JP6300344B2 - Ocean current estimation method and ocean current estimation system - Google Patents

Description

  The present invention relates to an ocean current estimation method and an ocean current estimation system for estimating the direction and velocity of an ocean current using a ship or the like on the sea.

  Seawater flows include tidal currents generated by tidal action and ocean currents that occur on a global scale due to different causes. While tidal currents change periodically within a relatively short time and can be predicted astronomically, temporal changes in ocean currents are generally slower than tidal currents, but are difficult to predict. On the other hand, this current has a great influence on the operation of ships. For this reason, recognizing the ocean current vector (the direction of the ocean current, the flow velocity (intensity)) or its distribution is extremely important for ship operation. For example, if the operation grasps the ocean current, the operation time can be shortened and the fuel consumption can be reduced.

  The ocean current is measured by, for example, measurement using an observation ship or mooring buoy, remote sensing using an artificial satellite, marine radar installed on the coast, and the like. The whole picture of the ocean current is obtained and made public by simulation (calculation) using such discrete measurement data. In such a case, it is necessary to increase the number of measurement points for actually measuring the ocean current and increase the accuracy of the measurement in order to accurately grasp the ocean current distribution. Various techniques have been proposed for detecting tidal currents and ocean currents. Patent Document 1 discloses a technique for calculating changes in the position of a ship as ship position information and a tidal current from the bow direction by calculation using a ship model and a motion model modeled based on the shape of the ship. Is described. The position of the ship can be recognized on the sea using, for example, GPS (Global Positioning System), and the bow direction can be recognized on the sea using, for example, a gyrocompass.

  Patent Document 2 describes a display device that can simultaneously display a trajectory of a ship position and a bow direction on a display so that the influence of a tidal current can be grasped visually.

  In Patent Document 3, each of a plurality of ships measures tidal currents, estimates the distribution of ocean currents by aggregating these information in a base station, and estimates tidal current information at locations other than locations where tidal currents are actually measured. The system to be described is described. A ship other than the ship that has actually measured the tidal current can operate by recognizing the tidal current at the location where the ship is located.

JP 2005-172618 A JP-A-8-114462 JP 2001-264437 A

  In the technique described in Patent Document 1, modeling based on the shape of a ship or the like is performed, and hydrodynamic calculation is performed to calculate the direction of the ocean current and the flow velocity. For this reason, there are very many preconditions used in the calculation, and it is rare that all these preconditions match the actual ship, and there are many cases where they are different from the actual situation. For this reason, it has been difficult to obtain a tidal (sea current) vector with high accuracy.

  Although it is easy to visually recognize the tidal current with the technique described in Patent Document 2, it is clear that it is difficult to accurately calculate the direction and the flow velocity. Since the technique described in Patent Document 3 is based on the premise that the tidal current can be accurately measured in each ship, the accuracy ultimately depends on the accuracy of tidal vector detection in each ship. For this reason, as with the technique described in Patent Document 1, it has been difficult to obtain information on tidal currents (ocean currents) with high accuracy. In addition, it was necessary for each ship to be equipped with dedicated equipment and to act in cooperation for the purpose of measuring the tidal current distribution only.

  Therefore, it has been difficult to accurately measure information (direction, flow velocity) about the ocean current.

  The present invention has been made in view of the above problems, and solves the above problems. An ocean current estimation method and an ocean current estimation system capable of accurately and easily estimating information (direction, velocity) relating to ocean currents are provided. The purpose is to provide.

In order to solve the above problems, the present invention has the following configurations.
The ocean current estimation method according to claim 1 of the present invention is a ocean current estimation method for estimating an ocean current vector that indicates the direction and strength of an ocean current by using a plurality of operation information in which conditions relating to the operation of a ship at sea are specified. The ground speed vector for each individual ship of the plurality of ships passing through the sea area where the ocean current is estimated as the operation information and the heading of the ship are obtained , and based on the ground speed vector and the heading direction for each ship , to calculate the currents vector in the waters for navigation of a plurality of the marine vessel, characterized in that to increase the estimation accuracy of the currents vector by increasing the number of vessels of the plurality of vessels to obtain the flight information.
In the present invention, a plurality of operation information including at least information on ground speed vectors and heading directions of a plurality of ships is acquired, and an ocean current vector (direction and strength of the ocean current) is calculated based on these information. Here, in particular, operation information for a plurality of ships is used.
In the ocean current estimation method according to claim 2 of the present invention, the navigation information includes ground speed information in which the ground speed of the ship is specified and local position information in which the ship's ground position is specified. The ocean current vector is calculated using the ground speed vector obtained from the ground speed and the ground position.
In this invention, in each operation information, the ground speed information in which the ground speed of the ship (the absolute value of the ground speed vector) is specified and the ground position information in which the local position (direction of the ground speed vector) is specified. Is included. Thereby, a ground speed vector is specified for each operation information.
Current estimation method according to claim 3 of the present invention, heading information the heading is determined, the ground speed information, and the ground orientation information ship automatic identification system (Automatic Identification System: AIS) is obtained by It is characterized by that.
In the present invention, the heading information, the ground speed information, and the local position information are acquired by an AIS that is required to be installed particularly on a large ship.

