Detection and Data Fusion Processing Method Based on ROV Carrying Multibeam and Cable Detector

Abstract

The present invention relates to a detection and data fusion processing method based on ROV equipped with multi-beam and cable instrument, comprising the following steps: S1, data solution of ROV absolute position; S2, ROV water depth acquisition and tidal correction; S3, acquisition and processing of position and burial depth data of buried sea pipes and cables. The advantages of the present invention are: the present method solves the problem that surface and underground detection cannot be taken into account at the same time, multi-sensor fusion and strict post-processing process ensure the operation accuracy, and the accuracy of the fine investigation is verified by inspection after removing the sea mud, indicating that the fine detection of cable and pipes by ROV equipped with multi-beam and TSS440 / 350 is an effective way.

Description

Technical Field

[0001] The present invention relates to a detection and data fusion processing method based on an ROV carrying a multi-beam and a pipeline cable detector, and is used for detecting buried pipelines and cables. Background Art

[0002] With the acceleration of the social and economic development and the process of ocean resource development, submarine pipelines and cables have increasingly become important infrastructure.

[0003] Submarine cables, also commonly known as subsea cables, include submarine power cables, optical cables, and hybrid power and optical cables. They have irreplaceable advantages in the fields of power transmission, cross-sea communication, ocean engineering, and new energy development. Submarine pipelines include submarine oil and gas pipelines and submarine water pipelines, etc. Among them, with the vigorous development of offshore oil resources, submarine oil and gas pipelines, as an efficient crude oil transportation means with continuity, speed, and large transportation volume, have become the main way of oil and gas transportation in the development of offshore oil and gas fields. Currently, a large number of submarine pipelines have been built successively in the Bohai Sea, the East China Sea, and the South China Sea in China. At present, CNOOC has laid more than 400 submarine pipelines, and the cumulative length has exceeded 7,000 km. The development of social economy has promoted the increasingly dense distribution of pipelines and cables laid in the offshore areas of China. For example, a large number of pipelines and cables are gathered near the Pearl River Estuary in the South China Sea. To ensure the safety of the laid pipelines and cables, the construction of newly started marine projects needs to accurately detect the position, orientation, burial depth, etc. of the existing pipelines and cables in the area. According to the requirements of GB 50217 "Code for Design of Electric Cables in Electric Power Engineering" and "Safety Rules for Offshore Fixed Platforms", the routes of pipelines and cables should avoid crossing as much as possible. In the inevitable situation, sufficient safety distances should be maintained and protective measures should be taken to ensure that the original pipelines or subsea cables are not damaged. Accurate detection of the in-place state of existing pipelines and cables, especially buried pipelines and cables, is of great significance for the subsequent implementation of protection projects. At the same time, considering that the safety of submarine pipelines and cables has a significant impact on the marine ecological environment and the national economy, regular detection and detection evaluation after laying and completion have become an indispensable part of the operation and maintenance of submarine pipelines and cables. In recent years, many experts and scholars have conducted a large number of studies on submarine pipeline and cable investigation technologies and applications, mainly focusing on the high-precision processing of topographic and geomorphic data based on acoustic equipment towed by surface vessels, the quantitative identification and characterization of pipeline states, and the magnetic detection of pipelines and cables based on magnetometers. Affected by factors such as sea waves, ocean currents, the speed of the towing vessel, cable length, and towing weight, the control of the water depth and the positioning accuracy are poor, and the detection accuracy cannot be guaranteed, which cannot meet the high-precision detection requirements for needs such as the installation of protection at crossover points. For the detection of buried pipelines and cables, some experts have studied the method of using an ROV equipped with a TSS440 / 350 based on the electromagnetic method. This method has a relatively high detection accuracy for flat seabed areas. However, based on the working principle of the TSS440 / 350, there are relatively large errors in the detection accuracy of the burial depth for undulating areas. Currently, pipeline and cable detection mostly focuses on the detection and processing of a single detection device, and there are few reports on the integrated detection and processing of pipelines and cables based on an ROV equipped with an acoustic multibeam and a TSS440 / 350. The present invention is based on an ROV equipped with multiple sensors and studies a high-precision detection and processing method that can take into account the detection and monitoring of different in-place states of submarine pipelines and cables.The present invention mainly solves key problems such as high-precision underwater positioning of the carrier, depth correction for long-distance pipeline and cable surveys, and fusion processing of detection data from multi-beam and TSS440 / 350 carried by ROV, providing theoretical support for improving detection accuracy and expanding safety operation analysis application scenarios such as pre-laying surveys, post-laying surveys, post-trenching surveys, post-burial surveys, buried stone protection surveys, and pipeline and cable protection monitoring of pipelines and cables. Summary of the Invention

