A method and related equipment for monitoring the spatiotemporal changes of island and reef coastlines

Abstract

This invention discloses a method and related equipment for monitoring the spatiotemporal changes of island and reef coastlines. By using circumferential sampling to detect radial width changes, this invention can accurately identify the locations of drastically changing sections along the island and reef coastline, effectively avoiding the problem of missing key change areas in traditional equidistant sampling. Based on width change data conditions, a target section group is constructed, ensuring that the section layout matches the actual dynamic characteristics of the coastline, significantly improving the monitoring accuracy of spatial changes in erosion and sedimentation. Furthermore, by combining key time points from the first and second time points for binarized overlay analysis, it can effectively capture key nodes of coastline changes and their net change rates. This overcomes the shortcomings of existing methods that rely solely on sedimentation and erosion rates, lacking spatial details and annual change information. This provides more scientific and reliable data support for predicting island and reef coastline evolution trends and making ecological protection decisions, and can be widely applied in the field of image processing technology.

Description

Technical Field

[0001] This invention relates to the field of image processing technology, and in particular to a method and related equipment for monitoring the spatiotemporal changes of island and reef coastlines. Background Technology

[0002] Islands and reefs are among the most biodiverse and productive areas in the ocean. Their coastlines are extremely sensitive to global environmental pressures such as sea-level rise, extreme weather events, and changes in sea temperature. Remote sensing technology can quantify and visualize the dynamic changes of islands and reefs, thereby revealing the "short-term fluctuations" and "long-term trends" of these changes. These patterns provide the scientific basis for effectively predicting future coastline evolution and developing effective protection and response strategies. Traditional methods for monitoring spatiotemporal changes in islands and reefs generally include the following steps: First, collecting and preprocessing long-term remote sensing images to construct an island and reef boundary extraction process based on the OTSU threshold segmentation algorithm using the NDWI water index; second, quantifying the coastline using methods such as the trend of coastline area and length changes, static movement distance, endpoint change rate, and linear regression rate; and finally, obtaining the spatiotemporal dynamic changes (deposition-erosion) of the coastline. This method allows for the effective extraction of island and reef coastlines from long-term images and the monitoring of their spatiotemporal dynamic changes.

[0003] While area and baseline methods can be used to monitor the spatiotemporal changes of island and reef coastlines, they have some drawbacks in terms of the generation of cross-sections and the spatial variations in erosion and sedimentation. First, existing technologies cannot accurately identify all significantly changing sections of the island or reef coastline; instead, they generate cross-sections at fixed intervals starting from the initial position of the coastline, easily overlooking areas of change within the coastline. Second, existing technologies primarily express erosion and sedimentation changes based on sedimentation and erosion rates, which is insufficient for capturing the spatial variations of island and reef coastlines and the spatial variations of significant annual changes. Summary of the Invention

[0004] The main objective of this invention is to provide a method, device, electronic device, storage medium, and program product for monitoring the spatiotemporal changes of island and reef coastlines, aiming to solve at least one problem in the prior art.

[0005] To achieve the above objectives, one aspect of this invention proposes a method for monitoring the spatiotemporal changes of island and reef coastlines, the method comprising: Long-term multi-source remote sensing images of the target islands and reefs are acquired, and multi-temporal remote sensing images are obtained through preprocessing operations. Based on multi-temporal remote sensing images, land and water are separated using the normalized water index to obtain long-term island and reef coastlines; the long-term island and reef coastlines include the island and reef coastlines of each temporal phase. Based on the changes in island and reef values ​​according to long-term island and reef coastline statistics, a numerical trend map and a first time point are obtained; among them, the island and reef values ​​include the island and reef perimeter and island and reef area, and the first time point represents the time point when the change in island and reef values ​​is greater than a first threshold. Based on long-term island and reef coastlines, radial width change is detected through circumferential sampling to obtain width change data; the width change data includes the starting angle, ending angle, intermediate angle, degree of change, and type of change of the target width change interval; Conditional determination is performed on the width variation data, and a target cross-section group is constructed in combination with the initial island and reef coastline; wherein, the initial island and reef coastline represents the island and reef coastline in the initial time phase, and the target cross-section group includes several cross-sections perpendicular to the initial island and reef coastline. Based on the intersection of the target cross section group and the long-term island and reef coastline, the change trends of all cross sections are transformed, and then the second time point is selected; among them, the second time point represents the time point where the average rate of change of the change trend is greater than the second threshold. Based on the island and reef coastlines corresponding to the first and second time points, the net rate of change at the target time point is obtained through binarized overlay analysis.

[0006] In some embodiments, based on multi-temporal remote sensing imagery, land-water separation is performed using a normalized water index to obtain long-term island and reef coastlines, including the following steps: The initial phase is taken as the first phase; Atmospheric top reflectance is extracted from the first time-corresponding remote sensing image in multi-temporal remote sensing images; wherein, atmospheric top reflectance includes the first atmospheric top reflectance in the green band and the second atmospheric top reflectance in the near-infrared band. Based on the reflectivity of the top of the atmosphere, the water index image of the first time phase was obtained by processing with the normalized water index. Based on water index images, the water and land are segmented using the Otsu threshold segmentation algorithm to obtain the island and reef coastline in the first time phase. The next time phase after the first time phase is taken as the first time phase. The process of extracting the atmospheric top reflectance from the remote sensing image corresponding to the first time phase in the multi-time phase remote sensing image is repeated until all time phases are traversed, and the long-time series island and reef coastline is obtained.

