**2.3 Three dimensional model building and updating technology of ballastless track**

Based on the results of (2.1) and (2.2) in this section, the 3D visualization building technology of ballastless track is developed, and the real-time dynamic updating of 3D model during construction is realized.

**Figure 6.**

*3D model building and updating technology of ballastless track.*

The track structure is composed of steel rails, fasteners, track slab, etc. There are many types of track components. To avoid repeated creation of models, a component library was developed. Unified standards and formats were used for creating component models, such as component classification, naming, material standards, modeling accuracy, etc.; Developing parametric modules to build models of the same type but with different sizes, such as track slabs and bases; Realizing the unified management of component models to facilitate the reuse of components at all stages. Based on the unified coding system, the detailed design model of track unit was constructed. Create component models with fixed dimensions such as rails, fasteners and sleepers, by inputting design parameters, parameterized design of different types of track slabs and different plane section bases can be achieved. For example, ballastless track structures (track slabs, etc.) can be rapidly designed according to the information of non-standard slabs and curve superelevation value generated by layout design. The creation of composite model is realized by inputting elevation, layout design, etc. Combined with the component model and the track engineering design data, the track model can be quickly created and updated according to the change of relevant professional information. By means of human-computer interaction, track components creation, data model generation, 3D digital model layout, etc. are all completed through the system interface (**Figure 6**).
