Prediction method for predicted influence time of green tide of marine ranching

Abstract

The invention discloses a marine ranching green tide prediction influence time prediction method, which comprises the following steps of performing radiometric calibration and atmospheric correction on remote sensing image data of a sea area where a marine ranching is located to obtain a water body remote sensing reflectivity image of a research sea area; a DVI algorithm is adopted to obtain green tide space distribution, green tide area is counted, and a green tide envelope line is obtained; calculating the distance from the marine ranch to each point of the near-shore side edge line, extracting the shortest distance, and calculating the direction theta of the position of the marine ranch at the position of the shortest distance; calculating a green tide drift speed V and a drift direction alpha; and predicting the time for the green tide to reach the marine ranching at the shortest distance position through the ratio of the shortest distance to the drift speed in the direction theta, wherein the time is the predicted time for the green tide to influence the marine ranching. The method disclosed by the invention is a simple and effective method for predicting the predicted influence time of the green tide of the marine ranch, and can accurately predict the time when the front end of the enteromorpha green tide main body intrudes into the marine ranch.

Description

Technical Field

[0001] The invention relates to the field of ocean monitoring, and in particular to a method for predicting the expected impact time of green tide on marine ranches. Background Art

[0002] In recent years, large algae have proliferated in the ocean, and their impact has gradually expanded. For example, the common green tide is an ecological disaster caused by the explosive growth and aggregation of opportunistic large algae in seawater under certain environmental conditions. The outbreak of green tides has a serious impact on the economy and ecological environment of coastal areas. The interception, salvage and beach cleaning of green tides at sea require a lot of manpower and material resources, which brings great challenges to the relevant departments in formulating prevention and control strategies and resource allocation plans.

[0003] The ecological and economic losses caused by frequent green tide disasters to marine ranches are becoming increasingly prominent, and have seriously affected the rapid and healthy development of marine ranches. During the outbreak of green tides, the normal nutrient balance of the water body is broken, which will lead to deterioration of water quality and decline in the quality of bottom sediments, affecting the health and stability of the entire ecosystem. In addition, the large-scale accumulation of green tides on the water surface not only directly affects the photosynthesis of underwater algae and reduces their growth rate, but also affects the dependence of farmed organisms such as sea cucumbers and abalone on light, reducing their range of activities and feeding opportunities, and ultimately leading to growth stunting or even death. Green tides consume dissolved oxygen in the water body when they breathe at night, especially during their large-scale reproduction and the beginning of corruption and decomposition, which will consume a large amount of oxygen, causing hypoxia in the water body and causing farmed organisms to suffocate and die due to hypoxia. During the main extinction stage of the green tide, large areas of green tides landed on the shore and accumulated, which not only affected the coastal landscape, but also the harmful substances released during its decomposition and decay directly changed the physical and chemical environment of the water body, leading to the deterioration of the ecological environment and the death of farmed organisms.

[0004] However, the current disaster monitoring of green tides in marine ranches mostly comes from disaster warnings issued by relevant marine departments. The focus is on the spatial distribution and coverage of green tides. It does not involve when the green tide can affect a specific marine ranch, which is not conducive to the formulation of marine ranch green tide prevention and control strategies. Research on green tides also focuses on remote sensing monitoring of green tides, green tide driving mechanisms, green tide drift speeds, and early prevention and control of green tides. Research on the expected impact time of green tides in marine ranches is still blank. Improving the marine ranch green tide disaster warning system and improving the marine disaster prevention capabilities in the daily operation of the ranch are important prerequisites for ensuring the high-quality and healthy development of marine ranches, and are also an inevitable requirement for the construction and management of large-scale modern marine ranches. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for predicting the expected impact time of the green tide on the marine ranch, so as to achieve the purpose of more accurately predicting the time when the front end of the green tide body invades the marine ranch.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for predicting the expected impact time of green tide in marine ranches, comprising the following steps:

[0008] Step 1: After the remote sensing image data of the sea area where the marine ranch is located is calibrated by radiation and corrected by atmosphere, a remote sensing reflectivity image of the water body in the research sea area is obtained;