[0007] In some embodiments, based on the changes in island and reef values ​​statistically analyzed over a long time series, a numerical trend map and a first time point are obtained, including the following steps: Based on the quantization of the island and reef coastline in each time phase of the long-term island and reef coastline, the island and reef perimeter and island and reef area corresponding to each time phase are obtained. The initial phase is taken as the second phase; The next phase after the second phase is taken as the third phase; The perimeter change value of the third time phase is obtained by quantifying the perimeter of the islands and reefs corresponding to the second time phase, and the area change value of the third time phase is obtained by quantifying the area of ​​the islands and reefs corresponding to the second time phase. If the change in perimeter is greater than the first perimeter threshold and / or the change in area is greater than the first area threshold, the time point corresponding to the third time point will be taken as the first candidate time point. Treat the third phase as the second phase, then return to execute the step of treating the next phase of the second phase as the third phase, until all phases have been traversed; A numerical trend chart is obtained by summarizing and converting the corresponding perimeter and area change values ​​for all times. The first time point is obtained by summing up all the first candidate time points.

[0008] In some embodiments, based on long-term island and reef coastlines, radial width change detection is performed through circumferential sampling to obtain width change data, including the following steps: Initialize the first angle; The radial distance extrema of all time phases are extracted from the long-time island and reef coastline along the direction of the first angle; where the radial distance extrema include the minimum radial distance and the maximum radial distance; The radial width variation value of the first angle is determined based on the difference between the maximum radial distance and the minimum radial distance; The first angle is incremented based on a preset angle step size. Then, the process returns to the step of extracting the radial distance extreme values ​​of all time phases from the long-term island and reef coastline along the direction of the first angle until a full circumferential sampling is performed to obtain the radial width change values ​​of all sampled angles. Initialize the second angle; The two adjacent angles that are spaced apart from the second angle by a preset angle step are successively used as the third angle and the fourth angle; The gradient of the second angle is obtained by performing first derivative and absolute value calculations based on the radial width change values ​​of the third angle, the radial width change values ​​of the fourth angle, and the preset angle step size. The second derivative is calculated based on the radial width change values ​​of the second angle, the third angle, the fourth angle, and the preset angle step size to obtain the curvature of the second angle. Based on a preset angle step size, the second angle is incremented, and then the process is repeated to take the two adjacent angles that are separated from the second angle by a preset angle step size as the third and fourth angles in turn, until a full circumferential sampling is completed, and the gradient and curvature of all sampled angles are obtained. The gradient mean and gradient standard deviation are obtained by calculating the gradient changes of all sampling angles, and the gradient threshold is obtained by converting the gradient mean and gradient standard deviation. The target width variation range is determined based on the continuous angular range where the gradient change is greater than the gradient threshold; Based on the angle range included in each target width variation interval, determine the starting angle, ending angle, and middle angle of the corresponding target width variation interval; The degree of change in the corresponding target width variation interval is determined based on the maximum change gradient of all sampling angles in each target width variation interval. Based on the curvature of the change in the midpoint angle of each target width variation range, the change type of the corresponding target width variation range is determined by mapping positive and negative cases.

[0009] In some embodiments, conditional determination is performed on the width variation data, and a target cross-section group is constructed in conjunction with the initial island / reef coastline, including the following steps: The average perimeter of the islands and reefs is obtained by averaging the perimeters of the islands and reefs across all time periods. The angular difference and interval angle are determined by mapping the numerical range of the average perimeter of the islands and reefs. Extract the first intersection point along the mid-angle direction from the initial island / reef coastline for each target width variation interval; Based on each first intersection point, a perpendicular line is constructed in the direction perpendicular to the initial island / reef coastline to form a cross section, and then the first cross section group is obtained by summing them up. Based on the difference between the ending angle and the starting angle corresponding to the target width variation interval, determine the angle difference for each target width variation interval; If there is an angle difference greater than the angle difference, extract the second intersection point of the target width variation range along the direction of the starting angle and the ending angle from the initial island / reef coastline; Based on each second intersection point, a perpendicular line is constructed in the direction perpendicular to the initial island / reef coastline to form a cross section, and then the second cross section group is obtained by summing them up. If the second cross-section group is not empty, the second cross-section group is used as a candidate cross-section group; otherwise, the second cross-section group is used as a candidate cross-section group. In the area between adjacent cross sections in the candidate cross section group, the initial island and reef coastline is located in the region between adjacent cross sections. Based on the interval angle, a vertical line perpendicular to the initial island and reef coastline is constructed as a cross section, and then the third cross section group is obtained by summarizing the results. The target cross-section group is obtained by summarizing the candidate cross-section group and the third cross-section group.

[0010] In some embodiments, based on the intersections of the target cross-section group and the long-term island / reef coastline, the changing trends of all cross-sections are transformed, and then a second time point is selected, including the following steps: Initialize the number of valid years, and take the next time phase after the initial time phase as the fourth time phase; The first section of the target section group is used as the quantization section; The intersection of the quantized section with the island and reef coastline of the initial time phase is taken as the third intersection point, and the intersection of the quantized section with the island and reef coastlines of all time phases from the initial time phase to the fourth time phase is taken as the fourth intersection point. The cumulative difference between each fourth intersection point and the third intersection point is used as the numerator, and the number of valid years minus one is used as the denominator to calculate the average rate of change of the quantified section in the fourth time phase. If the average rate of change is greater than the second threshold, the fourth time phase will be used as the second candidate time point; Take the next section of the target section group as the quantization section, return to execute the step of taking the intersection of the quantization section and the island reef coastline of the initial time phase as the third intersection point, until all sections of the target section group have been traversed. Increment the number of valid years, take the next time phase of the fourth time phase as the fourth time phase, return to execute the step of taking the first section of the target section group as the quantization section, until all time phases have been traversed; The trend of change is obtained by summarizing the average rate of change of the target cross section group in all time phases, and the second time point is obtained by summarizing all second candidate time points.

