JP5555904B2 - Acoustic tomography measurement system and acoustic tomography measurement method - Google Patents

Description

  The present invention relates to an acoustic tomography measurement system and an acoustic tomography measurement method for measuring a physical quantity such as a flow rate in a cross section of a river.

  From the viewpoints of flood control, river environmental management, water resource management, etc., the emergence of a method that can accurately measure the river flow rate is desired. In recent years, various methods such as a water level flow curve (HQ) method, an ADCP (Acoustic Doppler Current Profiler) method, an H-ADCP method, and an AVM method have been proposed as methods for measuring river flow (for example, Non-Patent Document 1).

  In addition, the inventors have proposed a method for monitoring river flow in a tidal zone where salt water is mixed (see, for example, Non-Patent Documents 2 and 3).

Two bottles, "Real river flow velocity and flow monitoring based on ultrasonic Doppler flow velocity distribution meter", Flow 26 (2007) Kawanishi et al., “Continuous monitoring of tidal flow and water temperature / salinity by next generation ultrasonic anemometer”, Journal of Water Engineering, Vol. 53, February 2009 Kawanishi et al., “Long-term continuous monitoring of tidal river flow with next-generation ultrasonic anemometer”, River Technology Papers, Vol. 15, June 2009

  However, the HQ method cannot be used in the tidal region, and calibration of the relational expression for obtaining the flow rate from the water level is required.

  The ADCP method is limited to spot observation, and long-term continuous observation and observation during floods are difficult.

  In the H-ADCP method, sound waves are refracted when going up salt water, and suspended sediments become obstacles to observation during floods.

  Furthermore, the AVM method requires a correction factor, which may be missing during floods. In addition, the apparatus becomes large and expensive.

  An object of the present invention is to provide an acoustic tomography measurement system and an acoustic tomography measurement method capable of measuring a physical quantity such as a flow rate of a river for a long period of time with high efficiency and high accuracy in any environment.

In order to achieve the above object, an acoustic tomography measurement system according to the first aspect of the present invention provides:
Acoustics that measure physical quantities related to river cross-sections using non-directional sound waves transmitted and received between an upstream acoustic wave transmitter / receiver installed on one riverside and a downstream acoustic wave transmitter / receiver installed on the other riverside A tomography measurement system,
Based on the correlation waveform between the data demodulated from the sound wave received by each sound wave transmitter / receiver and the predetermined data, based on the time when the sound wave was transmitted from each sound wave transmitter / receiver, the sound wave transmitter / receiver A time information calculation unit for calculating information on an average propagation time of the sound wave in a cross section of the river between;
To the sound ray length which is the length of the path of the sound wave transmitted and received between the upstream sound wave transmitter / receiver and the downstream sound wave transmitter / receiver, and the information related to the propagation time calculated by the time information calculation unit Based on the average information calculation unit for calculating at least one of the cross-sectional average sound velocity and the cross-sectional average flow velocity in the cross section of the river,
Based on the information calculated by the average information calculator, a physical quantity calculator that calculates a physical quantity related to the cross section of the river;
Is provided.

The time information calculator is
As the information on the propagation time of the sound wave, the average propagation time of the sound wave between the sound wave transceivers and the propagation time difference of the sound wave between the sound wave transceivers are calculated,
The average information calculation unit
Based on the sound ray length, the average propagation time, and the propagation time difference, the cross-sectional average flow velocity is calculated,
The physical quantity calculation unit
By multiplying the cross-sectional area of the cross section by the cross-sectional average flow velocity, the flow rate of the cross section is calculated as the physical quantity,
It is good as well.

The time information calculator is
As information on the propagation time of the sound wave, calculate the average propagation time of the sound wave between the sound wave transceivers,
The average information calculation unit
By dividing the average propagation time from the sound ray length, the cross-sectional average sound speed is calculated,
The physical quantity calculation unit
Using the relational expression between the cross-sectional average sound velocity, salinity, water temperature and water depth, either salinity or water temperature is calculated as the physical quantity.
It is good as well.

Based on the survey information of the cross section and the sound speed distribution of the cross section obtained from the distribution of water temperature and salinity, further comprising a sound ray analysis unit for calculating the sound ray length by performing sound ray analysis,
The average information calculation unit
Based on the sound ray length calculated by the sound ray analysis unit, calculate at least one of the cross-sectional average sound velocity and the cross-sectional average flow velocity,
It is good as well.

The cross-sectional average sound speed at a reference time is calculated based on the water temperature and salinity measured by a conductivity tempuracha depth profiler (CTD), and the cross-sectional average sound speed between the sound wave transmitter / receiver at the reference time A sound ray length calculation unit for calculating the sound ray length based on the average propagation time of the sound wave;
The average information calculation unit
Based on the sound ray length calculated by the sound ray length calculation unit, calculate at least one of the cross-sectional average sound velocity and the cross-sectional average flow velocity,
It is good as well.

The time information calculator is
A first time from when the sound wave is emitted from the upstream sound wave transmitter / receiver until a threshold is reached at the falling edge of the peak of the correlation waveform of the sound wave received by the downstream sound wave transmitter / receiver;
A second time from when the sound wave is emitted from the downstream sound wave transmitter / receiver until the threshold value is reached at the falling edge of the peak of the correlation waveform of the sound wave received by the upstream sound wave transmitter / receiver. ,
The average of the first time and the second time is calculated as the average propagation time of the sound wave between the sound wave transceivers,
Calculating the difference between the first time and the second time as a propagation time difference of sound waves between the sound wave transceivers;
It is good as well.

A sound ray analysis unit that calculates the sound ray length by performing sound ray analysis based on the survey information of the cross section, and the sound velocity distribution of the cross section obtained from the water temperature and salinity distribution,
Based on the sound ray length calculated by the sound ray analyzer and the cross-sectional average sound speed at a reference time obtained from the water temperature and salinity measured by a conductance tempuracha depth depth profiler (CTD) Calculates the average propagation time of the sound wave between the transceivers, calculates the average propagation time, the falling edge of the peak of the correlation waveform of the sound wave received by the downstream sound wave transceiver, and the upstream sound wave transceiver Further comprising a threshold value calculation unit for determining the threshold value based on the relationship with the fall of the peak of the correlation waveform of the sound wave received at
The time information calculator is
Calculating the first and second times using the threshold value determined by the threshold value calculation unit;
It is good as well.

