JP5049726B2 - Tidal current measuring device - Google Patents

Description

  The present invention relates to a tidal current measurement in which a tidal current is calculated from a difference between an absolute ship speed obtained from a navigation apparatus and an absolute ship speed obtained by transmitting ultrasonic waves from a ship into water and using the Doppler effect of the reflected wave. Relates to the device.

  Conventionally, in a tidal current measurement device, ultrasonic waves are transmitted obliquely downward in water from a ship, and a water flow (tidal current) at an arbitrary water depth is obtained based on the Doppler effect of the reflected wave (Patent Documents 1 to 3). 3). That is, the ship speed (vs. water speed) with respect to the water depth obtained by using the Doppler effect of the ultrasonic wave (reflected wave) reflected at the water depth, and the wave obtained from the reflected wave from the seabed The tidal current at the water depth can be obtained by calculating the difference between the ship's ship speed relative to the seabed (ground ship speed).

  By the way, a navigation device mounted on the ship and using GPS (Global Positioning System) or the like outputs a ship speed (absolute ship speed) of the ship obtained by absolute positioning. Therefore, in the tidal current measurement device, when the seabed depth is relatively shallow and the ship speed can be easily obtained, the difference between the ship speed and the ship speed or the absolute ship speed and the ship Calculates the tidal current from the difference between the speed and, on the other hand, calculates the tidal current from the difference between the absolute ship speed and the water speed when the water depth at the seabed is relatively deep and the ship speed against the ground cannot be obtained easily. is doing.

  In addition, since each ship speed described above is obtained at predetermined time intervals, the tidal current measurement apparatus calculates an averaging process (first process or first process) for reducing variation in each ship speed value when calculating the tidal current. 2). In other words, in the first process, the ship speed obtained by absolute positioning in the navigation device is averaged, and the ship speed after the averaging process is output as the absolute ship speed, while the Doppler of the reflected wave is output. An averaging process is performed on the speed of the watercraft obtained using the effect, and then the difference between the averaged ship speed and the speed of the watercraft is calculated to obtain the tidal current. In the second method, the navigation device outputs the ship speed before the averaging process as an absolute ship speed, while the average speed process is performed for the ship speed against water obtained using the Doppler effect of the reflected wave. After that, the tidal current is obtained by performing the averaging process on the difference between the absolute ship speed and the water speed.

JP-A-4-357463 Japanese Patent Laid-Open No. 5-80151 JP 2006-284242 A

  By the way, when the ship is stopped or navigating at a constant speed and a constant course, the tidal current measuring device described above can obtain an accurate tidal current. However, when the speed of the ship changes (acceleration / deceleration) or the course changes (turns over), the calculated tidal current includes a large error.

  FIGS. 3A and 3B are time series graphs of the absolute ship speed G1, the water speed W1 against water, and the tidal current C1 when the ship is accelerated and decelerated in a state where there is no tidal current. In this case, the absolute ship speed G1 and the water ship speed W1 indicate the ship speed after the averaging process, and so on. In FIG. 3A, the average boat speed G1 and the water speed W1 after the averaging process increase with time in the time zone from time t0 to time t1, and increase with time in the time zone after time t1. Decrease. Here, if the time constant of the averaging process for the absolute boat speed G1 and the time constant of the averaging process for the water speed W1 are different from each other, the difference between the water speed W1 and the absolute speed G1 A certain tidal current C1 (see FIG. 3B) has a positive value in the time zone from time t0 to t1, while it has a negative value in the time zone after time t1. However, as described above, since there is actually no tidal current, the tidal current measuring device calculates a false tidal current C1. That is, the false tidal current C1 includes an error caused by each time constant.

  FIGS. 4A and 4B are time series graphs of the course of the tidal current C2 and the course of the absolute ship speed G2 and the water speed W2 when the ship 1 (see FIG. 4C) changes (turns) the course in the absence of a tidal current. FIG. 4C shows the vectors of the absolute ship speed G2, the water ship speed W2 and the tidal current C2 at time t2. In FIG. 4A, the courses of the absolute ship speed G2 and the anti-water ship speed W2 change with time from the time t0, and maintain a constant course after a predetermined time. However, if the time constant of the averaging process with respect to the absolute ship speed G2 and the time constant of the averaging process with respect to the water speed W2 are different from each other, even if there is actually no tidal current, the tidal current measuring device Will calculate a false tidal current C2 (see FIG. 4B). That is, the false tidal current C2 includes an error caused by the course change (turning) of the ship 1 and the time constants.

