Abstract: The urban space is gradually moving from the ground to the synergistic development of the ground and underground and from two-dimensional to three-dimensional visual management, which puts forward a new demand and high level of data collection, processing, analysis, and application of the underground space. The fusion of 3D models has always been a hotspot of scholars' research, and higher requirements have been put forward for the aesthetics of the models. In this paper, we propose a feasible technical route to construct a fine 3D model of urban underground space, fusing the 3D model constructed in pieces with high-precision and rendering the model surface with cloud rendering technology, to satisfy the data fusion and display requirements of underground space, to provide data support for the drawing of the “natural resources 3D three-dimensional map”,and to promote the exploitation and utilization of underground space and promote the sustainable development of the city. It promotes the development and utilization of underground space and the sustainable development of the city.

Key words: underground space, 3D modelling, data fusion, visualisation, model rendering