The underwater acoustic positioning system enables the simultaneous tracking of the positions of many items or vehicles that are submerged in water based on acoustic transponders that are attached to those objects or vehicles. The position of the ROV, AUV, or research divers can be calculated with a high degree of precision using this method. In addition, activating the modem function on the devices allows for the transmission of a minuscule volume of information to the transponders that are linked to the devices.
Global Positioning System (GPS)
If you want to keep an eye on the way the Earth’s surface is shifting, the global positioning system (GPS) is a great instrument to use. Specifically, in subduction zones, GPS has documented coseismic, postseismic, slow transient, and interseismic deformation over the past two years. This past decade has also seen the actual application of GPS-acoustic systems, which make it possible to observe offshore deformation directly above slip zones.
SBL Positioning Systems
An acoustic transmitter mounted on the vehicle is used by a short baseline (SBL) acoustic locating system to send out timed pulses of transmitted acoustic energy. On the surface, numerous receivers are arranged in a geometric design to pick up these pulses as they travel through the air.
After determining when each receiver first recorded the acoustic pulse, a “time of flight” calculation is performed, which allows for the subsequent plotting of a consolidated location for the underwater vehicle. As a result of the flexible receiver locations, SBL systems are capable of delivering more accurate positioning results in highly reflecting settings.
USBL Positioning Systems
An ultra-short baseline (USBL) acoustic positioning system works in a way that is similar to that of an SBL system. In both instances, an acoustic pulse is first sent from a transmitter located on the vehicle to a receiver located on the surface. USBLs do not merely compute the amount of time spent in flight; rather, they compute the distance traveled and the bearing. USBL systems take up less space than SBL systems because the receiver transducers are all in one transceiver head.
The Workings of a USBL System
A full USBL system includes a transceiver that is installed on a pole underneath a ship, as well as a transponder or responder that is placed on the bottom, on a submersible vehicle, or a diver. The transceiver broadcasts an audible pulse into the water, which is then received by the underwater transponder and reflected.
The transceiver can pick up this return pulse without any problems. The time it takes for an auditory pulse to be transmitted and for a response to be received is one of the factors that the USBL system takes into consideration when it calculates the distance to an object.
In a USBL head, the transducers are spaced out along a centimeter- or decimeter-wide baseline. After the individual transducers pick up the pulse of the underwater transponder’s response, a phase-differencing technique is used inside the array to calculate an estimate of the bearing to the transponder.