Abstract: As the most accurate underwater acoustic positioning technology, long-baseline (LBL) positioning system can directly provide absolute position information for all kinds of deep-sea detection equipment, and it is widely used in navigational positioning of deep-sea exploration. The basic principle of LBL is introduced in brief. Then the deep-sea LBL systems of iXblue, Kongsberg, and Sonardyne are systematically introduced, and domestic development is also analyzed. Finally, the development trend of deep-sea LBL is prospected, such as rapid baseline calibration, combination of LBL and USBL, combination of LBL and digital underwater acoustic communication, multi-AUV mobile LBL and single beacon-aid navigation.

Key words: long baseline, deep sea, RAMSES, cPAP, ROVNav