Anomaly value data included in the time-series data of the physical quantity calculated by the physical quantity calculation unit is detected by performing wavelet transform,
A spike correction unit that corrects the abnormal value data based on a residual of the abnormal value data with respect to a statistical model based on other data excluding the abnormal value data among the time series data of the physical quantity, further includes:
It is good as well.

The time information calculation unit calculates information on the propagation time of the sound wave based on a time signal from a GPS satellite.
It is good as well.

The predetermined data is composed of pseudo-random numbers generated by the M-sequence method.
It is good as well.
The time information calculator is
When two peak waveforms appear in the correlation waveform, the second peak waveform is used to calculate information related to the average propagation time of the sound wave in the cross section of the river between the sound wave transceivers. ,
It is good as well.
The time information calculator is
By performing sound ray analysis based on the survey information of the cross section and the sound velocity distribution of the cross section obtained from the distribution of water temperature and salinity, and estimating the arrival time of each sound ray, the river between the sound wave transceivers Calculating information on the average propagation time of the sound wave in the cross section of
It is good as well.
The time information calculator is
When a plurality of peak waveforms appear in the correlation waveform, the information regarding the average propagation time of the sound wave in the cross section of the river between the sound wave transceivers is calculated using the largest peak waveform. ,
It is good as well.

Moreover, the acoustic tomography measurement method according to the second aspect of the present invention includes:
Acoustics that measure physical quantities related to river cross-sections using non-directional sound waves transmitted and received between an upstream acoustic wave transmitter / receiver installed on one riverside and a downstream acoustic wave transmitter / receiver installed on the other riverside A tomography measurement method,
Based on the correlation waveform between the data demodulated from the sound wave received by each sound wave transmitter / receiver and the predetermined data, based on the time when the sound wave was transmitted from each sound wave transmitter / receiver, the sound wave transmitter / receiver A time information calculating step for calculating information on an average propagation time of the sound wave in a cross section of the river between;
To the sound ray length which is the length of the path of the sound wave transmitted / received between the upstream sound wave transmitter / receiver and the downstream sound wave transmitter / receiver, and the information related to the propagation time calculated in the time information calculation step Based on the average information calculation step of calculating at least one information of the cross-sectional average sound speed and the cross-sectional average flow velocity in the cross section of the river,
A physical quantity calculating step for calculating a physical quantity related to a cross section of the river based on the information calculated in the average information calculating step;
including.

  According to the present invention, the physical quantity of the cross section is measured assuming that the cross section of the river is a waveguide of sound waves. That is, information on the propagation time of non-directional sound waves transmitted and received between an upstream acoustic wave transmitter / receiver installed on one river side and a downstream acoustic wave transmitter / receiver installed on the other river side is required, The cross-sectional average sound velocity or the cross-sectional average flow velocity is obtained based on the sound ray length and the information on the propagation time, and the physical quantity relating to the cross section of the river is obtained based on the information.

  The sound wave propagates through the cross section while being reflected and refracted by the water surface and river bed, and is received by the sound wave transmitter / receiver through various paths. For this reason, the information regarding the propagation time of the sound wave is a value correlated with the cross-sectional average sound velocity and the cross-sectional average flow velocity in the cross section. Therefore, if the acoustic ray length is known, the cross-sectional average sound velocity and the cross-sectional average flow velocity can be obtained with high accuracy from the information regarding the propagation time of the sound wave. This is the same during floods and in tidal areas.

  The information on the propagation time of the sound wave is obtained based on a correlation waveform between data demodulated from the received sound wave and predetermined data. In this way, the SN ratio can be improved.

  In addition, the relational expression between the propagation time information and the average cross-sectional sound velocity or cross-sectional average flow velocity, and the relational expression between the cross-sectional average sound speed or cross-sectional average flow velocity and the physical quantity of the river cross-section are coefficients that need to be corrected. Therefore, the physical quantity of the cross section of the river can be calculated with high accuracy using the calculation formula under any circumstances.

  As described above, according to the present invention, a physical quantity of a river cross section can be measured without performing calibration even in a flood or in a tidal area with only a pair of sound wave transceivers. Under any circumstance, the physical quantity of the river cross section can be measured for a long time with high efficiency and high accuracy.

FIG. 1A is a perspective view schematically showing the arrangement of transducers in the acoustic tomography measurement system according to the first embodiment of the present invention, and FIG. 1B is a diagram for explaining the arrangement of the transducers. It is a cross-sectional view of a river. It is a block diagram which shows the structure of the acoustic tomography measurement system which concerns on the 1st Embodiment of this invention. FIG. 3A is a graph showing an example of a correlation waveform generated by one time-series data creation unit, and FIG. 3B is an example of a correlation waveform generated by the other time-series data creation unit. FIG. 3C is a diagram showing the threshold C _C , the average propagation time t _m, and the propagation time difference Δt. It is a block diagram which shows the structure of the acoustic tomography measurement system which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the acoustic tomography measurement system which concerns on the 3rd Embodiment of this invention. 6A and 6B are diagrams for explaining an example of how to obtain a threshold value. It is a block diagram which shows the structure of the acoustic tomography measurement system which concerns on the 4th Embodiment of this invention. It is a flowchart of the main process of the spike correction part of FIG. It is a flowchart of the spike detection process of FIG. It is a flowchart of the spike replacement process of FIG. It is a graph for demonstrating a mode that spike data is corrected.

  Embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
First, a first embodiment of the present invention will be described.

  1A and 1B show the arrangement of transducers 2A and 2B as a pair of sound wave transceivers in this embodiment. The transducer 2A is installed on one river bank 3A side, and the transducer 2B is installed on the other river bank 3B side.

  The transducer 2A is installed downstream of the transducer 2B. An angle formed by a vector indicating the direction of the river flow and a line segment connecting the transducers 2A and 2B is defined as θ.

  The transducer 2A transmits a sound wave toward the transducer 2B, and the transducer 2B transmits a sound wave toward the transducer 2A. The transducer 2A receives the sound wave transmitted from the transducer 2B, and the transducer 2B receives the sound wave transmitted from the transducer 2A.

