Navigation system suitable for low visibility

Abstract

The invention relates to the technical field of navigation systems, in particular to a navigation system suitable for low visibility, which comprises a navigation channel determination module, a detection control module, a curve calculation module and an offset adjustment module. The control receiving unit controls the adjusting structure to adjust the detection angle of the visibility detector according to the curve angle calculated by the turning judgment unit and the detection angle, which needs to be adjusted, of the visibility detector when the ship turns, mapped by the control receiving unit, and then the control receiving unit controls the adjusting structure to adjust the detection angle of the visibility detector, so that errors and uncertainty caused by manual operation are reduced; and the visibility detector is ensured to always work at the optimal angle.

Description

Technical Field

[0001] The present invention relates to the technical field of navigation systems, and in particular to a navigation system suitable for low visibility. Background Art

[0002] Low visibility is an extremely serious problem. In severe weather conditions such as fog, haze, rain and snow, visibility is greatly reduced, making it impossible for drivers to clearly observe the surrounding environment, including other ships, obstacles, landmarks, etc. This will greatly increase the risk of ship collision.

[0003] During the navigation of a ship, in order to detect visibility in time, a visibility detector is usually installed on the ship. The visibility is detected through the output end of the visibility detector towards the direction of the ship's travel, and accurate data of the visibility value is obtained. The transmission speed control signal prompts the staff to control the speed of the ship, which is helpful to remind the user to adjust the navigation;

[0004] However, the current output direction of visibility detectors is mostly fixed (or the output angle is manually adjusted), which makes it inconvenient to adjust the output direction when facing different routes. For example, when turning, the output of the visibility detector is directed to other positions and cannot be accurately aligned with the route to be taken, resulting in inaccurate visibility measurement ahead, affecting the accuracy of transmitted navigation signals. In view of this, we propose a navigation system suitable for low visibility. Summary of the invention

[0005] The object of the present invention is to provide a navigation system suitable for low visibility to solve the problems raised in the above background technology.

[0006] To achieve the above-mentioned object, the present invention provides a navigation system suitable for low visibility, comprising a channel determination module, a detection control module and a curve calculation module;

[0007] The channel determination module establishes a connection with the navigation agency to send a channel information request signal, demodulates and decodes the channel information after obtaining the channel information, determines the channel of the ship, and the detection control module emits infrared light in the direction of the ship, and detects the visibility in the direction of the ship according to the reflected light generated by the infrared light and the aerosol particles, wherein:

[0008] The curve calculation module includes a coordinate point selection unit, a turn judgment unit, and a control receiving unit;

[0009] The coordinate point selection unit determines the starting point, midpoint and end point of the curve according to the difference angle between adjacent coordinate points in the channel. The turning judgment unit monitors the distance and offset changes between adjacent coordinate points in the channel to determine whether a curve appears in the channel. When a curve appears, the turning angle is calculated according to the starting point, midpoint and end point determined by the coordinate point selection unit, and a mapping relationship with the control receiving unit is established to map the offset value of the detection control module and the channel direction, and convert it into a control signal and transmit it to the detection control module to execute the adjustment signal.

[0010] The channel determination module includes a channel determination unit and a ship coordinate calculation unit;

[0011] The channel determination unit is used to sense navigation signals and establish a connection with a navigation agency. The navigation agency transmits channel information, and the channel determination unit demodulates and decodes the channel information to determine the channel coordinates of the ship when it is traveling.

[0012] The ship coordinate calculation unit captures the radio signals transmitted from multiple GPS satellites in real time through antennas, records the time it takes for the radio signals to propagate to the ship, and since the speed of light is known, calculates the distance from multiple GPS satellites to the ship based on time and distance, and then calculates the ship coordinates using a spatial distance formula.

[0013] The channel determination module also includes a ship deviation judgment unit;

[0014] The ship offset judgment unit receives the ship coordinates in the ship coordinate calculation unit and the channel coordinates in the channel determination unit, sets a difference threshold, calculates a range threshold through the ship coordinates and the difference threshold, compares the range threshold with the channel coordinates, and when the channel coordinates are within the range threshold, it means that the ship is at the current channel coordinates at this time.

