A ship traffic flow basic graph drawing method based on microscopic car following theory

Abstract

The application relates to a ship traffic flow basic map drawing method based on a microscopic car following theory, which comprises the following steps: S1, acquiring AIS data in a selected area, carrying out AIS data pretreatment, and establishing a rectangular coordinate system on the area; S2, segmenting a single channel according to a division standard, and preliminarily screening the pretreated AIS data; S3, drawing a ship trajectory map according to conversion information, and screening effective ship car following data pairs from the preliminarily screened AIS data; S4, drawing a speed-car following distance basic map; S5, drawing a speed-density basic map; S6, drawing a speed-traffic volume basic map; and S7, drawing a traffic volume-density basic map. The application screens effective ship car following data by processing AIS data in a selected area, draws a complete maritime traffic flow basic map according to the relationship among traffic flow characteristic parameters, and provides a reference basis for traffic characteristics and traffic conditions of the water area.

Description

Technical Field

[0001] This invention relates to the field of maritime traffic flow, and in particular to a method for drawing a basic diagram of ship traffic flow based on micro-level car-following theory. Background Technology

[0002] Water transport is a vital pillar industry for socio-economic development. The increasing freight volume and waterway mileage year by year indicate that waterway transport plays a growing role in my country's economy and transportation sector. However, the accompanying problems of waterway congestion, decreased operational efficiency, and frequent maritime accidents have caused significant losses to the global economy. This makes fully utilizing limited water resources, improving waterway service quality, and ensuring safe, efficient, and economical navigation for ships a key issue for the sustainable development of water transport.

[0003] A basic maritime traffic flow map can theoretically determine the maximum capacity, optimal density, and optimal speed of a waterway, providing a scientific theoretical basis for traffic control decisions by maritime authorities. However, due to the large size and slow rudder efficiency of ships, their maneuverability is far less than that of road vehicles. Furthermore, when ships navigate in water, the influence of weather factors such as wind, currents, and waves on the width of their wake must be considered. These factors result in larger following distances between ships within the waterway, leading to lower traffic density and less congestion. Therefore, a basic maritime traffic flow map cannot represent the entire picture. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and to provide a method for drawing basic ship traffic flow diagrams based on micro-following theory, taking into account characteristic factors such as following distance and following time distance between two ships.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for drawing a basic diagram of ship traffic flow based on micro-level car-following theory includes the following steps:

[0007] S1. Obtain AIS data from the selected area, perform AIS data preprocessing, and establish a rectangular coordinate system on the area;

[0008] S2. Divide the data into single channels according to the classification criteria and perform initial screening on the preprocessed AIS data;

[0009] S3. Draw a ship trajectory diagram based on the conversion information, and select valid ship following data pairs from the AIS data after initial screening;

[0010] S4. Calculate the following distance between the two ships and draw the speed-following distance basic diagram;

[0011] S5. Calculate the density of the ship and draw the basic speed-density diagram;

[0012] S6. Calculate the following-distance time between the front and rear ships and draw the basic speed-traffic volume diagram;

[0013] S7. Draw the basic traffic volume-density diagram. [[ID=I8]]

[0014] Furthermore, in step S1, the AIS data of the selected experimental waterway area is obtained by the point-ray method, which includes the ship navigation time, MMSI (Maritime Mobile Service Identity), ship longitude and latitude data, and ship speed. If the ship sails in the selected water area, the number of intersections of the ray emitted with the ship as the center and the boundary of the closed area is odd; if the ship sails outside the selected water area, the number of intersections of the ray emitted with the ship as the center and the boundary of the closed area is even.

[0015] Furthermore, the preprocessing of the AIS data in step S1 is specifically to delete abnormal data, and use the cubic spline interpolation method to interpolate the AIS data at an interval of 20 seconds.

[0016] Furthermore, in step S1, the longitude and latitude dynamic information in the preprocessed AIS data is converted into the ordinate and abscissa in the channel rectangular coordinate system. The abscissa x represents the actual longitudinal distance of the ship from the reference point, and the ordinate y represents the actual lateral distance of the ship from the reference point.

