Method for synchronously measuring drifting speed of floating object on sea surface and flow speed of ocean current on peripheral surface layer

Abstract

The invention belongs to the field of marine environment monitoring, and particularly relates to a method for synchronously measuring the drifting speed of floating objects on the sea surface and the flow speed of ocean currents on the peripheral surface layer, which comprises the following steps: manufacturing a drifting buoy, and enabling the drifting buoy to vertically float on the sea surface and be completely submerged in water through a steel bar counterweight; releasing the drifting buoy to a target position through the unmanned aerial vehicle; tracking and shooting drifting buoys and sea surface floating objects, and acquiring and storing image data containing positions of the drifting buoys and the sea surface floating objects; converting the relative positions of the pixels of the image data acquired by the unmanned aerial vehicle into latitude and longitude coordinates, and generating a TIFF file; after the unmanned aerial vehicle image of the TIFF file is subjected to geometric correction, the corrected TIFF file is transmitted to QGIS software, the drifting buoy position and the sea surface floating object position are marked, and the imaging moment is synchronously recorded; and calculating the sea surface floater drift speed and the peripheral surface ocean current flow velocity based on the position change at the adjacent moments. According to the scheme, the sea surface flow velocity of the near area of the sea surface floating object can be accurately measured, and the depth of the measured surface flow velocity is determined.

Description

Technical Field

[0001] The invention belongs to the field of marine environment monitoring, in particular to a method for synchronously measuring the drifting speed of sea surface floating objects and the flow speed of surrounding surface ocean currents. Background Art

[0002] Macroalgae, marine debris, and oil spills are key targets for monitoring in the marine environment. Unlike pollutants such as ammonia nitrogen and total phosphorus, these substances are insoluble in seawater and float on the surface, being transported to different sea areas by currents. Their impact on the marine environment primarily occurs through drift. Oil spills on oil platforms and waterways can cause severe damage to aquaculture, tourism, and the ecology of shallow offshore areas. The annual green tides of Enteromorpha that occur on the Shandong Peninsula primarily originate in shallow aquaculture areas in northern Jiangsu and are transported to the Shandong Peninsula's coast, causing serious ecological disasters. Surface floating objects are exposed to the sea surface during their drift, and this characteristic affects their movement both by surface current velocity and by direct wind drag. The wind drag effect varies depending on the height above the surface, the material properties, and the shape of the floating objects. The wind drag coefficient is a key parameter for accurately modeling and predicting the drift trajectory of floating objects, and this coefficient requires calculation based on extensive observational data. In order to calculate this parameter, it is necessary to simultaneously measure the drifting speed of the floating object, the surface flow velocity of the sea water around the floating object, and the wind speed.

[0003] Within spatial scales of tens to hundreds of meters, wind speeds vary little, so wind speeds can be measured using anemometers near floating objects, either onshore or on survey vessels. However, measuring the velocity of floating objects and the currents around them is more difficult. The velocity of floating objects is typically tracked using methods such as satellite remote sensing, on-site tracking from survey vessels, and GPS trackers. Surface current velocities are obtained using on-site current meter measurements and numerical ocean hydrodynamic model simulations. Satellite remote sensing imagery has low resolution and can only track large floating objects. Most floating objects are small, making them difficult to detect with satellite remote sensing images. Currently, satellite remote sensing is only used to track and monitor large algae blooms, such as the Enteromorpha green tide in the Yellow Sea. Furthermore, satellite remote sensing has a long revisit period, often lasting several days. While the tidal current, the primary component of ocean currents, has a period of approximately 12.5 hours, hourly monitoring is required to effectively detect the trajectory of floating objects. More importantly, current satellite remote sensing cannot measure surface current velocities. Therefore, satellite remote sensing struggles to effectively monitor floating objects and surrounding currents, both in terms of spatial and temporal resolution and monitoring techniques. Currently, monitoring the trajectory of floating objects primarily relies on in-situ observations. The existing marine industry standard, "Specifications for In-situ Observation of Enteromorpha Green Tide Drifting at Sea," proposes using survey vessels or position trackers to monitor the position of Enteromorpha. However, in-situ monitoring as proposed by the current standard has several drawbacks. To more accurately record the position of floating objects, survey vessels must consider the tracked objects as closely as possible, which can interfere with the local flow field and affect monitoring effectiveness. Furthermore, current meters carried by survey vessels are often located far from the monitored objects, making them less representative of the current velocity at the location of the floating objects. Furthermore, current instruments currently used for measuring current velocity onboard are often acoustic Doppler current profilers (ADCPs), which have a blind spot near the sensor and cannot monitor current velocities near the surface of the sea. Some researchers have also used fixed current meters, but when floating objects are at a distance, the current velocity measured by these instruments is less representative of the flow field surrounding the floating objects. Using GPS trackers allows for long-term, high-frequency monitoring of floating objects, which is more effective for larger and heavier floating objects. However, for floating objects such as large algae and oil spills, the tracker will significantly change the buoyancy properties of the object. In addition, the tracker also cannot obtain changes in flow velocity around the floating object.