[0004] To overcome the defects of the prior art, the purpose of the present invention is to provide a detection and data fusion processing method based on multi-beam and cable instrument carried by ROV, which has high operation efficiency and operation level, good safety, and a friendly result interface, and solves the problem that it is difficult to obtain accurate and high-precision data information on the in-situ states such as the position and burial depth of buried submarine pipelines and cables during the installation and maintenance of underwater projects. The technical solution of the present invention is as follows:

[0005] A detection and data fusion processing method based on multi-beam and cable instrument carried by ROV, comprising the following steps:

[0006] S1. Data solution of the absolute position of ROV;

[0007] S2. ROV water depth acquisition and tide correction;

[0008] S3. Acquisition and processing of the position and burial depth data of buried submarine pipelines and cables.

[0009] The specific step S1 is as follows:

[0010] Taking the difference in longitude and latitude obtained by dead reckoning based on the USBL position and the difference in height between the depth gauge and dead reckoning as the observed quantities, the measurement equation is expressed as:

[0011]

[0012] Where is the latitude measured by the real-time underwater positioning system, is the longitude measured by the real-time underwater positioning system, is the height measured by the real-time depth gauge, is the latitude of real-time dead reckoning, is the longitude of real-time dead reckoning, is the height of real-time dead reckoning, W USBLL is the latitude measurement error of USBL, W USBLλ is the longitude measurement error of USBL, W DEP is the depth measurement error of the depth gauge; iterative calculation is performed according to the calculation formula of the Kalman filter and real-time dead reckoning calibration is carried out to calculate the combined navigation position.

[0013] The specific steps of ROV water depth acquisition in step S2 are as follows:

[0014] Taking the three-dimensional position of the ROV as a reference and the real-time depth of the ROV as the benchmark longitudinally, the depth is measured by measuring the atmospheric pressure values of the sea surface and the pressure sensor carried by the ROV, and the accurate depth is calculated. The calculation formula is as follows:

[0015]

[0016] In the formula: D is the depth value, with the unit of m; P H is the pressure value of the hub surface, with the unit of Pa, P S is the sea surface pressure value, with the unit of Pa, g is the acceleration of gravity, with the unit of m / s^2, and ρ is the average density of seawater, with the unit of kg / m 3 .

[0017] The specific steps of ROV tidal correction in step S2 are as follows:

[0018] The tidal calculation module calculates the height of the mean sea level at this point relative to the reference ellipsoid through the mean sea level calculation model. The difference between the two ellipsoidal elevations is the tidal level value at this point. Its calculation formula can be summarized as follows:

[0019] OT = H el - MSS el (3); H el = G2 el - Z DGNSS-offset (4);

[0020] In the formula, OT is the tidal level value; H el is the ellipsoidal elevation of the hull reference point; MSS el is the height of the real-time mean sea level relative to the ellipsoid, Z DGNSS-offset is the height value from the antenna of the global navigation satellite system to the sea level; G2 el is the original ellipsoidal elevation of the global navigation satellite system.

[0021] Step S3 is specifically divided into four stages, which are the on-site recording stage, the data processing and merging stage, the fine processing and quality control stage, and the result output stage in sequence.