In the ocean current estimation method according to claim 4 of the present invention, the operation information includes position information in which the position of the ship when the operation information is acquired is specified, and the sea area is based on the position information. The ocean current vector at is calculated.
In the present invention, a plurality of operation information is selected and used based on the position of the ship. For example, two or more ships navigating the sea area where the ocean current should be estimated, two or more ships navigating in close proximity, etc. are selected and used for estimating (calculating) the ocean current vector in that sea area. Here, the “plurality of operation information” is not necessarily for a plurality of ships, as described above.
In the ocean current estimation method according to claim 5 of the present invention, the operation information specifies the position information where the position of the ship when the operation information is acquired and the time when the position information is acquired. The ground speed vector is calculated based on the position information and the time information.
In this invention, instead of using ground speed information and local position information, the ground speed vector is calculated from the time change of the ship position using the position information and time information in the operation information.
The current estimation method according to claim 6 of the present invention is characterized in that the heading information in which the heading is specified and the position information are acquired by a ship automatic identification system (AIS).
In the present invention, the position information is also acquired by AIS, similarly to the heading information.

The ocean current estimation method according to claim 7 of the present invention is characterized in that information used for calculating the ocean current vector is corrected based on the operation information and / or the acquisition status of the operation information.
In the present invention, the information used for calculating the ocean current vector (the ground speed vector obtained from the operation information, the heading direction, and other parameters used for calculating the ocean current vector) can be calculated with higher accuracy. It is used after being corrected.
In the ocean current estimation method according to claim 8 of the present invention, the information regarding the ocean current vector is used as a parameter, an objective function for each operation information is created for each of the operation information, and the objective function for each operation information for each of the plurality of operation information. The ocean current vector that optimizes the objective function that is the sum of the currents is calculated.
In the present invention, the ocean current vector is estimated by the optimization method. Here, the ocean current vector that gives the optimum value (for example, the minimum value) of the objective function defined using the ground speed vector, the heading and the ocean current vector in the plurality of operation information is assumed to be the estimated ocean current vector. The objective function is expressed as a sum of objective functions for each operation information defined for each operation information.
The ocean current estimation method according to claim 9 of the present invention creates an objective function for each operation information using each of the operation information using information on the current vector as a parameter, and the object for each operation information for each of the plurality of operation information. The current vector that optimizes an objective function that is a sum of values obtained by multiplying a function by a weighting factor is calculated, and the correction is performed by setting the weighting factor for each operation information.
In this invention, the said correction | amendment is performed by the setting of the weighting coefficient for every operation information.
In the ocean current estimation method according to claim 10 of the present invention, the weighting factor is estimated as a difference between a position where the operation information is acquired and a position where the operation current is estimated, a time when the operation information is acquired, and the ocean current. It is set based on at least one of the difference with the time to perform, the kind of ship which acquired the said operation information, or the calculation result of the ocean current vector performed in the past using the said operation information.
In the present invention, the weighting factor is set based on the position, time, ship type, and past calculation history. Thereby, the priority of the operation information used is set.

The ocean current estimation system according to claim 11 of the present invention comprises:
An ocean current estimation system that estimates an ocean current vector based on the ocean current estimation method according to any one of claims 1 to 10 , wherein the information acquisition unit acquires the operation information of a plurality of the ships ; Storage means for storing the acquired operation information, list-up means for listing a plurality of the ships navigating the sea area at a specific time, and the operation information of the listed ships from the storage means It comprises a reading means for reading and a current vector calculation unit for calculating the current vector based on the read operation information.
In this invention, an information acquisition part acquires the operation information of several ships , and this operation information is memorize | stored in a memory | storage means. Among these ships, the ships navigating the target sea area at a specific time by the list-up means are listed, and the corresponding operation information is read from the storage means. The ocean current vector calculation unit calculates an ocean current vector (direction and strength of the ocean current) based on the operation information read in this way .
In the ocean current estimation system according to claim 12 of the present invention, the information acquisition unit acquires previously predicted ocean state information, and the ocean current vector calculation unit corrects the estimated ocean current vector based on the ocean state information. It is characterized by doing.
In the present invention, for example, a tidal current is recognized from ocean state information obtained from the outside, and an original ocean current obtained by removing this tidal component is estimated from the estimated ocean current vector.
The ocean current estimation system according to claim 13 of the present invention is characterized in that the ocean current vector calculation unit estimates an ocean current distribution by calculating the ocean current vectors in a plurality of the ocean areas.
In the present invention, the ocean current distribution is estimated by estimating ocean current vectors in a plurality of ocean areas.
In the ocean current estimation system according to claim 14 of the present invention, the ocean current vector calculation unit assimilate the calculated ocean current vector with respect to the ocean current distributions predicted in advance in the plurality of ocean areas, and obtain a new ocean current distribution. It is characterized by estimating.
In the present invention, when there is a current distribution predicted in advance by calculation, a highly accurate current distribution is calculated by assimilating the estimated current vector data with the current distribution.
The ocean current estimation system according to claim 15 of the present invention is characterized by comprising a channel instruction unit that instructs a marine vessel based on the estimated ocean current distribution.
In the present invention, the route instruction unit instructs the optimum route calculated based on the estimated ocean current distribution.

