Three dimensional mapping of aquatic plants at shallow lakes using 1.8 MHz high-resolution acoustic imaging sonar and image processing technology

A new integrated measurement system that combines the acoustic imaging sonar of DIDSON (Dual-frequency IDentification SONar) with concentrator lenses, motion sensors, and differential global positioning system (DGPS) was used to classify different species of aquatic plants and make three-dimensional (3D) mapping of them at shallow lake. In the field experiment at the Lake Yunoko, the image was captured with a 3° concentrator lens. Difference of Gaussian (DoG) filtering was used to classify two species of aquatic plants, Chara globularis and Elodea nuttallii appeared in 2D acoustic images. After the classification, 3D acoustic image was reconstructed from the consecutive 2D processed images. The high-resolution acoustic images obtained allowed us to identify individual aquatic plants with high accuracy. The integrated DIDSON measurement system will contribute to the protection of endangered species in rapidly changing underwater environments.