[0017] Furthermore, in step S2, the single channel is divided according to five times the standard ship width d, and the y value of the ship AIS data point in the channel coordinate system, the left side line coordinate y1 of the single navigation segment, the right side line coordinate y i value, and the width d of the single channel are used to judge whether the ship is sailing in the selected divided single channel. Take the distance of the AIS data point from the right side line of the single channel as Δy: r and the relationship between the right side line coordinate y

[0018] Δy = y r -y i

[0019] If Δy < d and y i < y r , then the ship is sailing in the selected divided single channel; find the ship data pairs entering and leaving the single channel in the adjacent time before and after the single channel, and ensure that the following ship does not overtake in the single channel, so as to initially screen out the ship data pairs that meet the ship following conditions.

[0020] Furthermore, in step S3, the ship trajectory diagram is drawn with the x coordinate value as the ordinate and the time t as the abscissa. According to the drawn ship navigation trajectory diagram, find the starting point of the fluctuation of the front ship trajectory curve and find the corresponding time t iThis indicates that from this moment on, the ship in front suddenly decelerates, and the ship behind also decelerates accordingly. The fluctuation in the trajectory of the ship in front causes the fluctuation in the trajectory of the ship behind. Data pairs that conform to this pattern are valid ship following data pairs. Data from the entire year is processed to filter out valid ship following data pairs that conform to the pattern.

[0021] Furthermore, in step S4, the following distance S:

[0022] S = x1 - x2

[0023] Where S represents the following distance between the two ships, x1 represents the distance of the ship in the longitudinal direction, and x2 represents the distance of the ship in the longitudinal direction. For the valid ship following data pairs that have been selected in step S3, a speed-following distance basic diagram is drawn based on the speed data and the following distance data.

[0024] Furthermore, the density k of the ship in step S5 is:

[0025]

[0026]

[0027]

[0028] Where S represents the following distance between the two ships, L is the length of the unit segment, and N is the number of ships in the segment. The density k is the reciprocal of the following distance S. For the valid ship following data pairs that have been screened in step S3, a speed-density basic diagram is drawn based on the speed data and density data.

[0029] Furthermore, in step S6, the following time distance h:

[0030] h = S / v

[0031] Where h represents the following distance between ships, S represents the following distance between the two ships, and v represents the speed of the following ship, which is the time it takes for the following ship to travel to the position of the preceding ship at its current speed.

[0032] Based on the following distance h, the ship traffic volume q is calculated:

[0033]

[0034]

[0035]

[0036] Where T is the unit time and q is the ship traffic volume, the ship traffic volume q is the reciprocal of the following distance h, and a basic speed-traffic volume diagram is drawn based on the speed data and traffic volume data.

[0037] Furthermore, in step S7, a basic traffic volume-density diagram is drawn based on the two characteristic parameters of traffic volume and density calculated in steps S5 and S6.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. This invention processes AIS data within a selected area, filters out effective ship following data pairs, and derives three other basic maps from the speed-following distance basic map, thus completing the basic map of maritime traffic flow. It intuitively displays the relationship between the three major characteristic parameters of ship traffic volume, speed, and density, thereby facilitating the determination of the maximum capacity, optimal density, and optimal speed of the waterway, and providing a reference for the waterway authorities to understand the traffic characteristics and conditions of the waterway.

[0040] 2. This invention fully considers the essential differences between the characteristics of ships and vehicles and their traffic environments. Based on the micro-car-following theory, it calculates the car-following distance S and car-following time h, and thereby calculates the ship density k and ship traffic volume q. It explores the characteristics and laws of maritime traffic flow, completes the drawing of the basic map of ship traffic flow, strives to show the whole picture of the basic map of maritime traffic flow, enriches the theoretical system of maritime traffic, and promotes the development of maritime traffic towards intelligence. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the process of the present invention;

[0042] Figure 2 This is a nautical chart of the area to be screened in this invention;

[0043] Figure 3 This is a schematic diagram of the vessel's position in a single channel according to the present invention;

[0044] Figure 4 This is a diagram illustrating the ship's navigation trajectory according to the present invention.

