Page 435 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition
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428 CHAPTER 16 Acoustic Positioning
Reception at transmitter = 2 s after sending
Transmitter Transponder
Speed of sound = 5000 ft/s
Signal is sent to transponder Transponder received at 1 s after transmission
R = 0.5vt; therefore 0.5 x 5000 ft x 2 = 5000 ft range Sample transmitting time calculation.
FIGURE 16.1
Hull
Receiver
Depth
Resolve offset
Sub
FIGURE 16.2
Computation of vehicle offset.
Using round numbers, if the speed of sound in water is 5000 ft/s and it takes 2 s (disregarding any latency time) from sending the signal to reception back at the transmitter, the beacon is 5000 ft away (Figure 16.1).
All underwater acoustical range is “slant range” for computing raw offset to the vehicle (more to point, from transducer to transducer). When tracking underwater vehicles from the surface, the depth of the vehicle is easily resolved from the vehicle’s depth gauge. With the slant range and the depth producing two sides of a right-angled triangle, simple trigonometry will resolve the third side (Figure 16.2).
Slant range
