Applications of 3D City Models for a Better Understanding of the Built Environment

Abstract

The administration of modern cities is a complex task involving various disciplines. To satisfy their specific needs regarding planning and decision making, all of them require a virtual representation of the city. Semantic 3D city models offer a reliable and increasingly available virtual representation of real world objects in an urban context. They serve as an integration platform for information and applications around the city system, because data from different domains can be linked to the same objects representing real world urban objects. This work gives an overview on the current state of applications based on semantic 3D city models and how they can be categorized. Three use cases are explained in detail. Based on city models according to the CityGML standard, first a tool for estimating the solar irradiation on roofs and facades is introduced. By the combination of a transition model, sun position calculation, and an approximation of the hemisphere the direct, diffuse and global irradiation as well as the SkyViewFactor are computed. Second, an application for the simulation of detonations in urban space is presented. The city model is converted to a field-based representation for running a Computational Fluid Dynamics (CFD) simulation. By storing logical links between the object and the field-based representation of the city model, information exchange between the simulation tool and the city models is realized. The third application demonstrates the estimation of the energy demand of buildings based on official statistical data and the simulation of refurbishment measures. All three applications use a cloud-based 3D web client for visualization of the city model and the application results including interactive analysis capabilities.