Since the ocean current estimation method and ocean current estimation system of the present invention are configured as described above, ocean current vectors can be estimated with high accuracy.
Here, since the ground speed vector and heading can be obtained from the operation information that identifies the situation related to the operation of the ship, it is particularly easy to estimate the current vector using the normal equipment and operation information of the ship. Can do. In particular, accurate ground speed information, local position information, and heading information can be easily obtained by AIS that is required to be mounted on large ships. Thereby, said calculation can be performed with high precision and easily, without using a special operation information acquisition means.
Further, by using the position information and the time information together with the ground speed information and the heading information, the current vector can be calculated with higher accuracy. At this time, accurate position information can be easily obtained by AIS. The ground velocity vector can be accurately calculated based on the position information and time information, and thereby the ocean current vector can be calculated with higher accuracy. In addition, it is possible to specify the sea area where the ship that obtained the ocean current vector from the position information navigates.
Further, by creating an objective function using the operation information and estimating the ocean current vector by the optimization method, a more reliable ocean current vector can be estimated by using a wider range of data. At this time, if the weight of the objective function for each operation information is set in consideration of the position and time at which the current vector should be calculated, the current vector with the highest accuracy can be estimated according to the position and time.
In addition, it is possible to estimate ocean current vectors in a plurality of ocean areas and to estimate the ocean current distribution over a wide area. At this time, the original ocean current distribution obtained by removing the tidal current component from the obtained ocean current information can also be obtained by using the oceanographic information.
Further, when there is a low-accuracy ocean current distribution estimated in advance, it is possible to assimilate the estimated ocean current vector data and obtain a more accurate ocean current distribution. Using the estimated ocean current distribution, an optimized route can be indicated.

It is a figure explaining the principle of the ocean current estimation method (when there are two or less vessels) concerning an embodiment of the invention. It is a figure explaining the principle of the ocean current estimation method (when there are three ships) concerning an embodiment of the invention. It is a figure which shows typically an example of a structure of the ocean current estimation system which concerns on embodiment of this invention.

  Hereinafter, an ocean current estimation system and an ocean current estimation method according to embodiments of the present invention will be described. FIG. 1 is a diagram for explaining the principle of a method for estimating (calculating) ocean currents in this ocean current estimation system. First, here, a case where two or less ships are used will be described. Fig.1 (a) is the figure which looked at the operational condition in the sea of the ship 1 from the upper side, and has shown typically the motion of the ship 1 per unit time. However, in FIG. 1, the tidal current is included in the ocean current, and the entire seawater flow is referred to as the ocean current.

Here, when there is no ocean current, the ship 1 always proceeds with its water velocity (velocity with respect to the water surface) vector V _W along its heading (direction toward the bow), and the actual speed of the ship 1 (ground speed). : Velocity relative to absolute coordinates (ground)) Vector V _S is obviously equal to water velocity vector V _W. However, when the ocean current vector V _C is not zero, the ground velocity vector V _S is the sum of the ocean velocity vector V _W and the ocean current vector V _C. At this time, especially when the ocean current vector V _C having a heading perpendicular component is present, as shown in FIG. 1 (a), vessel heading 1 is shifted from the actual direction of travel. Here, the position information of the ship 1 itself can be recognized with high accuracy by a device using the GPS signal mounted on the ship 1 itself, and the ground speed vector V _S (actual The direction of speed and absolute value) can also be detected with high accuracy. Here, detecting the ground speed vector V _S means that the absolute value of the ground speed vector V _S and the position of the ground speed in the direction are detected. As shown in FIG. 1A, the position with respect to the _locality is defined as, for example, a clockwise angle θ _S with respect to the north direction. Further, if the heading of the ship 1 is similarly defined as the angle θ _W , it can be recognized with high accuracy as well. The heading θ _W is the direction of the water velocity vector V _W. In the following description, the absolute value of the ground speed vector is referred to as the ground speed, the direction (θ _S ) of the ground speed vector as the local position, and the absolute value of the water speed vector as the water speed. When currents vector V _C is zero (if ocean current does not exist), the ground speed and to water velocity equals, ground bearing and heading are equal.

Here, from FIG. 1 (a), if also known to water velocity vector V _W, it can be calculated currents vector V _C by the difference between the ground speed vector V _S. On the other hand, it is not impossible to detect the water velocity vector V _W using an anemometer or the like attached to the ship. However, unlike the ground speed vector V _S which recognizes its position using GPS signals or the like and is more accurately recognized than its time change, the reference for measuring the water speed vector V _W is seawater. Therefore, it is difficult to detect this with high accuracy as much as the ground speed vector V _S. For this reason, as described above, only the direction of the water velocity vector V _W is recognized with high accuracy as the heading θ _W like V _S, and it is difficult to detect the absolute value V _W0 with high accuracy. It is.

