Multibeam Sonar Theory of Operation

Multibeam Sonar Theory of Operation Detection Processing and Range Calculations
Figure Chapter 4 - -30: Offset of Ping Illumination Due to Pitch
Next, look at the echo from a single beam, which has an angle and TOA measurement from the
WMT and BDI calculations. Recall from the “Beam Steering” section in Chapter 2 that the
SEA BEAM 2100 beam is fan-shaped, narrow in the acrosstrack direction, but wide in the
alongtrack direction. It observes echoes from a long, narrow strip of the ocean floor, but only sees
echoes from transmitted pings in the small area where this strip intersects the area illuminated by
the ping (see Figure Chapter 4 - -31). This position will have an offset in the along-track direction
given by the pitch angle, and an offset in the across-track direction given by the beam DOAs. The
angle between the across-track direction and the direction to the position of the echo is called the
bearing angle. The angle between the vertical and the echo position (as seen by the ship) is
called the launch angle. Both the bearing angle and the launch angle can be determined from the
pitch and beam angles.
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