JPH02222852A - Method of fish detection - Google Patents

Abstract

PURPOSE:To facilitate a discrimination of bottom condition as well as fish school by emitting an ultrasonic wave having a narrow-range directional main beam and an ultrasonic wave having a wide-range directional main beam over the entire perimeter of the main beam to a water bottom from an ultrasonic wave emitter to record information on both of a water depth and a bottom condition simultaneously. CONSTITUTION:When an ultrasonic wave is emitted to a water bottom being incident askew, a difference in intensity is generated in reflected wave and a difference in bottom quality appears remarkably on an indicator. In sounding, it is necessary to emit a directional ultrasonic wave downward vertically. So, an ultrasonic wave incident askew and a directional ultrasonic wave are emitted simultaneously to show reflected waves of both the waves on the display device and by so doing, the former reflected wave indicates a bottom quality and the latter a water depth. Then, the ultrasonic wave incident askew from a vibrator A herein used is an ultrasonic wave having a wide-range directional main beam with an angle theta of incidence at the water bottom being a wide directive angle roughly to 60 deg.. When the angle is more than 60 deg., information due to the reflected wave is very dense but an area of the water bottom to be inspected is too large to accomplish the inspection of the water bottom right below accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting schools of fish, and more particularly, to a method for detecting schools of fish that allows easy identification of bottom sediment, etc.

[Conventional technology]

2. Description of the Related Art Conventionally, it has been widely used to detect schools of fish or measure water depth by emitting ultrasonic waves underwater and receiving their echoes.

By the way, when performing fish school detection, it is often necessary to obtain information on the bottom sediment at the same time in order to identify target fish and determine the fishing gear to be used.

In such cases, even with conventional detectors, it was possible to distinguish the bottom sediment to some extent by looking at the shading of the bottom record on the display, but this requires considerable skill and can be done by anyone. It wasn't something.

[Problems with conventional technology]

In view of the above, we focused on the difference in ultrasound transmittance depending on the bottom sediment,
Discrimination has been carried out using low-frequency sound waves and the length of the trailing record displayed on the back-reflected wave display, but it is still difficult to make a clear distinction (
Moreover, the gain for capturing schools of fish and the gain for determining sediment are different, making operation cumbersome and inconvenient.

[Problem to be solved by the invention]

In view of the above problems, this invention provides
The purpose of this invention was to obtain a method for detecting schools of fish that would make it very easy to detect schools of fish and determine the sediment on the bottom of the water.

[Technology to solve problems]

That is, in the fish detection method of the present invention, from an ultrasonic transmitter,
An ultrasonic wave having a directional main beam in a narrow range and an ultrasonic wave having a directional main beam in a wide range with a bottom incident angle θ of up to about 60° around the entire circumference of the main beam are emitted toward the water bottom, Thereafter, the information obtained from the underwater emitted waves of both main beams is displayed on the same display screen.

[Effect]

It is known that when ultrasonic waves are incident obliquely into water, the reflection coefficient from the water bottom in the direction of incidence varies significantly depending on the roughness of the water bottom surface.

For example, if the surface of the water bottom is smooth, such as mud or sand, the reflection coefficient for oblique incidence is small, and conversely, if the surface is rough, such as gravel, it is large.

Therefore, if ultrasonic waves are emitted toward the bottom of the water at oblique incidence,
Differences in intensity occur in the reflected waves, and differences in bottom sediment become noticeable on the display.

On the other hand, in order to measure water depth (including the depth of the fish bed, the same applies hereafter), it is necessary to emit directional ultrasonic waves vertically downward.

Therefore, if the above-mentioned obliquely incident ultrasonic waves and directional ultrasonic waves are emitted at the same time and the reflected waves of both are displayed on the same display, the former will display the bottom sediment, and the latter will display the water depth. It happens.

At this time, if both ultrasonic waves are emitted at the same time, the reflected wave of the obliquely incident ultrasonic wave always returns with a time delay compared to the reflected wave of the directional ultrasonic wave, so both indicators No confusion at the top.

In the above, as the ultrasonic waves obliquely incident from the transducer A, ultrasonic waves having a wide directional main beam are used, and the bottom incident angle θ is approximately 60° as shown in FIG.
It has a wide directivity angle of up to

The reason for this is that if the angle is greater than 60°, the information from the reflected waves will be denser, but the bottom area to be explored will become too large, creating the inconvenience of not being able to accurately explore the bottom of the water. .

〔Example〕

Next, the present invention will be explained using examples.

As shown in Figure 2, there is a transducer 1) that emits ultrasonic waves that have a narrow-range directional main beam with excellent directivity and no side lobes, and an ultrasonic wave that emits ultrasonic waves that have a very wide main beam. Water depth was measured using the emitted vibrator 12.

Next, when the apparatus of the example was used to detect a seabed with alternating sand and gravel, the record shown in FIG. 3 was obtained, and the bottom materials were clearly distinguished and displayed.

In FIG. 3, the area indicated by range 1 is a sandy dust layer with a low reflectance, and the area indicated by range 2 is a gravel layer with a high emission rate.

In addition, FIG. 4 is a record obtained by searching the same seabed using a conventional fish finder as a comparative example.

〔effect〕

As explained above, this invention utilizes the difference in the reflectance of ultrasonic waves obliquely incident on the water bottom to measure the bottom sediment and the water depth directly below with the main beam, and displays them on the same display screen. Therefore, information on both water depth and bottom sediment is recorded simultaneously, making it very easy to distinguish between them.Furthermore, since the information on each is obtained from two types of ultrasonic waves that are emitted at the same time, each ultrasonic wave is If you set the output adjustment of the transmitter at the beginning, you only need to adjust the gain during operation once.
It is extremely easy to operate.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operation of the present invention, FIG. 2 is an explanatory diagram of the configuration of an embodiment, FIG. 3 is an explanatory diagram of the recording state of the embodiment, and FIG. 4 is an explanatory diagram of the recording state of a comparative example. -7'/Zen72 Figure 3m ↑4[]

Claims (1)

[Claims] (1) An ultrasonic wave from an ultrasonic transmitter that has a directional main beam in a narrow range, and an ultrasonic wave that has a directional main beam in a wide range with a bottom incident angle θ of approximately 60° around the entire circumference of the main beam. A method for detecting a school of fish, characterized in that the main beams are emitted toward the bottom of the water, and then information obtained from the bottom emitted waves of both main beams is displayed on the same display screen.