DSM measurement for exposed gravel surface using close-range photogrammetry with multi-scale images

The geometry information of the exposed gravel surface geometry is important for understanding the flow characteristic. This research has developed a methodology to generate the Digital Surface Model (DSM) of gravel surface using multi-scale close-range photogrammetry. The camera was calibrated on-site with a self-calibration bundle adjustment using coded retro-reflective targets. The DSM of the gravel surface was generated for two scales. The small scale DSM was used as the control surface, and the large scale DSM contains more detailed elevation variation and is registered to the small scale DSM by iterative closest point (ICP). A field area of 6 m × 6 m has been tested and the results are provided.