Leaf Area Measurement Correction Based On Smartphone Orientation Sensor

Leaf area is a key parameter for plant growth,group photosynthetic efficiency and the crop cultivation measures.It is widely used in agricultural production and horticultural crop management.Thus the rapid and accurate non-destructive leaf area measurement is very significant.Considering the deficiency of the existing digital image processing methods of leaf area measurement,two improved methods of leaf area measurement were proposed and implemented on the Android smart phone.The main research contents and results are as follows:1.Research of leaf and reference segmentation algorithm under nature scene.Through a large number of segmentation statistical experiments under different illumination and different background,the YCbCr color space chrominance channels were selected for leaf and reference threshold segmentation,the leaf and reference can be accurately segmented after a series of post-processing filters.2.To solve the instability of the box vertex detection in the leaf area measurement based on the geometry correction with a square box,a new method of box vertex detection based on the red circle center was presented.The experimental results showed that the proposed method could locate the four vertices of the box quickly in the complex scene,and the measurement error of the elliptical virtual leaf was less than 1.8%,the real leaf area measurement error was less than 3%.3.Leaf area measurement accuracy was decreased when Smartphone camera's optical axis could not vertical with leaf plane,a new improved method of leaf area measurement base on Smartphone orientation sensor was put forward to solve this problem.The tilt angle model based on the pinhole camera model is the core of this method.The virtual and real leaf test results showed that the proposed method could effectively improve the leaf area measurement when the camera plane has a small tilt angle with the leaf plane.In addition,the tilt angle model can g:ive effective guidance to improve the leaf area measurement accuracy,such as reducing the center distance of leaf and reference,increasing the camera height,decreasing camera tilt angle under the premise that the leaf and reference can be accurately segmented.The running time of two leaf area measurement methods on the HUAWEI H30-L01 and REDMI NOTE3 Android Smartphone are both less than 0.5s.The leaf area measurement system has excellent operation stability,low repeatability of measurement error and other advantages,it has the ability to achieve single-leaf non-destructive measurement,multi-leaf destructive measurement and roughly estimate the whole plant seedling leaf area.It can be popularized and used widely in agricultural production and horticultural crop cultivation.