Complex Processing of Lidar Survey Data of Marine Areas
The complex processing of data from the shipborne lidar survey of the Black Sea coastal areas was carried out. In this area, internal waves are often observed according to contact and satellite observations. The source of probing linearly polarized laser pulses in the lidar is a solid-state laser with diode pumping of the YAG: Nd active element with a pulse power of 20 mJ at a wavelength of 532 nm and a duration of 7 ns. The co- and cross-polarized components of the echo signal were recorded during the lidar survey. The cross-polarized component of the echo signal was mainly used due to its greater sensitivity to various kinds of inhomogeneities in the vertical distribution of hydrooptical characteristics. The purpose of processing is to identify quasi-periodic structures in the spatial distribution of the characteristics of lidar echo signals caused the propagation of short-period internal waves. Three processing methods were applied: the approximation method, the wavelet analysis method, and the Hilbert-Huang transform method. A large array of data obtained during 50 hours of lidar survey has been processed. Three 60-minute tracks containing quasi-periodic structures have been identified. The three processing methods results are in good agreement with each other and make it possible to obtain the most complete information about the parameters of the studied processes. The parameters of the recorded quasi-periodic processes are typical for internal waves observed in the coastal areas of the Black Sea. In the future, when processing a large amount of lidar sounding data, it is advisable to carry out fast processing by automated spectral methods at the first stage, and to carry out detailed processing by the approximation method only for those survey areas where quasi-periodic processes have been identified.