  The sound waves transmitted from the transducers 2A and 2B have no directivity and propagate radially in water.

  The cross section in FIG. 1 (B) is a cross section that passes through the transducers 2A and 2B in FIG. 1 (A). As shown in FIG. 1B, some sound waves transmitted from the transducers 2A and 2B travel horizontally, while others travel while being reflected and refracted by the water surface and river bed. The sound wave thus propagates through the cross section and reaches the other transducer 2A, 2B through various paths.

  Here, the length of the sound wave path is hereinafter referred to as a sound ray length L.

  In FIG. 1 (B), the sound wave path is shown as a straight line. However, in the tide area that is hierarchized due to the difference in salt concentration such as the river mouth, the sound wave is refracted in water. The path becomes curved and more complicated.

  FIG. 2 shows a schematic configuration of an acoustic tomography measurement system 100 according to the present embodiment. As shown in FIG. 2, the acoustic tomography measurement system 100 further includes transmission / reception circuits 4A and 4B and a river information acquisition unit 5 in addition to the above-described transducers 2A and 2B.

  The transducer 2A includes a wave transmitter 2A1 (transmitter) that transmits sound waves and a wave receiver 2A2 (hydrophone) that receives sound waves. The transducer 2B includes a wave transmitter 2B1 (transmitter) that transmits sound waves and a wave receiver 2B2 (hydrophone) that receives sound waves.

  The transmission / reception circuit 4A includes a GPS (Global Positioning System) antenna 10, a time management unit 11, a transmission control unit 12, a transmission circuit unit 13, a reception circuit unit 14, and a reception control unit 15.

  The GPS antenna 10 receives GPS information from a GPS satellite (not shown). This GPS information includes time information.

  The time management unit 11 generates a reference clock signal based on the time information included in the GPS information received by the GPS antenna 10 and outputs the reference clock signal to the transmission control unit 12 and the reception control unit 15.

  The transmission control unit 12 outputs data including an identification code for identifying the own station to the transmission circuit unit 13. This identification code is generated by the M-sequence method, which is one of pseudo random number generation methods. In the transmission circuit unit 13, the identification code is D / A converted, phase-modulated, and a sound wave corresponding to the identification code is transmitted from the transmission unit 2 </ b> A <b> 1 of the transducer 2 </ b> A at a specific transmission time.

  On the other hand, the receiving circuit unit 14 A / D-converts and demodulates the signal received by the wave receiving unit 2A2 of the transducer 2A and outputs the demodulated signal to the reception control unit 15.

ここで、相関度は０〜１までの値をとり、その値が高ければ両者の相関性が高いということになる。算出された相関度は、そのときの時刻情報とともに随時出力される。 The reception control unit 15 calculates the degree of correlation between the digital data output from the reception circuit unit 14 and the identification code (M sequence) stored in advance. More specifically, the digital data output from the receiving circuit unit 14 is a vector x _i (i = 1 to n; n is a natural number of 2 or more), and the identification code is a vector y _i (i = 1 to m; m Is the Mth power of M sequence; m ≦ n), and the cross-correlation coefficient between the vector x _i and the vector y _i shown in the following equation is calculated as the degree of correlation.

Here, the degree of correlation takes a value from 0 to 1, and if the value is high, the correlation between the two is high. The calculated degree of correlation is output as needed together with the time information at that time.

  The configuration of the transmission / reception circuit 4B is the same as that of the transmission / reception circuit 4A.

  The river information acquisition unit 5 includes a CPU and a memory. By executing the program stored in the memory, the functions of the following constituent elements are realized.

  Time series data creation units 20A and 20B, a time information calculation unit 21, a threshold holding unit 22, a sound ray analysis unit 23, an average information calculation unit 24, and a physical quantity calculation unit 25 are provided.

  The time-series data creation unit 20A generates a correlation waveform (a waveform indicating a temporal change in the correlation degree) based on the time information output from the transmission / reception circuit 4A and the correlation degree at that time. FIG. 3A shows an example of a correlation waveform generated by the time series data creation unit 20A.

  In FIG. 3A, time 0 indicates the time when the sound wave is transmitted from the transducer 2B. The sound wave transmitted at time 0 is then received by the transducer 2A, but a sharp peak appears in the correlation waveform near the time when the sound wave is received.

  On the other hand, the time-series data creation unit 20B generates a correlation waveform based on the time information output from the transmission / reception circuit 4B and the degree of correlation of the time. FIG. 3B shows an example of a correlation waveform generated by the time series data creation unit 20B. The sound wave transmitted from the transducer 2A at time 0 is then received by the transducer 2B, but a sharp peak appears in the correlation waveform near the time when the sound wave is received.

  The graph of FIG. 3C is obtained by superimposing the graph of FIG. 3A and the graph of FIG. As shown in FIG. 3C, the peak of the correlation waveform generated by the time series data creation unit 20B is delayed from the peak of the correlation waveform generated by the time series data creation unit 20A. This delay is due to the Doppler effect caused by the river flow velocity.

ここで、Ｌは上述のように音線長である。 For example, if the average sound velocity (cross-sectional average sound velocity) of the sound wave in the cross section of the river is c _m and the component along the sound line of the river average flow velocity (cross-sectional average flow velocity) is u _m , the upstream transducer 2B The sound wave propagation time tA from the downstream transducer 2A to the downstream transducer 2A and the sound wave propagation time tB from the downstream transducer 2A to the upstream transducer 2B are expressed by the following equations, respectively.

Here, L is the acoustic ray length as described above.

ここで、ｔ_m、Δｔは次式のようになる。

以下では、ｔ_mを平均伝播時間といい、Δｔを伝播時間差という。すなわち、ｔ_mは、トランスデューサ２Ａ、２Ｂで音波が受信されたときのそれぞれの伝播時間の平均であり、Δｔは、トランスデューサ２Ａで音波が受信された時刻と、トランスデューサ２Ｂで音波が受信された時刻との時間差である。 In this case, the cross-sectional average sound velocity _cm and the cross-sectional average flow velocity u _m are obtained as follows.