[0011] In some embodiments, based on the island / reef coastline corresponding to the first and second time points, the net rate of change at the target time point is obtained through binarized overlay analysis, including the following steps: The target time point is determined by the union of the first time point and the second time point; The phase corresponding to the first time point in the target time point is taken as the fifth time phase; The phase preceding the fifth phase is taken as the sixth phase; The coastline inside and outside the islands and reefs in the fifth time phase is binarized to obtain the first island and reef coastline surface. The coastline inside and outside the islands and reefs in the sixth time phase is binarized to obtain the second island and reef coastline surface. The siltation zone and erosion zone are determined by subtracting the coastline of the second island from the coastline of the first island; and then the positive or negative values ​​of each region are used to determine the siltation zone and erosion zone. The net rate of change in the fifth time phase is obtained by subtracting the area of ​​the erosion zone from the area of ​​the siltation zone, and using the area of ​​the island and reef coastline in the fifth time phase as the denominator. Take the phase corresponding to the next time point in the target time point as the fifth phase, return to execute the step of taking the previous phase of the fifth phase as the sixth phase, until all time points of the target time point have been traversed.

[0012] To achieve the above objectives, another aspect of the present invention provides a device for monitoring the spatiotemporal changes of island and reef coastlines, the device comprising: The first module is used to acquire long-term multi-source remote sensing images of the target islands and reefs, and to obtain multi-temporal remote sensing images through preprocessing operations. The second module is used to perform land-water separation based on multi-temporal remote sensing images and normalized water index to obtain long-term island and reef coastlines; the long-term island and reef coastlines include the island and reef coastlines of each temporal phase. The third module is used to statistically analyze the changes in island and reef values ​​based on long-term island and reef coastlines, and to obtain a numerical trend map and a first time point. The island and reef values ​​include the island and reef perimeter and area, and the first time point represents the time point when the change in island and reef values ​​is greater than a first threshold. The fourth module is used to detect radial width changes based on long-term island and reef coastlines through circumferential sampling, and obtain width change data. The width change data includes the starting angle, ending angle, intermediate angle, degree of change, and type of change of the target width change interval. The fifth module is used to determine the conditions of the width change data and construct the target cross-section group in combination with the initial island and reef coastline; wherein, the initial island and reef coastline represents the island and reef coastline in the initial time phase, and the target cross-section group includes several cross-sections perpendicular to the initial island and reef coastline. The sixth module is used to transform the change trends of all cross sections based on the intersection of the cross sections of the target cross section group and the long-term island and reef coastline, and then filter to obtain the second time point; wherein, the second time point represents the time point where the average rate of change of the change trend is greater than the second threshold. The seventh module is used to obtain the net rate of change at the target time point based on the island and reef coastlines corresponding to the first and second time points through binarized overlay analysis.

[0013] To achieve the above objectives, another aspect of the present invention provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the aforementioned method.

[0014] To achieve the above objectives, another aspect of the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the aforementioned method.

[0015] To achieve the above objectives, another aspect of the present invention provides a computer program product, including a computer program that, when executed by a processor, implements the aforementioned method.

[0016] The embodiments of the present invention include at least the following beneficial effects: The present invention provides a method, device, electronic device, storage medium, and program product for monitoring the spatiotemporal changes of island and reef coastlines. This scheme acquires long-term multi-source remote sensing images of target islands and reefs, and processes them through preprocessing to obtain multi-temporal remote sensing images; based on the multi-temporal remote sensing images, land-water separation is performed using a normalized water index to obtain long-term island and reef coastlines; wherein, the long-term island and reef coastlines include island and reef coastlines at various temporal phases; based on the long-term island and reef coastlines, changes in island and reef values ​​are statistically analyzed to obtain a numerical trend map and a first time point; wherein, island and reef values ​​include island and reef perimeter and island and reef area, and the first time point characterizes the time point when the change in island and reef values ​​exceeds a first threshold; based on the long-term island and reef coastlines, radial width variation is measured through circumferential sampling. The width change data is obtained through detection. This data includes the starting angle, ending angle, intermediate angle, degree of change, and type of change within the target width change range. Conditional judgments are applied to the width change data, and a target cross-section group is constructed based on the initial island / reef coastline. The initial island / reef coastline represents the coastline at the initial time phase, and the target cross-section group includes several cross-sections perpendicular to the initial coastline. Based on the intersections of the cross-sections in the target cross-section group with the long-term island / reef coastline, the change trends of all cross-sections are transformed, and a second time point is selected. The second time point represents the time point where the average rate of change of the change trend is greater than a second threshold. Based on the island / reef coastlines corresponding to the first and second time points, the net rate of change at the target time point is obtained through binarized overlay analysis. This invention employs circumferential sampling to detect radial width changes, enabling precise identification of drastically changing cross-sectional locations along island and reef coastlines. This effectively avoids the problem of traditional equidistant sampling missing key change areas. Based on width change data conditions, a target cross-section group is constructed, ensuring the cross-section layout matches the actual dynamic characteristics of the coastline, significantly improving the monitoring accuracy of erosion and sedimentation spatial changes. Furthermore, by combining key time points from the first and second time points for binarized overlay analysis, key nodes of coastline changes and their net change rates can be effectively captured. This overcomes the shortcomings of existing methods that rely solely on sedimentation and erosion rates, lacking spatial details and annual change information. This provides more scientific and reliable data support for predicting island and reef coastline evolution trends and making ecological protection decisions. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an implementation environment for a method for monitoring the spatiotemporal changes of island and reef coastlines provided in an embodiment of the present invention; Figure 2 This is a flowchart illustrating the method for monitoring the spatiotemporal changes of island and reef coastlines provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the overall process of the island and reef coastline spatiotemporal change monitoring method provided in the embodiments of the present invention; Figure 4This is a schematic diagram illustrating the effect of monitoring the spatiotemporal changes of island and reef coastlines provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the spatiotemporal change monitoring device for island and reef coastlines provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the electronic device provided in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the embodiments of this invention; they are merely examples of apparatuses and methods consistent with some aspects of the embodiments of this invention as detailed in the appended claims.