In this case, in FIG. 1 (b), the since the heading theta _W and ground speed vector V _S is definite precisely, (the end point of the to water velocity vector V _W) start point of ocean current vector V _C is not determined, ocean currents vector it is not possible to determine the V _C uniquely. For example, in FIG. 1B, all of the vectors V _C1 , V _CP , and V _C2 are candidates for the ocean current vector V _C. Here, the vector V _CP is perpendicular to the bow direction (water velocity vector V _W ). From this result, it is clear that the component of the ocean current vector V _{C in} the direction perpendicular to the bow direction becomes the vector V _CP in the vectors V _C1 and V _C2 . That is, when the ground speed vector V _S and heading theta _W of the ship 1 can be recognized, the direction of the ocean current vector V _C, it is difficult to accurately calculate the absolute value, and heading of the ocean current vector V _C The vertical direction component can be uniquely calculated. In steering the ship, providing a particularly large impact heading perpendicular component of the currents vector V _C it is clear. For this reason, the above-described method for calculating V _CP by drawing only the ground speed vector V _S of the ship 1 and the heading θ _W without using the water speed vector V _W and performing the drawing of FIG. Is valid.

If to water velocity direction of the vector V _W only (heading) is known that the absolute value (to water velocity) is not known, to calculate the other components of the currents vector V _C, for example, the components in the heading is not are possible, the orientation of the currents vector V _C, it is impossible to uniquely determine the absolute value. However, in addition to the ship 1 having the ground speed vector V _S1 and the heading θ _W1 , the ship 2 (ground speed vector V _S2 , heading θ _W2 ) is navigating, and the ground speed vector V _S2 , heading θ _W2 is detected accurately, and if currents vector _{V C} is common to the ship 1 and 2, be an absolute value of to water velocity vector _{V W1, V W2} of the ship 1 and 2 unknown As shown in FIG. 1C, the ocean current vector V _C is uniquely determined. For example, if the proximity distance of the ship 1 and the ship 2 is ocean current vector V _C between them can be considered common. In this case, the ocean current vector V _C (the direction and intensity of the ocean current) can be accurately calculated. Alternatively, even if the ship 1 and 2 are separated, even if these are considered ocean current vector V _C is equal in waters sailing, it is similar.

Specifically, this calculation method is as follows. Here, as shown in FIG. 1A, when the x and y axes are taken and the water velocity vector V _W is (V _Wx , V _Wy ), the water velocity is V _W0 , and V _W0 X (cos θ _W , sin θ _W ) can be written. Here, V _W0 is indefinite and θ _W is known. If the ground speed vector V _S is (V _Sx , V _Sy ), this is also known. When the current vector V _C to be calculated is (V _Cx , V _Cy ), the expressions (1) and (2) are established between them.

Here, from the equations (1) and (2), when V _W0 which is indefinite is deleted, the equation (3) is obtained.

Assuming that the equation (3) is established for each of the vessels 1 and 2 and V _Cx and V _Cy are common to both vessels, V _Sx , V _Sy and θ _W for the vessels 1 and 2 are subscripts 1 and 2. (4) is established.

Thereby, the ocean current vector V _C = (V _Cx , V _Cy ) is calculated by the equation (5).

For this reason, when θ _W1 ≠ θ _W2 , that is, when the heading of the ship 1 and the ship 2 is different, (V _Cx , V _Cy ) can be calculated. The direction of the ocean current based on the north direction (defined in the same way as θ _W and θ _S ) is tan ⁻¹ (V _Cx / V _Cy ), and the absolute value (strength) of the ocean current is (V _Cx ² + V _Cy ^2). ) ^1/2 .

As described above, necessary for the calculation of currents vector _{V C} is the ground speed vector _{V S (V Sx, V Sy} ) of the ship and is heading theta _W. What is required for the calculation of the ground speed vector V _S is ground speed information in which the ground speed is specified, and ground position information in which the local position θ _S is specified. Furthermore, heading information heading theta _W is identified is required. As described above, such information on the ship can be obtained using GPS or the like.

  On the other hand, according to the 1974 Convention on the Safety of Life at Sea (SOLAS 74), large vessels, for example, vessels with 300 gross tons or more engaged in international voyages, are equipped with an automatic identification system (AIS). Is required. According to AIS, a ship is obliged to transmit AIS information related to its own ship by radio waves in the VHF band, and can receive and obtain AIS information of other ships. Thereby, the safety of navigation of a ship can be aimed at. For details on the details of AIS, see, for example, http: // www6. kaiho. mlit. go. jp / osakawan / others / ais / ais. htm et al. Among the AIS information, the dynamic information indicating the state of the ship includes the position information of the ship, time (world standard time), position relative to the local area (ground course), ground speed, heading direction, turnover rate (time change rate of heading direction) ) Etc.

For this reason, the ground speed information, the local position information, and the heading information are included in the AIS information. The ground speed vector V _S is obtained from the ground speed and the local position in the AIS information. Alternatively, the ground speed vector can be calculated from the time change of the position information in the AIS information. That is, the ground speed vector V _S can be uniquely calculated from the AIS information. For this reason, if it is a ship carrying AIS, the ground speed vector V _S of the own ship and the heading θ _W can be recognized. Thus, it is possible to calculate heading perpendicular component of the currents vector V _C a (V _CP).

A ship equipped with an AIS can also receive AIS information (ground speed information, position information with respect to the head, heading information) with respect to other ships. Therefore, this ship can similarly recognize the ground speed vector V _{S1 (2)} and the bow direction θ _{W1 (2)} in FIG. Furthermore, even a ground station having an AIS receiving function can recognize such information in a plurality of ships equipped with AIS. Therefore, the calculation of the currents vector V _C, on a ship, can be carried out in either the ground station.