  On the other hand, the absolute ship speed signal output from the navigation device is often a serial signal defined by IEC61162, for example. Based on the length of the serial signal and the interval at which the serial signal is output from the navigation device, the absolute ship speed is delayed by about 1 s to 3 s compared to the speed of the water ship when calculating the tidal current. The error caused by is included in the current.

  5A and 5B are time series graphs of the absolute ship speed G3, the water ship speed W3, and the tidal current C3 when the absolute ship speed G3 is delayed with respect to the water ship speed W3 in the absence of a tidal current. . In FIG. 5A, the speed V3 with water increases with time in the time zone from time t0 to time t4, and decreases with time in the time zone after time t4. On the other hand, the absolute boat speed G3 increases with time in the time zone from time t3 to time t5 delayed by a predetermined time from time t0, and decreases with time in the time zone after time t5. In this case, since the absolute ship speed G3 has a time delay of (t3-t0) and (t5-t4) with respect to the water speed W3, the tidal current of FIG. C3 includes an error caused by each time delay.

  6A and 6B show that there is a time delay similar to that in FIGS. 5A and 5B between the absolute boat speed G4 and the watercraft speed W4 in the absence of a tidal current, and the average with respect to the watercraft speed W4. It is a time series graph of the absolute ship speed G4, the water speed V4 with respect to water, and the tidal current C4 when the time constant of the conversion process and the time constant of the averaging process with respect to the absolute ship speed G4 are different from each other. In FIG. 6A, the absolute ship speed G4 has a time delay of (t3-t0) and (t5-t4) with respect to the water speed W4, and the time constants are different. 6B, the current C4 in FIG. 6B includes an error due to the difference in each time constant in addition to the error due to each time delay. Becomes even bigger.

  The present invention has been made in consideration of such a problem, and when calculating the tidal current from the difference between the absolute ship speed and the speed of the watercraft, even if there is acceleration / deceleration or turning of the ship, it is always An object of the present invention is to provide a tidal current measuring device capable of obtaining a stable tidal current.

  In the present invention, when the tidal current is calculated by the tidal current calculation circuit, if there is a time difference between the input of the water speed to the tidal current calculation circuit and the input of the absolute boat speed to the tidal current calculation circuit, The correction means corrects the time difference, while the time constant of the averaging process for the anti-water vessel speed in the anti-water vessel speed measurement circuit or the tidal current arithmetic circuit and the absolute value in the navigation device or the tidal current arithmetic circuit When the time constant of the averaging process with respect to the boat speed is different from each other, the averaging time constant correcting means corrects at least one of the time constants.

  According to the present invention, the acceleration / deceleration and turning of the ship, the difference in the time constant of the averaging process with respect to the absolute ship speed and the water speed, and the water speed from the water speed measurement circuit in the tidal current calculation circuit Even when there is a time difference between the input and the absolute ship speed input from the navigation device, the error in the tidal current caused by each of the above factors is achieved by the correction processing in the delay correction means and the averaging time constant correction means. Therefore, the power flow can always be stably output from the power flow measuring device regardless of the acceleration / deceleration, the turning, the difference of each time constant, and the occurrence of the time difference.

  A tidal current measurement device 4 according to an embodiment of the present invention is mounted on a ship 1 (see FIG. 4C), and as shown in FIG. 1, a transducer 40, a transmission / reception circuit 41, an anti-water vessel speed measurement circuit 42, a tidal current calculation, and the like. A circuit 43, a power flow value output circuit 44, an acceleration / deceleration detecting means 45, a turning state detecting means 46, an averaging time constant correcting means 47, a delay correcting means 48, and an operation stopping means 49. The calculation stop means 49 includes an adder 50 and a switch 51. In addition to the tidal current measuring device 4, the ship 1 is equipped with a navigation device 3 using GPS and a gyro compass 2 as a direction sensor.

