Abstract
In this study, a hyperspectral imaging system of 866.4–1701.0 nm was selected and combined with multivariate methods to identify wheat kernels with different concentrations of omethoate on the surface. In order to obtain the optimal model combination, three preprocessing methods (standard normal variate (SNV), Savitzky–Golay first derivative (SG1), and multivariate scatter correction (MSC)), three feature extraction algorithms (successive projections algorithm (SPA), random frog (RF), and neighborhood component analysis (NCA)), and three classifier models (decision tree (DT), k-nearest neighbor (KNN), and support vector machine (SVM)) were applied to make a comparison. Firstly, based on the full wavelengths modeling analysis, it was found that the spectral data after MSC processing performed best in the three classifier models. Secondly, three feature extraction algorithms were used to extract the feature wavelength of MSC processed data and based on feature wavelengths modeling analysis. As a result, the MSC–NCA–SVM model performed best and was selected as the best model. Finally, in order to verify the reliability of the selected model, the hyperspectral image was substituted into the MSC–NCA–SVM model and the object-wise method was used to visualize the image classification. The overall classification accuracy of the four types of wheat kernels reached 98.75%, which indicates that the selected model is reliable.
Highlights
Wheat is one of the main food crops and is widely grown worldwide
Hyperspectral cube data with different concentrations of pesticide wheat grains were obtained by selecting the hyperspectral imaging system of 866.4–1701.0 nm
In order to reduce the dimension of the original spectrum and improve the performance of the model, the MSC preprocessed spectral data were selected for feature wavelength extraction
Summary
Due to the long growth cycle of wheat, it generally undergoes several stages, such as emergence stage, tillering stage, jointing stage, heading stage, flowering stage, filling stage, and maturity stage. Wheat plants are most vulnerable to pests, such as aphids, during their growth and the most common method used by farmers is to spray the corresponding pesticides to prevent pests [1,2]. During the wheat growth cycle, it is generally required to spray pesticides. Most of the pesticides have strong adsorption properties. They are transported to the whole wheat plant through the spraying parts or residual pesticides in the soil, which will inevitably lead to pesticide residues in the wheat grains and endanger people’s health. Wheat kernels can be used to produce many products, such as bread, Sensors 2019, 19, 3147; doi:10.3390/s19143147 www.mdpi.com/journal/sensors
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