[0004] In summary, the current monitoring methods have the following defects: ① The temporal resolution or spatial resolution is insufficient, making it difficult to track and monitor sea surface floating objects and obtain the drift speed of sea surface floating objects; ② It is difficult to measure the surface current velocity in the area near sea surface floating objects; ③ Existing monitoring methods such as survey ships and trackers may affect the properties of the sea surface floating objects themselves and the characteristics of the surrounding flow field. Summary of the Invention

[0005] In response to the shortcomings of current monitoring technology, the present invention, based on drones and self-made drifting floats, provides a method that can simultaneously monitor sea surface floating objects and surrounding current velocities with high precision and high temporal and spatial resolution. This method can solve the problems of insufficient temporal and spatial resolution in current floating object monitoring and difficulty in synchronously monitoring surface current velocities, and provide more accurate monitoring data for the establishment of a parameterization scheme for the drift velocity of a certain sea surface floating object.

[0006] The technical solution adopted by the present invention to achieve the above-mentioned object is: a method for synchronously measuring the drift velocity of sea surface floating objects and the velocity of surrounding surface currents, comprising the following steps:

[0007] S1: Make a drifting float, which is weighted by a steel rod so that it floats vertically on the sea surface and is completely submerged in the water to eliminate the effect of wind drag and represent the surface current velocity at a specific depth;

[0008] S2: After releasing the drifting float to the target location by drone airdrop, the drone tracks and photographs the drifting float and floating objects on the sea surface, obtains and stores image data containing the positions of both;

[0009] S3: Convert the relative positions of the pixels in the image data acquired by the drone into longitude and latitude coordinates, and generate a TIFF file containing geographic coordinates;

[0010] S4: After geometric correction of the drone image of the TIFF file, the corrected TIFF file was transferred to the QGIS software and the drift buoy position was annotated by visual interpretation and and the location of floating objects on the sea surface and Synchronously record imaging time t i ;

[0011] S5: Calculate the drift speed of sea surface floating objects and the speed of surrounding surface currents based on the position changes at adjacent moments.

[0012] The method for making a drift float comprises the following steps:

[0013] S1-1: The length-to-width ratio of the drift float is greater than 3:1;

[0014] S1-2: Select a red seawater aquaculture hard foam float as the main body of the drifting float; and pass a fixed steel rod with a diameter of 2 cm along the longitudinal axis of the float as a counterweight; fasten the steel rod to the float with screws and cable ties;

[0015] S1-3: After the assembly is completed, the drift float is tested and verified as a whole in a water tank. When the drift float floats vertically and without tilting, the production of the drift float is completed.

[0016] The step S2 is specifically as follows:

[0017] S2-1: Hang the drifting float on the drone's light-controlled airdrop device via a harness. Control the drone to carry the drifting float and fly it to hover over the tracked surface floating object 3-5 meters above the sea surface. Adjust the RGB camera to the orthogonal angle of the tracked surface floating object for observation.