In the above calculation, as shown in FIG. 1C, the ground speed vectors and heading information of the two ships 1 and 2 were used. Here, the ship 1 and 2 need not be different vessels, for example sail 1 vessels is changed heading in the time, currents vector V _C in waters the ship is sailing in this time If not changed, the ground speed vector and heading information at different times or positions in the ship can be used in place of the above-mentioned ground speed vectors and heading information of the two ships.

  Information used in the above calculation is not limited to AIS information. For example, it is obvious that the information can be used in the same manner as long as it is information obtained by monitoring the operational status of the ship for each shipping company and includes ground speed information, information on local position, and heading information. . Further, for example, information on a plurality of different times in one ship can be used. In other words, in order to perform the above calculation, a plurality of pieces of arbitrary operation information (information specifying the situation regarding the operation of a ship at sea) including a ship's ground speed information, information on local position, and heading information are used. Can do. In the case of information at a plurality of different times in one ship, the operation information does not need to be information transmitted from the ship to the outside like the AIS information.

In the above, the ship two vessels (or flight information two) located, in order to have as ocean current vector V _C in the respective waters are equal exactly, it was possible to uniquely calculate the currents vector V _C. In practice, however, the ocean current vectors V _C are often not exactly equal between the two ocean areas. In such a case, the most accurate ocean current vector can be estimated using data of three or more ships (three or more pieces of operation information). When two ships (two operational information) are used, the current vector V _C is uniquely determined as described above, but the measurement of V _{S1 (2)} and θ _{W1 (2) used for} the calculation is performed. An error due to the error occurs. To reduce such errors, in order to increase the accuracy of ocean current vector V _C to be estimated, it is clear that it is preferable to use a data which more vessels (flight information). Method for calculating the currents vector V _C in this case (estimation method) will be described below.

First, when the ocean current vector _{V C} is strictly a same for 3 vessels 1, 2 and 3, any two of the vessels 1, 2 and 3 the same relation with FIG. 1 (c) Since the relationship is established between the ships, the relationship between the vectors is as shown in FIG. In this figure, the end point of each water velocity vector V _W or the intersection of the straight lines (directions of water velocity vector V _W ) facing the heading of each ship coincide at point C ₁ , and each ground velocity The end point of the vector V _S coincides at the point C ₂ . In FIG. 2A, the ocean current vector V _C is uniquely determined as a vector having a point C ₁ as a start point and a point C ₂ as an end point.

However, strictly speaking, when the relationship of FIG. 2A is not established, as shown in FIG. 2B, a point C ₂ (x ₁ , x ₂ ) that is the end point of the ocean current vector V _C is obtained. Is defined, the straight lines facing the heading of each ship do not have a common intersection. Therefore, it is impossible to determine the position of the C ₁ that are to be the starting point of the ocean current vector V _C, it is impossible to strictly calculate the currents vector V _C. In this case, as known as optimization method, the x _0, y ₀ at the point to be the starting point of the ocean current vector V _C P (x _{0, y 0),} such that the objective function is a minimum value It can be determined as a value.

In this optimization, as shown in FIG. 2C, the point P corresponds to a straight line L ₁ corresponding to the water speed vector V _W1 of the ship ₁ and a straight line L corresponding to the water speed vector V _W2 of the ship 2. ₂ and distances between the ship 3 and the straight line L ₃ corresponding to the water velocity vector V _W3 (referred to as h ₁ , h ₂ , and h ₃ , respectively) can be defined as points that become shorter. As shown in FIG. 2C, this point P exists in a triangle surrounded by straight lines L ₁ , L ₂ , and L ₃ .

The estimated currents vector _{V C} start to become a point P of coordinates _(x 0, _{y 0),} for example, the square sum of the distance between the point P and the straight lines _{L 1,} L 2, _{L 3} The objective function can be set to minimize this value. When the straight line L is represented by ax + by = 1, the distance h between the point P (x ₀ , y ₀ ) and the straight line L is given by equation (6). Here, the distance between the point P and the straight line L is the distance between the point P and the intersection of the straight line L that is orthogonal to the straight line L and passes through the point P.

For this reason, the distance h from the point P to each straight line L _i is set to h _i , the square of h _i is set to the objective function by operation information, and the objective function f to be minimized is the objective function by operation information h _i ² The sum (h ₁ ² + h ₂ ² + h ₃ ² ) can be used. In this case, assuming that the straight line L _i (i = 1, 2, 3) is represented by a _i x + b _i y = 1, the objective function f is given by equation (7). Here, since the ground speed vectors V _S1 , V _S2 , and V _S3 of each ship are known, the end positions of the ground speed vectors V _S1 , V _S2 , and V _S3 are the positions of the ships in FIG. determined as a single point C _2. In addition, since the ship headings θ _W1 , θ _W2 , θ _{W3 of} each ship are also known, a _i , b _i (so that the straight line L _i is a straight line passing through the position of the ship _i and facing the bow direction θ _i. i = 1, 2, 3) is uniquely determined.

