to-volume, line-to-line, line-to-region, line-to-volume, region-to-region, region-to-volume and volume-to-volume. The 36-IM is represented by a 12×3 intersection matrix that can be simplified into a 3×3 intersection matrix that holds the highest dimension of intersection. As a result, topological relationships between 3D objects could be determined without any decomposition into lower dimension objects. This is due to the nature of 36IM that handles ten topological groups which includes equal and cross dimension objects. The geometrical integrity of objects is preserved while maintaining accurate 3D topological information.