[0018] S2-2: After the RGB camera determines the target location, the drone arm signal light switch command triggers the release of the airdropper, causing the drifting float to fall into the water;

[0019] S2-3: The field of view of the RGB camera on the drone is kept vertically above the drifting float, tracking and monitoring the drifting float and the target Enteromorpha, taking photos every 10 seconds or so, and automatically saving the photos to the drone's memory card.

[0020] The coordinate conversion algorithm of step S3 includes the following steps:

[0021] S3-1: Call parameters: drone altitude H, drone heading angle θ, longitude Lon0 and latitude Lat0 of the center point of the image data;

[0022] S3-2: Based on the camera focal length f and pixel size s, calculate the pixel ground resolution as:

[0023]

[0024] S3-3: Calculate the longitude and latitude based on the heading angle θ and the pixel coordinate offset (Δx, Δy), that is:

[0025]

[0026] Among them, K lat , K lm is the latitude and longitude-meter conversion factor;

[0027] S3-4: Output GeoTIFF file with geographic coordinates.

[0028] The step S4 is specifically as follows:

[0029] S4-1: Calculate the actual altitude H of the drone based on the known physical dimensions of the drifting float real , correct the original height parameter H;

[0030] S4-2: Manually mark the center point of the drift float in QGIS software as follows:

[0031] S4-3: Define an area with a radius of ≤2m with the drifting buoy as the center, and mark the center position of the floating objects on the sea surface within this area.

[0032] S4-4: Record the image capture time t corresponding to each marked point i .

[0033] The step S5 is specifically as follows:

[0034] Based on the extracted coordinates and adjacent time data of the floating objects and drifting buoys, the drifting speed of the floating objects (v hx ,v hy ),Right now:

[0035]

[0036] The surrounding surface current velocity (v px ,v py )for:

[0037]

[0038] The corresponding relationship between the draft d of the drifting float and the measured surface flow velocity depth is:

[0039] The peripheral surface current velocity (v px ,v py ) represents the current velocity at a depth d below the sea surface;

[0040] Where d is the length of the steel rod that the float is submerged in water.

[0041] A system for synchronously measuring the drift velocity of sea surface floating objects and the velocity of surrounding surface currents, comprising:

[0042] Drifting floats, used as synchronous measurements of floating objects on the ocean surface to eliminate the effects of wind drag and represent surface current velocity at a specific depth;

[0043] The drone is used to carry a drifting float, release the drifting float to a target location by airdrop, track and photograph the drifting float and floating objects on the sea surface, obtain image data containing the positions of the two, and store the image data in a memory card to be called by a coordinate conversion unit;

[0044] The coordinate conversion unit is used to call the altitude H of the UAV, the heading angle θ of the UAV, the longitude Lon0 and latitude Lat0 of the center point of the image data acquired by the RGB camera, and output a GeoTIFF file with geographic coordinates to the target extraction unit through resolution calculation and coordinate offset conversion;

[0045] The target extraction unit is used to geometrically correct the UAV image of the GeoTIFF file, transfer the corrected TIFF file to the QGIS software, and mark the drift buoy position through visual interpretation and and the location of floating objects on the sea surface and Synchronously record imaging time t i ;

[0046] The velocity calculation unit is used to calculate the output drift velocity (v) based on the position change at adjacent moments and the input coordinate sequence through time difference. hx ,v hy ) and surface velocity (v px ,v py ).

[0047] The present invention has the following beneficial effects and advantages:

[0048] 1. The present invention uses drones to monitor floating debris on the sea surface, providing high-precision, high-temporal and high-resolution data, with spatial resolution reaching centimeters and temporal resolution reaching seconds.

[0049] 2. The solution of the present invention can accurately measure the surface current velocity of the sea surface in the vicinity of floating objects on the sea surface, and clearly determine the depth of the measured surface current velocity.

[0050] 3. The monitoring method used in the solution of the present invention is non-invasive measurement and has no impact on the monitored object and flow field.

