page_title: Long baseline acoustic positioning system
hierarchical_section_title: Long baseline acoustic positioning system
caption_attribution_description: English: Method of operation of a long-baseline (LBL) underwater acoustic positioning system for divers. A diver mounted transponder (A) emits an acoustic signal or 'ping' that travels to baseline transponders (B, C, D). The transponder replies travel back to (A), which measures the two-way signal run time. Using a measured or assumed speed of sound, the corresponding distances are determined. These distance measurements are sent to the diver terminal (E) which uses a search algorithm or geometric computations to establish the diver position. Position data and related information such as position accuracy, depth, distance and bearing to a waypoint are displayed on a screen similar to that of a handheld GPS receiver.
context_page_description: A long baseline acoustic positioning system is one of three broad classes of underwater acoustic positioning systems that are used to track underwater vehicles and divers. The other two classes are ultra short baseline systems and short baseline systems. LBL systems are unique in that they use networks of sea-floor mounted baseline transponders as reference points for navigation. These are generally deployed around the perimeter of a work site. The LBL technique results in very high positioning accuracy and position stability that is independent of water depth. It is generally better than 1-meter and can reach a few centimeters accuracy. LBL systems are generally employed for precision underwater survey work where the accuracy or position stability of ship-based positioning systems does not suffice.
context_section_description: A long baseline (LBL) acoustic positioning system is one of three broad classes of underwater acoustic positioning systems that are used to track underwater vehicles and divers. The other two classes are ultra short baseline systems (USBL) and short baseline systems (SBL). LBL systems are unique in that they use networks of sea-floor mounted baseline transponders as reference points for navigation. These are generally deployed around the perimeter of a work site. The LBL technique results in very high positioning accuracy and position stability that is independent of water depth.  It is generally better than 1-meter and can reach a few centimeters accuracy. LBL systems are generally employed for precision underwater survey work where the accuracy or position stability of ship-based (SBL, USBL) positioning systems does not suffice.
caption: Figure 1: Method of the operation of a long baseline (LBL) acoustic positioning system
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