X ₀ and y ₀ that minimize the objective function f are determined as ∂f / ∂x ₀ = 0 and ∂f / ∂y ₀ = 0. As a result, the coordinates x ₀ and y ₀ of P are given by equations (8) and (9). Here, A, B, C, D, and E are given by equations (10) to (14). That is, x ₀ and y ₀ can be calculated by this, and the estimated ocean current vector V _C is estimated to be a vector from the point P to the point C ₂ , so (V _Cx , V _Cy ) = (x _{1 -x 0, y 1 -y 0} ) to become.

That is, in this calculation, x ₀ and y ₀ which are information on the ocean current vector V _C are used as parameters, and an objective function for each operation information is obtained for each operation information used (ground speed information, information on local position, heading information). The objective function is defined as the sum of the calculation, and the ocean current vector V _C is calculated (estimated) as an optimization (minimization in the above case) of the objective function.

In the example of FIG. 2, the ship but is described for the three vessels, vessel 4 vessels or more, or even when using three or more flight information, as well as to be able to calculate the currents vector V _C clear is there.

In the case of calculating the currents vector V _C using the above equation (1) to (14) is operated information (ground speed information, ground azimuth information, heading information) ground speed vector identified by, heading It was calculated currents vector V _C using. However, in order to calculate the currents vector V _C higher accuracy, ground speed vector identified by the flight information, and corrects the heading, it is also possible to calculate the currents vector V _C using these. Moreover, this correction is the ground speed vector, not only for heading can be made for other information used for calculating the currents vector V _C (for example, information about the operational information by the objective function).

  For example, the ground speed information and the heading information are often acquired at a constant time interval, and this time interval may be different for each ship. For this reason, when using data of a plurality of ships, not all the ships have ground speed information and heading information at a fixed time when the current vector should be estimated. In such a case, the ground speed vector, the heading, etc. corrected to be data at the same time based on the time information in the AIS information of each ship can be used for the above calculation. In this correction, for example, a ground speed vector, a heading direction is newly obtained by interpolating or extrapolating data such as a ground speed vector and a heading obtained at a time different from the time at which the ocean current vector should be estimated. Create data such as. This new data can be handled as data at the time when the ocean current vector should be estimated. As for the heading, the turn rate data in the AIS information can also be used.

In addition, for example, the ship 1 is navigating near the middle of the ship 2 and the ship 3, the headings θ _W2 and θ _{W3 of} the ship 2 and the ship 3 are substantially the same, and the heading θ _W1 of the ship 1 is Consider a different case. In this case, by interpolating the ground speed vector V _S2 of the ship ₂ and the ground speed vector V _S3 of the ship 3, it is assumed that the same sea area as the ship 1 is navigated with the heading θ _W3 (θ _W2 ). A ground speed vector V _S23 can be calculated. In this case, in order to calculate the ocean current vector V _C in the sea area where the ship 1 navigates, the ground speed vector V _S23 interpolated, the heading θ _W3 (θ _W2 ), and the ship 1 are actually measured. The ocean current vector V _C can be calculated using the ground speed vector V _S1 and the heading θ _W1 . That is, not only the ground speed vector V _S is corrected based on the time information, but also the ocean current vector V _C can be estimated more accurately by using the ground speed vector V _S corrected based on the position information. It becomes. Alternatively, the ground speed vector V _S and the heading θ _W corrected based on both time information and position information may be used.

In the above two examples, the ground speed vector V _S and the heading θ _W are corrected in order to calculate the ocean current vector V _C with higher accuracy. On the other hand, the case where the information regarding the objective function classified by operation information is corrected will be described below.

In the above example using the objective function f (Equation (7)), the objective function h _i ² for each ship information is calculated for each ship, and the sum is used as the objective function f. In this case, for example, marine vessel 1 and the vessels 2 are sailing in the vicinity of the waters to be calculated currents vector V _C, the ship 3 is sometimes are in waters slightly away from this area. In such a case, it is preferable to weight the data by each ship and to make the weight of the data (h ₃ ) by the ship 3 lower than the data (h ₁ , h ₂ ) by the ships ₁ and ₂ . Specifically, x ₀ and y ₀ are determined so that the weighting coefficient of the ship i is w _i and the objective function g defined by the equation (15) is minimized instead of the objective function f of the equation (7). Just do it. In this example, w ₁ and w ₂ >> w ₃ may be set. The objective function f (equation (7)) corresponds to the case where w _i ≡1 (i = 1, 2, 3), and weighting for each operation information is not performed. This corresponds to correction of information related to information-specific objective functions.

In this case, the above A to E are A to E given by the following formulas (16) to (20) instead of the formulas (10) to (14), and x ₀ and y ₀ are Like (8) and (9).

As the setting for the weighting coefficients w _i, for example, a large value for the ship in a position close to the sea area to be calculated the inherent currents vector V _C, as the vessels are from this area located far becomes a small value, the currents vector V _C W _i can be set as a function of the distance of the vessel from the sea area to be calculated. That is, this weight coefficient w _i can also be determined from the AIS information (position information) of the ship i.