[0022] The on-site recording stage is specifically as follows: Record the original time-series data of each sensor during the detection process, and record the original time-series data of the ROV position, heading, attitude, water depth, multibeam, and the detection distance of the TSS440 / 350 coil in real time. Use the digital video system to record the video information during the investigation process, and use the event recording system to record the information of buried, suspended, and damaged events.

[0023] The data processing and merging stage is specifically as follows: the original data of position, heading, attitude, water depth, multi-beam, and TSS440 / 350 coil detection distance are respectively quality controlled and noise points are eliminated through the data processing system, and the plane position and water depth of the multi-beam emission center and the TSS440 / 350 coil center point are calculated and combined, and the three-dimensional coordinates of each ground point are calculated according to the sound speed, attitude, heading, multi-beam emission center position and water depth of each beam angle and beam transmission time of the multi-beam. The three-dimensional coordinates of the top of the buried cable are obtained by combining the position of the center point of the coil with the water depth and the attitude and heading data; the longitudinal coordinate Z of the plane coordinate in the three-dimensional coordinates of the underwater carrying system is not affected by the heave when calculating, and the ROV absolute water depth is used in the calculation. The longitudinal coordinate is obtained as follows: Z = dZ + D-Tide, where dZ is the sum of the multi-beam and TSS440 / 350 offset distances and the longitudinal distance measured by the instrument, D is the real-time depth of the ROV, and Tide is the real-time tidal correction value; after comprehensive data processing, all data are imported into the database through the import and export modules.

[0024] The specific details of the fine processing and quality control stage are as follows: the editing module extracts the imported sensor data, multi-beam data, the top coordinates of the cable and the real-time tidal data detected by the TSS440 / 350 coil from the database, and uses the cross-section, longitudinal section, top view, and three-dimensional simulation diagram to synchronously display the relative relationship between the cable and the seabed, and performs fine processing such as translation, elimination, interpolation, plane position smoothing, and depth data smoothing to obtain the cable position, water depth, burial depth and other data. The calculation formula for the burial depth data is:

[0025] COV=D pipetop -D seabed ; where COV is the burial depth, D pipetop is the absolute water depth at the top of the cable, D seabed is the depth of the top of the pipe and cable normal to the ground point;

[0026] During the processing, the digital video of the location is played back synchronously to assist in accurately determining the status of the pipe and cable in place, and to make corresponding adjustments based on the events recorded during the real-time recording process.

[0027] The advantages of the present invention are:

[0028] This method effectively solves the problem of being unable to take both surface and underground detection into account. Multi-sensor fusion and strict post-processing procedures ensure the accuracy of the operation. The accuracy of this detailed survey was verified by inspection after the removal of sea mud, indicating that the detailed detection of pipes and cables using ROV equipped with multi-beam and TSS440 / 350 is an effective method.

[0029] The advantages of the present invention are:

[0030] 1. Strong universality, applicable to all existing submarine cable surveys including burial, support, and suspension.

[0031] 2. Wide application scenarios, can be applied to pre - survey, post - laying survey, post - trenching survey, in - situ monitoring of cables, etc.

[0032] 3. Selectable modes, can detect cables using active and passive modes according to operation needs.

[0033] 4. High precision. Compared with the traditional geophysical mode with an accuracy of 5 - 10 meters, the detection accuracy of position and depth is improved to the sub - meter level. Compared with the application of the detection coil of TSS440 / 350 alone minus the altimeter data, the detection accuracy of buried depth is greatly improved, especially suitable for various complex terrains.

[0034] 5. High efficiency. The operation is carried out along the cable instead of cutting across the cable, greatly improving the operation efficiency, enhancing the operation timeliness, and saving project costs.

[0035] 6. User - friendly interface. Provide an underwater detection management system (SIMS) for digital display of results, synchronously display ROV digital video and the processing results of detection sensors. The processing results of detection sensors are presented in digital terrain models, three - dimensional perspective views, cross - sectional views, longitudinal sectional views, top - view diagrams, and event data lists.

