Estimating Insect Body Size From Radar Observations Using Feature Selection and Machine Learning

For insect radar observations, exploiting radar echoes from insects to accurately estimate size parameters, such as body mass, length, and width of insects, can help to identify insect species. At present, the commonly used method for estimating insect body size parameters in insect radar is to use the monotonic mapping relationship between insect radar cross section (RCS) parameters of a single frequency (mainly 9.4 GHz) and body size and obtain the empirical formula for body size estimation by polynomial fitting. However, the useful information used by the traditional methods is limited (1-2 features), and these retrieval methods are simple and with limited estimation accuracy. This article proposed a feature-selection-based machine learning method for insect body size estimation, which could effectively improve the body size parameter estimation accuracy of insect radars. First of all, based on the published insect scattering dataset (9.4 GHz, 366 specimens of 76 species), stepwise regression was used to select the optimal feature combinations for body size estimation, and then, three machine learning methods, such as random forest regression (RFR), support vector regression (SVR), and multilayer perceptron (MLP), were adopted to achieve the estimation of insect body size. Among them, RFR has the best performance (mass 18.83%, length 11.37%, and width 16.87%). Subsequently, based on the measured dataset of migratory insects (5532 specimens of 23 species), the influence of the estimation error of insect body size on the identification accuracy of migratory insect species was analyzed. When incorporating the estimation error of the feature-selection-based RFR method, the insect identification rate of 83.68% was reached.