  A plurality of transducers 40 are arranged on the bottom of the ship 1 and transmit (transmit) an ultrasonic beam in the water in an obliquely downward direction of the ship, and the transmitted ultrasonic beam reaches an arbitrary depth or seabed. Receives (receives) the reflected wave when reflected. The transmission / reception circuit 41 outputs the transmission signal of the ultrasonic beam to the transmitter / receiver 40, while outputting the reception signal of the reflected wave to the watercraft speed measurement circuit 42. Based on the received signal including the Doppler shift of the reflected wave and the bow direction of the ship 1 output from the gyrocompass 2, the ship speed measurement circuit 42 against the water (vs. ship speed (vs. The water vessel speed) is calculated and the calculated water vessel speed is output to the tidal current calculation circuit 43 and the averaging time constant correcting means 47. The tidal current calculation circuit 43 calculates the difference between the ship speed against water and the ship speed (absolute ship speed) of the ship 1 obtained by the absolute positioning output from the navigation device 3 as the water flow (tidal current) at the arbitrary water depth. ). The tide value output circuit 44 outputs the tide value input from the tide calculation circuit 43 via the switch 51 of the calculation stop means 49 to various devices in the ship 1 connected to the tide measurement device 4.

  The acceleration / deceleration detection unit 45 detects that the ship 1 is in an acceleration state or a deceleration state based on the absolute boat speed output from the navigation device 3, and outputs the detection result to the adder 50 of the calculation stop unit 49. . The acceleration / deceleration detecting means 45 only needs to be able to detect that the ship 1 is in an accelerating state or a decelerating state. Therefore, instead of the absolute ship speed, as shown by a broken line in FIG. It is also possible to detect that the ship 1 is in an acceleration state or a deceleration state.

  The turning state detection means 46 detects that the ship 1 is in a turning state based on the heading output from the gyrocompass 2 and outputs the detection result to the adder 50.

  When the detection result from the acceleration / deceleration detection unit 45 or the detection result from the turning state detection unit 46 is input, the adder 50 of the calculation stop unit 49 receives the power flow calculation circuit 43 and the power flow value output circuit 44 in the switch 51. The switch 51 is controlled so as to switch the connection state from the on state to the off state. Therefore, in the time zone in which the detection results are input to the adder 50, the connection state between the power flow calculation circuit 43 and the power flow value output circuit 44 in the switch 51 is off, while the detection results are added. In a time zone not input to the device 50, the connection state is an on state. That is, when the ship 1 is in an accelerating state or a decelerating state, or when the ship 1 is in a turning state, the switch 51 is turned off, and the power flow can be output from the power flow calculation circuit 43 to the power flow value output circuit 44. Can not. On the other hand, when the ship 1 is not in an accelerated state or a decelerated state, or when the ship 1 is not in a turning state, the switch 51 is turned on so that the power flow can be output from the power flow calculation circuit 43 to the power flow value output circuit 44. It is.

  In addition, since the absolute ship speed and the water ship speed are obtained at predetermined time intervals, in the tidal current measuring device 4, the navigation device 3 or the tidal current calculation circuit 43 is used to reduce the variation in the values of the respective ship speeds. On the other hand, the averaging process for the water speed is performed in the anti-water speed measurement circuit 42 or the tidal current calculation circuit 43. Therefore, the averaging time constant correcting means 47, when the time constant of the averaging process with respect to the water speed and the time constant of the averaging process with respect to the absolute ship speed are different from each other, at least one of the time constants. A predetermined correction process for correcting the time constant is performed. Further, when the tidal current calculating circuit 43 calculates the tidal current, the delay correcting means 48 has a time difference between the input of the speed of the water vessel to the tidal current calculating circuit 43 and the input of the absolute boat speed to the tidal current calculating circuit 43. In some cases, the time difference is corrected.

  Next, the functions of the acceleration / deceleration detection means 45, the turning state detection means 46, the averaging time constant correction means 47, the delay correction means 48, and the calculation stop means 49 described above will be specifically described with reference to FIGS. explain.

  When the ship 1 has a speed change such as acceleration / deceleration, the navigation apparatus 3 or the tidal current calculation circuit 43 performs an averaging process on the absolute ship speed, while the anti-water ship speed measuring circuit 42 or the tidal current arithmetic circuit 43 When the averaging process is performed on the water vessel speed, the tidal current calculation circuit 43, as described above, generates false values based on the difference between the time constant of the averaging process for the absolute vessel speed and the time constant of the averaging process for the water vessel speed. The tidal current C1 (see FIG. 3B) is calculated.