[0036] As the number of submarine cables increases, the demand for cable survey operations in construction and safe operation will continue to grow. As an effective high - precision detection method, the fine detection of cables with ROV - mounted multi - beam and TSS440 / 350 will be more and more widely used. Specific implementation mode

[0037] The following describes the present invention in further detail with specific embodiments. The advantages and features of the present invention will become clearer with the description. However, these embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. Those skilled in the art should understand that the details and forms of the technical solutions of the present invention can be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the protection scope of the present invention.

[0038] The present invention relates to a detection and data fusion processing method based on ROV - mounted multi - beam and cable detector, including the following steps:

[0039] S1. Data calculation of the absolute position of ROV;

[0040] S2. Acquisition of ROV water depth and tidal correction;

[0041] S3. Acquisition and processing of the position and buried depth data of buried submarine pipes and cables.

[0042] In the step S1, the position of the ROV mother ship is mainly provided by the global navigation satellite system for the absolute position. The integrated navigation system combines the measurement-level compass data and attitude sensors to calculate the absolute position of any point on the ship, including the transducer of the underwater positioning system. The underwater positioning system transmits and receives acoustic signals to judge the azimuth and distance of the ROV-mounted acoustic beacon, and calculates the absolute position of the acoustic beacon through the internal processor. Due to its inherent characteristics, the accuracy of the underwater positioning system is generally greater than 1 meter and decreases with the increase of water depth, and the data update rate is also less than 1 Hz, which cannot meet the accuracy requirements of the position source for the ROV-mounted multi-beam fine survey. In this study, a Doppler velocity log (DVL) is introduced and the velocity data in the bottom tracking mode is used to accurately judge the movement of the ROV. The water depth data is introduced to judge the heave of the ROV. The ROV heading and attitude data are introduced and combined with the underwater inertial navigation combined system to apply the Kalman filter to comprehensively calculate and obtain the high-precision absolute position of the ROV. Specifically:

[0043] Taking the difference between the longitude and latitude of the dead reckoning based on the USBL (Ultra-Short Baseline) position and the difference between the height measured by the depth gauge and the height of the dead reckoning as the observation quantities, the measurement equation is expressed as:

[0044]

[0045] where is the latitude measured by the real-time underwater positioning system, is the longitude measured by the real-time underwater positioning system, is the height measured by the real-time depth gauge, is the latitude of the real-time dead reckoning, is the longitude of the real-time dead reckoning, is the height of the real-time dead reckoning, W USBLL is the latitude measurement error of the USBL, W USBLλ is the longitude measurement error of the USBL, W DEP is the depth measurement error of the depth gauge; Iteration is carried out according to the calculation formula of the Kalman filter and real-time dead reckoning calibration is carried out to calculate the combined navigation position.

[0046] Integrated navigation refers to a navigation system that combines various navigation devices and is controlled by a monitor and a computer. Most integrated navigation systems are mainly based on inertial navigation systems. The main reasons are that inertial navigation can provide relatively many navigation parameters and can also provide full attitude information parameters, which are incomparable to other navigation systems. When various navigation systems are used alone, it is difficult to meet the navigation performance requirements. An effective way to improve the overall performance of the navigation system is to adopt integrated navigation technology, that is, to use two or more non-similar navigation systems to measure and solve the same navigation information to form measurements, and calculate and correct the errors of each navigation system from these measurements. A system that adopts integrated navigation technology is called an integrated navigation system. Compared with a single navigation system, the integrated navigation system has the following advantages:

[0047] (1) It can effectively utilize the navigation information of each navigation subsystem and improve the positioning accuracy of the integrated system. For example, the INS / GPS integrated navigation system can effectively utilize the short-term accuracy maintenance characteristics of INS and the long-term accuracy maintenance characteristics of GPS, and its output information characteristics are better than those of INS and GPS as single systems.

