Ship heeling difference draft rapid measurement method based on laser leveler

Abstract

A rapid method for measuring ship heel and draft based on a laser level is characterized by comprising a reference establishment end, a distance acquisition end, an inclination calculation end, a draft calculation end, and a correction and optimization end. Specifically, it includes the following steps: S1. Installing a laser level on the centerline of the ship's deck to construct a three-dimensional reference plane; S2. The laser level laterally scans multiple symmetrical points on the port and starboard sides of the ship, simultaneously measuring the distance from each point to the laser and calculating the actual water level height data; S3. Fitting a straight line of water level inclination based on the actual water level height data to calculate the ship's heel angle and heel difference reference value; S4. Calculating the actual draft depth on the port and starboard sides based on the ship's heel angle and heel difference reference value to obtain the heel difference draft value; S5. Performing environmental factor correction and averaging of multiple measurements on the measurement results, outputting the final corrected heel difference draft measurement value. This method effectively reduces human observation errors, significantly improves measurement efficiency, and achieves rapid and accurate measurement of ship heel and draft.

Description

Technical Field

[0001] This invention relates to the field of ship measurement technology, specifically a rapid method for measuring ship heel and draft based on a laser level. Background Technology

[0002] The difference in draft between the port and starboard sides refers to the difference in draft caused when a ship tilts to one side due to uneven loading on either side or external factors. Its core function is to reflect the ship's heel state, directly affecting navigational safety and performance. Excessive heel difference reduces ship stability and increases the risk of capsizing, requiring adjustment of the center of gravity through the ballast water system. Unequal draft between the port and starboard sides increases hull drag, reduces speed, and weakens rudder effectiveness and maneuverability, making the ship prone to deviating from its course. Properly controlling the heel difference can reduce uneven stress on the hull, prevent damage to the bow and bottom from wave impacts, and is a key indicator for assessing the ship's balance, crucial for stability, efficiency, and safety.

[0003] Traditional methods for measuring ship heel and draft rely primarily on manual observation and simple tools, which have significant limitations. Operators must visually read the boundary between the waterline and the draft gauge on both sides of the ship and calculate the draft difference based on the ship's beam parameters. The accuracy of this method is constrained by wave motion and insufficient lighting; in rough seas, severe water surface fluctuations significantly increase the error of manual readings. In some scenarios, simple devices such as transparent plastic tubes or U-shaped tubes are used to indirectly calculate the draft difference by observing the water level difference on both sides. However, these tools are prone to introducing additional errors due to misalignment or insufficient sealing, severely impacting measurement reliability. Traditional methods cannot construct a three-dimensional reference plane, causing the measurement reference to be affected by changes in ship attitude; the sparsity of manually collected data points also limits the fitting accuracy of the waterline tilt state. Furthermore, the lack of a systematic correction mechanism in data processing, relying solely on simple proportional calculations to correct the heel angle while ignoring the elimination of multi-period environmental interference, makes the measurement results susceptible to random fluctuations. Summary of the Invention

[0004] In view of this, the present invention aims to propose a rapid method for measuring the ship's heel difference draft based on a laser level. By installing a laser level on the centerline of the ship's deck, a three-dimensional reference plane is constructed. The laser level scans multiple symmetrical points on the port and starboard sides of the ship laterally, simultaneously measuring the distance from each point to the laser and calculating the actual water level height data. Based on the actual water level height data, a straight line of water surface inclination is fitted to calculate the ship's heel angle and heel difference reference value. Based on the ship's heel angle and heel difference reference value, the actual draft on the port and starboard sides is calculated, yielding the heel difference draft value. The measurement results are then corrected for environmental factors and averaged from multiple measurements to output the final corrected heel difference draft measurement value, effectively solving the problems mentioned in the background art.

[0005] The objective of this invention can be achieved through the following technical solution: a rapid measurement method for ship heel and draft based on a laser level, characterized by comprising a benchmark establishment end, a distance acquisition end, an inclination calculation end, a draft calculation end, and a correction and optimization end, specifically including the following steps:

[0006] S1. Install a laser level along the centerline of the ship's deck to construct a three-dimensional reference plane;

[0007] S2. The laser level instrument scans multiple symmetrical points on the port and starboard sides of the ship laterally, simultaneously measuring the distance from each point to the laser and calculating the actual water surface height data.

[0008] S3. Fit a straight line of water surface inclination based on the actual water surface height data, and calculate the reference values ​​of the ship's heel angle and heel difference;

[0009] S4. Based on the ship's heel angle and heel difference reference value, calculate the actual draft on the port and starboard sides to obtain the heel difference draft value.