Similarly, ground speed information acquired in the time close to the time to be calculated the inherent currents vector V _C, a large value for the flight information with heading information, time away from time to be calculated currents vector V _C W _i can also be a function of this time difference so that the navigation information with data has a small value. As described above, since the information (time information) about the time when the position information, ground speed information, and heading information of each ship are acquired can be read from the AIS information, this setting is also performed based on the AIS information. be able to. Alternatively, the weighting factor w _i can be set as a function of both position and time. Alternatively, setting the w _i by turning rate in flight information, for example, times when the head index is large, it is possible to reduce the w _i determines that the influence of ocean currents hardly comes into operation of the ship. The w _i is set according to the type of the ship corresponding to the operation information. For example, the ship data that is easily affected by wind can be determined to have low credibility, and the w _i can be reduced. In addition, w _i is set based on the history of past calculation results using the same operation information. For example, w _i is reduced even for operation information in which hi in FIG. can do. Thus, for data that is determined to have low credibility as data about ocean currents by setting small weight coefficient w _i, it is possible to improve the accuracy of calculation of the currents vector V _C.

Further, for example, data of two vessels are used, if the number of data by the two vessels are significantly different, by decreasing the weight coefficient w _i of the ship data towards the number of data is large, 2 vessels It is also possible to perform processing such as handling the data of

  In other words, the weighting factor is set for the difference between the position where the operation information is acquired and the position of the sea area where the ocean current is estimated, the difference between the time when the operation information is acquired and the time when the ocean current is estimated, or acquired in a single ship. This can be done based on the number of operation information used. This setting can also be made according to other criteria. In addition, the weighting coefficient can be set using the ground speed vector corrected as in the above example.

The configuration of the entire ocean current estimation system for calculating (estimating) the currents vector V _C as described above is shown in FIG. In FIG. 3, the ships 1 to 5 are traveling on the ocean current 100. Each ship is equipped with an AIS, and each of the ships 1 to 5 transmits its own AIS information. This AIS information can be received by another ship or the antenna 11 of the information acquisition unit 10 on the ground. The information acquisition unit 10 transmits the received AIS information to the server (ocean current vector calculation unit) 20 via a network or the like. The server 20 stores the received AIS information as a database in the storage device 21, and performs the above calculation using this. The route instruction unit 22 instructs the ships 1 to 5 to specify an optimum route. The antenna 11 connected to the information acquisition unit (AIS information acquisition unit) 10 and the antenna 11 connected to the server (ocean current vector calculation unit) 20 have a communication capacity, a wavelength used for communication, a signal system, and the like. Depending on the case, the optimum one can be used. About this point, it is the same also about the antenna used in the ships 1-5.

For example, the server 20 may be in certain waters near lists ships sailing near a specific time, reads the AIS information from the storage unit 21, estimates the ocean current vector V _C in the time of this area it can. By setting the latest (current) time as this time, the latest ocean current information can be estimated and transmitted to each ship.

  Further, by performing this operation in a plurality of sea areas and a plurality of times, it is possible to estimate a temporal change in the ocean current up to the present time. This makes it possible to predict future ocean currents.

The server 20 can perform ground speed vector to be used for estimating the currents vector V _C, the position information regarding heading, the correction based on the time information, and the like.

  In the configuration of FIG. 3, the server (sea current vector calculation unit) 20 and the storage device 21 are installed on the ground separately from each ship, and the information acquisition unit 10 is also installed on the ground for this purpose. However, these can be configured using a commonly used computer, and since these are simple configurations, they can be mounted on each ship. In this case, the AIS of the ship functions as an information acquisition unit for acquiring the AIS information of the ship. The AIS information of other ships can be obtained by the information acquisition unit 10 and the above processing can be performed. It is also possible to transmit information on the current vector calculated here toward another ship or the ground.

  At this time, the server 20 can perform not only simple estimation (calculation) of ocean current vectors but also various processes using the results. First, as described above, there are tidal currents generated by tidal action and ocean currents that occur on a global scale (original currents) due to different causes of tidal currents. It is a flow in which a tidal current is added to the ocean current. Here, since the tidal current is periodic and easy to predict, data relating to the tidal current can be obtained from the outside as sea state information, and this data can be stored in the storage device 21 in advance. . In this case, the current vector can be corrected using the tidal current data to calculate a vector corresponding to the original current.

  Moreover, the distribution of the ocean current in a wide area can be estimated by estimating the ocean current in a plurality of ocean areas on the sea. The distribution of the ocean current estimated at each time can be stored in the storage device 21 and transmitted to each ship. Since each ship always transmits AIS information, when the server 20 receives the updated AIS information, the ocean current distribution thus estimated can be updated and stored in the storage device 21. At this time, if the original ocean current distribution calculated corresponding to the case where there is no tidal current based on the oceanographic information is stored in the storage device 21, the temporal change of the original ocean current distribution can be easily traced.

  At this time, if there is data of low-accuracy ocean current distribution calculated in advance, the storage device 21 stores this data, and assimilates the ocean current vector estimated by the above-described ocean current estimation method to this ocean current distribution, so that higher accuracy can be obtained. The ocean current distribution can be estimated (data assimilation). Such an assimilation method is described in, for example, Japanese Patent Application Laid-Open No. 2010-223639. It is possible for the server 20 to perform such assimilation processing using the storage device 21, and the server 20 can also send information regarding the highly accurate ocean current distribution to the outside.

