||With the continuous urbanization of Hong Kong, the complexity and heterogeneity of spatial data in three- and temporal-dimensions raise new challenges to the traditional 2D geodatabases. Although the current OGC standard, CityGML 2.0, has already been tested in some cities in Europe, Singapore, and Malaysia, its limitations make it cannot be directly applied to 3D GIS applications in Hong Kong. Meanwhile, smart city has been identified as one strategically important area for Hong Kong, and there is an urgent need to innovate corresponding key technologies, including 3D spatial data infrastructure. This project aims to develop a 3D geodatabase framework for Hong Kong on the demand of Lands Department for its wide GIS applications for the whole Hong Kong, enabling its applications in effective and efficient 3D urban environment. The key issue for implementing the proposed framework is the corresponding data capture technology, and a lightweight 3D Seamless Spatial Data Acquisition System (SSDAS) is thus proposed for the corresponding 3D data capture. The System synergizes progressive spatial information technologies, and a specialized software package for processing, generating and visualizing 3D spatial data. The deliverables of this project include a) a 3D geodatabase framework designed for Hong Kong; b) a synergized hardware platform; c) a post-processing software; and d) 3D geodatabases of pilot areas. The key innovative features of the proposed research include: a) a detailed 3D GIS model for the framework covering 3D geometric and topology modelling integrated with semantics; b) enabling multi-source and multi-format data exchange; c) lightweight hardware platform by replacing the traditional inertial measurement unit (IMU) with 3D LiDAR and using new material for the backpack platform; and d) seamless data acquisition by providing data capturing technology for both outdoor and indoor environments. The developed geodatabase and the corresponding data capture system, SSDAS, will be widely utilized in many fields, including lands and resources surveying and management, civil engineering, autopilot, intelligent transport, highways maintenance and urban planning. These are the key areas that need spatial information infrastructure in Smart City. Although this system will be innovated in Hong Kong, it has a great potential to be further introduced to the markets in Chinese Mainland and worldwide, due to its very practical features and technological innovations.