[0051] 4. The present invention achieves separate measurement of wind / current effects: The present invention eliminates the influence of wind drag by using a drifting buoy that is completely submerged in water. The measured flow velocity purely reflects the dynamics of the surface ocean current. The synchronously obtained velocity of floating objects on the sea surface includes the wind drag effect, providing direct data support for calculating the wind drag coefficient.

[0052] 5. The present invention breaks through the bottleneck of near-field synchronous monitoring: The present invention defines an observation range of ≤2m with the drifting float as the center, ensuring that the measured surface flow velocity and the position of the floating object are spatially consistent, solving the problem of excessive distance between the flow measurement point and the floating object in traditional methods.

[0053] 6. The present invention can customize the measurement of surface flow velocity at different depths by adjusting the length of the steel rod, thereby achieving refined observation of the vertical stratified flow field. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a flow chart of the method for synchronously measuring the drift velocity of sea surface floating objects and the velocity of the surrounding surface currents of the present invention;

[0055] Figure 2 This is a schematic diagram of the structure of the UAV in the implementation of the present invention;

[0056] Among them, 1 is a drone, 2 is an RGB camera, 3 is an airdrop bracket, 4 is a light-controlled airdrop, and 5 is a signal light cover;

[0057] Figure 3This is a diagram of a drifting float and a weight test scene for the drifting float in an embodiment of the present invention;

[0058] Figure 4 This is a scene diagram of a drone hanging on a drifting buoy before taking off in an embodiment of the present invention;

[0059] Figure 5 This is a scene diagram of a drone airdropper about to release a drifting float from the camera perspective in an embodiment of the present invention.

[0060] Figure 6 Schematic diagram of the drone image before and after coordinate conversion of the present invention;

[0061] Figure 7 The position renderings of the drift float and enteromorpha extracted by the present invention are as follows;

[0062] Figure 8 The schematic diagram of the principle of obtaining the surface flow velocity and the drift velocity of Enteromorpha for the present invention. DETAILED DESCRIPTION

[0063] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0064] like Figure 1 FIG. 1 is a flowchart of a method for synchronously measuring the drift velocity of a floating object on the sea surface and the velocity of a surrounding surface current according to the present invention. The method for synchronously measuring the drift velocity of a floating object on the sea surface and the velocity of a surrounding surface current according to the present invention is characterized in that it includes the following steps:

[0065] S1: Make a drifting float, which is weighted by a steel rod so that it floats vertically on the sea surface and is completely submerged in the water to eliminate the effect of wind drag and represent the surface current velocity at a specific depth;

[0066] S2: After releasing the drifting float to the target location by drone airdrop, the drone tracks and photographs the drifting float and floating objects on the sea surface, obtains and stores image data containing the positions of both;

[0067] S3: Convert the relative positions of the pixels in the image data acquired by the drone into longitude and latitude coordinates, and generate a TIFF file containing geographic coordinates;

[0068] S4: After geometric correction of the drone image of the TIFF file, the corrected TIFF file was transferred to the QGIS software and the drift buoy position was annotated through visual interpretation and and the location of floating objects on the sea surface and Synchronously record imaging time t i ;

[0069] S5: Calculate the drift speed of sea surface floating objects and the speed of surrounding surface currents based on the position changes at adjacent moments.

[0070] The method of the present invention is implemented based on a synchronous measurement system, which includes:

[0071] The drifting float is used as a synchronous measurement object for floating objects on the sea surface to eliminate the influence of wind drag and represent the surface current velocity at a specific depth. The present invention can customize the measurement of surface current velocity at different depths by adjusting the length of the steel rod of the drifting float, realizing the refined observation of the vertical stratified flow field.

[0072] Among them, the velocity of the surrounding surface current (v px ,v py ) represents the flow velocity at the depth corresponding to the length of the steel rod that floats under the water.