[0009] Step 2, using the DVI algorithm to extract green tide information by combining dynamic threshold with visual interpretation of false color images, and obtaining the spatial distribution of green tide; and counting the number of pixels of each green tide spot on the remote sensing image, and counting the green tide area;

[0010] Step 3, merging the green tide surface elements that meet the minimum area requirement within the specified distance into a new surface element to obtain the green tide envelope;

[0011] Step 4, according to the position of the coastline, extract the nearshore edge line of the green tide based on the green tide envelope line; and divide the nearshore edge line into segments, extract the midpoints of the segments, and convert the nearshore edge line into points;

[0012] Step 5: Based on the principle of nearest neighbor analysis, calculate the distance from the marine ranch to each point on the nearshore edge line, extract the shortest distance, and record the location information of the shortest distance and the shortest distance L;

[0013] Step 6, combining the location information of the target marine ranch and the location information of the shortest distance of the nearshore edge line of the green tide, calculate the direction θ of the marine ranch location at the shortest distance position;

[0014] Step 7, based on the spatial distribution of the green tide obtained by remote sensing image monitoring at two different times, calculate the green tide distribution center, and record the position information of the green tide distribution center at two different times; calculate the green tide drift speed V and drift direction α through the change of the green tide distribution center combined with the satellite spatial resolution;

[0015] Step 8, calculate the northward drift speed V1 and westward drift speed V2 of the green tide according to the green tide drift speed V and drift direction α; calculate the drift speed V of the green tide in direction θ θ The time when the green tide reaches the marine ranch at the shortest distance is predicted by the ratio of the shortest distance to the drift speed in the direction θ, which is the time when the green tide is expected to affect the marine ranch.

[0016] In the above scheme, in step 2, the DVI algorithm formula is as follows:

[0017] DVI=R NIR -R Red

[0018] Among them, DVI represents the difference vegetation index value of each pixel on the remote sensing image, R NIR and R Red They represent the reflectivity of each pixel in the remote sensing image in the red and near-infrared bands respectively.

[0019] In the above scheme, in step 2, the green tide area calculation formula is as follows:

[0020] Area=PS×N

[0021] Among them, Area represents the green tide area, the unit is km 2 ; PS represents the size of the ground area corresponding to a pixel in the remote sensing image, in km 2 ; N represents the number of green tide pixels detected.

[0022] In the above scheme, in step 5, the principle of neighbor analysis is to determine the distance between each element in the input element and the nearest element in the neighboring element within the search radius, the input element is the spatial position of the marine ranch, and the neighboring element is each point on the nearshore edge line. The search radius is adjusted based on the daily green tide spatial distribution and the position of the marine ranch.

[0023] In the above scheme, in step 5, the formula for calculating the distance from the marine ranch to each point on the nearshore edge line is as follows:

[0024]

[0025] Among them, i is a point target, (X i ,Y i ) is the position of each point on the nearshore edge line, (X H ,Y H ) is the location of the marine ranch, and L is the distance from each point on the nearshore edge line to the location of the marine ranch.

[0026] In the above scheme, in step 6, the calculation formula for the direction θ of the ocean ranch position at the shortest distance position is as follows:

[0027]

[0028] Among them, (X H ,Y H ) is the location of the ocean ranch, (X D ,Y D ) is the position with the shortest distance.

[0029] In the above scheme, in step 7, the calculation formula of the green tide distribution center is as follows:

[0030]

[0031]

[0032] Where i is a discrete target object, i.e., the green tide patch extracted from remote sensing images; W i is the weight of the target object, and the weight is set according to the area of ​​the green tide patch. (X i ,Y i ) is the coordinate of the green tide patch, (X n ,Y n ) is the location of the green tide distribution center.

[0033] In the above scheme, in step 7, the calculation formulas for the green tide drift speed V and drift direction α are as follows:

[0034]

[0035]

[0036] Among them, (X1, Y1) and (X2, Y2) are the distribution center positions of the green tide at two different times, T1 and T2 are two different times of collection, and PS represents the size of the ground area corresponding to a pixel of the satellite image, in km 2 .

