Influence of Nonhorizontal Orientation on Measurement of Insect Biological Parameters with Entomological Radar

Up till now, measurement of the biological parameters of insects traversing the beam of an entomological radar has been based on the assumption that the insects maintain a horizontal flight attitude. However, recent studies have revealed that some migrating insects fly with their bodies pitched upwards. This article analyzes the influence of nonhorizontal orientation (i.e., pitch and roll angles) on measurements of insect biological parameters with an entomological radar. The scattering matrices (SMs) of 15 insect specimens have been measured at different pitch and roll angles with a purpose-designed multiaspect fully polarimetric laboratory rig. It is found that pitch angle has little influence on the discrimination of 'parallel' and 'perpendicular' insects, but it affects the measurement accuracy of orientation and estimation of mass and body length. The roll angle has little influence on the insect class discrimination, and the measurement of orientation and body length, and slightly affects the accuracy of the mass estimation. The influence of a general combination of pitch and roll angles is approximately the linear superposition of the influence of pitch angle and roll angle.