[0045] Figure 5 This is a schematic diagram of the speed-follow-gap distance of the present invention;

[0046] Figure 6 This is the basic velocity-density diagram of the present invention;

[0047] Figure 7 This is the basic speed-traffic volume diagram of the present invention;

[0048] Figure 8 This is the basic flow-density diagram of the present invention. Detailed Implementation

[0049] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0050] Car-following theory is the foundation for modeling and simulating traffic micro-behavior. Studying car-following theory can reveal macro-traffic flow phenomena from a micro perspective and explore the formation mechanism of macro-traffic flow characteristics.

[0051] like Figure 1 The diagram illustrates a method for drawing a basic ship traffic flow map based on micro-level car-following theory, comprising the following steps:

[0052] S1. Obtain AIS data from the selected area, perform AIS data preprocessing, and establish a rectangular coordinate system on the area;

[0053] S2. Divide the data into single channels according to the classification criteria and perform initial screening on the preprocessed AIS data;

[0054] S3. Draw a ship trajectory diagram based on the conversion information, and select valid ship following data pairs from the AIS data after initial screening;

[0055] S4. Calculate the following distance between the two ships and draw the speed-following distance basic diagram;

[0056] S5. Calculate the density of the ship and draw the basic speed-density diagram;

[0057] S6. Calculate the following distance between the two ships and draw a basic speed-traffic volume diagram.

[0058] S7. Draw a basic traffic volume-density diagram.

[0059] Step 1: The experimental area is the waters between buoys S33 and S37 in the upper section of the South Channel of the Yangtze River Estuary in Shanghai Port. The nautical chart for this area is as follows: Figure 2 As shown;

[0060] The AIS data for the entire year of 2018 for the South Channel was selected as the data source. Ray casting was used to filter out the AIS data passing through this channel segment from the massive amount of AIS data in the area. Since AIS data transmission is subject to delays and errors, resulting in missing, duplicate, and abnormal data, preprocessing of the filtered AIS data is necessary. Because AIS equipment transmits information at non-uniform intervals, the received AIS data also receives data at non-uniform time intervals. Since ship tracking studies focus on the behavior of two ships in the same time and space, cubic spline interpolation is used, with 20-second intervals, to interpolate the AIS data.

[0061] Establish a rectangular coordinate system on the selected water area, and convert the longitude and latitude dynamic information in the ship AIS data into the ordinate and abscissa in the channel rectangular coordinate system. The abscissa x represents the actual longitudinal distance of the ship from the reference point, and the ordinate y represents the actual lateral distance of the ship from the reference point.

[0062] Step 2: Use Python programming to statistically analyze the AIS data to obtain the average ship width of the ships in this channel. Divide the channel with five times the average ship width d as the division standard for a single channel. Use the y value of the ship AIS data point in the channel coordinate system, the coordinate y1 of the left side line of a single navigation segment, and the coordinate y of the right side line to determine whether the ship is traveling within the selected divided single channel. Take the distance of the AIS data point from the right side line of the single channel as Δy: i value, the coordinate y1 of the left side line of a single navigation segment, and the coordinate y of the right side line r of the single navigation segment to determine whether the ship is traveling within the selected divided single channel. Take the distance of the AIS data point from the right side line of the single channel as Δy:

[0063] Δy = y r - y i

[0064] If Δy < d and y i < y r , it can be determined that the ship AIS is traveling within the selected divided single channel, ensuring that the ship passes through the starting point and the ending point of this channel; otherwise, the ship is deviating from the single channel. Then, it is necessary to roughly screen out the data that generally conforms to the following-following law from a large amount of AIS data, and find the ship pair data entering and leaving this single channel within adjacent times before and after the single channel, because only when ships are traveling one after another can there be a chance of following-following behavior; finally, it is necessary to ensure that the following ship does not overtake within the single channel. If all the above conditions are met, the ship pair data that meets the ship following-following conditions can be initially and roughly screened out, including ship coordinates, time, navigation speed, following-following distance, and following-following time interval. However, these data do not exactly conform to following-following. It is necessary to further screen from these data to discover the specific behavior law of ship following-following behavior.

