PURPOSE: To obtain equivalent direction resolution by connecting each wave reception array and receiving wave with a hypothetical long array even when a ship carrying the array is rolling and is unable to move on a straight line.

CONSTITUTION: To realize a higher resolution than one obtained with the length of an array 2, a system is constituted of an input/output device 5 to transfer the data from each wave accepter on the array 2 to a data signal processing device 4 a memory device to store the output data, a central processing unit(CPU) 6, a position detector 10 to detect the position of a ship and an indicator 9 to indicate the results of the calculation. Therefore, even in the case the ship carrying the array is rolling and is unable to move on a straight line, a direction resolution equivalent to connecting each reception array and receiving with a hypothetical long array can be obtained.