Development and evaluation of automated radar systems for monitoring and characterising echoes from insect targets

摘要

This thesis describes the construction of a mobile Insect Monitoring Radars(IMR) and investigations of: the reliability of IMRs for observing insectmigration in inland Australia; possible biases in IMR migration estimates; therelation between an insect’s size and its radar properties; radar discriminationbetween insect species; the effect of weather on the migrations of Australianplague locusts and of moths; the scale of these migrations; and here IMRs arebest located.The principles of entomological radar design, and the main features of insectmigration in inland Australia, are reviewed. The main procedures used in thestudy are: calculation of radar performance and of insect radar cross sections(RCSs); reanalysis of a laboratory RCS dataset; statistical analysis of a fouryeardataset of IMR and weather observations; and a field campaign using bothtwo existing fixed IMRs and the new mobile unit. Statistical techniques usedinclude correlation, multiple regression, discriminant analysis, and principalcomponents analysis.The original results of this work include design details of the mobile IMR,extension of radar performance calculations to IMRs and evaluation of flightspeed biases, a holistic approach to IMR design, the relation of insect RCSmagnitudes and polarization patterns to morphological variables, an estimate ofthe accuracy of the retrieved parameters, evaluations of three approaches (oneparameter, theory-based, and a novel two-stage method) to target identification,and verification of inferred target identities using results from nearby lighttraps. Possible sites for future IMRs are identified. The major conclusions are that: a mobile IMR can be built with a performance equal to that of a fixed IMR but at half the cost; significant biases in the signal processing results arise from insect speed; locusts and moths can be distinguished if all RCS parameters are used; IMRs can be designed to match particular requirements; weather has a significant effect on insect migration, the best single predictor of insect numbers being temperature; moonlight has no effect; the spatial correlation of migration properties falls to 50% at a separation of 300 km; and migrating insects can be carried by the wind for 500 km in a single night