AUTOMATED DETECTION OF WEEDS AND EVALUATION OF CROP SPROUTS QUALITY BASED ON RGB IMAGES

Abstract

In this paper, we propose a method of automated data processing allowing to detect weeds and assess crop sprouts quality and quantity based on RGB images obtained by unmanned aerial vehicles (UAVs). The process consists of four main stages: 1) vegetation map generation with the use of modified Triangular Greenness Index (TGI); the index is defined as the area of a triangle formed by 3 points on a spectral curve with wavelengths of 480, 550 and 670 nm and estimates leaf chlorophyll content based on RGB images; 2) determination of the position of crop rows and spaces between rows based on the vegetation map; 3) detection of weeds and generation of an appropriate weed map; 4) division of crop rows into non-intersecting fragments and calculating vegetation density in each (the ratio of vegetation area to the total fragment area). By changing the empirically defined parameters of map thresholds of fragment density, one can obtain a map that describes quality of crop sprouts. Unlike existing methods, the proposed scheme does not require presence of infrared data and can be applied to usual RGB images with the use of wide-spread types of UAVs. The method was tested on RGB images of flax and sunflower sprouts collected with SONY ILCE6000 camera in June, 2017 in Altai Territory. The images were taken at the height of 150 m, spatial resolution was 1.5 cm/pixel. The size of each image was 6000x4000 pixels. Test results confirmed high efficiency of the proposed method.