Further, if the server 20 can estimate the ocean current distribution on the route of the ship, the optimum route of the ship based on this can be calculated. In this case, for example, when the absolute value V _W0 of the water velocity is determined, the bow direction θ _W can be set so that the ground velocity vector V _S in FIG. 1A connects the shortest distance to the destination. . Thereby, in the case of the same _VW0 , it becomes possible to make a navigation distance the shortest and to reduce the fuel consumption of a ship. That is, the server 20 can also give instructions regarding the navigation of the ship. The route instructing unit 22 in FIG. 3 instructs the marine vessels 1 to 5 on the basis of the ocean current distribution thus estimated. Incidentally, the optimal route indication can be carried out, including any vessel not involved in providing flight information hitting the calculation of currents vector V _C.

  As described above, the ocean current estimation system and the ocean current estimation method are used to estimate the flow of seawater using a marine vessel. For example, the current is also estimated in a wide lake or river. Obviously it can be done. Further, it is clear that the same measurement (estimation) can be performed not only on a large ship equipped with an AIS but also on a small model ship or the like as a ship.

1-5 Ship 10 Information Acquisition Unit 11 Antenna 20 Server (Sea Current Vector Calculation Unit)
21 storage device 22 route instruction section 100 ocean current θ _W , θ _W1 , θ _W2 heading V _S , V _S1 , V _S2 ground velocity vector V _C ocean current vector

Claims (15)

An ocean current estimation method for estimating an ocean current vector that indicates the direction and strength of an ocean current by using a plurality of operation information in which conditions relating to the operation of a marine vessel are specified,
The ground speed vector for each individual ship of the plurality of ships that pass through the sea area where the ocean current is estimated as the operation information and the heading of the ship are obtained , and based on the ground speed vector and the heading direction for each ship , a plurality of to calculate the currents vector in the waters for navigation of the marine vessel, ocean currents estimation method characterized by increasing the estimation accuracy of the currents vector by increasing the number of vessels of the plurality of vessels to obtain the flight information.   The navigation information includes ground speed information in which the ship's ground speed is specified, and ground position information in which the ship's ground position is specified, and is obtained from the ground speed and the ground position. The ocean current estimation method according to claim 1, wherein the ocean current vector is calculated using a ground velocity vector. Heading information the heading is determined, the ground speed information, and the ground orientation information ship automatic identification system (Automatic Identification System: AIS) and obtaining by ocean currents estimation of claim 2 Method.   The navigation information includes position information in which a position of the ship when the operation information is acquired is specified, and the ocean current vector in the sea area is calculated based on the position information. The ocean current estimation method according to any one of claims 1 to 3.   The operation information includes position information that specifies the position of the ship when the operation information is acquired, and time information that specifies the time when the position information is acquired, and the position information and the The ocean current estimation method according to claim 1, wherein the ground velocity vector is calculated based on time information. 6. The ocean current estimation method according to claim 5, wherein the heading information in which the heading is specified and the position information are acquired by an automatic identification system (AIS).   7. The ocean current estimation method according to claim 1, wherein information used for calculating the ocean current vector is corrected based on the operation information and / or an acquisition situation of the operation information. . Using information on the ocean current vector as a parameter, creating an objective function for each operation information for each operation information,
The said ocean current vector which optimizes the objective function which is the sum total of the said objective function according to each operation information for every said some operation information is calculated, The any one of Claim 1 to 7 characterized by the above-mentioned. Current estimation method. Create an objective function for each operation information using each of the operation information using information on the current vector as a parameter,
Calculate the current vector that optimizes the objective function, which is the sum of values obtained by multiplying the objective function by operation information for each of the plurality of operation information by a weighting coefficient, and the correction by setting the weighting coefficient for each of the operation information The ocean current estimation method according to claim 7, wherein:   The weighting factor is the difference between the position where the operation information is acquired and the position where the ocean current is estimated, the difference between the time when the operation information is acquired and the time when the ocean current is estimated, and the ship which acquired the operation information The ocean current estimation method according to claim 9, wherein the ocean current estimation method is set based on at least one of the type of the ocean current or the calculation result of the ocean current vector performed in the past using the operation information. An ocean current estimation system that estimates an ocean current vector based on the ocean current estimation method according to any one of claims 1 to 10 , wherein the information acquisition unit acquires the operation information of a plurality of the ships ; Storage means for storing the acquired operation information, list-up means for listing a plurality of the ships navigating the sea area at a specific time, and the operation information of the listed ships from the storage means An ocean current estimation system comprising: reading means for reading; and an ocean current vector calculation unit that calculates the ocean current vector based on the read operation information.   The ocean current according to claim 11, wherein the information acquisition unit acquires ocean state information predicted in advance, and the ocean current vector calculation unit corrects the estimated ocean current vector based on the ocean state information. Estimation system.   The ocean current estimation system according to claim 11 or 12, wherein the ocean current vector calculation unit estimates an ocean current distribution by calculating the ocean current vectors in a plurality of the ocean areas.   The ocean current vector calculation unit is configured to assimilate the calculated ocean current vector and estimate a new ocean current distribution with respect to ocean current distributions in a plurality of the sea areas predicted in advance. Ocean current estimation system.   15. The ocean current estimation system according to claim 13 or 14, further comprising a navigation channel instruction unit that instructs a marine vessel based on the estimated ocean current distribution.

Images