[0048] (2) It allows automatic switching between the working modes of the navigation subsystems, thereby further improving the working reliability of the system. Since each navigation subsystem can output the motion information of the ship, the integrated navigation system has sufficient measurement redundancy. When a part of the measurement information fails, the system can automatically switch to another combination mode and continue to work.

[0049] (3) It can calibrate the errors of each navigation subsystem and its components, thereby relaxing the requirements for the technical indicators of the navigation subsystems. For example, when INS and GPS are combined in a loose coupling mode, the combined output of position, speed, and attitude will be fed back to INS and GPS to calibrate the corresponding error quantities of INS and GPS.

[0050] The specific steps for ROV water depth acquisition in step S2 are as follows:

[0051] Taking the three-dimensional spatial position of the ROV as a reference and the real-time depth of the ROV as the benchmark longitudinally, the depth measurement is obtained by measuring the atmospheric pressure values of the sea surface and the pressure sensor carried by the ROV, and the accurate depth is calculated. The calculation formula is as follows:

[0052]

[0053] In the formula: D is the depth value, with the unit of m; P H is the pressure value of the hub surface, with the unit of Pa, P S is the sea surface pressure value, with the unit of Pa, g is the acceleration due to gravity, with the unit of m / s^2, and ρ is the average density of seawater, with the unit of kg / m 3 .

[0054] Tides cause periodic up-and-down fluctuations on the sea surface, which affect the calculation of the absolute depth of the seabed topography measurement. During the operation, tidal correction of the water depth is required to obtain the absolute water depth. If real-time tide gauging is used for tide level correction, not only is the operation relatively complex, but also the project cost is increased. Usually, predicted tide data is used for water depth correction, but it is difficult to guarantee the accuracy when applying predicted tides. With the upgrade and development of differential global navigation satellite system technology nowadays, high-precision satellite differential positioning systems are emerging continuously. It has become possible to obtain elevation data through the global navigation satellite system and combine it with the mean sea level model to obtain sea tide data. In the present invention, through a real-time tide calculation module, the ellipsoidal height of the hull reference point is calculated by accessing high-precision DGNSS position, antenna offset, and attitude sensors; the specific steps of ROV tide correction in the step S2 are as follows:

[0055] The tide calculation module calculates the height of the mean sea level at this point relative to the reference ellipsoid through the mean sea level calculation model. The difference between the two ellipsoidal elevations is the tide level value at this point, and its calculation formula can be summarized as follows:

[0056] OT = H el - MSS el (3); H el = G2 el - Z DGNSS-offset (4);

[0057] In the formula, OT is the tide level value; H el is the ellipsoidal elevation of the hull reference point; MSS el is the height of the real-time mean sea level relative to the ellipsoid; Z DGNSS-offset is the height value from the antenna of the global navigation satellite system to the sea level; G2 el is the original ellipsoidal elevation of the global navigation satellite system.

[0058] The step S3 is specifically divided into four stages, which are successively the on-site recording stage, the data processing and merging stage, the fine processing and quality control stage, and the result output stage.

[0059] The on-site recording stage is specifically as follows: Record the original time series data of each sensor during the detection process, and record the original time series data of the ROV position, heading, attitude, water depth, multibeam, and the detection distance of the TSS440 / 350 coil in real time. Use the digital video system to record the video information during the investigation process, and use the event recording system to record the information of burial, suspension, and damage events.

[0060] The specific data processing and merging stage is as follows: The original data of position, heading, attitude, water depth, multibeam, and detection distance of the TSS440 / 350 coil are respectively subjected to quality control by the data processing system to remove noise points, and the plane positions and water depths of the multibeam emission center and the center point of the TSS440 / 350 coil are calculated and merged. The three-dimensional coordinates of each ground point are obtained by comprehensively calculating the sound velocity, attitude, heading, multibeam emission center position, and water depth according to each beam angle and beam transmission time of the multibeam. The three-dimensional coordinates of the top of the buried pipeline are obtained by comprehensively calculating the detection distance of the TSS440 / 350 coil, the position of the center point of the coil, and the water depth, as well as the attitude and heading data. The calculation of the plane coordinates in the three-dimensional coordinates of the underwater carrier system is similar to that of the surface system. Different from the surface carrier system, the longitudinal coordinate (Z) is not affected by heave during calculation. When calculating, the absolute water depth of the ROV is applied. The acquisition method of the longitudinal coordinate is: Z = dZ + D - Tide, where dZ is the sum of the offset of the instrument (multibeam and TSS440 / 350) and the longitudinal distance measured by the instrument, D is the real-time depth of the ROV, and Tide is the real-time tidal correction value. After comprehensive data processing, all data are imported into the database through the import / export module.

