Application of UAV photography 3D modeling in surveying and mapping for water conservancy project

To explore the coordinate conversion error issue in the 3D modeling of drone aerial photography for water conservancy engineering surveying and mapping, Laozhushui River in Heze City of Shandong Province was taken as an example.Basic horizontal control and longitudinal and cross-sectional measurements were carried out in the survey area by using the Huace T10 inertial navigation system (INS) Real-Time Kinematic (RTK).National fourth-order leveling was conducted using a WILD NA2 level and a wooden double-sided ruler.A 3D model of the water conservancy engineering river channel was constructed based on the DJI Matrice 600 Pro drone equipped with Ruibo RIY-DG5 five-lens oblique photography technology.The control point elevations obtained through indirect adjustment of the fourth-order leveling were compared with the control point elevations extracted from the 3D model.After correcting the 3D model, digital line drawings were drawn.The cross-sections obtained through RTK actual measurement and those extracted from the 3D model were used to verify the elevation and horizontal accuracy of the 3D model.The results showed that the average difference between the control point leveling elevations before model correction and the model point elevations was -0.047 m, while the difference between the two after correction was -0.001 m, indicating higher model accuracy after correction.The research findings can provide a references for water conservancy engineering surveying and mapping.