[0065] Step 3: Use the rectangular coordinate data obtained in Step 1 to draw a ship trajectory map, and screen out the effective ship following-following data pairs from the preliminarily screened AIS data.

[0066] The ship position information in the filtered AIS data has been converted into rectangular coordinate data. Ship trajectory diagrams can be plotted using the x-coordinate as the ordinate and time as the abscissa. Ships travel in an orderly fashion in the channel, following each other in the same direction and exhibiting similar kinematic characteristics. The displacement-time curves, velocity-time curves, and acceleration-time curves of the preceding and following ships show similar shapes with time delays. If the preceding ship suddenly notices another ship crossing the channel at time t, it will immediately decelerate to avoid a collision. The following ship will also decelerate to avoid a collision. Therefore, at the instant of deceleration, the ship's speed will decrease, resulting in fluctuations on the ship trajectory diagram. A simplified diagram is shown below. Figure 4 As shown, this situation corresponds to ships exhibiting micro-level ship following behavior. Data pairs that conform to this pattern are considered valid ship following data pairs. By processing a year's worth of data, valid ship following data pairs that conform to this pattern are selected.

[0067] Step 4: Draw the basic speed-follow-gap diagram.

[0068] Caliper spacing S:

[0069] S = x1 - x2

[0070] Where S represents the following distance between the two ships, x1 represents the distance of the foreship along the longitudinal axis, and x2 represents the distance of the followership along the longitudinal axis. Based on the valid ship following data pairs selected in step three, a basic speed-following distance diagram can be drawn using the speed and following distance data. A simplified schematic diagram is shown below. Figure 5 As shown.

[0071] Step 5: Draw the basic velocity-density diagram.

[0072] The density k of the ship:

[0073]

[0074]

[0075]

[0076] Where S represents the following distance between two ships, L is the length of a unit segment, and N is the number of ships in that segment, the density k is the reciprocal of the following distance S. Therefore, based on these two data points (speed and density), a basic speed-density diagram can be drawn, as shown in the simplified diagram below. Figure 6 As shown.

[0077] Step 6: Draw a basic speed-traffic volume graph.

[0078] Calculate the following distance h between the preceding and following vessels when the following action occurs:

[0079] h = S / v

[0080] Where h represents the following distance, S represents the following distance between the two ships, and v represents the speed of the following ship, which is the time it takes for the following ship to travel to the position of the preceding ship at its current speed.

[0081] Based on the following distance h, the ship traffic volume q is calculated:

[0082]

[0083]

[0084]

[0085] Where T is the unit time and q is the ship traffic volume, the ship traffic volume q is the reciprocal of the following distance h. Based on these two data points, speed-traffic volume is plotted, as shown in the simplified diagram below. Figure 7 As shown.

[0086] Step 7: Draw the basic flow-density diagram.

[0087] Based on the traffic volume and density parameters obtained in steps five and six, a basic traffic volume-density diagram can be drawn, as shown in the simplified diagram below. Figure 8 As shown.

