Digital image-based water level recognizing system and method
Xu Xing1,2,3, Hong Tiansheng1,2,3, Yue Xuejun1,2,3,4, Cai Kun1,2,3, Huang Shuangping1,2,3, Liu Yongxin1,2,3
1.Key Laboratory of Key Technology on Agricultural Machine and Equipment, Ministry of Education, South China Agricultural University, Guangzhou, Guangdong 510642, China; 2.Division of Citrus Machinery, China Agriculture Research System, Guangzhou, Guangdong 510642, China; 3.College of Engineering, South China Agricultural University, Guangzhou, Guangdong 510642, China; 4.Faculty of Engineering and Surveying, University of Southern Queensland, Toowoomba QLD4350, Australia
In order to monitor water level efficiently and provide instantaneous and effective information for guiding water conservancy and agriculture irrigation, a digital image-based water level recognizing system was designed. In the system, a red spherical buoy was installed on a rod which was fixed vertically in water. Since the water level was derived by change in the relative position of buoy, the water level information could be specified by processing the buoy images snatched by a digital camera. For an instantaneous water level could be obtained through a conversion formula between the spherical centre coordinates and the height of water level, an adaptive spherical buoy capturing algorithm for identifying the red region and extracting the characteristics of red sphere and a calculation and correction algorithm for the sphere centre coordinates were proposed. It was shown experimentally that the maximum error in measurement was 0.216 91 cm, which is far below 1cm error specified in the new edition of China National Standard(GB/T 50138—2010)under 6 megapixel camera, 71 cm shoot height, and 282 cm distance between the camera and the fixed rod. Importantly, the system needs no expansive water level gauge or complex sensors and is subject to a relatively low cost. Additionally, the system relies on non-contact measurement only, and unnecessarily affected by interference factors, such as water temperature, quality, sediment etc. This innovative system has a simple structure, can be installed conveniently and used easily, and it has an even better feasibility in water level monitoring sector.
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