JPH0350459Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a tidal current display device suitable for, for example, casting nets in purse seine fishing.

Purse seine fishing, as is well known, is a fishing method in which a net boat casts a net to encircle a school of fish while circling around the school of fish, and when the bottom of the net reaches a predetermined depth, the bottom of the net is squeezed to capture the school of fish.

The direction and speed of currents have a significant influence on this fishing method. If the direction and speed of the current in the upper and lower layers are different, the net will not settle in its normal position,
They can twist or settle in unexpected directions, affecting fishing.

For this reason, it is necessary to simultaneously measure the direction and speed of currents in the upper and lower layers.

Conventionally, this type of display device includes a display device in which light-emitting elements such as light-emitting diodes are arranged in a circle or in a circumferential direction representing the tidal direction, and the light-emitting elements corresponding to the tidal direction emit light (for example, Japanese Patent Publication No. 30-5949). is proposed. However, in this display method, only one of the light emitting elements is selectively displayed, so even if the direction of the current can be roughly determined, the speed cannot be determined. Therefore, a separate indicator must be prepared for tidal current speed. Furthermore, not only the current at a specific depth,
When simultaneously displaying tides at different depths, a large number of display elements will emit light at the same time, making it impossible to grasp the correspondence with the display depth. As a solution to this
It has been proposed to display tidal currents by installing multiple indicators corresponding to the tidal currents at each depth, but the narrow bridge limits the number of indicators that can be installed, and even if it were possible to do so, each depth Comparative observations are extremely difficult because the currents are displayed on separate displays.

This idea uses a display capable of displaying images, such as a color cathode ray tube, to simultaneously display tidal current information at different depths on a common display.

Examples of the invention will be described below.

FIG. 1 shows an example of the display, in which an image display such as a color cathode ray tube is used as the display.

On the display screen 1, direction markers 2, 2 representing the direction of the tidal current are displayed in the circumferential direction, and straight lines 10, 1 extending in the radial direction from the center of the direction marker 2 are displayed.
1 and 12 indicate the direction and speed of the current. The direction of the tidal current is expressed by the direction of a straight line from the center, and the speed of the tidal current is expressed by the length of the straight line. The straight lines 10, 11, and 12 are displayed in different display colors, such as blue, red, and green, respectively, and correspond to currents at different depths (upper layer, middle layer, and lower layer).

Therefore, by observing these straight lines 10, 11, and 12, it is possible to know the current at each depth. In the example displayed in the figure, it can be seen that the tidal current speed is the highest in the upper layer and the lowest in the middle layer, and that the direction of the tidal current is twisted clockwise as it goes from the upper layer to the middle layer and the lower layer.

In the above, for the tidal current data displayed on the display screen, a device (for example, the device described in Japanese Patent Application Laid-Open No. 51-68282) that utilizes the principle that ultrasonic waves are reflected from a body of water is used. As is well known, ultrasonic waves transmitted underwater are affected by the Doppler effect due to tidal currents, so this device detects the Doppler frequency to measure the current velocity at different depths, and also transmits ultrasonic waves in multiple directions to determine the direction of the tidal current. It is used to measure

As explained above, this invention displays tidal currents at different depths on a common display screen in colors that correspond to the depths, and displays the tidal current direction by displaying lines in the radial direction relative to the azimuth marker on the circumference. The tidal current speed is displayed by the display length.

Therefore, the direction of the current at each depth,
It is possible to easily understand not only the speed, but also the overall state of the tidal current from the upper layer to the lower layer, as well as the relative relationship between the tidal currents in each layer.

Furthermore, since the tidal currents in each layer are displayed in different colors, if the tidal current directions in each layer match, it is possible to determine whether the tidal current directions match based on the composite color.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of this invention.

Claims (1)

[Claims for Utility Model Registration] Tidal current direction at at least first and second depths measured based on Doppler frequency components contained in underwater reflected waves returning from different depths by transmitting and receiving ultrasonic signals underwater. and speed, the image display is a circumferential azimuth scale and a line display corresponding to the direction of the current in a radial direction from the center of the circumferential scale, and the line display A tidal flow display device characterized in that the display length corresponds to the tidal current velocity, and the line display color corresponds to the tidal current at the first and second depths.