Levels of detail in urban 3D models: selection criteria for critical infrastructure operators
Three-dimensional modelling of urban environments has acquired operational relevance in sectors such as critical infrastructure management, communications network planning, and emergency response coordination. The construction of these models involves engineering decisions that directly affect the processing chain: from data capture using airborne or terrestrial sensors through to storage, spatial indexing, and the computational capacity required for their exploitation in operational time. The geometric level of detail selected conditions each of these links. In practice, urban models are structured in progressively increasing levels of fidelity. The most basic levels represent simplified building volumetry, sufficient for communications coverage analysis, shadow estimation, or line-of-sight evaluation. As geometric fidelity increases, the model incorporates elements such as articulated roofing, textured façades, or street furniture, which increases data volume and processing requirements in a non-linear manner. This relationship between fidelity and computational cost is not uniform: areas of high building density generate a disproportionate penalty in storage and rendering time compared to peripheral areas with more regular morphology. The choice of the appropriate level of detail must derive from the intended use case, not from data availability. For strategic planning applications or territorial impact analysis, a low geometric fidelity model with precise semantic attributes is operationally more efficient than a high-resolution digital twin. By contrast, the simulation of signal propagation in high frequency bands, the evaluation of interference in dense environments, or the planning of trajectories for unmanned aerial systems require a more detailed geometric representation for the model results to be valid. In emergency response scenarios, access latency and model portability take precedence over geometric fidelity. An operator managing a contingency in real time requires data that can be consulted with limited computational resources and over degraded communications networks. In this context, maintaining versions of the model at different levels of detail, with incremental update mechanisms, represents a more robust data architecture than relying on a single high-resolution model. For administrations and critical infrastructure operators within the European Union, the management of 3D urban models also raises implications regarding data sovereignty, interoperability between platforms of different administrations, and update cycles compatible with the rates of change of the built environment. Defining a level-of-detail policy that is coherent with the operational processes of each organisation therefore constitutes a systems architecture decision with long-term consequences for institutional efficiency and response capability.
NASSAT - Network Satellite Systems