[0010] S5. Perform environmental factor correction and multiple measurement averaging on the measurement results, and output the final corrected tilt difference draft measurement value.

[0011] The method for constructing the three-dimensional reference plane is as follows: a laser level is installed on the centerline of the ship's deck; a laser reference plane perpendicular to the direction of gravity is established using a built-in gyroscope and a leveling bubble device; the distance from the laser transmitter to the known waterline is measured using the laser ranging function, and the absolute installation height of the laser transmitter is calculated by combining the design height data of the waterline mark, while the levelness deviation detected during the calibration process is recorded.

[0012] The method for calculating the actual water surface height data is as follows: a laser level is used to scan the ship laterally, and n measurement points are set at symmetrical positions on the port and starboard sides; the distance from each point to the laser transmitter is measured; the lateral coordinates of each measurement point and the corresponding laser ranging value are recorded simultaneously; the laser reference surface is calibrated, and the actual water surface height is calculated.

[0013] The actual water level height can be calculated using the following expression: H i H0 is the actual water surface height, D is the installation height of the laser emitter, and H0 is the actual water surface height. i c0 represents the laser ranging value corresponding to each measurement point, and c0 represents the levelness deviation.

[0014] The method for calculating the ship's heel angle is as follows: A straight line of water surface inclination is fitted based on the actual water surface height data, which can be obtained through the expression H=aX+b; specifically, the slope 'a' can be expressed as: , where Xi is the coordinate of the measurement point and Hi is the corresponding laser ranging value;

[0015] The intercept b can be expressed by the following expression: , where n is the total number of measurement points;

[0016] Given the slope 'a', the tilt angle 'θ' can be calculated using the expression: .

[0017] The method for calculating the heel difference reference value is as follows: Based on the fitted water surface inclination line, the water surface height difference between the two sides of the ship is calculated, i.e., the heel difference reference value, which can be expressed by the following expression: , where HR is the water level at the starboard boundary and HL is the water level at the port boundary.

[0018] The method for calculating the actual draft on the port and starboard sides is as follows: Based on the ship's design waterline and the reference value for the roll difference, the actual draft on the port and starboard sides can be calculated using the following expression: , Where D0 is the design draft.

[0019] Preferably, the method for calculating the differential draft is as follows: Based on the actual draft depths on the port and starboard sides, the differential draft can be calculated using the following expression: , where △D is the actual difference in draft due to tilt.

[0020] Preferably, the method for correcting the heel difference draft measurement is as follows: Real-time monitoring of the ship's six-degree-of-freedom motion state; decomposing the measurement signal into ship motion, wave disturbance, and actual heel components; performing multiple rounds of repeated measurements within a preset time window; statistically eliminating outliers and calculating the average value; real-time monitoring of temperature and humidity; setting a correction coefficient K for the influence of laser propagation; and correcting the heel difference draft value using the following expression: The final difference in draft is obtained.

[0021] Combining all the above technical solutions, the positive effects of this invention are as follows: 1. This invention constructs a three-dimensional reference plane using a laser level and simultaneously collects distance data and actual water surface height information by scanning multiple symmetrical points on the port and starboard sides of the ship laterally. The multi-point layout improves the comprehensiveness of data coverage, and the accuracy of the water surface tilt line obtained after fitting is higher, providing a reliable basis for calculating the reference values ​​of the heel angle and heel difference. Compared with traditional measurement methods, it effectively reduces human observation errors, significantly improves measurement efficiency, and realizes rapid and accurate measurement of the ship's heel difference and draft.

[0022] 2. By incorporating an environmental factor correction step, this invention effectively counteracts the interference of complex environmental factors such as wind and wave disturbances and changes in lighting on measurement data, ensuring measurement stability even under adverse sea conditions. Furthermore, its measurement process is widely applicable to vessels of different tonnages and types, requiring no complex, targeted adjustments, significantly enhancing the method's practical value and potential for wider application.

[0023] 3. This invention, by introducing a multiple measurement averaging mechanism, further reduces the impact of random errors on the results, resulting in higher accuracy and reliability of the final corrected measurement values. Precise draft data can provide key technical support for ship loading optimization, stability assessment, and navigation safety assurance, helping to reduce operational risks caused by inaccurate draft measurements, improving the economy and safety of ship transportation, and having a positive impact on the standardized development of the shipping industry. Attached Figure Description

[0024] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0025] Figure 1 This is a flowchart illustrating the implementation steps of the method of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] See Figure 1 As shown, this invention proposes a rapid measurement method for ship heel and draft based on a laser level, including a benchmark establishment end, a distance acquisition end, an inclination calculation end, a draft calculation end, and a correction and optimization end.