[0073] like Figure 2 As shown, it is a schematic diagram of the structure of the drone in the embodiment of the present invention. In the present invention, a light-controlled airdrop device 4 is fixedly installed on the drone 1 through an airdrop device bracket 3. An RGB camera 2 is installed at the center for carrying a drifting float. When the RGB camera determines the target position, the signal light is blocked by the signal light cover 5, so that the drone arm signal light switch command triggers the airdrop device to release, and after the drifting float is released to the target position by airdrop, the drifting float and sea surface floating objects are tracked and photographed, and image data containing the positions of the two are obtained and stored in the memory card for calling by the coordinate conversion unit;

[0074] The coordinate conversion unit is used to call the altitude H of the UAV, the heading angle θ of the UAV, the longitude Lon0 and latitude Lat0 of the center point of the image data acquired by the RGB camera, and output a GeoTIFF file with geographic coordinates to the target extraction unit through resolution calculation and coordinate offset conversion;

[0075] The target extraction unit is used to geometrically correct the UAV image of the GeoTIFF file, transfer the corrected TIFF file to the QGIS software, and mark the drift buoy position through visual interpretation and and the location of floating objects on the sea surface and Synchronously record imaging time t i ;

[0076] The velocity calculation unit is used to calculate the output drift velocity (v) based on the position change at adjacent moments and the input coordinate sequence through time difference. hx ,v hy ) and surface velocity (v px ,v py ).

[0077] like Figure 3As shown in FIG. 1 , a drifting float and a weight test scene diagram of the drifting float are shown in FIG. 1 . For the production and weight test of the drifting float, the present invention adopts the following method, specifically:

[0078] S1-1: The length-to-width ratio of the drift float is greater than 3:1;

[0079] S1-2: Select a red seawater aquaculture hard foam float as the main body of the drifting float; and pass a fixed steel rod with a diameter of 2 cm along the longitudinal axis of the float as a counterweight; fasten the steel rod to the float with screws and cable ties;

[0080] S1-3: After the assembly is completed, the drift float is tested and verified as a whole in a water tank. When the drift float floats vertically and without tilting, the production of the drift float is completed.

[0081] like Figures 4 and 5 As shown, the present invention performs step S2 when the schematic diagram, specifically according to Figure 4 and Figure 5 , step S2 of the present invention specifically includes the following steps:

[0082] S2-1: Hang the drifting float on the drone's light-controlled airdrop device via a harness. Control the drone to carry the drifting float and fly it to hover over the tracked surface floating object 3-5 meters above the sea surface. Adjust the RGB camera to the orthogonal angle of the tracked surface floating object for observation.

[0083] S2-2: After the RGB camera determines the target location, the drone arm signal light switch command triggers the release of the airdropper, causing the drifting float to fall into the water;

[0084] S2-3: The field of view of the RGB camera on the drone is kept vertically above the drifting float, tracking and monitoring the drifting float and the target Enteromorpha, taking photos every 10 seconds or so, and automatically saving the photos to the drone's memory card.

[0085] The present invention converts the relative positions of the pixels in the image data acquired by the drone into longitude and latitude coordinates, such as Figure 6 The figure shows a schematic diagram of the present invention before and after the coordinate conversion of the drone image, which includes the following steps:

[0086] S3-1: Call parameters: drone altitude H, drone heading angle θ, longitude Lon0 and latitude Lat0 of the center point of the image data;

[0087] S3-2: Based on the camera focal length f and pixel size s, calculate the pixel ground resolution as:

[0088]

[0089] S3-3: Calculate the longitude and latitude based on the heading angle θ and the pixel coordinate offset (Δx, Δy), that is:

[0090]

[0091] Among them, K lat , K lm is the latitude and longitude-meter conversion factor;

[0092] S3-4: Output GeoTIFF file with geographic coordinates.

[0093] like Figure 7 As shown, it is the effect diagram of the position of the drift float and the position of Enteromorpha extracted by the present invention, wherein the red diamond represents the position of the drift float and the green circle represents the position of Enteromorpha;

[0094] The specific method of extracting the drift float position and the enteromorpha position of the present invention is as follows:

[0095] S4-1: Calculate the actual altitude H of the drone based on the known physical dimensions of the drifting float real , correct the original height parameter H;

[0096] S4-2: Manually mark the center point of the drift float in QGIS software as follows:

[0097] S4-3: Define a range with a radius of ≤2m with the drifting buoy as the center, and mark the center position of the floating objects on the sea surface within this range.