[0019] It is understood that the terms "first," "second," etc., used in this invention may be used to describe various concepts, but unless specifically stated otherwise, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another. For example, without departing from the scope of embodiments of this invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the words "if" or "when" as used herein may be interpreted as "when," "in response to determination," or "in the event of a determination."

[0020] The terms “at least one,” “multiple,” “each,” “any,” etc., used in this invention, “at least one” includes one, two, or more than two; “multiple” includes two or more than two; “each” refers to each of the corresponding multiple; and “any” refers to any one of the multiple.

[0021] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this invention is for descriptive purposes only and is not intended to limit the invention.

[0022] Among related technologies, how to improve the efficiency, accuracy, and flexibility of monitoring the spatiotemporal dynamic changes of island and reef coastlines based on long-term remote sensing images remains an urgent problem to be solved by existing technologies.

[0023] In view of this, this invention provides a method and related equipment for monitoring the spatiotemporal changes of island and reef coastlines. This method acquires long-term multi-source remote sensing images of target islands and reefs, and processes these images through preprocessing to obtain multi-temporal remote sensing images. Based on the multi-temporal remote sensing images, land-water separation is performed using the normalized water index to obtain the long-term island and reef coastline. The long-term island and reef coastline includes the coastline of each temporal phase. Changes in island and reef values ​​are statistically analyzed based on the long-term island and reef coastline to obtain a numerical trend map and a first time point. The island and reef values ​​include the island and reef perimeter and area, and the first time point represents the time point when the change in island and reef values ​​exceeds a first threshold. Based on the long-term island and reef coastline, radial width changes are detected through circumferential sampling to obtain the width change. The data includes width variation data such as the starting angle, ending angle, intermediate angle, degree of change, and type of change of the target width variation range; conditional judgment is performed on the width variation data, and a target cross-section group is constructed in conjunction with the initial island and reef coastline; the initial island and reef coastline represents the island and reef coastline in the initial time phase, and the target cross-section group includes several cross-sections perpendicular to the initial island and reef coastline; based on the intersection points of the cross-sections in the target cross-section group and the long-term island and reef coastline, the change trends of all cross-sections are transformed, and then the second time point is selected; the second time point represents the time point where the average rate of change of the change trend is greater than the second threshold; based on the island and reef coastlines of the corresponding time phases of the first and second time points, the net rate of change of the target time point is obtained through binarization overlay analysis. This invention employs circumferential sampling to detect radial width changes, enabling precise identification of drastically changing cross-sectional locations along island and reef coastlines. This effectively avoids the problem of traditional equidistant sampling missing key change areas. Based on width change data conditions, a target cross-section group is constructed, ensuring the cross-section layout matches the actual dynamic characteristics of the coastline, significantly improving the monitoring accuracy of erosion and sedimentation spatial changes. Furthermore, by combining key time points from the first and second time points for binarized overlay analysis, key nodes of coastline changes and their net change rates can be effectively captured. This overcomes the shortcomings of existing methods that rely solely on sedimentation and erosion rates, lacking spatial details and annual change information. This provides more scientific and reliable data support for predicting island and reef coastline evolution trends and making ecological protection decisions.

[0024] It is understood that the method for monitoring the spatiotemporal changes of island and reef coastlines provided by this invention can be applied to any computer device with data processing and computing capabilities, and this computer device can be various types of terminals or servers. When the computer device in the embodiment is a server, the server is an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, CDN (Content Delivery Network), and big data and artificial intelligence platforms. Optionally, the terminal can be a smartphone, tablet, laptop, or desktop computer, but it is not limited to these.

[0025] like Figure 1 The diagram shown is a schematic representation of an implementation environment provided by an embodiment of the present invention. (Refer to...) Figure 1 The implementation environment includes at least one terminal 102 and a server 101. The terminal 102 and the server 101 can be connected via a network, either wirelessly or via a wired connection, to complete data transmission and exchange.

[0026] Server 101 can be a standalone physical server, a server cluster or distributed system consisting of multiple physical servers, or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, CDN (Content Delivery Network), and big data and artificial intelligence platforms.