Here, t _m and Δt are as follows.

Hereinafter, t _{m is referred} to as an average propagation time, and Δt is referred to as a propagation time difference. That is, t _m is an average of propagation times when sound waves are received by the transducers 2A and 2B, and Δt is a time when the sound waves are received by the transducer 2A and a time when the sound waves are received by the transducer 2B. And the time difference.

As shown in FIG. 3C, the time information calculation unit 21 uses the time 0 at which the sound wave is transmitted from the transducers 2A and 2B as a reference, based on the correlation waveform read from the time series data generation units 20A and 20B, As information regarding the average propagation time t _m and the propagation time difference Δt.

As shown in FIG. 3C, a threshold value _CC is necessary to obtain the average propagation time t _m and the average propagation time Δt. The threshold value C _C is held in the threshold value holding unit 22. Time information calculator 21 reads the threshold value C _C from the threshold holder 22. The time information calculation unit 21 performs the first operation from when the sound wave is emitted from the upstream transducer 2B (time 0) until the threshold value _CC is reached at the falling edge of the peak of the correlation waveform of the sound wave received by the downstream transducer 2A. TA as the time of? Furthermore, the time information calculation unit 21 starts from the time when the sound wave is emitted from the downstream transducer 2A (time 0) until the threshold value C _C is reached at the falling edge of the peak of the correlation waveform of the sound wave received by the upstream transducer 2B. Find tB as the second time.

Further, the time information calculation unit 21 obtains the average propagation time t _m and the propagation time difference Δt using the above equation (5). That is, the time information calculation unit 21 calculates the average of tA and tB as the average propagation time t _m of the sound wave between the transducers 2A and 2B. Further, the time information calculation unit 21 calculates the difference between tA and tB as a sound wave propagation time difference Δt between the transducers 2A and 2B.

If the average propagation time t _m and the propagation time difference Δt are obtained, then the cross-sectional average sound velocity _cm and the cross-sectional average flow velocity u _m must be obtained. In order to obtain the cross-sectional average sound velocity c _m and the cross-sectional average flow velocity u _m , it is necessary to obtain the sound ray length L. The sound ray analysis unit 23 obtains the sound velocity distribution in the cross section obtained from the survey information (data such as water depth) of the cross section measured in advance, the water temperature distribution f (r, z), and the salinity distribution g (r, z). Based on the above, the sound ray length L is calculated by performing sound ray analysis. Here, r and z are the horizontal and vertical position coordinates of the cross section, respectively. The water temperature distribution f (r, z) and the salinity distribution g (r, z) are obtained by interpolating the water temperature and the salinity measured as discrete values in the cross section at certain intervals by the CTD 6 described later.

ここで、Ｄは水深である。 More specifically, the sound ray analysis unit 23 uses, for example, the following equation (Medwin's equation) based on the water temperature distribution f (r, z) and the salinity distribution g (r, z) to calculate the sound velocity distribution. c (r, z) is calculated.

Here, D is the water depth.

ここで、式（７ａ）は、スネルの法則を表したものである。音線解析部２３は、上記式（７ａ）、式（７ｂ）の連立方程式を解くことにより、音波の軌跡上におけるｄｚ／ｄｒの値を求める。続いて、音線解析部２３は、求められたｄｚ／ｄｒを、次の平面曲線長を求める式に代入することにより、音線長Ｌを求める。 In this way, using the obtained sound velocity distribution c (r, z), the angle from the horizontal of the sound ray (incidence complementary angle φ, the vertical coordinate z of the sound wave, and the propagation time t of the sound wave are expressed by the following equation ( 7a) to 7c).

Here, Expression (7a) represents Snell's law. The sound ray analysis unit 23 obtains the value of dz / dr on the trajectory of the sound wave by solving the simultaneous equations of the above formulas (7a) and (7b). Subsequently, the sound ray analysis unit 23 obtains the sound ray length L by substituting the obtained dz / dr into an expression for obtaining the next plane curve length.

ここで、Ｒは、トランスデューサ間の直線距離である。

Here, R is a linear distance between the transducers.

The average information calculation unit 24 substitutes the sound ray length L, the average propagation time t _m, and the propagation time difference Δt thus obtained for the above formulas (3) and (4), respectively, and calculates the average cross-section sound speed c. _m and the cross-sectional average flow velocity u _m are calculated. That is, the average information calculation unit 24 determines the sound ray length L transmitted and received between the upstream transducer 2B and the downstream transducer 2A, the average propagation time t _m and the propagation time difference Δt calculated by the time information calculation unit 21. based on, calculating at least one of information of the cross-sectional average sound velocity c _m and a cross-sectional average flow velocity u _m in cross section of the river 1.

The physical quantity calculation unit 25 multiplies the cross-sectional area A (h) of the cross section based on the cross-sectional average flow velocity u _m calculated by the average information calculation unit 24 by using the following equation to obtain the flow rate Q of the cross-section as a physical quantity. As one of the following. Here, h is a water level.

ここで、Ｔ_mは水温（℃）、Ｓ_mは塩分、Ｄは水深である。 The physical quantity calculation unit 25, based on the cross-sectional average velocity of sound c _m, for example using the following equation (equation Medwin), calculates the temperature T _m or salinity S _m rivers.

Here, T _m is water temperature (° C.), S _m is salinity, and D is water depth.

  The CTD 6 is a conductivity tempuracha depth profiler, and is an apparatus for observing electrical conductivity, temperature, and water depth. In CTD6, salinity is calculated from electrical conductivity, water temperature, and the like.

The physical quantity calculation unit 25 inputs either the water temperature T _m or the salinity S _m from the CTD 6. Physical quantity calculation unit 25, and a cross-sectional average sound velocity c _m entered, one of the water temperature T _m or salinity S _m input to the equation (10), calculates the remaining water temperature T _m or salinity S _m.

  By the way, as shown in FIGS. 3 (A) and 3 (B), the correlation waveform becomes a unimodal waveform (single peak) because the arrival time of the sound ray passing through the transverse section is almost the same. Is the case. This is a phenomenon observed when measuring a single-section river without a run-up of salt water, in which the propagation distance of the radially emitted sound waves is almost the same and the sound speed is constant. Note that sound waves that reach the transducers 2A and 2B along a path that detours in the horizontal plane of the river are negligible and can be ignored.

