The article deals with the determination of coordinates and orientation angles of the autonomous underwater vehicle (AUV) relative to the stationary landing platform using high-frequency near-range hydroacoustic system. The navigation task implies maneuvering the vehicle and approaching the underwater station, which is associated with the formation of zones with different acoustic visibility of the station's emitters by the receiving elements of the vehicle. Three zones of acoustic visibility can be distinguished. The first zone is characterized by observation of signals of all beacons of the underwater station. As a consequence, this zone is the most informative for solving the problem of positioning and orientation determination of the AUV. The second zone corresponds to partial reduction of the number of observed beacons, which does not critically influence the possibility of problem solving. The third zone (landing) is defined by essential reduction of a number of observed beacons, that, as consequence, considerably complicates the solution of the positioning problem, taking into account the increased requirements on accuracy at the moment of landing of the device caused by provision of safety. To maintain positioning accuracy and determine the underwater vehicle orientation in the landing zone, it is proposed to use the results obtained in the early stages of approach of the vehicle to the underwater station (the first and second zones). A mathematical statement of the problem is given in the work, and the algorithm of its solution is described. When finding the AUV in the first and second zones, the solution algorithm consists of two subtasks. The first subtask is a rough estimation of location vicinity and angles of vehicle orientation using K-nearest neighbors method; the second subtask is specification of estimations using pseudo-dimensional method by solving system of algebraic equations with Levenberg-Marquardt algorithm. In addition, estimation of beacon emission time is carried out. At finding ANPA in the third zone the algorithm is reduced to solution of system of algebraic equations with use of forecast of time of signal emission by a beacon, received at finding of the device in zones one and two. The results of simulation modeling and results of algorithm approbation obtained using a mockup of the vehicle and a mockup of the underwater station in the test pool are presented.