[0027] Additionally, server 101 can also be a node server in a blockchain network. Blockchain is a novel application model of computer technologies such as distributed data storage, peer-to-peer transmission, consensus mechanisms, and encryption algorithms.

[0028] Terminal 102 can be a smartphone, tablet computer, laptop computer, desktop computer, smart speaker, smartwatch, etc., but is not limited to these. Terminal 102 and server 101 can be directly or indirectly connected via wired or wireless communication, and this embodiment of the invention does not impose any limitations.

[0029] For example, based on Figure 1 The implementation environment shown in this embodiment of the invention provides a method for monitoring the spatiotemporal changes of island and reef coastlines. The following description uses the application of this method in server 101 as an example. It can be understood that this method can also be applied in terminal 102.

[0030] Reference Figure 2 , Figure 2 This is an optional flowchart of the island and reef coastline spatiotemporal change monitoring method provided in the embodiments of the present invention. The executing entity of the island and reef coastline spatiotemporal change monitoring method can be any of the aforementioned computer devices (including servers or terminals). Figure 2 The method may include, but is not limited to, steps S100 to S700.

[0031] Step S100: Acquire long-term multi-source remote sensing images of the target islands and reefs, and process them through preprocessing operations to obtain multi-temporal remote sensing images. For example, in some specific implementations, high-resolution remote sensing images are first collected as the primary data source, enabling accurate extraction of information such as the morphology, coastline, and area of ​​small islands in the open sea. Image selection must ensure that the study area is free from cloud cover, has clear image quality, and that image acquisition time avoids the period before and after typhoon passage to prevent interference from short-term changes on the research results. Preprocessing of the selected remote sensing images mainly includes radiometric calibration, atmospheric correction, and geometric correction.

[0032] Step S200: Based on multi-temporal remote sensing images, land and water are separated using the normalized water index to obtain long-term island and reef coastlines. Among them, the long-term island and reef coastline includes the island and reef coastline in various time phases; It should be noted that in some embodiments, step S200 may include the following steps: taking the initial time phase as the first time phase; extracting the atmospheric top reflectance based on the remote sensing image corresponding to the first time phase in the multi-temporal remote sensing images; wherein, the atmospheric top reflectance includes the first atmospheric top reflectance in the green band and the second atmospheric top reflectance in the near-infrared band; based on the atmospheric top reflectance, processing with the normalized water index to obtain the water index image of the first time phase; based on the water index image, segmenting water and land using the Otsu threshold segmentation algorithm to obtain the island and reef coastline of the first time phase; taking the next time phase of the first time phase as the first time phase, returning to execute the step of extracting the atmospheric top reflectance based on the remote sensing image corresponding to the first time phase in the multi-temporal remote sensing images, until all time phases have been traversed, and summarizing to obtain the long-term island and reef coastline.

[0033] For example, in some specific embodiments, the water body index of remote sensing images is obtained by calculating it on a time-phase basis. The images are then processed using the OTSU algorithm to automatically select the optimal value between two peaks (water and land in this invention) in the grayscale image histogram to obtain long-term island and reef coastlines. Water index ( The formula is as follows:

[0034] in, and These are the atmospheric top reflectance values ​​for the green light (560nm) band and the near-infrared (858nm) band, respectively.

[0035] Step S300: Based on the changes in island and reef values ​​in long-term time series island and reef coastline statistics, obtain the numerical trend map and the first time point; Among them, the island and reef values ​​include the island and reef perimeter and the island and reef area, and the first time point represents the time point when the change of the island and reef values ​​is greater than the first threshold. It should be noted that, in some embodiments, step S300 may include the following steps: quantizing the island and reef coastline of each time phase in the long-term island and reef coastline to obtain the island and reef perimeter and island and reef area corresponding to each time phase; taking the initial time phase as the second time phase; taking the next time phase of the second time phase as the third time phase; quantizing the island and reef perimeter corresponding to the third time phase and the second time phase to obtain the perimeter change value of the third time phase, and quantizing the island and reef area corresponding to the third time phase and the second time phase to obtain the area change value of the third time phase; if the perimeter change value is greater than the first perimeter threshold and / or the area change value is greater than the first area threshold, taking the time point corresponding to the third time phase as the first candidate time point; taking the third time phase as the second time phase, returning to execute the step of taking the next time phase of the second time phase as the third time phase, until all time phases have been traversed; summarizing and converting the perimeter change value and area change value corresponding to all time phases to obtain a numerical trend graph; summarizing all the first candidate time points to obtain the first time point.

[0036] For example, in some specific implementations, the length (perimeter) and area of ​​the island and reef coastline are directly calculated based on long-term time series results. A line graph of the length and area of ​​the island and reef coastline is plotted to analyze the trend of change and the years with large changes. The changes in the island and reef coastline in those years are analyzed in detail (for example, years with area changes greater than an area threshold or perimeter changes greater than a perimeter threshold are marked as PY, i.e., the first time point; in addition, years with area changes greater than an area threshold and perimeter changes greater than a perimeter threshold can also be marked as PY).