On the other hand, when the transducers 2A and 2B are placed on the high sill of a river with a multi-section during flooding, the sound wave that passes through the high water sill only and the sound wave that enters the low water channel and reflects off the bottom surface reaches Since the arrival times are significantly different, there are cases where two peaks appear instead of the cases shown in FIGS. 3 (A) and 3 (B). In this case, in order to obtain the cross-sectional average flow velocity u _m , it is desirable to obtain the average propagation time t _m and the propagation time difference Δt using the second (later) peak waveform instead of the first peak.

In tidal rivers that run upstream with salt water, the propagation of sound waves is complicated, so the average propagation time t _m , propagation time difference is estimated by performing the sound ray analysis as described above and estimating the arrival time of each sound ray. A peak for obtaining Δt may be selected. Also, the largest peak among the plurality of peaks may be selected.

  Next, the operation of the acoustic tomography measurement system 100 according to this embodiment will be described.

  The transmission control unit 12 of the transmission / reception circuits 4A and 4B refers to the time information output from the time management unit 11, and when the specific time 0 is reached, the transmission unit 2A1 of the transducers 2A and 2B via the transmission circuit unit 13 2B1 transmits sound waves.

  When the sound wave is received by the wave receiving units 2A2 and 2B2 of the transducers 2A and 2B after a while, the sound wave is demodulated by the receiving circuit unit 14, the correlation degree is calculated by the reception control unit 15, and output from the time management unit 11 Is output together with the time information.

The time-series data creation units 20 </ b> A and 20 </ b> B of the river information acquisition unit 5 create respective correlation waveforms and output them to the time information calculation unit 21. The time information calculation unit 21 uses the threshold value C _C held by the threshold value holding unit 22 to obtain times tA and tB at which the peaks of the correlation waveforms reach the threshold value C _C , and based on the times tA and tB. Then, the average propagation time t _m and the propagation time difference Δt are calculated (time information calculation step).

The average information calculation unit 24 calculates the cross-sectional average sound velocity c _m and the cross-sectional average flow velocity u _m based on the average propagation time t _m , the propagation time difference Δt, and the sound ray length L output from the sound ray analysis unit 23. (Average information calculation step).

The physical quantity calculation unit 25 calculates the flow rate Q by multiplying the cross-sectional average flow velocity u _m by the cross-sectional area of the cross section. The physical quantity calculation unit 25, and a cross-sectional average sound velocity c _m, based on one of the water temperature T _m or salinity S _m output from CTD6, calculates the temperature T _m or salinity S _m (physical quantity calculation step).

According to the present embodiment, the physical quantity of the cross section is measured assuming that the cross section of the river 1 is a waveguide of sound waves. That is, information on the propagation time of a non-directional sound wave transmitted and received between the upstream transducer 2B installed on one river bank 3B side and the downstream transducer 2A installed on the other river bank 3A side is obtained, The cross-sectional average sound velocity _cm or the cross-sectional average flow velocity u _m is obtained based on the sound ray length L, the average propagation time t _m , and the propagation time difference Δt, and the physical quantity related to the cross section of the river 1 is obtained based on the information. .

The sound wave propagates through the cross section while being reflected and refracted by the water surface and river bed, and is received by the transducers 2A and 2B through various paths. Therefore, cross-sectional average velocity of sound c _m or cross-sectional average flow velocity u _m is a cross-sectional average velocity of sound c _m or value that cross-correlation between the average flow velocity u _m relationship in its cross section. Therefore, if known sound line length L, it can be obtained from the cross-sectional average velocity of sound c _m or cross-sectional average flow speed u _m, accurately sectional average sound velocity c _m and cross-sectional average flow speed u _m. This is the same during floods and in tidal areas.

The average propagation time t _m and the propagation time difference Δt are obtained based on the correlation waveform between the data demodulated from the received sound wave and the M-sequence data. In this way, the SN ratio can be significantly improved.

The average propagation time t _m, the relational expression and the cross section of the cross-sectional average sound velocity c _m or cross-sectional average flow velocity u _m and river between sectional average sound velocity c _m or cross-sectional average flow velocity u _m based on the propagation time difference Δt The relationship between the physical quantity (flow rate Q, water temperature T _m or salinity S _m ) does not include a coefficient that needs to be corrected. Thus, the physical quantity (flow rate Q, water temperature T _m or salinity S _m ) of the cross section of the river can be accurately calculated.

  As described above, according to the present invention, the physical quantity of the cross section of the river 1 can be measured with only a pair of transducers 2A and 2B without performing calibration even in a flood or a tidal zone. Therefore, under any environment, the physical quantity of the river cross section can be measured for a long time with high efficiency and high accuracy.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.

  FIG. 4 shows the configuration of an acoustic tomography measurement system 100 according to this embodiment. As shown in FIG. 4, the acoustic tomography measurement system 100 according to the present embodiment includes an acoustic ray length calculation unit 26 instead of the acoustic ray analysis unit 23 in that the acoustic tomography measurement according to the first embodiment is performed. Different from the configuration of the system 100.

The sound ray length calculation unit 26 calculates the cross-sectional average sound velocity c _m0 at the reference time based on the water temperature T _m0 and the salinity S _m0 at the reference time measured by the CTD 6, and is calculated by the time information calculation unit 21. Based on the average propagation time t _m0 between the transducers 2A and 2B at the reference time, the acoustic ray length L ₀ is calculated (= c _m0 × t _m0 ).

Based on the sound ray length L ₀ calculated by the sound ray length calculation unit 26, the average information calculation unit 24 calculates the cross-sectional average sound velocity _cm and the cross-sectional average flow velocity u _m at the time t _{m as} in the first embodiment. Calculate in the same way.

  The acoustic tomography measurement system 100 according to the present embodiment is suitable when it is difficult to obtain the sound ray length by sound ray analysis. For example, it is particularly suitable for flood observation when the transducers 2A and 2B are lowered from a sluice or a bridge.

(Third embodiment)
Next, a third embodiment of the present invention will be described.

