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Evaluation of a laser scanning sensor on detection of complex shaped targets for variable-rate sprayer development
- Hui Liu, Heping Zhu
- Transactions of the ASABE 2016 v.59 no.5 pp. 1181-1192
- accuracy, algorithms, cameras, canopy, computers, cylinders, data collection, detection, equipment performance, image analysis, lasers, ornamental trees, sensors (equipment), sprayers
- Sensors that can accurately measure canopy structures are prerequisites for development of advanced variable-rate sprayers. A 270° radial range laser sensor was evaluated for its accuracy to measure dimensions of target surfaces with complex shapes and sizes. An algorithm for data acquisition and 3-dimensional canopy image construction were designed and processed with an embedded computer. Test targets included three beach balls at three heights, a rectangular box, a cylinder, two artificial and three field-grown ornamental trees. Other variables included 2, 3, 4, and 5 m detection distances and sensor travel speeds of 3.2, 4.8, 6.4, and 8.0 km h-1. The laser sensor measurements of test targets were statistically similar with the actual measurements. The mean RMS errors and CVs varied slightly with the detection distance and travel speed. Among all the measurements of dimensions in the ranges of 0.58 to 2.54 m in X direction, 0.58 to 2.54 m in Y direction, and 0.58 to 2.94 m in Z direction, the highest average root mean square error (RMS) was 68 mm occurred in Z direction and the highest average CV was 8.6% occurred in Y direction. Similarity of paired images from the laser sensor and a camera for all targets was greater than 0.85. These tests confirmed the capability of the laser sensor and the algorithm to accurately measure the complex shaped targets, offering potentials for integration of the sensor and algorithm into sprayers that will make real-time adjustment on spray outputs to match plant structures and travel speeds.