Unbiased pitch detection and phase estimation in entomological lidar

Abstract: Good insect monitoring is important for both disease vector control and e?cient usage of pesticides in farming. Entomological lidar has been proven useful for detecting and monitoring insects. For every insect that transit the laser beam a backscatter signal containing species-specific information is obtained. Esti- mating the fundamental wing beat frequency of an observation is important for determining the species. In this thesis, four non-parametric spectral estimation techniques have been evaluated on their ability to estimate the fundamental wing beat frequency. Furthermore, a method for phase estimation, the matched phase reassignment, has been investigated for estimating the relative phase of the harmonic overtones. All four techniques managed to estimate the fundamen- tal wing beat frequency in simulated signals to a high degree, even for short and noisy signals. The techniques were fairly equally successful in estimating the fundamental frequency, although the periodogram and the Wigner-Ville distri- bution proved somewhat better than the spectrogram and the scaled reassigned spectrogram. The matched phase reassignment can not be deemed reliable in estimating the relative phase of the overtones in entomological lidar signals due to sensitivity to noise.