Study On The Waveform Simulation And Signal Processing In Airborne Lidar

Airborne Lidar Bathymetry(ALB)is a hot research area in the field of oceanography.It is widely used in the exploration and development of shallow water area,for the reason that it is basically not restricted by the navigation conditions in the sea and has the characteristics of aerial operation and high efficiency.Due to the influence of seawater turbidity,seafloor geology,seawater depth and other factors,the echo signal varies with a large dynamic range and the bottom echo signal is too weak.Therefore,the effective reception of the large dynamic range signal and the extraction of the bottom echo signal become the major problems in ALB system.The research on the reception and processing of the large dynamic range signal has been carried out based on 532 nanometer underwater scanning bathymetry system.First of all,system architecture design based on the system requirements has been completed.The dual-channel multi-channel parallel processing method is adopted to realize the separation measurement in shallow sea and deep sea,effectively improving the capability of processing large dynamic range signals and the extraction of weak echo in large dynamic range signal for the system.Secondly,the waveform simulation of the laser echo signal is performed according to the parameters of the system and the environment,in the meanwhile the processing circuit level simulation is carried out by using the parameters in the circuit,such as gain,quantization bits and etc.At the same time,an additive stitching algorithm is proposed to stitch the multi-path parallel signal.Afterwards,based on the waveform data obtained from the simulation,the bottom echo positions are successively extracted by using echo signal processing methods.The simulation results show that the single channel multi-path parallel processing circuit can receive and process the signals with a dynamic range of 64.5 dB,the maximum deviation is 5.9 cm and the maximum standard deviation is 0.2 cm,which meets the system requirements.Finally,based on the designed system architecture,the performance testing of the core components is completed.At the same time,the function of the additive splicing algorithm and the echo processing algorithm is tested,whose measured results are analyzed statistically.The experimental results show that the system architecture designed in this paper can receive signals with a large dynamic range and the proposed additive splicing algorithm and echo extraction algorithm can process the weak bottom echo signals effectively.