[0015] The ship coordinates received in the ship coordinate calculation unit are (X p ,Y p ), the channel coordinates in the channel determination unit are composed of a series of coordinate points, which is (X 1 ,Y 1 ),(X 2 ,Y 2 ),…(X n ,Y n );

[0016] The difference threshold is T, then with the ship coordinates as the center, in the horizontal direction, the left and right boundary coordinates of the range threshold are (X p -T,X p +T); in the vertical direction, the upper and lower boundary coordinates of the range threshold are (Y p -T,Y p +T);

[0017] Each channel coordinate point (X n ,Y n ), satisfying X p -T≤X n ≤X p +T and Y p -T≤Y n ≤Y p +T, it means that the ship is in the current channel coordinates. If any channel coordinate point does not meet this condition, it means that the ship is not in the current channel coordinates.

[0018] The detection control module includes a visibility detector and an adjustment structure;

[0019] The output end of the visibility detector emits infrared light of different lengths in the direction of the ship. The infrared light propagates in the atmosphere and contacts aerosol particles in the atmosphere. The surface of the aerosol particles contacts the infrared light and causes reflection. The receiving end receives the reflected light and calculates the length of the received reflected light. The visibility in the direction of the ship is obtained according to the different lengths.

[0020] The adjustment structure includes a cylinder detachably connected to the ship, a rack is fixedly connected to the output shaft end of the cylinder, a gear is meshedly connected to one side of the rack, a rotating rod is fixedly connected to the inside of the gear, the rotating rod is rotatably connected to the ship, and one end of the rotating rod is detachably connected to the visibility detector.

[0021] The coordinate point selection unit is used to calculate the difference angle between each coordinate point in the channel, and the steps are as follows:

[0022] Suppose a series of coordinate points on the course in the course determination unit are A(X 9 ,Y 9 ), B(X 8 ,Y 8 ) and C(X 7 ,Y 7 );

[0023] Calculating vectors Then, based on the positive direction of the X axis, the inverse tangent function is used to calculate the vector Angle with the positive direction of the X axis Then the vector and Angle θ with the positive direction of the X axis r1 The calculation method is the same as above, and the difference angle at coordinate point B is Δθ 1 =θ r1 -θ r |.

[0024] The coordinate point selection unit determines the coordinate point of the starting point, the midpoint and the end point of the curve, including the following steps:

[0025] Set the angle threshold to Q 1 , the difference angle Δθ calculated by the coordinate point selection unit 1 Compared with the angle threshold, Δθ 1 >Q 1 , then continue to select the next coordinate point in the channel, Δθ 1 ≤Q 1 When , the compared coordinate points are summarized, the first coordinate point whose difference angle is greater than the angle threshold is taken as the coordinate point of the starting point of the curve, the midpoint of the summarized coordinate points is taken as the midpoint coordinate point, and the last coordinate point whose difference angle is greater than the angle threshold is taken as the coordinate point of the end point of the curve.

[0026] When the turning judgment unit judges whether a curve appears in the waterway, the turning judgment unit comprises the following steps:

[0027] A preset time node is reached. When the time node is reached, a driving signal is transmitted to the ship coordinate calculation unit to output the current ship coordinates, and the two channel coordinates close to the ship's driving direction are determined by the current ship coordinates, and the distance and offset between the two channel coordinate points are calculated. If the distance ≥ the distance threshold and the offset ≥ the direction threshold, a turn signal is output, otherwise, a straight signal is output.

[0028] When calculating the angle of the curve, the turning judgment unit includes the following steps:

[0029] The sensing coordinate point selection unit selects the starting point coordinate point, midpoint coordinate point and end point coordinate point of the curve respectively: A(X Q ,Y Q ), B(X W ,Y W ) and C(X E ,Y E );

[0030] The coordinates of point A are subtracted from the coordinates of point B, and the coordinates of point B are subtracted from the coordinates of point C. and

[0031] Compute the vector between three coordinates:

[0032] Calculate the angle between the vector and the positive direction of the x-axis using the inverse tangent function:

[0033] vector Angle with the positive x-axis

[0034] vector Angle with the positive x-axis

[0035] Calculate the difference between the two angles, that is, the curvature of the channel at point B, that is, the angle of the bend:

[0036]

[0037] in, is the angle of the bend.