  Therefore, the acceleration / deceleration detecting means 45 has the absolute value of the time differential value of the absolute ship speed, or the absolute value of the change amount between the absolute ship speed value obtained last time and the absolute ship speed value obtained this time, It is determined whether or not it exceeds a certain value, and when the absolute value of the time differential value or the absolute value of the change amount exceeds the certain value, it is determined that the ship 1 is in an acceleration state or a deceleration state, The determination result (detection result) is output to the adder 50 of the calculation stop means 49. The adder 50 controls the switch 51 so that the connection at the switch 51 is switched from the on state to the off state based on the determination result from the acceleration / deceleration detecting means 45. Thereby, the output of the power flow from the power flow calculation circuit 43 to the power flow value output circuit 44 is stopped, and the power flow calculation in the power flow calculation circuit 43 is actually temporarily stopped. As a result, the power flow value output circuit 44 outputs the previously calculated power flow value to the outside, and can prevent the false power flow value C1 from being output to the outside.

  In addition, the tidal current calculation circuit 43 calculates a false tidal current C2 (see FIG. 4B) even when the course of the ship 1 is changed (turning).

  Therefore, the turning state detection means 46 has a constant value of the absolute value of the time differential value of the heading or the absolute value of the change amount between the previous heading value and the current heading value. It is determined whether or not it is exceeded, and when the absolute value of the time differential value or the absolute value of the change amount exceeds the constant value, it is determined that the course change (turning) of the ship 1 has occurred. The determination result (detection result) is output to the adder 50. The adder 50 controls the switch 51 so as to switch the connection in the switch 51 from the on state to the off state based on the determination result from the turning state detecting means 46. Even in this case, since the output of the power flow from the power flow calculation circuit 43 to the power flow value output circuit 44 is stopped and the calculation of the power flow in the power flow calculation circuit 43 actually stops temporarily, the power flow value output circuit By outputting the tidal current value calculated last time from 44 to the outside, it is possible to prevent the false tidal current value C2 from being output to the outside.

  Further, at the time when the tidal current calculation circuit 43 performs the tidal current calculation, if there is a time difference (time delay) between the input of the ship speed against water to the tidal current calculation circuit 43 and the input of the absolute ship speed to the tidal current calculation circuit 43. As described above, the tidal current calculation circuit 43 calculates the false tidal current C3 (see FIG. 5B). Furthermore, if the time constant of the averaging process with respect to the water speed and the time constant of the averaging process with respect to the absolute ship speed are different from each other in addition to the time delay, the tidal current calculation circuit 43 causes a larger error. A false tidal current C4 (see FIG. 6B) is calculated.

  Here, the delay amount (time delay) of the absolute ship speed with respect to the water speed, the time constant of the averaging process with respect to the water speed, and the time constant of the averaging process with respect to the absolute ship speed are as follows: It is a unique value.

  Therefore, the averaging time constant correction means 47 further performs an averaging process with a predetermined time constant on the speed of the watercraft after the averaging process so that the time constants are the same. Next, the delay correction means 48 performs a delay process for delaying the watercraft speed that has been further averaged by a predetermined time (a delay time of the absolute ship speed with respect to the watercraft speed), and the pair after the delay process. The water vessel speed is output to the tidal current calculation circuit 43. When there is a time difference between the input of the absolute ship speed from the navigation device 3 and the input of the anti-water ship speed from the anti-water ship speed measurement circuit 42, the tidal current calculation circuit 43 calculates the absolute ship speed and the delay. The tidal current is obtained by calculating the difference from the speed of the ship against water input from the correction means 48 after the delay process. Thereby, the tidal current which does not contain each error mentioned above is obtained.

  2A and 2B are time series graphs of the absolute boat speed G4, the water speeds W4, W51, and W5, and the tidal currents C4 and C5 in the state where the time delay and the time constants are different as described above. Here, the anti-water vessel speed measurement circuit 42 performs an averaging process on the anti-water vessel speed to output the anti-water vessel speed W4, and the navigation device 3 performs an averaging process on the absolute vessel speed to obtain the absolute ship speed G4. Shall be output. Further, it is assumed that the ship 1 has no change (turning) of the course, and further, there is no temporal change of the tidal current.