[0037] Step S400: Based on the long-term time series of island and reef coastlines, radial width change detection is performed through circumferential sampling to obtain width change data; The width variation data includes the starting angle, ending angle, middle angle, degree of variation, and type of variation of the target width variation range; It should be noted that in some embodiments, step S400 may include the following steps: initializing a first angle; extracting the radial distance extremes of all time phases from the long-time island reef coastline along the direction of the first angle; wherein, the radial distance extremes include the minimum radial distance and the maximum radial distance; determining the radial width change value of the first angle based on the difference between the maximum radial distance and the minimum radial distance; incrementing the first angle based on a preset angle step size, and returning to execute the step of extracting the radial distance extremes of all time phases from the long-time island reef coastline along the direction of the first angle, until circumferential sampling is completed, obtaining the radial width change value of all sampled angles; initializing a second angle; taking two adjacent angles separated from the second angle by a preset angle step size as the third angle and the fourth angle respectively; performing first derivative and absolute value operations based on the radial width change value of the third angle, the radial width change value of the fourth angle, and the preset angle step size to obtain the change gradient of the second angle; and determining the radial width change value of the second angle based on the radial width change value of the third angle, the radial width change value of the fourth angle, and the radial width change value of the fourth angle. The process involves performing a second derivative operation on the width change value and a preset angle step size to obtain the curvature of the second angle. The second angle is then incremented based on the preset angle step size, and the process continues until a full circumferential sampling is completed, yielding the gradient and curvature of all sampled angles. The gradient mean and standard deviation are calculated from the gradients of all sampled angles, and a gradient threshold is derived from these. The target width change interval is determined based on the continuous angle intervals where the gradient is greater than the gradient threshold. The starting angle, ending angle, and middle angle of each target width change interval are determined based on the angle range it encompasses. The degree of change in each target width change interval is determined based on the maximum gradient of all sampled angles within that interval. Finally, the type of change in each target width change interval is determined by mapping positive and negative cases based on the curvature of the middle angle.

[0038] For example, in some specific implementations, a clockwise direction is set based on the long-term island and reef coastline, and the coastlines of all periods are enclosed in a torus, where the width of the torus directly reflects the magnitude of the coastline changes. The curvature changes of the radial width are analyzed to output the starting angle, ending angle, and intermediate angle of any "bulge" or "depression" in the torus. The specific steps for identifying changes in the torus are as follows: (1) Construct a variable-width torus: Sample the torus into n points with equal arc lengths along the pointer direction (it is recommended that n be [360, 720]). For each torus position Calculate the minimum radial distance (Minimum value for all periods), maximum radial distance (Maximum value across all periods), width = (2) Identify locations where the width changes drastically: Calculate the first derivative of the width. (Gradient | Absolute value represents the degree of change) and the second derivative of width (Curvature | used for precise boundary positioning); Calculation The mean and standard deviation, and a threshold are set. Extract the mean plus twice the standard deviation. A continuous interval greater than the threshold. Second derivative. The extreme point corresponds to the position where the width changes most drastically, and the extreme point of the second derivative is greater than 0 for siltation and the opposite for erosion. (3) Precisely locate the boundary and center of the changing region: For each continuous interval, the starting angle is the angle corresponding to the starting point of the interval. The final angle is the angle corresponding to the end point of the interval. The intermediate angle is half the sum of the initial angle and the final angle, and the degree of change is the maximum value of the absolute value of the first derivative of the width within the interval.

[0039] The first derivative of the width: = ; The second derivative of the width: = ; In the formula, Set threshold ,extract Continuous intervals.

[0040] Step S500: Perform conditional judgment on the width change data and construct the target cross-section group in combination with the initial island and reef coastline; Among them, the initial island and reef coastline represents the island and reef coastline in the initial time phase, and the target cross-section group includes several cross-sections perpendicular to the initial island and reef coastline. It should be noted that in some embodiments, step S500 may include the following steps: averaging the perimeters of the islands and reefs across all time phases to obtain the average perimeter; determining the angle difference and interval angle based on the numerical range mapping of the average perimeter; extracting the first intersection point along the direction of the middle angle for each target width variation interval from the initial island and reef coastline; constructing a perpendicular line as a cross-section based on the direction perpendicular to the initial island and reef coastline at each first intersection point, and then summarizing them to obtain a first cross-section group; determining the angle difference for each target width variation interval based on the difference between the ending angle and the starting angle corresponding to the target width variation interval; if there is an angle difference greater than... For the angle difference, extract the second intersection point along the direction of the starting angle and the ending angle of the target width variation range from the initial island / reef coastline; construct a perpendicular line as a cross section based on the direction perpendicular to the initial island / reef coastline for each second intersection point, and then summarize to obtain the second cross section group; if the second cross section group is not empty, use the second cross section group as the candidate cross section group; otherwise, use the second cross section group as the candidate cross section group; in the area where the initial island / reef coastline is located between adjacent cross sections in the candidate cross section group, construct a perpendicular line perpendicular to the initial island / reef coastline as a cross section based on the interval angle, and then summarize to obtain the third cross section group; summarize the candidate cross section group and the third cross section group to obtain the target cross section group.

[0041] For example, in some specific implementations, section group A is first generated at the intermediate angle, and then the difference between the ending angle and the starting angle is greater than the angle difference ( (See Table 1) Then the starting angle and ending angle generate section group A1. Finally, if there is an A1, only A1 is calculated; otherwise, A is calculated directly. The interval between A1 and A is an angle. (See Table 1) Generate section group B. A section refers to the intersection of the angle of change of the torus and the starting shoreline, and the perpendicular line from this intersection to the starting shoreline.