[0038] The control receiving unit receives the curve angle calculated by the turning judgment unit and establishes a mapping relationship with the turning judgment unit. In the mapping relationship, the curve angle and the turning judgment unit are in a fixed corresponding relationship. When a ship is traveling on a curve, it will be affected by the centripetal force, which makes the ship tend to deviate to the inside of the curve. The mapping relationship is an angle opposite to that when the ship turns. After calculation, the control receiving unit outputs a control signal to the adjustment structure to adjust the visibility detector.

[0039] When a ship is traveling on a curve, it will be affected by the centripetal force, which will cause the ship to tend to deviate to the inside of the curve. In order to ensure that the visibility detector can be adjusted in time, the adjustment angle of the visibility detector is opposite to the curve angle.

[0040] The mapping relationship is as follows:

[0041]

[0042] For example, when a ship turns left, the centripetal force will make the ship tend to deviate to the left side of the curve. If the visibility detector is also adjusted to the left, its field of view may focus more on the area inside the curve, while the area outside the curve is not monitored enough. On the contrary, adjusting the visibility detector to the right by a certain angle can cover the area outside the curve, and at the same time, the ship's driving trajectory on the curve can be better observed, providing more comprehensive information for the crew;

[0043] When the cylinder receives an adjustment signal, the adjustment signal includes a signal for controlling the cylinder movement speed. When the cylinder is started, the rack is driven to slide inside the ship through its output shaft end. At this time, the rack drives the gear to rotate, and the gear drives the visibility detector to adjust according to the adjustment signal through the rotating rod.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] In the navigation system suitable for low visibility, the visibility of the ship's driving direction is detected by a visibility detector, and then before the ship enters the bend of the channel selected in the channel determination unit, the turning angle of the ship when sailing is calculated by the bend calculation module, and in this process, the coordinate point selection unit determines the starting coordinate point, the midpoint coordinate point and the end point coordinate point of the bend, the turning judgment unit calculates the bend angle according to the starting coordinate point, the midpoint coordinate point and the end point coordinate point of the bend determined by the coordinate point selection unit, and then the control receiving unit maps the detection angle that the visibility detector needs to adjust when the ship turns, and outputs a signal to the adjustment structure to adjust the detection angle of the visibility detector when turning, and the bend angle is calculated by accurately determining the starting coordinate point, the midpoint and the end point coordinate points of the bend, so that the adjustment angle of the visibility detector is more accurate, and compared with the manual adjustment of the visibility detector based on experience, it is better adapted to bends with different curvatures and lengths, ensuring that the ship can obtain a suitable visibility detection range during the entire bend navigation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is the overall module principle diagram of the present invention;

[0047] Figure 2 It is a schematic diagram of the relationship between the visibility detector of the present invention and the position of the ship;

[0048] Figure 3 This is a schematic diagram of the angle adjustment principle of the visibility detector of the present invention.

[0049] The meaning of each number in the figure is:

[0050] 100. Channel determination module; 110. Channel determination unit; 120. Ship coordinate calculation unit; 130. Ship offset judgment unit; 200. Detection control module; 210. Visibility detector; 220. Adjustment structure; 221. Cylinder; 222. Rack; 223. Gear; 224. Rotating rod; 300. Curve calculation module; 310. Turn judgment unit; 320. Coordinate point selection unit; 330. Control receiving unit. DETAILED DESCRIPTION

[0051] The following will be combined with the accompanying drawings in the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] A navigation system suitable for low visibility includes a channel determination module 100, a detection control module 200 and a curve calculation module 300;

[0053] The channel determination module 100 establishes a connection with the navigation agency and sends a channel information request signal. After obtaining the channel information, the channel information is demodulated and decoded to determine the channel of the ship. The detection control module 200 emits infrared light in the direction of the ship, and detects the visibility in the direction of the ship according to the reflected light generated by the infrared light and the aerosol particles, wherein:

