The acoustic distance measurements may be augmented by depth sensor data to obtain better positioning accuracy in the three-dimensional underwater space.Īcoustic positioning systems can yield an accuracy of a few centimeters to tens of meters and can be used over operating distance from tens of meters to tens of kilometers. The signal time-of-flight or the corresponding distances A-B, A-C, A-D and A-E are transmitted via the ROV umbilical (F) to the surface, where the ROV position is computed and displayed on a tracking screen. The reply of the baseline transponders is received again at the ROV. The interrogator transmits an acoustic signal that is received by the baseline transponders (B, C, D, E). In the long baseline example (see figure 1), an interrogator (A) is mounted on the ROV that is to be tracked. Some systems assist this task with an automated acoustic self-survey, and in other cases GPS is used to establish the position of each baseline transponder as it is deployed or after deployment.įollowing the baseline deployment and survey, the acoustic positioning system is ready for operations. The location of the baseline transponders either relative to each other or in global coordinates must then be measured precisely. In the case of a long-baseline (LBL) system, a set of three or more baseline transponders are deployed on the sea floor. Figure 1: Method of the operation of a Long Baseline (LBL) acoustic positioning system for ROV Baseline station deployment and surveyĪcoustic positioning systems measure positions relative to a framework of baseline stations, which must be deployed prior to operations.
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