[0061] The specific fine processing and quality control stage is as follows: The editing module (Starfix.Edit) extracts the imported data of each sensor, multibeam data, the top coordinates of the pipeline detected by the TSS440 / 350 coil, and real-time tidal data from the database, and synchronously displays the relative relationship between the pipeline and the seabed surface using cross-sections, longitudinal sections, top views, and three-dimensional simulation diagrams, and performs fine processing such as translation, deletion, interpolation, plane position smoothing, and depth data smoothing to obtain data such as pipeline position, water depth, and burial depth. The calculation formula for the burial depth data is: COV = D pipetop - D seabed ; where COV is the burial depth, D pipetop is the absolute water depth at the top of the pipeline, and D seabed is the depth of the normal ground point at the top of the pipeline;

[0062] During the processing, the digital video at the corresponding point is played back synchronously to assist in accurately judging the in-position state of the pipeline, and corresponding adjustments are made for the events recorded during the real-time recording process.

[0063] The comprehensive and detailed investigation results of this specification are as follows:

[0064] (1) Investigation results of buried pipelines:

[0065] For pipeline surveys, after final data processing, the resulting data usually includes data information such as KP values, coordinate positions, pipeline plane deviation values, absolute depth of the pipe top, absolute depth of the pipe bottom, absolute depth of the natural seabed, depth of adjacent points of the pipeline, suspended / buried status, buried depth, etc., which are used to comprehensively display the pipeline status. To visually display the in-situ status of the pipeline, an underwater detection management system (SIMS) is provided for digital display of the results, synchronously displaying the ROV digital video and the processing results of the detection sensors. The processing results of the detection sensors are presented in the form of digital terrain models, three-dimensional perspective views, cross-sectional views, longitudinal sectional views, top views, and event data lists.

[0066] (2) Results of buried submarine cable surveys:

[0067] According to the requirements of the "Safety Rules for Offshore Fixed Platforms" and GB50217 "Code for Design of Electric Power Engineering Cables", submarine cables are strictly prohibited from crossing and overlapping. The route should avoid cross-overs between submarine pipelines and submarine cables to the greatest extent possible. In unavoidable cases, sufficient safety distances should be maintained and protective measures should be taken to ensure that the original pipeline or submarine cable is not damaged. The distribution of submarine pipelines and cables is complex, and it is inevitable that the proposed pipeline will cross the existing submarine pipelines / cables in terms of route. To avoid risks during operation and reduce difficulties during subsequent pipeline or cable maintenance operations, necessary pretreatment is usually carried out at the crossing positions on the laying route of the newly built submarine pipelines and cables to effectively protect the existing pipelines and cables. Traditional shipborne towing acoustic and magnetic detection methods are usually cross-cutting detections, which only provide point data, the route is discontinuous, and at the same time the position accuracy is relatively low, unable to meet the accuracy requirements for submarine cable detection in engineering installation. In this study, acoustic multi-beam and electromagnetic induction technologies are used to survey buried optical cables. On the basis of ensuring the positioning accuracy, through data superposition, data information such as the position of the submarine cable route, the absolute depth of the seabed points above the normal line of the submarine cable, the absolute depth of the natural seabed, and the buried depth are intuitively reflected. Similar to the display method of submarine pipelines, an underwater detection management system (SIMS) can be provided for digital display of the results. Taking the continuous route results of the submarine cable at the pipeline-cable crossing point before the laying of the submarine pipeline in the South China Sea and the sleepers pre-installed with this as a reference, to ensure absolute safety, before installing the sleepers, the seabed mud was cleared according to the survey results to verify the detection results, indicating that the position and depth data provided by this survey method are accurate and reliable and can be effectively applied to the high-precision installation of submarine facilities.