[0028] In a more specific application of this invention, the installation of a laser level along the centerline of a ship's deck to construct a three-dimensional reference plane can be achieved by: precisely positioning and fixing the laser level. The operator must select a suitable installation point on the centerline of the ship's deck, ensuring that the point is in a stable and unobstructed location within the deck structure. Then, a dedicated fixing device is used to firmly secure the laser level in the selected position, preventing instrument displacement due to ship swaying or vibration, which would affect the accuracy of the subsequent reference plane.

[0029] After the instrument is installed, the reference plane is leveled. This can be done by using the laser level's built-in gyroscope and bubble leveling device to gradually adjust the instrument's level. The gyroscope monitors the instrument's spatial attitude in real time and feeds the data back to the control system. The operator can make coarse adjustments by adjusting the leveling knob at the bottom of the instrument based on the gyroscope's display. At the same time, observe the bubble leveling device. When the bubble is in the center position, it indicates that the instrument has reached a level state. At this point, the established laser reference plane is perpendicular to the direction of gravity, laying the foundation for the subsequent construction of a three-dimensional reference plane.

[0030] The absolute installation height of the laser emitter can be measured and calculated by activating the laser rangefinder function of a laser level, projecting the laser beam onto a known waterline marker on the deck. The instrument automatically measures and records the straight-line distance from the laser emitter to the waterline marker. Since the design height of the waterline marker is predetermined—that is, the height of the waterline relative to the ship's reference plane is known—the absolute installation height of the laser emitter, i.e., the actual height of the laser emitter relative to the ship's reference plane, can be calculated by adding or subtracting the measured distance from the laser emitter to the waterline marker from the design height of the waterline marker.

[0031] During calibration, the levelness deviation value can be detected and recorded in real time by the built-in sensor of the laser level. This deviation value reflects the degree of deviation between the laser reference plane and the ideal level state, providing important reference data for subsequent correction of the reference plane and installation and commissioning of ship-related equipment, ensuring that the constructed three-dimensional reference plane can meet the accuracy requirements of ship construction or maintenance.

[0032] A laser level scans multiple symmetrical points on the port and starboard sides of the ship, simultaneously measuring the distance from each point to the laser and calculating the actual water level height. This can be achieved by setting up n measurement points symmetrically on both the port and starboard sides of the ship. The selection of measurement points must follow the principle of uniform distribution and avoid obstacles on the deck to ensure that the laser beam can reach each point smoothly. Simultaneously, a dedicated coordinate measuring tool is used to determine the lateral coordinates of each measurement point, i.e., the horizontal distance of each point relative to the deck centerline, providing spatial location data for subsequent data processing.

[0033] Activate the lateral scanning function of the laser level, allowing the laser beam to sequentially scan the various measurement points on both the port and starboard sides along a preset path. During the scanning process, the instrument will automatically activate the distance measurement function, measuring and recording the straight-line distance from each measurement point to the laser emitter in real time. The laser reference plane has been determined through prior calibration; it is perpendicular to the direction of gravity and its absolute height is known. Therefore, while measuring the distance, it is necessary to simultaneously record the lateral coordinates of each measurement point and the corresponding laser distance measurement value to form a complete set of raw data, avoiding data confusion that could affect subsequent calculations.

[0034] By combining the calibration parameters of the laser reference surface, including the absolute installation height of the laser emitter and the levelness deviation, the actual water surface height at each measurement point is calculated. Using the laser ranging value, the lateral coordinates of the measurement point, and the spatial parameters of the laser reference surface, the actual water surface height corresponding to each measurement point is obtained through geometric calculations.

[0035] The actual water level can be calculated using the following expression: H i H0 is the actual water surface height, D is the installation height of the laser emitter, and H0 is the actual water surface height. i c0 represents the laser ranging value corresponding to each measurement point, and c0 represents the levelness deviation.

[0036] By considering the impact of levelness deviation on the calculation results, we can ensure that the final actual water surface height data is accurate and reliable, providing a precise reference for the relevant inspection and commissioning work of the ship.

