In response to the rising demand for digital twins, the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) launched Project PLATEAU, a 3D city model initiative. Japan has over 1,700 municipalities, each with unique characteristics that may lead to diverse 3D city models. However, differing specifications may compromise data reusability.

This paper presents the "Standard Data Product Specification for 3D City Models" (SDPS-3DCM), designed to facilitate the development, utilization, and availability of 3D city models. The SDPS-3DCM adopts CityGML and its Urban Planning Application Domain Extension (i-UR) as its application schema. We provided feedback to i-UR based on city use cases regarding missing features and attributes. Incorporating the updated i-UR improved the comprehensiveness of the SDPS-3DCM. Additionally, the SDPS-D3CM defines the subdivisions of Level of Detail (LOD) to promote a common understanding among data creators and users, increasing production efficiency and ensuring consistency. Each city can localize its specification by profiling the SDPS-3DCM, resulting in a 3D city model grounded in a unified specification while allowing for specific contextual variations. By 2023, over 200 cities developed 3D city models compliant with the SDPS-3DCM and made them publicly available as open data. The SDPS-3DCM not only accelerates the rapid development of 3D city models but also streamlines the creation and utilization of related tools. The SDPS-3DCM is expected to standardize 3D city models, address societal issues, and create new value across public and private sectors.