[0054] The curve calculation module 300 includes a coordinate point selection unit 310, a turn judgment unit 320 and a control receiving unit 330;

[0055] The coordinate point selection unit determines the starting point, midpoint and end point of the curve according to the difference angles between adjacent coordinate points in the channel. The turning judgment unit 320 monitors the distance and offset changes between adjacent coordinate points in the channel to determine whether a curve appears in the channel, and calculates the curve angle according to the changes between adjacent coordinate points, and establishes a mapping relationship with the control receiving unit 330, mapping the offset value of the detection control module 200 and the channel direction, and converts it into a control signal and transmits it to the detection control module 200 to execute the adjustment signal.

[0056] The channel determination module 100 includes a channel determination unit 110 and a ship coordinate calculation unit 120;

[0057] The channel determination unit 110 is used to sense navigation signals and establish a connection with a navigation agency. The navigation agency transmits channel information, and the channel determination unit 110 demodulates and decodes the channel information to determine the coordinates of the ship's navigation channel;

[0058] The ship coordinate calculation unit 120 captures the radio signals transmitted from multiple GPS satellites in real time through the antenna. The radio signals include the position and time information of the GPS satellites. The time when the radio signals propagate to the ship is recorded. Since the speed of light is known, the distances from multiple GPS satellites to the ship are calculated based on the time and distance, and the ship coordinates are calculated using the spatial distance formula.

[0059] It is known that the speed of light is c and the signal propagation time is Δt i , then the distance d i =c×Δt i ,

[0060] Set the coordinates of a ship (X o ,Y o ,Z o ), and the coordinates of multiple GPS satellites are known (X u ,Y u ,Z u ), and then establish a set of equations based on the spatial distance formula to determine the coordinates of the ship:

[0061]

[0062] Where a is usually multiple satellites;

[0063] Then solve the above equations to determine the coordinates of the ship (X o ,Y o ,Z o );

[0064] The channel determination module 100 further includes a ship deviation determination unit 130;

[0065] The ship deviation judgment unit 130 receives the ship coordinates in the ship coordinate calculation unit 120 and the channel coordinates in the channel determination unit 110, sets a difference threshold, calculates a range threshold through the ship coordinates and the difference threshold, compares the range threshold with the channel coordinates, and when the channel coordinates are within the range threshold, it means that the ship is in the current channel coordinates at this time. When it is determined that the ship is in the channel, the staff can estimate the navigation time through the current speed of the ship and the coordinates of the ship, and at the same time promptly determine the position of the ship in the channel to avoid the situation that the ship deviates from the channel during the navigation process;

[0066] The ship coordinates in the receiving ship coordinate calculation unit 120 are (X p ,Y p ), the course coordinates in the course determination unit 110 are composed of a series of coordinate points, which is (X 1 ,Y 1 ),(X 2 ,Y 2 ),…(X n ,Y n );

[0067] The difference threshold is T, then with the ship coordinates as the center, in the horizontal direction, the left and right boundary coordinates of the range threshold are (X p -T,X p +T); in the vertical direction, the upper and lower boundary coordinates of the range threshold are (Y p -T,Y p +T);

[0068] Each channel coordinate point (X n ,Y n ), satisfying X p -T≤X n ≤X p +T and Y p -T≤Y n ≤Y p +T, it means that the ship is in the current channel coordinates. If any channel coordinate point does not meet this condition, it means that the ship is not in the current channel coordinates.

[0069] The detection control module 200 includes a visibility detector 210 and an adjustment structure 220;

[0070] The output end of the visibility detector 210 emits infrared light of different lengths in the direction of the ship. The infrared light propagates in the atmosphere and contacts the aerosol particles in the atmosphere. The surface of the aerosol particles contacts the infrared light and causes reflection. The receiving end receives the reflected light and then calculates the length of the received reflected light. The visibility in the direction of the ship is determined according to the different lengths.

