4.Application of forward design Compared with the traditional two-dimensional DLG data, the BIM design scheme based on spatial mapping data has the characteristics of strong reality, clear expression, high degree of visualization and rich information. Figure 8 shows that the high-density point cloud data are integrated into CATIA after lightweight processing. BIM road design based on point cloud data provides external space reference for designers to avoid unreasonable spatial planning and missing spatial location information of models. Figure 9 shows the BIM elevated design scheme superimposed on the basis of fine model modification of traffic facilities after 40% lightweight of the actual model data of Qianjin Street in a city. The scheme design, display, comparison and modification are carried out directly in BIM design platform without the help of third-party software, so as to avoid the repeated comparison and modification of multiple platforms.