  The averaging time constant correcting means 47 performs further averaging processing T on the anti-water vessel speed W4 input from the anti-water vessel speed measuring circuit 42, and delays the anti-water vessel speed W51 after the averaging processing T. It outputs to the correction means 48. The delay correction means 48 performs a predetermined delay process based on the time difference D of (t0−t3) with respect to the watercraft speed W51, and outputs the watercraft speed W5 after the delay process to the power flow calculation circuit 43. The tidal current calculation circuit 43 is input with the anti-water vessel speed W4 from the anti-water vessel speed measurement circuit 42, is input with the anti-water vessel speed W51 from the delay correction means 48, and is further input with the absolute vessel speed G4 from the navigation device 3. Has been. In this case, the tidal current calculation circuit 43 calculates the difference between the water speed W51 with no time error from the absolute boat speed G4 and the absolute boat speed G4, and sets the calculation result as the tidal current C5 to the switch 51 and the tidal current. The value is output to the outside via the value output circuit 44. In this case, the tidal current calculation circuit 43 outputs the difference between the watercraft speed W51 subjected to the averaging process T and the delay process and the absolute ship speed G4 as a tidal current C5. It does not include the error due to the factor, so the result matches the actual current.

  As described above, the tidal current measuring device 4 according to this embodiment includes the acceleration / deceleration detection means 45 that detects whether the ship 1 is in the acceleration state or the deceleration state based on the absolute ship speed or the water speed against water, and the acceleration / deceleration detection. Calculation stop means 49 for stopping the calculation of the power flow in the power flow calculation circuit 43 based on the detection result of the means 45 is provided.

  Thereby, when the ship 1 is in an acceleration state or a deceleration state, the tidal current calculation in the tidal current calculation circuit 43 is actually temporarily stopped. Therefore, in the time zone in which an error occurs in the tidal current due to acceleration / deceleration of the ship 1, No tidal current is output from the arithmetic circuit 43 to the outside via the switch 51 of the arithmetic stop means 49 and the tidal value output circuit 44. Therefore, the tidal current is apparently output from the tidal current measuring device 4 regardless of the acceleration / deceleration. It becomes possible to output stably.

  Further, the tidal current measuring device 4 further includes a turning state detecting means 46 for detecting that the ship 1 is in a turning state based on the heading of the ship 1 outputted from the gyrocompass 2, and the calculation stopping means 49 is Based on the detection result of the acceleration / deceleration detecting means 45 or the turning state detecting means 46, the tidal current calculation in the tidal current calculating circuit 43 is stopped.

  As a result, even in a time zone in which an error occurs in the tide due to a change (turning) in the course of the ship 1, the tide is output from the tide calculation circuit 43 via the switch 51 of the calculation stop means 49 and the tide value output circuit 44. Therefore, regardless of the change (turning) of the course, it is possible to output the tidal current stably from the tidal current measuring device 4 in appearance.

  Further, when the tidal current measuring device 4 calculates the tidal current in the tidal current calculating circuit 43, there is a time difference between the input of the ship speed against water to the tidal current calculating circuit 43 and the input of the absolute ship speed to the tidal current calculating circuit 43. In some cases, the delay correction means 48 for correcting the time difference, the time constant of the averaging process with respect to the watercraft speed in the watercraft speed measurement circuit 42 or the powerflow computation circuit 43, the navigation device 3 or the powerflow computation circuit 43 When the time constant of the averaging process with respect to the absolute ship speed is different from each other, there is further provided an averaging time constant correcting means 47 for correcting at least one of the time constants.

  As a result, the acceleration / deceleration and turning of the ship 1, the difference in the time constant of the averaging process with respect to the absolute ship speed and the water speed, and the water speed from the water speed measurement circuit 42 in the tidal current calculation circuit 43 Even in the case where a time difference occurs between the input and the absolute ship speed input from the navigation device 3, the correction processing in the delay correction means 48 and the averaging time constant correction means 47 is caused by the above factors. Since a tidal current error can be eliminated, the tidal current can always be stably output from the tidal current measuring device 4 regardless of the acceleration / deceleration and the turning, the difference in each time constant, and the occurrence of the time difference. it can.