[0088] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for drawing a basic diagram of ship traffic flow based on microscopic car-following theory, characterized in that, Includes the following steps: S1. Obtain AIS data from the selected area, perform AIS data preprocessing, and establish a rectangular coordinate system on the area; S2. Divide the data into single channels according to the classification criteria and perform initial screening on the preprocessed AIS data; S3. Draw a ship trajectory diagram based on the conversion information, and select valid ship following data pairs from the AIS data after initial screening; S4. Calculate the following distance between the two ships and draw the speed-following distance basic diagram; S5. Calculate the density of the ship and draw the basic speed-density diagram; S6. Calculate the following distance between the two ships and draw a basic speed-traffic volume diagram. S7. Draw a basic traffic volume-density diagram; In step S2, a single channel was divided according to five times the standard ship beam, and the ship's AIS data points were used in the channel coordinate system. Value, left-side coordinates of a single flight segment Right side coordinates and the width of a single channel The relationship is used to determine whether the vessel is operating within the selected segmented single channel, taking the distance of the AIS data point from the right edge of the single channel as... : If satisfied and If the vessel is in the selected segmented single channel, then the vessel will travel within the selected segmented single channel. Find the vessel data pairs that enter and exit the single channel in adjacent time periods before and after the single channel, and ensure that the following vessel does not overtake within the single channel. In this way, the vessel data pairs that meet the vessel following conditions are initially screened out. The density of the ship in step S5 : in, Indicates the following distance between two ships. The length of a unit flight segment The density is obtained by determining the number of ships in this section of the waterway. For the following distance The reciprocal of the speed-density basic diagram is plotted based on the speed and density data for the valid ship following data pairs that have been filtered in step S3. Follow-up timing in step S6 : in, Represents the time interval between ship following. Indicates the following distance between two ships. This represents the speed of the following ship, and the time it takes for the following ship to travel to the position of the preceding ship at its current speed. Based on following distance The ship traffic volume was obtained. : in, For a unit of time, For ship traffic volume, the ship traffic volume is obtained. To follow the car's distance Based on the speed and traffic volume data, draw a basic speed-traffic volume graph.

2. The method for drawing a basic ship traffic flow diagram based on microscopic car-following theory according to claim 1, characterized in that, In step S1, AIS data for the selected experimental waterway area is obtained using the spot-shot method. This data includes the ship's sailing time, MMSI, ship's latitude and longitude, and ship speed. If the ship is sailing in the selected waterway, the number of intersections between the rays emanating from the ship and the boundary of the closed area is odd. If the ship is sailing outside the selected waterway, the number of intersections between the rays emanating from the ship and the boundary of the closed area is even.

3. The method for drawing a basic ship traffic flow diagram based on microscopic car-following theory according to claim 1, characterized in that, The preprocessing of AIS data in step S1 specifically involves deleting abnormal data and using cubic spline interpolation to interpolate the AIS data at 20-second intervals.

4. The method for drawing a basic ship traffic flow diagram based on microscopic car-following theory according to claim 1, characterized in that, In step S1, the latitude and longitude dynamic information in the preprocessed AIS data is converted into ordinate and abscissa in the waterway rectangular coordinate system. The vertical axis represents the actual longitudinal distance between the ship and the reference point. This indicates the actual lateral distance between the ship and the reference point.

5. The method for drawing a basic ship traffic flow diagram based on microscopic car-following theory according to claim 1, characterized in that, In step S3, the following methods are used The coordinates are ordinates and time. Plot the ship's trajectory on the horizontal axis. Based on the plotted ship trajectory, find the starting point of the fluctuation in the trajectory curve of the preceding ship and determine the corresponding time. This indicates that from this moment on, the ship in front suddenly decelerates, and the ship behind also decelerates accordingly. The fluctuation in the trajectory of the ship in front causes the fluctuation in the trajectory of the ship behind. Data pairs that conform to this pattern are valid ship following data pairs. Data from the entire year is processed to filter out valid ship following data pairs that conform to the pattern.

6. The method for drawing a basic ship traffic flow diagram based on microscopic car-following theory according to claim 1, characterized in that, The following distance in step S4 : in, Indicates the following distance between two ships. This indicates the distance of the preceding ship along the longitudinal axis. This indicates the distance of the following vessel in the longitudinal direction. For the valid vessel following data pairs that have been selected in step S3, a basic speed-following distance diagram is drawn based on the speed data and following distance data.

7. The method for drawing a basic ship traffic flow diagram based on microscopic car-following theory according to claim 1, characterized in that, In step S7, a basic traffic volume-density diagram is drawn based on the two characteristic parameters of traffic volume and density calculated in steps S5 and S6.

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