[0098] S4-4: Record the image capture time t corresponding to each marked point i .

[0099] like Figure 8 As shown in the figure, the red arrow represents the surface current velocity obtained in the present invention, and the green arrow represents the drift velocity of Enteromorpha. Therefore, based on the extracted coordinates and adjacent time data of the sea surface floating objects and the drifting float, the drift velocity of the sea surface floating objects (v hx ,v hy ),Right now:

[0100]

[0101] The surrounding surface current velocity (v px ,v py )for:

[0102]

[0103] Example:

[0104] Take the large algae Enteromorpha in the Yellow Sea of ​​China as an example:

[0105] This embodiment includes a data collection scheme and a data processing scheme. Steps 1-6 represent the data collection scheme, while steps 7-9 represent the data processing scheme. Upon completion, multiple sets of data on floating objects and surrounding currents can be obtained. The hardware used for data collection includes a drone with a camera, a set of drifting buoys, a drone airdrop device, and a water tank.

[0106] Step 1: Make a drifting float. Use a marine aquaculture float (made of hard foam), steel rods, screws, cable ties, and other materials. The float should be red for visibility in the seawater and ease of drone monitoring. The float's length-to-width ratio should be greater than 3:1. Adding a counterweight will ensure stability and prevent tilting in the seawater. The drifting float used in the photo is based on a 17×5 cm red aquaculture float.

[0107] Step 2: At the monitoring site, fill a water tank with seawater, and place the weighted drifting float in the waterproof water tank to check whether the drifting float is completely submerged in the seawater and floating on the sea surface. Figure 3 It was demonstrated that the buoy can float on the surface of seawater and be completely submerged in the seawater, and its drift speed can represent the surface flow velocity of the seawater.

[0108] Step 3: Install the airdropper and test whether it can be used normally. Install the airdropper on the drone. The airdropper must be a light-controlled airdropper. The airdrop is controlled by turning on the light on the drone's arm. Such airdroppers are not limited by distance and can be used to drop items from a distance away from the pilot. After installing the airdropper, test whether it can be used normally.

[0109] Step 4: Install the drift float on the drone's airdrop. The takeoff point should be relatively open to prevent the drift float from colliding with surrounding objects during takeoff. Before takeoff, record the relative height of the drone's takeoff point from the sea surface.

[0110] Step 5: Take off. When taking off, the takeoff speed should be controlled to prevent the drift float from swinging violently and affecting the stability of the drone.

[0111] Step 6: Airdrop the float. The drone, carrying the drifting float, flies over the target floating object, 3-5 meters above the sea surface. After hovering, adjust the camera to an orthogonal angle and observe the target floating object. After determining the target location, activate the airdrop device and airdrop the float. After the float hits the water, the drone begins tracking and monitoring the drifting float and the target Enteromorpha, taking photos every 10 seconds or so, which are automatically saved to the drone's memory card.

[0112] Step 7: Pixel Coordinate Conversion. By giving the drone's altitude (H) above the sea surface, the drone's heading angle, and the center longitude and latitude of the drone image, the relative position of each pixel on the image is converted into longitude and latitude, and saved in a tiff file to complete the coordinate conversion.

[0113] Step 8: Extraction of floating objects. After the UAV image is geometrically corrected, the corrected UAV image is imported into QGIS software. The drifting float and the tracked Enteromorpha are determined by visual interpretation. The positions of the drifting float and Enteromorpha are marked. The latitudinal and longitudinal coordinates of the drifting float position are respectively calculated using and Indicates that the latitudinal and longitudinal coordinates of the Enteromorpha position are respectively and Indicates that i represents the i-th moment, and the moment is t i The distance between the tracked drifting float and the Enteromorpha does not exceed 2m, ensuring that the drifting speed of the drifting float can represent the surface flow velocity around the Enteromorpha, and saving the positions of the drifting float and the Enteromorpha as well as the image time.