[0068] (3) Results of long-term monitoring:

[0069] The "Specification for Submarine Pipeline Systems" (DNV2000) of DNV GL stipulates that the pipeline sections vulnerable to damage and those significantly affected by changes in seabed conditions (such as the supported and buried sections of the pipeline) are usually inspected annually. Special inspections should also be carried out in case of earthquakes, severe storms or serious mechanical damage. During the operation of submarine pipelines, by regularly inspecting the relative position between the pipeline body and the seabed, the burial condition of the pipeline body, whether there are local suspensions and the trend of seabed erosion and deposition changes can be ascertained, and pipeline hazards can be detected in a timely manner. This is an effective means to ensure the safe operation of submarine pipelines during their in-service period. By using an ROV equipped with a multi-beam and a combined 440 / 350 system and a post-processing system, a certain submarine pipeline in the South China Sea has been regularly inspected for 5 consecutive years, and a comprehensive comparative analysis has been carried out on the suspension, burial and artificial support protection of the submarine pipeline, providing the number of suspensions, suspension lengths, suspension heights, suspension characteristics in key areas and changes over the years in the same interval, providing the number of burials, burial lengths, burial depths, burial characteristics in key areas and changes over the years in the same interval, showing the evolution process of the suspension at KP50.625 from non-existent to a length of 35m and a depth of 0.6m in a longitudinal section, and showing the evolution trend of the suspension at KP50.687, the riprap protection condition and the topographic change process in the riprap area. The operation shows that the ROV equipped with a multi-beam and a combined 440 / 350 system can accurately quantify the relative position relationship between the submarine pipeline and the seabed. Through professional data post-processing, accurate submarine pipeline suspension data, burial depth data and long-term evolution data can be obtained, with an accuracy of centimeter level, which is much higher than the shipborne towing geophysical method. At the same time, the cross-section sampling interval of this method is usually 1m and can be adjusted to 0.1m as needed, and cross-sections at the required positions can be provided as needed, which has incomparable advantages over the geophysical method. It is of great significance for studying the service life of submarine pipelines, pipeline fatigue failure and pipeline safety.

[0070] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A detection and data fusion processing method based on an ROV carrying a multibeam and a pipeline cable detector, characterized in that, it includes the following steps: S1. Data calculation of the absolute position of the ROV; S2. Acquisition of the ROV water depth and tidal correction; S3. Acquisition and processing of the position and burial depth data of buried submarine pipelines and cables; The step S3 is specifically divided into four stages, which are successively the on-site recording stage, the data processing and merging stage, the fine processing and quality control stage, and the result output stage; The specific process of the data processing and merging stage is as follows: The data processing system performs quality control on the original data of position, heading, attitude, water depth, multibeam, and detection distance of the TSS440 / 350 coil respectively, and eliminates noise points. Calculate and merge the plane position and water depth of the multibeam emission center and the center point of the TSS440 / 350 coil. Calculate the three-dimensional coordinates of each ground point according to the beam angle of each multibeam and the beam transmission time, combined with the sound speed, attitude, heading, multibeam emission center position, and water depth. Obtain the three-dimensional coordinates of the top of the buried pipeline and cable according to the detection distance of the TSS440 / 350 coil, the position of the center point of the coil, and the water depth, combined with the attitude and heading data. When calculating the longitudinal coordinate Z of the plane coordinate in the three-dimensional coordinates of the underwater carrying system, it is not affected by heave. When calculating, the absolute water depth of the ROV is applied. The acquisition method of the longitudinal coordinate is: Z = dZ + D - Tide, where dZ is the sum of the offsets of the multibeam and the TSS440 / 350 and the longitudinal distance measured by the instrument, D is the real-time depth of the ROV, and Tide is the real-time tidal correction value. After comprehensive data processing, all data is imported into the database through the import and export module; The specific process of the fine processing and quality control stage is as follows: The editing module extracts the imported data of each sensor, multibeam data, the top coordinates of the pipeline and cable detected by the TSS440 / 350 coil, and real-time tidal data from the database. Use cross-section, longitudinal section, top view, and three-dimensional simulation diagrams to synchronously display the relative relationship between the pipeline and cable and the seabed surface. Perform fine processing such as translation, elimination, interpolation, plane position smoothing, and depth data smoothing to obtain the pipeline position, water depth, and burial depth data. The calculation formula for the burial depth data is: COV = D pipetop -D seabed ; where COV is the burial depth, D pipetop is the absolute water depth at the top of the pipeline and cable, D seabed is the depth of the normal ground point at the top of the pipeline and cable; During the processing, the digital video at the corresponding point is played back synchronously to assist in accurately judging the in-position state of the pipeline and cable, and corresponding adjustments are made for the events recorded during the real-time recording process.

