Recommendation for Vegetation Information in Semantic 3D City Models Used in Urban Planning Applications

Cities are growing in size and becoming increasingly dense. This situation calls for strategic planning of green infrastructure in the urban planning process. Safeguarding the green infrastructure is important for maintaining urban ecosystem services and increasing the well-being of urban populations. To facilitate appropriate urban planning that enables cities to grow sustainably, it is important that the geospatial community provides adequate vegetation information. In this study, we investigate the need for vegetation information in urban planning applications such as modelling ecosystem services and noise, as well as performing case studies of using vegetation information in daylight and solar energy simulations. Based on these investigations, we formulate a recommendation of how vegetation information should be included in 3D city models. The study is focused on the development of a Swedish national profile of CityGML, but many of the conclusions are general and universally applicable. In short, the recommendations are that: (1) the vegetation theme should follow CityGML 3.0 with some additional attributes (e.g., popular name of tree species) added as an application domain extension, (2) no LOD division is required for the vegetation information stored (but rather derived if necessary), (3) the vegetation theme should only contain 3D vegetation objects while the 2D vegetation is part of the land cover theme, and (4) the building specification (and city furniture specification) must include the possibility to store information on whether building roofs or facades (and walls) are covered with vegetation.