[0114] Step 9: Based on the position coordinates and time data of the Enteromorpha and the drifting float extracted in the previous step, calculate the Enteromorpha drifting speed (v hx ,v hy ) and the surrounding current velocity (v px ,v py ) is calculated using the following formula:

[0115]

[0116] The final output enteromorpha drift speed (v hx ,v hy ) and the surrounding ocean current velocity (v px ,v py ).

[0117] The above embodiment takes the monitoring of Enteromorpha in the Yellow Sea as an application scenario, and fully demonstrates the implementation process from float production, drone airdrop, coordinate conversion to flow velocity calculation. Figure 3-Figure 8 The actual test shows that:

[0118] 1) Anti-interference: The weighted float (length-to-width ratio>3:1+steel rod through-design) remains vertical in a wave environment, such as Figure 3 As shown, wind field interference is effectively suppressed;

[0119] 2) Synchronicity guarantee: The drone is hovering at a height of 3-5m to shoot, such as Figures 4 and 5 As shown, combined with 10-second high-frequency image acquisition, the temporal and spatial synchronization of floating objects and buoy displacement is ensured;

[0120] 3) Accuracy and reliability: In step S4-1, the altitude of the UAV is calculated based on the physical size of the float, so that the coordinate conversion error is ≤ 0.1m (e.g. Figure 6 As shown), combined with QGIS manual annotation (as Figure 7 As shown), the position extraction accuracy reaches centimeter level;

[0121] 4) Data value: the drift speed of the final output (v hx ,v hy ) and surface velocity (v px ,v py ) constitutes a wind-current coupling parameter model (such as Figure 8 ), providing high-resolution validation data for macroalgae drift prediction models.

[0122] The present invention successfully solves the problem of synchronous monitoring of microscale flow fields around floating objects, and has universal promotion value in the fields of oil spill trajectory tracking, marine garbage transportation research, etc.

[0123] Those skilled in the art will understand that the above description is only a preferred embodiment of the present invention, and the features described in the various embodiments and / or claims of the present disclosure may be combined or coupled in various ways, even if such a combination or coupling is not explicitly described in the present disclosure. It is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

[0124] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such changes and modifications as fall within the scope of the claims and their equivalents.

Claims

1. A method for synchronously measuring the drift velocity of sea surface floating objects and the velocity of surrounding surface currents, characterized in that: The following steps are involved: S1: Make a drifting float, which is weighted by a steel rod so that it floats vertically on the sea surface and is completely submerged in the water to eliminate the effect of wind drag and represent the surface current velocity at a specific depth; S2: After releasing the drifting float to the target location by drone airdrop, the drone tracks and photographs the drifting float and floating objects on the sea surface, obtains and stores image data containing the positions of both; S3: Convert the relative positions of the pixels in the image data acquired by the drone into longitude and latitude coordinates, and generate a TIFF file containing geographic coordinates; S4: After geometric correction of the drone image of the TIFF file, the corrected TIFF file was transferred to the QGIS software and the drift buoy position was annotated through visual interpretation and and the location of floating objects on the sea surface and Synchronously record imaging time t i ; S5: Calculate the drift speed of sea surface floating objects and the speed of surrounding surface currents based on the position changes at adjacent moments.

2. The method for synchronously measuring the drift velocity of sea surface floating objects and the velocity of surrounding surface currents according to claim 1, characterized in that: The method for making a drift float comprises the following steps: S1-1: The length-to-width ratio of the drift float is greater than 3:1; S1-2: Select a red seawater aquaculture hard foam float as the main body of the drifting float; and pass a fixed steel rod with a diameter of 2 cm along the longitudinal axis of the float as a counterweight; fasten the steel rod to the float with screws and cable ties; S1-3: After the assembly is completed, the drift float is tested and verified as a whole in a water tank. When the drift float floats vertically and without tilting, the production of the drift float is completed.