2. The detection and data fusion processing method based on an ROV carrying a multibeam and a pipeline cable detector according to claim 1, characterized in that, the step S1 is specifically as follows: Taking the difference between the dead reckoning longitude and latitude based on the USBL position and the difference between the depth gauge and the height of the dead reckoning as the observables, the measurement equation is expressed as: (1); where is the latitude measured by the real-time underwater positioning system, is the longitude measured by the real-time underwater positioning system, is the altitude measured by the real-time depth gauge, is the latitude of the real-time dead reckoning, is the longitude of the real-time dead reckoning, is the altitude of the real-time dead reckoning, is the latitude measurement error of the USBL, is the longitude measurement error of the USBL, is the depth measurement error of the depth gauge; iterate according to the calculation formula of the Kalman filter and perform real-time dead reckoning calibration to calculate the integrated navigation position.

3. The detection and data fusion processing method based on an ROV carrying a multibeam and a pipeline cable detector according to claim 1, characterized in that, the specific steps of the ROV water depth acquisition in the step S2 are as follows: Taking the three-dimensional spatial position of the ROV as a reference, with the real-time depth of the ROV as the benchmark longitudinally, the depth measurement is carried out by measuring the atmospheric pressure values of the sea surface and the pressure sensor carried by the ROV, and the accurate depth is calculated. The calculation formula is as follows: （2）； Where: D is the depth value, with the unit of m; is the pressure value of the hub surface, with the unit of Pa, is the sea surface pressure value, with the unit of Pa, g is the acceleration due to gravity, with the unit of m / s 2 , is the average density of seawater, with the unit of kg / m³.

4. The detection and data fusion processing method based on ROV carrying multi-beam and cable detector according to claim 1, characterized in that, the specific steps of ROV tide correction in step S2 are as follows: The tide calculation module calculates the height of the point mean sea level relative to the reference ellipsoid through the mean sea level calculation model. The difference between the two ellipsoid elevations is the point tide level value, and its calculation formula can be summarized as follows: （3）； （4）； Wherein, OT is the tide level value; is the ellipsoidal elevation of the hull reference point; is the height of the real-time mean sea level relative to the ellipsoid, is the height value from the antenna of the global navigation satellite system to the sea level; is the original ellipsoidal elevation of the global navigation satellite system.

5. The detection and data fusion processing method based on ROV carrying multi-beam and cable detector according to claim 1, characterized in that, the on-site recording stage is specifically as follows: record the original timing data of each sensor during the detection process, and record in real time the original timing data of the ROV position, heading, attitude, water depth, multi-beam, and the detection distance of the TSS440 / 350 coil. Use the digital video system to record the video information during the investigation process, and use the event recording system to record the information of buried, suspended, and damaged events.

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