  FIG. 5 shows a configuration of an acoustic tomography measurement system 100 according to the present embodiment. As shown in FIG. 5, the acoustic tomography measurement system 100 is different from the acoustic tomography measurement system 100 according to the first embodiment in that a threshold calculation unit 27 is provided.

The threshold calculation unit 27 sets the sound ray length L calculated by the sound ray analysis unit 23 and the cross-sectional average sound velocity c _m0 at the reference time obtained from the water temperature T ₀ and the salinity S ₀ at the reference time measured by the CTD 6. Based on this, an average propagation time t _m0 (= L / c _m0 ) is calculated. Further, the threshold calculation unit 27 uses the calculated average propagation time t _m0 and based on the correlation waveform input from the time series data creation units 20A and 20B, the correlation waveform of the sound wave received by the downstream transducer 2A. Based on the relationship between the fall of the peak and the fall of the peak of the correlation waveform of the sound wave received by the upstream transducer 2B, the threshold value _CC is determined (see FIG. 3C).

More specifically, as shown in FIG. _6A , the peak of the correlation waveform peak of the sound wave received by the downstream transducer 2A when shifted by the time dt in the minus direction with the average propagation time t _m0 as a reference. The time dt (= Δt / 2) at which the falling value and the falling value of the peak of the correlation waveform of the sound wave received by the upstream transducer 2B when shifted in the plus direction by the time dt are the same value Explore. FIG. 6B shows a time dt when both values are the same. As shown in FIG. 6B, the threshold calculation unit 27 determines the value of the correlation waveform at that time as the threshold C _C.

The time information calculation unit 21 calculates times tA and tB using the threshold value C _C determined by the threshold value calculation unit 27.

According to this embodiment, it is possible to determine the threshold value C _C depending on the temperature T ₀ and salt S ₀ of the cross section of the river 1 to be measured, the more accurate, Ya mean propagation time t _m of the sound wave The propagation time difference Δt can be obtained.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described.

  FIG. 7 shows a configuration of an acoustic tomography measurement system 100 according to the present embodiment. As shown in FIG. 7, the acoustic tomography measurement system 100 is different from the acoustic tomography measurement system 100 according to the first embodiment in that a spike correction unit 28 is provided.

The spike correction unit 28 detects the abnormal value data (spike data) included in the time series data of the physical quantity (flow rate Q, water temperature T _m , salinity S _m ) calculated by the physical quantity calculation unit 25 by performing wavelet transform. Subsequently, the spike correction unit 28 performs abnormal value data based on the residual of the abnormal value data (spike data) with respect to the statistical model based on other data excluding the abnormal value data (spike data) among the time-series data of physical quantities. To correct.

  FIG. 8 shows the main processing of the spike correction unit 28. The spike correction unit 28 performs this main process at a predetermined interval.

  As shown in FIG. 8, the spike correction unit 28 reads the time-series data of the physical quantity output from the physical quantity calculation unit 25 (step S1). Subsequently, the spike correction unit 28 performs a spike detection subroutine (step S2). Subsequently, the spike correction unit 28 determines whether or not spike data is detected in the spike detection process (step S3). If spike data has been detected (step S3; Yes), the spike correction unit 28 temporarily stores the spike data detection result (step S4). Subsequently, the spike correction unit 28 performs a spike replacement processing subroutine (step S5). After executing the spike replacement process, the spike correction unit 28 returns to step S2.

  In this way, steps S 2 → S 3 → S 4 → S 5 are repeated until it is determined in step S 3 that spike data is not detected.

  When spike data is not detected (step S3; No), the spike correction unit 28 stores time-series data of physical quantities for which spike data has been corrected (or spike data has not been detected) (step S6). The process ends.

  FIG. 9 shows a subroutine of spike detection processing in step S2. As shown in FIG. 9, the spike correcting unit 28 reads time-series data of physical quantities (step S11). Subsequently, the spike correction unit 28 determines whether or not the read time-series data of the physical quantity is long-term data (step S12). If this determination is affirmed (step S12; Yes), the spike correction unit 28 removes the low frequency component from the time-series data of the physical quantity (step S14).

  Subsequently, the spike correction unit 28 selects a wavelet transform filter (step S15), and performs wavelet transform on the time-series data (step S16). Subsequently, the spike correction unit 28 performs a predetermined calculation to calculate a threshold value (step S17), and performs a filtering process using the threshold value (step S18). Thereafter, the spike correction unit 28 performs wavelet inverse transformation on the wavelet transformed data (step S19).

  Subsequently, the spike correction unit 28 detects the position (spike position) of the spike data by comparing the time-series data of the physical quantity obtained by the wavelet inverse transformation and the time-series data of the original physical quantity (step) S20) The spike data string length (spike length) is detected (step S21).

  Subsequently, the spike correction unit 28 detects the data length (normal value data length) of the normal value data (normal value data) before the spike data string (step S22). The spike correction unit 28 stores the detection results so far (step S23). After execution of step S23, the spike correction unit 28 ends the spike detection process.

  FIG. 10 shows a subroutine for spike replacement processing. As shown in FIG. 10, the spike correction unit 28 reads time-series data around the spike data (step S31). Subsequently, the spike correction unit 28 determines whether or not the read time-series data is long-term data (step S32). If this determination is affirmative (step S32; Yes), the spike correction unit 28 selects normal value data before the spike data string (step S33).

  Subsequently, the spike correction unit 28 estimates the six parameters of the autoregressive model (AR model) using the selected normal value data (step S34). Subsequently, the spike correction unit 28 performs model estimation using the conditional maximum likelihood estimation method using the selected normal value data (step S35). Subsequently, the spike correction unit 28 estimates an optimal model based on AIC (Akaike Information Criterion) using the selected normal value data (step S36).

  Subsequently, the spike correction unit 28 checks the correlation of the residuals in the time series data with respect to the statistical models obtained in steps S34, S35, and S36, and determines whether or not the difference in residuals is within a predetermined allowable range. Is tested (step S37). Further, the spike correction unit 28 tests the continuity of the model (step S38).

  Subsequently, the spike correction unit 28 determines whether or not the selected data has passed the two tests of Steps S36 and S37 (Step S39).