[0071] The calculation formula is as follows:

[0072]

[0073] Where Q is visibility, K is the calibration coefficient, which is calculated by the staff based on the relationship between reflected light and visibility, and I is the reflected light received by the receiving end;

[0074] Under low visibility conditions, the concentration of aerosol particles in the atmosphere is high. Aerosol particles include fog droplets, haze particles, dust particles, etc. During the propagation of infrared light, they will frequently come into contact with particles and reflect, resulting in a large number and high intensity of reflected light received by the receiving end. This indicates that visibility is low. On the contrary, under high visibility conditions, the concentration of aerosol particles is low, and the number and intensity of reflected light are small.

[0075] The adjustment structure 220 includes a cylinder 221 which is detachably connected to the ship, a rack 222 is fixedly connected to the output shaft end of the cylinder 221, a gear 223 is meshedly connected to one side of the rack 222, a rotating rod 224 is fixedly connected inside the gear 223, the rotating rod 224 is rotatably connected to the ship, and one end of the rotating rod 224 is detachably connected to the visibility detector 210.

[0076] The coordinate point selection unit 310 is used to calculate the difference angle between each coordinate point in the course when the turning judgment unit 320 selects three coordinate points in the course of the course determination unit 110;

[0077] The calculation formula is as follows:

[0078] Suppose a series of coordinate points on the waterway are A(X 9 ,Y 9 ), B(X 8 ,Y 8 ) and C(X 7 ,Y 7 );

[0079] Calculating vectors Then, based on the positive direction of the X axis, the inverse tangent function is used to calculate the vector Angle with the positive direction of the X axis Then the vector and Angle θ with the positive direction of the X axis r1 The calculation method is the same as above, and the difference angle at coordinate point B is Δθ 1 =|θ r1 -θ r |;

[0080] The coordinate point selection unit 310 determines the coordinate point of the starting point, the midpoint and the end point of the curve, including the following steps:

[0081] Set the angle threshold to Q 1 , compare the difference angle with the angle threshold, the difference angle Δθ 1 >Q 1 , then continue to select the next coordinate point in the channel, Δθ 1 ≤Q 1 When the compared coordinate points are summarized, the first coordinate point whose difference angle is greater than the angle threshold is taken as the coordinate point of the starting point of the curve, the midpoint of the summarized coordinate points is taken as the midpoint coordinate point, and the last coordinate point whose difference angle is greater than the angle threshold is taken as the coordinate point of the end point of the curve. At the same time, the difference angle is calculated for the starting point coordinate point, the midpoint coordinate point and the end point coordinate point in the curve, so that when the ship is sailing in a low visibility situation, the visibility detector 210 needs to adjust the angle to be calculated in time, so as to avoid the situation that the channel coordinate point selected by the turning judgment unit 320 is inaccurate, resulting in the deviation of the calculated adjustment angle;

[0082] When the turning judgment unit 320 judges whether there is a curve in the waterway, the following steps are included:

[0083] A preset time node is set. When the time node is reached, a driving signal is transmitted to the ship coordinate calculation unit 120 to output the current ship coordinates. The current ship coordinates are used to determine the two channel coordinates that are close to the ship's travel direction. The distance and offset between the two channel coordinate points are calculated. If the distance is ≥ the distance threshold and the offset is ≥ the direction threshold, a turn signal is output. Otherwise, a straight signal is output. When the straight signal is output, the ship's crew can adjust the ship's travel speed appropriately. In addition, due to the long-term navigation process of the crew, timely prompts can arouse the crew's alertness.

[0084] The sensing coordinate point selection unit 310 selects the starting point coordinate point, the midpoint coordinate point and the end point coordinate point of the curve as follows: Q ,Y Q ), B(X W ,Y W ) and C(X E ,Y E );

[0085] The coordinates of point A are subtracted from the coordinates of point B, and the coordinates of point B are subtracted from the coordinates of point C. and

[0086] Compute the vector between three coordinates:

[0087] Calculate the angle between the vector and the positive direction of the x-axis using the inverse tangent function:

[0088] vector Angle with the positive x-axis

[0089] vector Angle with the positive x-axis

[0090] Calculate the difference between the two angles, that is, the curvature of the channel at point B, that is, the angle of the bend:

[0091]

[0092] in, is the angle of the bend.