[0037] By fitting a straight line to the water surface tilt based on actual water level height data, the ship's heel angle and heel difference reference values ​​can be calculated. This can be achieved using the expression H=aX+b. Since the water surface exhibits a linear tilt when the ship heels, the actual water level heights at symmetrical measurement points on the port and starboard sides will show a regular difference. If the ship heels to port, the actual water level height at the port measurement points will generally be higher than the corresponding points on the starboard side; if it heels to starboard, the height at the starboard measurement points will generally be higher. By importing this height data into a data processing system and using a least squares fitting algorithm, a straight line that accurately reflects the water surface tilt trend can be generated. The slope of this line directly corresponds to the degree of water surface tilt.

[0038] In specific calculations, the slope 'a' can be expressed by the following expression: , where Xi is the coordinate of the measurement point and Hi is the corresponding laser ranging value;

[0039] The intercept b can be expressed by the following expression: , where n is the total number of measurement points;

[0040] Given the slope 'a', the tilt angle 'θ' can be calculated using the expression: .

[0041] The method for calculating the heel difference baseline is as follows: Based on the fitted water surface inclination line, the difference in water surface height between the two sides of the ship is calculated, i.e., the heel difference baseline value, which can be expressed by the following expression: , where HR is the water level at the starboard boundary and HL is the water level at the port boundary.

[0042] The heel difference benchmark value refers to the difference between the actual heel angle and the ship's design benchmark state. As a quantitative indicator for assessing the ship's current tilt deviation from the ideal state, it provides a reference standard for the subsequent monitoring and correction of the ship's tilt state. It can promptly detect and adjust heeling that exceeds the safe range, ensuring navigation safety.

[0043] Based on the ship's heel angle and heel difference reference values, the actual draft on both port and starboard sides is calculated, yielding the heel difference draft. This can be achieved using the following expression: , Where D0 is the design draft.

[0044] For the actual draft on the port side, if the ship is listing to port, its value equals the draft in its upright state plus the additional draft caused by the list; if it is listing to starboard, the corresponding additional draft is subtracted. The calculation of the actual draft on the starboard side is the opposite: the value increases when the ship is listing to starboard and decreases when it is listing to port. The difference in draft between the port and starboard sides is the difference in actual draft between the two sides, which directly reflects the degree of difference in draft caused by the list.

[0045] The method for calculating the differential draft is as follows: Based on the actual draft on both the port and starboard sides, calculate the differential draft using the following expression: , where △D is the actual difference in draft due to tilt.

[0046] The difference in draft between the ship's heel and ballast can be used to determine whether the load on both sides of the vessel is balanced, thus guiding operators to adjust the cargo or ballast water to ensure the vessel's center of gravity is in a proper position. The difference in draft between the ship's heel and ballast is a crucial indicator for assessing navigational safety. Excessive heel difference causes uneven water resistance during navigation, affecting the vessel's maneuverability and potentially leading to capsizing. Monitoring and controlling the difference in draft between the ship's heel and ballast can effectively reduce navigational risks.

[0047] The measurement results are corrected for environmental factors and averaged from multiple measurements to output the final corrected draft measurement value for the heel difference. This can be achieved by: real-time monitoring of the ship's six degrees of freedom motion state; continuously capturing dynamic changes in six directions (pitch, roll, heel, longitudinal yaw, transverse yaw, and yaw) using onboard motion sensors; and then using signal processing algorithms to decompose the original measurement signal into three key components: the ship's own periodic motion, instantaneous fluctuations caused by wave disturbances, and a stable component reflecting the ship's true heel state. The core is to eliminate interference factors and accurately extract the effective signal related to the heel difference, laying the foundation for subsequent correction.

[0048] After signal decomposition, multiple rounds of repeated measurements are performed within a preset time window. The time window setting needs to be combined with the ship's navigation environment, usually covering several wave cycles to ensure that the data reflects a relatively stable state. Multiple acquisitions of heel and draft measurements are performed within the time window, and statistical testing methods are used to identify and eliminate outliers caused by sudden interference. The average value is then calculated from the remaining valid data, which reduces the impact of random errors and makes the measurement results closer to the true values.

[0049] Simultaneously, it is necessary to monitor the temperature and humidity parameters of the measurement environment in real time. The propagation speed of the laser in the air is affected by temperature and humidity, leading to ranging errors. Therefore, based on the real-time monitored temperature and humidity data, a corresponding laser propagation correction coefficient K needs to be calculated using a pre-established environmental impact model. This coefficient is used to compensate for the interference of environmental factors on the accuracy of laser ranging, ensuring the physical accuracy of the original measurement data.

[0050] The true tilt component obtained from the previous processing, the average value of multiple measurements, and the environmental correction factor K are substituted into the preset correction expression. The initial tilt difference draft value was comprehensively corrected.