  If both tests are passed (step S39; Yes), the spike correction unit 28 calculates a model error (residual) (step S44), and a predicted value to be replaced with spike data based on the model error. Is calculated (step S45). Then, the spike correction unit 28 replaces the spike data with the predicted value (step S46). FIG. 11 schematically shows how spike data (abnormal value data) is corrected to a predicted value for a physical quantity that varies in the short term.

  Subsequently, the spike correction unit 28 determines whether or not the selection of time-series data for all physical quantities has been completed (step S47). If this determination is negative (step S47; No), the spike correction unit 28 returns to step S31.

  The spike correction unit 28 again performs partial reading of the physical quantity time-series data (step S31), and determines whether or not the read time-series data is long-term data (step S32). If this determination is negative (step S32; No), the spike correction unit 28 performs cubic polynomial interpolation on the normal value data to obtain an interpolation value to be replaced with the spike data (step S42). The spike data is replaced with an interpolation value (step S43). Thereafter, the spike correction unit 28 determines whether or not all the data has been selected (step S47). If this determination is negative (step S47; No), the spike correction unit 28 returns to step S31.

  Thereafter, the process proceeds from step S31 → S32 → S33 → S34 → S35 → S36 → S37 → S38, and if the determination in step S39 is negative, the spike correction unit 28 determines whether or not the test failure is the first time. (Step S40). If the test failure is the first time (step S40; Yes), the spike correction unit 28 additionally selects normal value data (step S41) and returns to step S34.

  Thereafter, with the data added, three models are estimated in steps S34 → S35 → S36, and a residual correlation test and a continuity test are performed (step S38). If both test pass determinations are negative (step S39; No) and the test failure is not the first time (step S40; No), the spike correction unit 28 performs the cubic polynomial interpolation on the normal value data and spikes. An interpolation value to be replaced with data is obtained (step S42), and spike data is replaced with the interpolation value (step S43). Thereafter, the spike correction unit 28 determines whether or not all the data has been selected (step S47).

  In this way, the process is repeated until it is determined in step S47 that all data has been selected. If it is determined that all data has been selected (step S47; Yes), the spike correction unit 28 determines that the spike data has been selected. The time-series data of the replaced physical quantity is stored as a processing result (step S48), and the spike replacement process is terminated.

As described above, according to the present embodiment, the abnormal value data included in the time-series data of the obtained physical quantity can be corrected. Thereby, highly accurate measurement becomes possible. In this way, for example, it is possible to accurately detect short-term fluctuations in the flow rate Q, the water temperature T _m , the salinity S _m , and the like. This method is also effective when it is not appropriate to reject abnormal value data because the acquired data is small.

  In the present embodiment, an autoregressive (AR) model, a model based on a conditional maximum likelihood estimation method, a model based on AIC, and the like are applied as a statistical model of time-series data of physical quantities. However, the present invention is not limited to this, and a model based on a Kalman filter is used. May be applied.

  In the acoustic tomography measurement system 100 according to this embodiment, for example, in a tidal river upstream of salt water, the bidirectionality of sound wave propagation is lost, and the correlation waveforms obtained from both transducers 2A and 2B are not similar. This is particularly effective in reducing spike data generated due to this.

  In each of the above embodiments, the time information is from a GPS satellite. In this way, it is possible to measure the propagation time of a sound wave and the like very accurately.

  In the above embodiment, the program to be executed is a computer-readable recording such as a flexible disk, a CD-ROM (Compact Disk Read-Only Memory), a DVD (Digital Versatile Disk), and an MO (Magneto-Optical Disk). A system that executes the above-described processing may be configured by storing and distributing the program on a medium and installing the program.

  Further, the program may be stored in a disk device or the like of a predetermined server device on a communication network such as the Internet, and may be downloaded, for example, superimposed on a carrier wave.

  In addition, when the above functions are realized by sharing an OS (Operating System), or when the functions are realized by cooperation between the OS and an application, only the part other than the OS may be stored in a medium and distributed. You may also download it.

  In addition, this invention is not limited by the said embodiment and drawing. It goes without saying that the embodiments and the drawings can be modified without changing the gist of the present invention.

  The present invention is ideal for measuring physical quantities related to river cross sections such as flow rate, water temperature, salinity, etc., especially for tidal zones where salt is mixed near the river mouth, and for measuring physical quantities of rivers during floods, etc. It is.

1 River 2A, 2B Transducer 2A1, 2B1 Transmitter 2A2, 2B2 Receiver 3A, 3B River 4A, 4B Transceiver Circuit 5 River Information Acquisition Unit 6 CTD (Conductivity Tempuracha Depth Profiler)
DESCRIPTION OF SYMBOLS 10 GPS antenna 11 Time management part 12 Transmission control part 13 Transmission circuit part 14 Reception circuit part 15 Reception control part 20A, 20B Time series data creation part 21 Time information calculation part 22 Threshold holding part 23 Sound ray analysis part 24 Average information calculation part 25 physical quantity calculation unit 26 sound ray length calculation unit 27 threshold calculation unit 28 spike correction unit 100 acoustic tomography measurement system

Claims (14)