[0037] In the above scheme, in step 8, the calculation formulas for the northward drift speed V1 and the westward drift speed V2 of the green tide are as follows:

[0038] V1=V×sinα

[0039] V2=V×cosα

[0040] The drift velocity V of the green tide in direction θ θ The calculation formula is as follows:

[0041] V θ =V1cosθ+V2sinθ.

[0042] In the above scheme, in step 8, the time T for the shortest distance of the green tide to reach the ocean ranch is calculated as follows:

[0043] T=L / V θ .

[0044] Through the above technical solution, the method for predicting the expected impact time of green tide in marine ranches provided by the present invention has the following characteristics:

[0045] Beneficial effects:

[0046] Based on the spatial distribution, drift speed and drift direction of the green tide, the present invention combines the location information of the marine ranch to establish a method for predicting the expected impact time of the green tide on the marine ranch. This method can more accurately predict the time when the front end of the main body of the green tide invades the marine ranch, filling the technical gap in the industry, providing scientific guidance for the marine ranch to independently respond to the green tide disaster, and providing technical support for the fishery authorities to carry out refined disaster reduction. The expected impact time of the green tide on the four marine ranches in 2023 predicted by this method is relatively consistent with the actual impact time, with a difference of no more than 3 days, filling the gap in the industry. The idea of ​​this method can be extended to the time estimation of similar floating large algae disasters affecting offshore fisheries, aquaculture, and marine ranches. In practical applications, due to the influence of factors such as the atmosphere and optical differences in the sea surface environment, it is necessary to consider the remote sensing monitoring of floating large algae and the calculation of drift speed and drift direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0048] Figure 1 The present invention is a flowchart of a method for predicting the expected impact time of green tide on marine ranches disclosed in an embodiment of the present invention.

[0049] Figure 2 The process of obtaining the green tide envelope;

[0050] Figure 3 is the result of patch merging;

[0051] Figure 4 This is a diagram showing the shortest distance. DETAILED DESCRIPTION

[0052] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0053] The present invention provides a method for predicting the expected impact time of green tide in marine ranches, and the specific embodiments are as follows:

[0054] A method for predicting the expected impact time of green tide in marine ranches, comprising the following steps:

[0055] Step 1: After radiometric calibration and atmospheric correction, the remote sensing image data of the sea area where the marine ranch is located is subjected to water remote sensing reflectivity image of the research sea area.

[0056] Step 2: Use the DVI algorithm to extract green tide information by combining dynamic threshold with visual interpretation of false color images to obtain the spatial distribution of green tides; and count the number of pixels of each green tide spot on the remote sensing image to calculate the green tide area.

[0057] Specifically, the DVI algorithm formula is as follows:

[0058] DVI=R NIR -R Red

[0059] Among them, DVI represents the difference vegetation index value of each pixel on the remote sensing image, R NIR and R Red They represent the reflectivity of each pixel in the remote sensing image in the red and near-infrared bands respectively.

[0060] The calculation formula of green tide area is as follows:

[0061] Area=PS×N

[0062] Among them, Area represents the green tide area, the unit is km 2 ; PS represents the size of the ground area corresponding to a pixel in the remote sensing image, in km 2 ; N represents the number of green tide pixels detected.

[0063] Step 3: Considering that the green tide is dispersed at sea, the green tide surface elements that meet the minimum area requirement within the specified distance are merged into new surface elements to obtain the green tide envelope.

[0064] like Figure 2 As shown, the specific process is:

[0065] According to the spatial distribution of green tide and the area of ​​each green tide spot obtained by remote sensing image monitoring, the distance and minimum area are specified first, and then it is determined whether each adjacent spot falls within the specified distance. If not, the original element is retained. If so, it is calculated whether the spot area is less than or equal to the minimum area. If not, the original element is retained. If the spot area is less than or equal to the minimum area, the spots are merged to obtain a new element. The merging result is as follows: Figure 3 shown.

[0066] Step 4: According to the position of the coastline, the nearshore edge line of the green tide is extracted based on the green tide envelope line; the nearshore edge line is segmented at intervals of 1 m, the midpoints of the line segments are extracted, and the nearshore edge line is converted into points.

[0067] Step 5: Based on the principle of nearest neighbor analysis, calculate the distance from the marine ranch to each point on the nearshore edge line, extract the shortest distance, and record the location information of the shortest distance and the shortest distance L.