[0051] By integrating the results of dynamic disturbance stripping, random error reduction, and environmental impact compensation, the final corrected draft value of the heel difference is obtained, making it more consistent with the actual state of the ship and providing high-precision data support for ship load adjustment and stability assessment.

[0052] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0053] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A rapid method for measuring the roll difference and draft of a ship based on a laser level, characterized in that, It includes a benchmark establishment end, a distance measurement and acquisition end, an inclination calculation end, a draft calculation end, and a correction and optimization end, specifically including the following steps: S1. Install a laser level along the centerline of the ship's deck to construct a three-dimensional reference plane; S2. The laser level instrument scans multiple symmetrical points on the port and starboard sides of the ship laterally, simultaneously measuring the distance from each point to the laser and calculating the actual water surface height data. S3. Fit a straight line of water surface inclination based on the actual water surface height data, and calculate the reference values ​​of the ship's heel angle and heel difference; The method for calculating the ship's heel angle is as follows: A straight line of water surface inclination is fitted based on the actual water surface height data, which can be obtained through the expression H=aX+b; specifically, the slope 'a' can be expressed as: ； Where Xi is the coordinate of the measurement point, and Hi is the corresponding laser ranging value; The intercept b can be expressed by the following expression: ； Where n is the total number of measurement points; Given the slope 'a', the tilt angle 'θ' can be calculated using the expression: ； The method for calculating the heel difference reference value is as follows: Based on the fitted water surface inclination straight line, the difference in water surface height between the two sides of the ship is calculated, i.e., the heel difference reference value, which can be expressed by the following expression: ； Where HR is the water level at the starboard boundary and HL is the water level at the port boundary; S4. Based on the ship's heel angle and heel difference reference value, calculate the actual draft on the port and starboard sides to obtain the heel difference draft value. S5. Perform environmental factor correction and multiple measurement averaging on the measurement results, and output the final corrected tilt difference draft measurement value.

2. The method for rapid measurement of ship roll difference and draft based on a laser level as described in claim 1, characterized in that: The method for constructing the three-dimensional reference plane is as follows: a laser level is installed on the centerline of the ship's deck; a laser reference plane perpendicular to the direction of gravity is established using a built-in gyroscope and a leveling bubble device; the distance from the laser transmitter to the known waterline is measured using the laser ranging function, and the absolute installation height of the laser transmitter is calculated by combining the design height data of the waterline mark, while the levelness deviation detected during the calibration process is recorded.

3. The method for rapid measurement of ship roll difference and draft based on a laser level as described in claim 1, characterized in that: The method for calculating the actual water surface height data is as follows: a laser level is used to scan the ship laterally, and n measurement points are set at symmetrical positions on the port and starboard sides; the distance from each point to the laser transmitter is measured; the lateral coordinates of each measurement point and the corresponding laser ranging value are recorded simultaneously; the laser reference surface is calibrated, and the actual water surface height is calculated.

4. The method for rapid measurement of ship roll difference and draft based on a laser level as described in claim 3, characterized in that: The actual water level height can be calculated using the following expression: ； Where H i H0 is the actual water surface height, D is the installation height of the laser emitter, and H0 is the actual water surface height. i c0 represents the laser ranging value corresponding to each measurement point, and c0 represents the levelness deviation.

5. The method for rapid measurement of ship roll difference and draft based on a laser level as described in claim 1, characterized in that: The method for calculating the actual draft on the port and starboard sides is as follows: Based on the ship's design waterline and the reference value for the roll difference, the actual draft on the port and starboard sides can be calculated using the following expression: ； ； Where D0 is the design draft.

6. The method for rapid measurement of ship roll difference and draft based on a laser level as described in claim 1, characterized in that: The method for calculating the differential draft is as follows: Based on the actual draft on both the port and starboard sides, the differential draft can be calculated using the following expression: ； Where △D represents the actual difference in draft due to tilt.

7. The method for rapid measurement of ship roll difference and draft based on a laser level as described in claim 1, characterized in that: The method for correcting the draft measurement of the roll difference is as follows: real-time monitoring of the ship's six degrees of freedom motion state, and decomposition of the measurement signal into ship motion, wave disturbance and true roll components; Multiple rounds of repeated measurements were performed within a preset time window. Outliers were removed through statistical testing, and the average value was calculated. Temperature and humidity were monitored in real time, and a correction factor K was set for the impact on laser propagation. The draft value of the tilt difference was corrected using the following expression: The final difference in draft is obtained.

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