Acoustics that measure physical quantities related to river cross-sections using non-directional sound waves transmitted and received between an upstream acoustic wave transmitter / receiver installed on one riverside and a downstream acoustic wave transmitter / receiver installed on the other riverside A tomography measurement system,
Based on the correlation waveform between the data demodulated from the sound wave received by each sound wave transmitter / receiver and the predetermined data, based on the time when the sound wave was transmitted from each sound wave transmitter / receiver, the sound wave transmitter / receiver A time information calculation unit for calculating information on an average propagation time of the sound wave in a cross section of the river between;
To the sound ray length which is the length of the path of the sound wave transmitted and received between the upstream sound wave transmitter / receiver and the downstream sound wave transmitter / receiver, and the information related to the propagation time calculated by the time information calculation unit Based on the average information calculation unit for calculating at least one of the cross-sectional average sound velocity and the cross-sectional average flow velocity in the cross section of the river,
Based on the information calculated by the average information calculator, a physical quantity calculator that calculates a physical quantity related to the cross section of the river;
An acoustic tomography measurement system comprising: The time information calculator is
As the information on the propagation time of the sound wave, the average propagation time of the sound wave between the sound wave transceivers and the propagation time difference of the sound wave between the sound wave transceivers are calculated,
The average information calculation unit
Based on the sound ray length, the average propagation time, and the propagation time difference, the cross-sectional average flow velocity is calculated,
The physical quantity calculation unit
By multiplying the cross-sectional area of the cross section by the cross-sectional average flow velocity, the flow rate of the cross section is calculated as the physical quantity,
The acoustic tomography measurement system according to claim 1. The time information calculator is
As information on the propagation time of the sound wave, calculate the average propagation time of the sound wave between the sound wave transceivers,
The average information calculation unit
By dividing the average propagation time from the sound ray length, the cross-sectional average sound speed is calculated,
The physical quantity calculation unit
Using the relational expression between the cross-sectional average sound velocity, salinity, water temperature and water depth, either salinity or water temperature is calculated as the physical quantity.
The acoustic tomography measurement system according to claim 1. Based on the survey information of the cross section and the sound speed distribution of the cross section obtained from the distribution of water temperature and salinity, further comprising a sound ray analysis unit for calculating the sound ray length by performing sound ray analysis,
The average information calculation unit
Based on the sound ray length calculated by the sound ray analysis unit, calculate at least one of the cross-sectional average sound velocity and the cross-sectional average flow velocity,
The acoustic tomography measurement system according to any one of claims 1 to 3. The cross-sectional average sound speed at a reference time is calculated based on the water temperature and salinity measured by a conductivity tempuracha depth profiler (CTD), and the cross-sectional average sound speed between the sound wave transmitter / receiver at the reference time A sound ray length calculation unit for calculating the sound ray length based on the average propagation time of the sound wave;
The average information calculation unit
Based on the sound ray length calculated by the sound ray length calculation unit, calculate at least one of the cross-sectional average sound velocity and the cross-sectional average flow velocity,
The acoustic tomography measurement system according to any one of claims 1 to 3. The time information calculator is
A first time from when the sound wave is emitted from the upstream sound wave transmitter / receiver until a threshold is reached at the falling edge of the peak of the correlation waveform of the sound wave received by the downstream sound wave transmitter / receiver;
A second time from when the sound wave is emitted from the downstream sound wave transmitter / receiver until the threshold value is reached at the falling edge of the peak of the correlation waveform of the sound wave received by the upstream sound wave transmitter / receiver. ,
The average of the first time and the second time is calculated as the average propagation time of the sound wave between the sound wave transceivers,
Calculating the difference between the first time and the second time as a propagation time difference of sound waves between the sound wave transceivers;
The acoustic tomography measurement system according to any one of claims 1 to 3. A sound ray analysis unit that calculates the sound ray length by performing sound ray analysis based on the survey information of the cross section, and the sound velocity distribution of the cross section obtained from the water temperature and salinity distribution,
Based on the sound ray length calculated by the sound ray analyzer and the cross-sectional average sound speed at a reference time obtained from the water temperature and salinity measured by a conductance tempuracha depth depth profiler (CTD) Calculates the average propagation time of the sound wave between the transceivers, calculates the average propagation time, the falling edge of the peak of the correlation waveform of the sound wave received by the downstream sound wave transceiver, and the upstream sound wave transceiver Further comprising a threshold value calculation unit for determining the threshold value based on the relationship with the fall of the peak of the correlation waveform of the sound wave received at
The time information calculator is
Calculating the first and second times using the threshold value determined by the threshold value calculation unit;
The acoustic tomography measurement system according to claim 6. Anomaly value data included in the time-series data of the physical quantity calculated by the physical quantity calculation unit is detected by performing wavelet transform,
A spike correction unit that corrects the abnormal value data based on a residual of the abnormal value data with respect to a statistical model based on other data excluding the abnormal value data among the time series data of the physical quantity, further includes:
The acoustic tomography measurement system according to any one of claims 1 to 7, wherein The time information calculation unit calculates information on the propagation time of the sound wave based on a time signal from a GPS satellite.
The acoustic tomography measurement system according to any one of claims 1 to 8, wherein The predetermined data is composed of pseudo-random numbers generated by the M-sequence method.
The acoustic tomography measurement system according to any one of claims 1 to 9, wherein The time information calculator is
When two peak waveforms appear in the correlation waveform, the second peak waveform is used to calculate information related to the average propagation time of the sound wave in the cross section of the river between the sound wave transceivers. ,
The acoustic tomography measurement system according to any one of claims 1 to 10. The time information calculator is
By performing sound ray analysis based on the survey information of the cross section and the sound velocity distribution of the cross section obtained from the distribution of water temperature and salinity, and estimating the arrival time of each sound ray, the river between the sound wave transceivers Calculating information on the average propagation time of the sound wave in the cross section of
The acoustic tomography measurement system according to any one of claims 1 to 10. The time information calculator is
  When a plurality of peak waveforms appear in the correlation waveform, the information regarding the average propagation time of the sound wave in the cross section of the river between the sound wave transceivers is calculated using the largest peak waveform. ,
The acoustic tomography measurement system according to any one of claims 1 to 10. Acoustics that measure physical quantities related to river cross-sections using non-directional sound waves transmitted and received between an upstream acoustic wave transmitter / receiver installed on one riverside and a downstream acoustic wave transmitter / receiver installed on the other riverside A tomography measurement method,
Based on the correlation waveform between the data demodulated from the sound wave received by each sound wave transmitter / receiver and the predetermined data, based on the time when the sound wave was transmitted from each sound wave transmitter / receiver, the sound wave transmitter / receiver A time information calculating step for calculating information on an average propagation time of the sound wave in a cross section of the river between;
To the sound ray length which is the length of the path of the sound wave transmitted / received between the upstream sound wave transmitter / receiver and the downstream sound wave transmitter / receiver, and the information related to the propagation time calculated in the time information calculation step Based on the average information calculation step of calculating at least one information of the cross-sectional average sound speed and the cross-sectional average flow velocity in the cross section of the river,
A physical quantity calculating step for calculating a physical quantity related to a cross section of the river based on the information calculated in the average information calculating step;
Acoustic tomography measurement method including

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