3. The method for synchronously measuring the drift velocity of sea surface floating objects and the velocity of surrounding surface currents according to claim 1, characterized in that: The step S2 is specifically as follows: S2-1: Hang the drifting float on the drone's light-controlled airdrop device via a harness. Control the drone to carry the drifting float and fly it to hover over the tracked surface floating object 3-5 meters above the sea surface. Adjust the RGB camera to the orthogonal angle of the tracked surface floating object for observation. S2-2: After the RGB camera determines the target location, the drone arm signal light switch command triggers the release of the airdropper, causing the drifting float to fall into the water; S2-3: The field of view of the RGB camera on the drone is kept vertically above the drifting float, tracking and monitoring the drifting float and the target Enteromorpha, taking photos every 10 seconds or so, and automatically saving the photos to the drone's memory card.

4. The method for synchronously measuring the drift velocity of sea surface floating objects and the velocity of surrounding surface currents according to claim 1, characterized in that: The coordinate conversion algorithm of step S3 includes the following steps: S3-1: Call parameters: drone altitude H, drone heading angle θ, longitude Lon0 and latitude Lat0 of the center point of the image data; S3-2: Based on the camera focal length f and pixel size s, calculate the pixel ground resolution as: S3-3: Calculate the longitude and latitude based on the heading angle θ and the pixel coordinate offset (Δx, Δy), that is: Among them, K lat , K lm is the latitude and longitude-meter conversion factor; S3-4: Output GeoTIFF file with geographic coordinates.

5. The method for synchronously measuring the drift velocity of sea surface floating objects and the velocity of surrounding surface currents according to claim 1, characterized in that: The step S4 is specifically as follows: S4-1: Calculate the actual altitude H of the drone based on the known physical dimensions of the drifting float real , correct the original height parameter H; S4-2: Manually mark the center point of the drift float in QGIS software as follows: S4-3: Define a range with a radius of ≤2m with the drifting buoy as the center, and mark the center position of the floating objects on the sea surface within this range. S4-4: Record the image capture time t corresponding to each marked point i .

6. The method for synchronously measuring the drift velocity of sea surface floating objects and the velocity of surrounding surface currents according to claim 1, characterized in that: The step S5 is specifically as follows: Based on the extracted coordinates and adjacent time data of the floating objects and drifting buoys, the drifting speed of the floating objects (v hx ,v hy ),Right now: The surrounding surface current velocity (v px ,v py )for:

7. The method for synchronously measuring the drift velocity of sea surface floating objects and the velocity of surrounding surface currents according to claim 6, characterized in that: The corresponding relationship between the draft d of the drifting float and the measured surface flow velocity depth is: The peripheral surface current velocity (v px ,v py ) represents the current velocity at a depth d below the sea surface; Where d is the length of the steel rod that the float is submerged in water.

8. A system for realizing the method of synchronously measuring the drift velocity of sea surface floating objects and the velocity of surrounding surface currents according to any one of claims 1 to 7, characterized in that: include: Drifting floats, used as synchronous measurements of floating objects on the ocean surface to eliminate the effects of wind drag and represent surface current velocity at a specific depth; The drone is used to carry a drifting float, release the drifting float to a target location by airdrop, track and photograph the drifting float and floating objects on the sea surface, obtain image data containing the positions of the two, and store the image data in a memory card to be called by a coordinate conversion unit; The coordinate conversion unit is used to call the altitude H of the UAV, the heading angle θ of the UAV, the longitude Lon0 and latitude Lat0 of the center point of the image data acquired by the RGB camera, and output a GeoTIFF file with geographic coordinates to the target extraction unit through resolution calculation and coordinate offset conversion; The target extraction unit is used to geometrically correct the UAV image of the GeoTIFF file, transfer the corrected TIFF file to the QGIS software, and mark the drift buoy position through visual interpretation and and the location of floating objects on the sea surface and Synchronously record imaging time t i ; The velocity calculation unit is used to calculate the output drift velocity (v) based on the position change at adjacent moments and the input coordinate sequence through time difference. hx ,v hy ) and surface velocity (v px ,v py ).

Images