[0042] Table 1

[0043] Step S600: Based on the intersection of the target cross section group and the long-term island and reef coastline, the change trend of all cross sections is obtained, and then the second time point is selected. Among them, the second time point is the time point where the average rate of change representing the trend of change is greater than the second threshold; It should be noted that in some embodiments, step S600 may include the following steps: initializing the number of valid years, taking the next time phase after the initial time phase as the fourth time phase; taking the first cross section of the target cross section group as the quantization cross section; taking the intersection of the quantization cross section and the island / reef coastline of the initial time phase as the third intersection point, and taking the intersection of the quantization cross section and the island / reef coastlines of all time phases from the initial time phase to the fourth time phase as the fourth intersection point; taking the cumulative difference between each fourth intersection point and the third intersection point as the numerator, and the number of valid years minus one as the denominator, to calculate the average rate of change of the quantization cross section in the fourth time phase; if the average rate of change is greater than the second The threshold is used to select the fourth time phase as the second candidate time point; the next cross section of the target cross section group is used as the quantized cross section, and the process of selecting the intersection of the quantized cross section and the island / reef coastline of the initial time phase as the third intersection point is repeated until all cross sections of the target cross section group are traversed; the number of valid years is incremented, the next time phase of the fourth time phase is used as the fourth time phase, and the process of selecting the first cross section of the target cross section group as the quantized cross section is repeated until all time phases are traversed; the trend of change is obtained by summarizing the average rate of change of the target cross section group in all time phases, and the second time point is obtained by summarizing all second candidate time points.

[0044] For example, in some specific implementations, for all cross-sections along the island / reef coastline, the net coastline movement for the first year and all other years is calculated one by one. Then, the net movement for all years is calculated and divided by the total number of years. The average annual change for all cross-sections is then statistically analyzed, and a trend chart is plotted. Years with significant changes in the cross-section group are analyzed one by one (for example, a change rate threshold can be set, and years with an average change rate greater than the threshold are marked as MY, i.e., the second time point). The calculation formula is as follows: Annual average rate of change of cross section =

[0045] In the formula: Indicates the location of the coastline of islands and reefs; This represents the i-th year; Indicates the initial time point. This represents the effective number of years of the island / reef coastline on the cross-section (initially 2). Among them, The origin is the point where the island / reef coastline intersects the cross-section in the initial year, and the outward direction of the cross-section is the positive direction. Let be the intersection of the island / reef coastline and the cross-section in year i. Let be the distance between the island / reef coastline in year i and the island / reef coastline in the initial year on the cross-section.

[0046] Step S700: Based on the island and reef coastlines corresponding to the first and second time points, the net rate of change at the target time point is obtained through binarization overlay analysis. It should be noted that in some embodiments, step S700 may include the following steps: determining the target time point based on the union of the first time point and the second time point; taking the time phase corresponding to the first time point in the target time point as the fifth time phase; taking the previous time phase of the fifth time phase as the sixth time phase; performing binarization on the island and reef coastline inside and outside the fifth time phase to obtain the first island and reef coastline surface, and performing binarization on the island and reef coastline inside and outside the sixth time phase to obtain the second island and reef coastline surface; subtracting the second island and reef coastline surface from the first island and reef coastline surface, and then determining the siltation area and erosion area based on the positive and negative values ​​of each region; using the area of ​​the siltation area minus the area of ​​the erosion area as the numerator, and the island and reef area of ​​the island and reef coastline in the fifth time phase as the denominator, and obtaining the net rate of change of the fifth time phase through proportional calculation; taking the time phase corresponding to the next time point in the target time point as the fifth time phase, and returning to execute the step of taking the previous time phase of the fifth time phase as the sixth time phase, until all time points of the target time point have been traversed.

[0047] For example, in some specific implementations, for statistical years MY and PY, the year groups are first merged and then deduplicated to output the year groups. For example, MY is (2012-2018-2023), and PY is (2012-2013-2018-2022), where 2012 and 2018 are duplicates. The final output is (2012-2013-2018-2022-2023). For each year, the surface data is statistically analyzed by overlaying it with the preceding and following years. Specific steps: Set the in-surface attribute value of the island / reef coastline to 1 and the out-of-surface attribute value to 0. Subtract island / reef coastline B from island / reef coastline surface A. Areas with an attribute value of 0 in the resulting surface are stable areas, indicating that both periods are land; areas with an attribute value of -1 are siltation areas, indicating that island / reef coastline surface A is ocean and island / reef coastline surface B is land; areas with an attribute value of 1 are erosion areas, indicating that island / reef coastline surface A is land and island / reef coastline surface B is ocean. The areas of siltation and erosion are statistically analyzed, and the net rate of change is calculated. The formula is as follows: Net rate of change = (Siltation area - Erosion area) / Area A of the island / reef coastline × 100%.

[0048] To explain in detail the principle of the technical solution of the present invention, the overall process of the present invention will be described below with reference to some specific embodiments. It is easy to understand that the following is an explanation of the technical principle of the present invention and should not be regarded as a limitation of the present invention.

