## 4 Conclusions  
As a type of typical artificial terrain, accurate road DEM construction is an important basis for artificially mixed-terrain DEM construction. On the basis of comprehensive analysis of road semantic characteristics, this study took the high-definition image data observed by UAVs as the basic data source, designed a road DEM construction method incorporating semantic information, and developed a corresponding road DEM construction method focusing on both morphological expression priority and functional expression priority. This study selected typical experimental areas in which to carry out road DEM construction experiments. The main conclusions are as follows:  
1. As an artificial surface, roads have clear functional attributes which determine the consistency of surface morphology and the elevation fluctuation of different roads in local areas. Therefore, the precise modeling of road DEM can be achieved by using the local control equation proposed in this study, which takes the sideline and centerline of the road as the macro-morphological constraints and integrates the morphological and semantic features. Slope mapping analysis demonstrated that compared with the traditional road DEM generated by the interpolation method, the road DEM shape constructed in this study is more consistent with the actual road surface.
2. The terrain modeling data used in DEM construction have high density and accuracy. At this time, the adjustment in the elevation value of the nodes on the sideline and the centerline of the road will not lead to a loss in elevation accuracy. Their purpose is to eliminate jitter in the local range of the sideline and the centerline of the road to improve the surface smoothness of the final road DEM. The statistical results of the maximum elevation, average elevation, and other parameters of the road DEM constructed by different methods in this paper indicate that the elevation difference of the road was small, and abnormal road surface jitter was eliminated.
3. For relatively flat roads, the traditional DEM generation method was unable to correctly express the surface water catchment process. However, the road surface DEM elevation correction algorithm based on the constraint of the drain proposed in this study can ensure that the backwater path of the road surface points to the drain on the side of the road, and that the runoff simulation results of the road surface are correct. At the same time, the correction algorithm had a very small impact on the elevation change in the original DEM data, resulting in an average change of less than 1 cm. The function of the surface correction algorithm is to finetune the height relationship of different locations of the road so that it can correctly simulate the surface water catchment path, but the algorithm does not affect the elevation accuracy of the road DEM.  
Conceptualization, M.Z. and N.Z.; methodology, N.Z.; validation, M.Z. and N.Z.; formal analysis, M.Z.; investigation, M.Z.; resources, M.Z.; data curation, N.Z.; writing--original draft preparation, M.Z. and N.Z.; writing--review and editing, M.Z. and N.Z.; visualization, N.Z.; supervision, M.Z. and N.Z.; project administration, M.Z. and N.Z.; funding acquisition, M.Z. and N.Z. All authors have read and agreed to the published version of the manuscript.  
This work was supported by a grant from the Major Program of National Natural Science Foundation of China (No. 42293270), the National Program of National Natural Science Foundation of China (No. 42071374), Anhui Province Universities Outstanding Talented Person Support Project (No. gxyq2022097), Major Project of Natural Science Research of Anhui Provincial Department of Education (No. 2022 AH040150), The guiding plan project of Chuzhou science and Technology Bureau (No. 2021 ZD008), and the Key Project of Innovation LREIS (KPI001).  
Not applicable.  
Data Availability StatementData are available from the corresponding author upon request by email.