Length classification device, underwater detection device, and body length classification method

摘要

A method and apparatus for determining the size and type of an object, such as fish, aquatic or marine life, the apparatus 1 comprising, an echo signal input means 11 to receive an echo signal of an ultrasonic wave transmitted underwater. An individual object determining means 13 to determine an individual object based on amplitude information of the echo signal. A reflection intensity calculating means 14 configured to calculate reflection intensities of the echo signal at respective frequencies within a predetermined range that indicate the individual object. A reflection intensity distribution memory 15 to store the reflection intensity distribution at frequencies corresponding to one of, pairs of a length, and a type for every pair. A length-and-type selecting means 16 to select one of the pairs that corresponds to the individual object by comparing the reflection intensity distributions stored in the reflection intensity distribution memory 15 with the reflection intensities calculated by the reflection intensity calculating means 14.