[0093] The control receiving unit 330 receives the curve angle calculated by the turning judgment unit 320, and establishes a mapping relationship with the turning judgment unit 320. In the mapping relationship, the curve angle and the turning judgment unit 320 are in a fixed corresponding relationship. When a ship is traveling on a curve, it will be affected by the centripetal force, which makes the ship tend to deviate to the inside of the curve. The mapping relationship is an angle opposite to that when the ship turns. After calculation, the control receiving unit 330 outputs a control signal to the adjustment structure 220 to adjust the visibility detector 210.

[0094] When a ship is traveling on a curve, it will be affected by the centripetal force, which will cause the ship to tend to deviate to the inside of the curve. In order to ensure that the visibility detector 210 can be adjusted in time, the adjustment angle of the visibility detector 210 is opposite to the curve angle.

[0095] The mapping relationship is as follows:

[0096]

[0097] For example, when the ship turns left, the centripetal force will make the ship tend to deviate to the left side of the curve. If the visibility detector 210 is also adjusted to the left, its field of view may focus more on the area inside the curve, while insufficiently monitoring the area outside the curve. On the contrary, adjusting the visibility detector 210 to the right by a certain angle can cover the area outside the curve, and at the same time, the ship's driving track on the curve can be better observed, providing more comprehensive information for the crew;

[0098] When the cylinder 221 receives an adjustment signal, the adjustment signal includes a signal for controlling the movement speed of the cylinder 221. When the cylinder 221 is started, the rack 222 is driven to slide inside the ship through its output shaft end. At this time, the rack 222 drives the gear 223 to rotate, and the gear 223 drives the visibility detector 210 to adjust according to the adjustment signal through the rotating rod 224.

[0099] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A navigation system suitable for low visibility, characterized in that: It comprises a channel determination module (100), a detection control module (200) and a curve calculation module (300); The channel determination module (100) establishes a connection with a navigation agency and sends a channel information request signal. After acquiring the channel information, the channel information is demodulated and decoded to determine the channel of the ship. The detection control module (200) emits infrared light in the direction of the ship, and detects the visibility in the direction of the ship based on the reflected light generated by the infrared light and aerosol particles, wherein: The curve calculation module (300) comprises a coordinate point selection unit (310), a curve determination unit (320), and a control receiving unit (330); The coordinate point selection unit (310) determines the starting point, midpoint and end point of the curve according to the difference angles of adjacent coordinate points in the channel, and the turning judgment unit (320) monitors the distance and offset changes between adjacent coordinate points in the channel to determine whether a curve appears in the channel. When a curve appears, the angle of the curve is calculated according to the starting point, midpoint and end point determined by the coordinate point selection unit (310), and a mapping relationship is established with the control receiving unit (330), mapping the offset value of the detection control module (200) and the channel direction, and converting it into a control signal and transmitting it to the detection control module (200) to execute the adjustment signal.

2. The low-visibility navigation system according to claim 1, characterized in that: The waterway determination module (100) comprises a waterway determination unit (110) and a ship coordinate calculation unit (120); The channel determination unit (110) is used to sense navigation signals and establish a connection with a navigation agency. The navigation agency transmits channel information, and the channel determination unit (110) demodulates and decodes the channel information to determine the channel coordinates of the ship when it is traveling. The ship coordinate calculation unit (120) captures radio signals emitted by multiple GPS satellites in real time through an antenna, records the time when the radio signals propagate to the ship, and then calculates the ship coordinates through a spatial distance formula.

3. The low-visibility navigation system according to claim 2, characterized in that: The waterway determination module (100) further comprises a ship deviation judgment unit (130); The ship deviation judgment unit (130) receives the ship coordinates in the ship coordinate calculation unit (120) and the channel coordinates in the channel determination unit (110), sets a difference threshold, calculates a range threshold through the ship coordinates and the difference threshold, compares the range threshold with the channel coordinates, and when the channel coordinates are within the range threshold, it means that the ship is currently within the current channel coordinates.