[0068] Specifically, Figure 4As shown in the figure, the principle of neighbor analysis is to determine the distance between each element in the input element and the nearest element in the neighboring element within the search radius. The input element is the spatial location of the marine ranch, and the neighboring elements are the points on the nearshore edge line. The search radius is adjusted based on the daily green tide spatial distribution and the location of the marine ranch.

[0069] The formula for calculating the distance from the marine ranch to each point on the nearshore edge line is as follows:

[0070]

[0071] Among them, i is a point target, (X i ,Y i ) is the position of each point on the nearshore edge line, (X H ,Y H ) is the location of the marine ranch, and L is the distance from each point on the nearshore edge line to the location of the marine ranch.

[0072] Step 6, combining the location information of the target marine ranch and the location information of the shortest distance to the nearshore edge of the green tide, calculate the direction θ of the marine ranch location at the shortest distance position.

[0073] Specifically, the calculation formula for the direction θ of the ocean ranch position at the shortest distance position is as follows:

[0074]

[0075] Among them, (X H ,Y H ) is the location of the ocean ranch, (X D ,Y D ) is the position with the shortest distance.

[0076] Step 7, based on the spatial distribution of the green tide obtained by remote sensing image monitoring at two different times, calculate the green tide distribution center, and record the position information of the green tide distribution center at two different times; calculate the green tide drift speed V and drift direction α through the changes in the green tide distribution center combined with the satellite spatial resolution.

[0077] Specifically, the calculation formula of the green tide distribution center is as follows:

[0078]

[0079]

[0080] Where i is a discrete target object, i.e., the green tide patch extracted from remote sensing images; W i is the weight of the target object, and the weight is set according to the area of ​​the green tide patch. (X i ,Y i ) is the coordinate of the green tide patch, (Xn ,Y n ) is the location of the green tide distribution center.

[0081] The calculation formulas for the green tide drift velocity V and drift direction α are as follows:

[0082]

[0083]

[0084] Among them, (X1, Y1) and (X2, Y2) are the distribution center positions of the green tide at two different times, T1 and T2 are two different times of collection, and PS represents the size of the ground area corresponding to a pixel of the satellite image, in km 2 .

[0085] Step 8, calculate the northward drift speed V1 and westward drift speed V2 of the green tide according to the green tide drift speed V and drift direction α; calculate the drift speed V of the green tide in direction θ θ The time when the green tide reaches the marine ranch at the shortest distance is predicted by the ratio of the shortest distance to the drift speed in the direction θ, which is the time when the green tide is expected to affect the marine ranch.

[0086] Specifically, the calculation formulas for the northward drift velocity V1 and the westward drift velocity V2 of the green tide are as follows:

[0087] V1=V×sinα

[0088] V2=V×cosα

[0089] The drift velocity V of the green tide in direction θ θ The calculation formula is as follows:

[0090] V θ =V1cosθ+V2sinθ.

[0091] The calculation formula for the time T of the shortest distance from the green tide to the marine ranch is as follows:

[0092] T=L / V θ .

[0093] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for predicting the expected impact time of green tide in marine ranches, characterized in that: The steps include: Step 1: After the remote sensing image data of the sea area where the marine ranch is located is calibrated by radiation and corrected by atmosphere, a remote sensing reflectivity image of the water body in the research sea area is obtained; Step 2, using the DVI algorithm to extract green tide information by combining dynamic threshold with visual interpretation of false color images, and obtaining the spatial distribution of green tide; and counting the number of pixels of each green tide spot on the remote sensing image, and counting the green tide area; Step 3, merging the green tide surface elements that meet the minimum area requirement within the specified distance into a new surface element to obtain the green tide envelope; Step 4, according to the position of the coastline, extract the nearshore edge line of the green tide based on the green tide envelope line; and divide the nearshore edge line into segments, extract the midpoints of the segments, and convert the nearshore edge line into points; Step 5: Based on the principle of nearest neighbor analysis, calculate the distance from the marine ranch to each point on the nearshore edge line, extract the shortest distance, and record the location information of the shortest distance and the shortest distance L; Step 6, combining the location information of the target marine ranch and the location information of the shortest distance of the nearshore edge line of the green tide, calculate the direction θ of the marine ranch location at the shortest distance position; Step 7, based on the spatial distribution of the green tide obtained by remote sensing image monitoring at two different times, calculate the green tide distribution center, and record the position information of the green tide distribution center at two different times; calculate the green tide drift speed V and drift direction α through the change of the green tide distribution center combined with the satellite spatial resolution; Step 8, calculate the northward drift speed V1 and westward drift speed V2 of the green tide according to the green tide drift speed V and drift direction α; calculate the drift speed V of the green tide in direction θ θ The time when the green tide reaches the marine ranch at the shortest distance is predicted by the ratio of the shortest distance to the drift speed in the direction θ, which is the time when the green tide is expected to affect the marine ranch.