  In the tidal current measuring device 4 described above, the acceleration / deceleration detecting means 45, the turning state detecting means 46, the averaging time constant correcting means 47, the delay correcting means 48 and the calculation stopping means 49 are selected according to the acceleration / deceleration and turning of the ship 1. It is also possible to operate automatically. For example, if the acceleration / deceleration and / or turning of the ship 1 is relatively slow, the averaging time constant correcting means 47 and the delay correcting means 48 are operated, and the acceleration / deceleration detecting means 45, the turning state detecting means 46, and the calculation stop. The means 49 is stopped. On the other hand, if the acceleration / deceleration and / or turning of the ship 1 is relatively abrupt, the acceleration / deceleration detecting means 45, the turning state detecting means 46, and the calculation stopping means 49 are operated, and the averaging time constant correcting means 47 and the delay are operated. The correction unit 48 is stopped, or the acceleration / deceleration detection unit 45, the turning state detection unit 46, the averaging time constant correction unit 47, the delay correction unit 48, and the calculation stop unit 49 are all operated.

  Of course, the present invention is not limited to the above-described embodiment, and may employ various configurations.

It is a block diagram of the tidal current measuring device concerning this embodiment. FIG. 2A is a time-series graph showing processing for absolute ship speed and anti-water ship speed in the tidal current measuring device of FIG. 1, and FIG. 2B is a time-series graph of tidal current. FIG. 3A is a time-series graph of absolute ship speed and anti-water ship speed when the ship is accelerated / decelerated in the absence of tidal current, and FIG. 3B shows the difference between the absolute ship speed and the anti-water ship speed of FIG. 3A. It is a time series graph of the tidal current calculated. FIG. 4A is a time-series graph of the course of the absolute ship speed and the anti-water ship speed when the course of the ship is changed (turned) in the absence of a tidal current, and FIG. 4B shows the absolute ship speed and the anti-water ratio of FIG. It is a time-series graph of the tidal current calculated from the difference with ship speed. FIG. 4C is an explanatory diagram illustrating the absolute ship speed, the water ship speed, and the tidal current vectors at time t2 in FIGS. 4A and 4B. FIG. 5A is a time-series graph of the absolute ship speed and the anti-water ship speed when the absolute ship speed is delayed with respect to the anti-water ship speed in the absence of a tidal current, and FIG. 5B is an absolute ship of FIG. 5A. It is a time series graph of the tidal current calculated from the difference between the speed and the speed against water. FIG. 6A shows the absolute ship speed and the absolute ship speed when the absolute ship speed is delayed with respect to the water ship speed in the absence of tidal current, and the time constants are different in the averaging process for the absolute ship speed and the water ship speed. FIG. 6B is a time series graph of a tidal current calculated from the difference between the absolute ship speed and the water speed of FIG. 6A.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ship 2 ... Gyrocompass 3 ... Navigation apparatus 4 ... Tidal current measuring device 40 ... Transmitter / receiver 41 ... Transmission / reception circuit 42 ... Anti-water vessel speed measuring circuit 43 ... Tidal current calculation circuit 44 ... Tidal current value output circuit 45 ... Acceleration / deceleration detection means 46: Turning state detecting means 47 ... Average time constant correcting means 48 ... Delay correcting means 49 ... Calculation stop means 50 ... Adder 51 ... Switch

Claims (3)

A transducer that transmits ultrasonic waves from a ship to the water and receives the reflected waves;
An anti-ship speed measurement circuit for calculating an anti-ship speed of the ship from the Doppler effect of the reflected wave;
A tidal current calculation circuit that calculates a tidal current from the difference between the absolute ship speed of the ship output from the navigation device and the speed of the ship against water,
When calculating the tidal current in the tidal current calculation circuit, if there is a time difference between the input of the speed of water vessel to the tidal current calculation circuit and the input of the absolute boat speed to the tidal current calculation circuit, Delay correction means for correcting the time difference;
A time constant of the averaging process for the anti-ship speed in the anti-ship speed measurement circuit or the tidal current calculation circuit, and a time constant of the averaging process for the absolute ship speed in the navigation device or the tidal current calculation circuit, And a mean time constant correcting means for correcting at least one of the time constants when the time constants are different from each other. In the tidal current measuring device according to claim 1,
Acceleration / deceleration detection means for detecting that the ship is in an accelerating state or a decelerating state based on the absolute ship speed or the water speed against water,
A tidal current measuring device further comprising calculation stop means for stopping calculation of the tidal current in the tidal current calculation circuit based on a detection result of the acceleration / deceleration detecting means. In the tidal current measuring device according to claim 1 or 2,
Further comprising a turning state detection means for detecting that the ship is in a turning state based on the direction of the ship output from an orientation sensor,
The calculation stop means stops the calculation of the power flow in the power flow calculation circuit based on the detection result of the turning state detection means.

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