Grid algorithm for large-scale topographic oblique photogrammetry precision enhancement in vegetation coverage areas

In areas covered by vegetation, large-scale topographic mapping by UAV oblique photogrammetry normally obtain elevations from vegetation instead of ground points, resulting in lower elevation precision. This study developed an precision improvement grid algorithm and associated SOP for large-scale topographic surveying and mapping in vegetation coverage areas by UAV oblique photogrammetry. The procedures of generating a three-dimensional model for topographical surveying was proposed using Guanlang project as an experimental case study. The UAV flight route and the course overlap and side overlap of UAV oblique photogrammetry were designed, and the image control point layout in the experimental field was carried out. CTI T3 high-precision intelligent RTK was used for image control point measurement. A grid algorithm based on elevation maps was developed and validated in the Guanlang experimental field to improve the elevation precision in vegetation coverage areas.