3D stadsmodeller för mindre kommuner - vad är behoven och vilka standarder krävs?

Sammanfattning: A 3D city model is commonly used by Swedish municipalities in for example city planning or building permit assessment. There are however various kinds of 3D city models of which some are described in this report, for example a semantic 3D object model, mesh model, CIM model or a digital twin model. Even though a 3D city model is common and there are standards available, there are no nationwide recommendations for the specifications of a 3D city model in Sweden. This leaves municipalities with the option to structure the 3D city model mostly by forming their own specifications, which hopefully fit their needs. In the study some of the known 3D city model standards where examined such as CityGML, Lantmäteriets nationella specifikationer för byggnad and 3CIM. The aim was partly to study municipalities and their need for the models, while also identifying which standards and specifications that could meet their needs. Among Sweden’s 290 municipalities, a majority are countryside city municipalities. In this work a case study was conducted where three municipalities were interviewed, two small ones and one large. The case study were conducted to investigate which type of 3D city models are being used and what the different sized municipalities needs and applications are. The case study showed that two smaller municipalities foremost need for a 3D city model is as a tool to assess building permits. The study also describes some of the most common applications for a 3D city model in Sweden, for example, the application as a visualization tool in the planning process or to study the amount of shadow casting in the city. A small-town city block was restructured to follow the new 3CIM standard, 3CIMver1. This was done to investigate the amount of work it takes to adapt a small-town 3D city model to 3CIMver1. The study showed that it is possible to restructure a small part of the city model to 3CIMver1, but it also shows that it might prove difficult when managing a bigger amount of data. The study also formulates recommendations on specifications for a 3D city model according to the needs and applications studied. One recommendation is modelling the building footprint after the building facade and not the exterior roof edge, especially if the model is to be used in building permit assessment.