4. The low-visibility navigation system according to claim 1, characterized in that: The detection control module (200) comprises a visibility detector (210) and an adjustment structure (220); The output end of the visibility detector (210) emits infrared light of different lengths in the direction of the ship's travel. The infrared light propagates in the atmosphere and contacts aerosol particles in the atmosphere. The surfaces of the aerosol particles contact the infrared light and reflect it. The receiving end receives the reflected light, calculates the length of the received reflected light, and obtains the visibility in the direction of the ship's travel based on the different lengths. The adjustment structure (220) comprises a cylinder (221) detachably connected to the ship, the output shaft end of the cylinder (221) is fixedly connected to a rack (222), one side of the rack (222) is meshingly connected to a gear (223), the interior of the gear (223) is fixedly connected to a rotating rod (224), the rotating rod (224) is rotatably connected to the ship, and one end of the rotating rod (224) is detachably connected to the visibility detector (210).

5. The low-visibility navigation system according to claim 1, characterized in that: The coordinate point selection unit (310) is used to calculate the difference angle between each coordinate point in the channel, and the steps are as follows: Assume that a series of coordinate points on the course in the course determination unit (110) are A (X9, Y9), B (X8, Y8) and C (X7, Y7); Calculating vectors Then, based on the positive direction of the X axis, the inverse tangent function is used to calculate the vector Angle with the positive direction of the X axis Then the vector and Angle θ with the positive direction of the X axis r1 The calculation method is the same as above, the difference angle at coordinate point B is Δθ1=|θ r1 -θ r |.

6. The low-visibility navigation system according to claim 4, characterized in that: The coordinate point selection unit (310) determines the coordinate point of the starting point, the coordinate point of the middle point and the coordinate point of the end point of the curve, including the following steps: The angle threshold is set to Q1, and the difference angle Δθ1 calculated by the coordinate point selection unit (310) is compared with the angle threshold. When Δθ1>Q1, the next coordinate point in the waterway is selected. When Δθ1≤Q1, the compared coordinate points are summarized, and the first coordinate point whose difference angle is greater than the angle threshold is used as the coordinate point of the starting point of the curve, the midpoint of the summarized coordinate points is used as the midpoint coordinate point, and the last coordinate point whose difference angle is greater than the angle threshold is used as the coordinate point of the end point of the curve.

7. The low-visibility navigation system according to claim 2, characterized in that: When judging whether a curve appears in the waterway, the turning judgment unit (320) comprises the following steps: A time node is preset, and when the time node is reached, a driving signal is transmitted to a ship coordinate calculation unit (120) to output the current ship coordinates, and two channel coordinates close to the ship's travel direction are determined by the current ship coordinates, and the distance and offset between the two channel coordinate points are calculated. If the distance is greater than or equal to a distance threshold, and the offset is greater than or equal to a direction threshold, a turning signal is output, otherwise, a straight signal is output.

8. The low-visibility navigation system according to claim 6, characterized in that: When calculating the angle of a curve, the turning judgment unit (320) comprises the following steps: The sensing coordinate point selection unit (310) selects the starting point coordinate point, the midpoint coordinate point and the end point coordinate point of the curve respectively: A(X Q ,Y Q ), B(X W ,Y W ) and C(X E ,Y E ); The coordinates of point A are subtracted from the coordinates of point B, and the coordinates of point B are subtracted from the coordinates of point C. and Compute the vector between three coordinates: Calculate the angle between the vector and the positive direction of the x-axis using the inverse tangent function: vector Angle with the positive x-axis vector Angle with the positive x-axis Calculate the difference between the two angles, that is, the curvature of the channel at point B, that is, the angle of the bend: in, is the angle of the bend.

9. The low-visibility navigation system according to claim 8, characterized in that: The control receiving unit (330) receives the curve angle calculated by the turning judgment unit (320) and establishes a mapping relationship with the turning judgment unit (320). After calculation, the control receiving unit (330) outputs a control signal to the adjustment structure (220) to adjust the visibility detector (210).

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