2. The method for predicting the expected impact time of green tide in marine ranches according to claim 1 is characterized in that: In step 2, the DVI algorithm formula is as follows: DVI=R NIR -R Red Among them, DVI represents the difference vegetation index value of each pixel on the remote sensing image, R NIR and R Red They represent the reflectivity of each pixel in the remote sensing image in the red and near-infrared bands respectively.

3. The method for predicting the expected impact time of green tide in marine ranches according to claim 1 is characterized in that: In step 2, the green tide area calculation formula is as follows: Area=PS×N Among them, Area represents the green tide area, the unit is km 2 ; PS represents the size of the ground area corresponding to a pixel in the remote sensing image, in km 2 ; N represents the number of green tide pixels detected.

4. The method for predicting the expected impact time of green tide in marine ranches according to claim 1 is characterized in that: In step 5, the principle of nearest neighbor analysis is to determine the distance between each element in the input element and the nearest element in the adjacent element within the search radius. The input element is the spatial location of the marine ranch, and the adjacent elements are the points on the nearshore edge line. The search radius is adjusted based on the daily green tide spatial distribution and the location of the marine ranch.

5. The method for predicting the expected impact time of green tide in marine ranches according to claim 1 is characterized in that: In step 5, the distance formula from the marine ranch to each point on the nearshore edge line is calculated as follows: Among them, i is a point target, (X i ,Y i ) is the position of each point on the nearshore edge line, (X H ,Y H ) is the location of the marine ranch, and L is the distance from each point on the nearshore edge line to the location of the marine ranch.

6. The method for predicting the expected impact time of green tide in marine ranches according to claim 1 is characterized in that: In step 6, the calculation formula for the direction θ of the ocean ranch position at the shortest distance position is as follows: Among them, (X H ,Y H ) is the location of the ocean ranch, (X D ,Y D ) is the position with the shortest distance.

7. The method for predicting the expected impact time of green tide in marine ranches according to claim 1 is characterized in that: In step 7, the calculation formula of the green tide distribution center is as follows: Where i is a discrete target object, i.e., the green tide patch extracted from remote sensing images; W i is the weight of the target object, and the weight is set according to the area of ​​the green tide patch. (X i ,Y i ) is the coordinate of the green tide patch, (X n ,Y n ) is the location of the green tide distribution center.

8. The method for predicting the expected impact time of green tide in marine ranches according to claim 1 is characterized in that: In step 7, the calculation formulas for the green tide drift velocity V and drift direction α are as follows: Among them, (X1, Y1) and (X2, Y2) are the distribution center positions of the green tide at two different times, T1 and T2 are two different times of collection, and PS represents the size of the ground area corresponding to a pixel of the satellite image, in km 2 .

9. The method for predicting the expected impact time of green tide in marine ranches according to claim 1 is characterized in that: In step 8, the calculation formulas for the northward drift velocity V1 and the westward drift velocity V2 of the green tide are as follows: V1=V×sinα V2=V×cosα The drift velocity V of the green tide in direction θ θ The calculation formula is as follows: V θ =V1cosθ+V2sinθ。 10. The method for predicting the expected impact time of green tide in marine ranches according to claim 1, characterized in that: In step 8, the time T for the shortest distance of the green tide to reach the ocean ranch is calculated as follows: T=L / V θ 。

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