Fig.1

Flow chart of detection and reconstruction of fast-moving targets based on deep-water MBES"

Fig.2

Imaging schematic diagram of traditional MBES"

Fig.3

Traditional MBES water body diagram"

Fig.4

Planar array with staggered arrangement of elementary elements"

Fig.5

Imaging schematic diagram of 3D-WCD"

Fig.6

Interval along the trajectory of traditional MBES and 3D-WCD"

Fig.7

Detection duration of traditional MBES and 3D-WCD"

Fig.8

Linear array directional diagram"

Fig.9

Composite beam footprint （$\gamma = \left[ { - {3^ \circ },{0^ \circ },{3^ \circ }} \right]$，$\eta = {0^ \circ }$）"

Fig.10

Composite beam footprint （$\gamma = \left[ { - {3^ \circ },{0^ \circ },{3^ \circ }} \right]$，$\eta = {30^ \circ }$）"

Fig.11

Simulation of underwater gas column"

Table 1

Simulation parameter settings"

Fig.12

Water body imaging diagram of underwater gas column （traditional MBES）"

Fig.13

Water body imaging diagram of simulated underwater gas column（the proposed algorithm）"

Fig.14

Water body imaging diagram of underwater gas column after Otsu threshold segmentation （traditional MBES）"

Fig.15

Water body imaging diagram of underwater gas column after Otsu threshold segmentation （the proposed algorithm）"

Fig.16

Comparison graph between threshold segmentation and true value （traditional MBES）"

Fig.17

Comparison graph between threshold segmentation and true value （the proposed algorithm）"

Fig.18

Scatter diagram of secondary iteration Otsu threshold segmentation （the proposed algorithm）"

Fig.19

Simulated gas column imaging diagram after NRBO-DBSCAN clustering"

Fig.20

Water body diagram of sea test gas column"

Fig.21

Histogram of backscatter intensity of water body with gas column"

Fig.22

Otsu threshold segmentation for sea test gas column water body imaging"

Fig.23

Histogram of backscatter intensity of water body with gas column after Otsu threshold segmentation"

Fig.24

Water body imaging of gas column after NRBO-DBSCAN clustering"

Fig.25

Histogram of backscatter intensity of water body with gas column after NRBO-DBSCAN clustering"

Fig.26

Comparison of backscatter intensity histograms of water body with gas column before and after treatment"