ATLAS North America Proprietary
Sea Scan® ARC Explorer™ Manual
1 of 1
Page: 9
Issue: 4.2.1
2SFT1-0001
Manual
2.2.1
How to Read Sonar Data
2.2.1.1
Sonar Beam
Vertical Beam Angle
How wide the beam angle is; it is measured from the sea bottom to the top of the sound that was
projected from the transducer.
Figure 6: The vertical beam angle
Horizontal Beam Width
The width of the sound wave determines the expanse of the area covered horizontally, and the
speed of the boat determines the ping spacing. The slower the vessel moves, the more overlapping
coverage that will be obtained. This approach yields more data for a higher quality image.
Figure 7: The horizontal beam width
2.2.1.2
Surface and Bottom Returns
Two distinct returns should be noted.
Figure 8: Surface and bottom returns in the waterfall
First Bottom Return
: This is the initial data from the point where the sound meets the seabed.
First Surface Return
: This is the first data from the point where the meets the water's surface. As
in the picture, this is usually a wavy, sparse, non-solid return, which appears mainly in shallow
scanning situations. In deeper water, the sound beam will not reach the surface.
