Underwater acoustic positioning system is generally divided into USBL (ultra-short baseline), SBL (short baseline) and LBL (long baseline). USBL is easy to use and has low positioning accuracy. LBL has high positioning accuracy, but it takes a long time to put the submarine transponder in the earlier stage. The SBL positioning accuracy is between the above two, and the transponder can be mounted on the ship's side, suitable for all types of ROV.