Abstract: The combined method of Global Positioning System-Real Time Kinematic (GPS-RTK) and a depth sounder is an important technology in modern underwater topographic measurement. This study integrates this method with unmanned boat technology to construct an unmanned measurement system suitable for underwater topographic survey of stilling basins. The system was applied to the practical measurement of the Tingzikou stilling basin. This paper focuses on a systematical discussion on its working principle, standardized operation flow, and three-dimensional construction method. Combining with the survey data and a three-dimensional model, we analyze elevation parameters for the selected sections: spillway dam, apron, tail sill, end section, and after-end river channel. The results show that the structure of this stilling basin is complete and sediment deposition over the section from the dam to tail sill is not obvious. And in the basin, no noticeable accumulation or structural anomaly is detected, but the elevation of end section and after-end river channel is increased significantly due to accumulation of bedrocks and cofferdam gravels. Application of unmanned measurement technology improves the acquisition accuracy and timeliness of underwater topographic survey.

Key words: unmanned boat, GPS-RTK, sonic sounding, stilling basin, underwater topographical survey