[0049] In view of the shortcomings of existing technologies, this invention proposes an optimized island and reef coastline algorithm for monitoring spatiotemporal changes of islands and reefs based on long-term remote sensing imagery, addressing issues such as cross-section generation, spatial information variation, and significant annual spatial variations. This algorithm extracts the island and reef coastline, calculates the island and reef perimeter and area, extracts the coastline, generates cross-sections using the radial width change rate detection method, and calculates the long-term mean coastline change value, ultimately obtaining the temporal trend of dynamic changes in the island and reef coastline and an erosion and sedimentation map. This effectively improves application efficiency and accuracy, comprehensively monitors all changes in the island and reef coastline, and increases application rate. It is particularly suitable for local, large-scale, and sustainable island and reef coastline change monitoring, solving several key problems of existing technologies. Figure 3 As shown, the technical solution of the present invention can be specifically implemented as follows: High-resolution remote sensing imagery is the primary data source, enabling accurate extraction of information such as morphology, coastline, and area of ​​small, offshore islands. Image selection must ensure the study area is free of cloud cover, has clear image quality, and is timed to avoid the period before and after typhoons to minimize interference from short-term changes. Preprocessing of the selected remote sensing images includes radiometric calibration, atmospheric correction, and geometric correction.

[0050] Water body index acquisition from time-phase calculation of remote sensing images The images are then analyzed, and the OTSU algorithm is used to automatically select the optimal value between two peaks (water and land in this invention) in the grayscale image histogram to obtain the long-term island / reef coastline. The water index formula is as follows:

[0051] in, and These are the atmospheric top reflectance values ​​for the green light (560nm) band and the near-infrared (858nm) band, respectively.

[0052] Based on long-term time series island and reef coastline results, the length and area of ​​the island and reef coastline are directly calculated, and line graphs of the length and area of ​​the island and reef coastline are drawn. The trend of change and the years with greater changes are analyzed, and the changes of the island and reef coastline in the year are analyzed in detail (the year is marked as PY).

[0053] Based on a long-term time series of island and reef coastlines, a clockwise direction is used to enclose the coastlines of all periods into a torus. The width of the torus directly reflects the magnitude of coastline changes. Curvature analysis of the radial width is used to analyze these changes, outputting the starting angle, ending angle, and intermediate angle where the torus shows "bulges" or "depressions." First, the intermediate angle generates section group A. Then, the difference between the ending angle and the starting angle is greater than the angle difference (…). (See Table 1 above). The starting angle and ending angle generate section group A1. If A1 exists, only A1 is calculated; otherwise, A is calculated directly. The interval between A1 and A is an angle. (See Table 1 above) Generate section group B. A section refers to the intersection of the angle of change of the torus and the starting shoreline, and the perpendicular line from this intersection to the starting shoreline.

[0054] The specific steps for identifying changes in the torus are as follows: (1) Construct a variable-width torus: Sample the torus into n points with equal arc lengths along the pointer direction (it is recommended that n be [360, 720]). For each circumferential position Calculate the minimum radial distance (Minimum value for all periods), maximum radial distance (Maximum value across all periods), width = (2) Identify locations where the width changes drastically: Calculate the first derivative of the width. (Gradient | Absolute value represents the degree of change) and the second derivative of width (Curvature | used for precise boundary positioning); Calculation The mean and standard deviation, and a threshold are set. Extract the mean plus twice the standard deviation. A continuous interval greater than the threshold. Second derivative. The extreme point corresponds to the position where the width changes most drastically, and the extreme point of the second derivative is greater than 0 for siltation and the opposite for erosion. (3) Precisely locate the boundary and center of the changing region: For each continuous interval, the starting angle is the angle corresponding to the starting point of the interval. The final angle is the angle corresponding to the end point of the interval. The intermediate angle is half the sum of the initial angle and the final angle, and the degree of change is the maximum value of the absolute value of the first derivative of the width within the interval.

[0055] The first derivative of the width: = ; The second derivative of the width: = ; In the formula, Set threshold ,extract Continuous intervals.

[0056] For all cross-sections along the island / reef coastline, calculate the net coastline movement for the first year and all other years. Then, calculate the net movement for all years and divide by the total number of years. Statistically analyze the annual average change for all cross-sections and plot a trend graph. Analyze the years with the largest changes in each cross-section group (labeled MY). The calculation formula is as follows: Annual average rate of change of cross section =

[0057] In the formula: Indicates the location of the coastline of islands and reefs; This represents the i-th year; Indicates the initial time point. This represents the effective number of years of the island / reef coastline on the cross-section (initially 2). Among them, The origin is the point where the island / reef coastline intersects the cross-section in the initial year, and the outward direction of the cross-section is the positive direction. Let be the intersection of the island / reef coastline and the cross-section in year i. Let be the distance between the island / reef coastline in year i and the island / reef coastline in the initial year on the cross-section.

[0058] Indicates the location of the coastline of islands and reefs. The distance between the two points is calculated by subtracting the intersection of the first and second island / reef lines on the cross-section from the intersection of the second and initial island / reef lines on the cross-section. This distance can have positive or negative values; a positive value indicates deposition, and a negative value indicates erosion. For the statistical years MY and PY, first merge and then remove duplicates to output the year groups. For example, MY is (2012-2018-2023), and PY is (2012-2013-2018-2022), where 2012 and 2018 are duplicates. The final output is (2012-2013-2018-2022-2023). For each year, the surface data is statistically analyzed by overlaying it with the preceding and following years. Specific steps: Set the in-surface attribute value of the island / reef coastline to 1 and the out-of-surface attribute value to 0, and subtract the island / reef coastline surface B from island / reef coastline surface A. For example... Figure 4 As shown: the region with an attribute value of 0 on the result surface is the stable region, indicating that both periods were land. Figure 4 The gray area represents the sedimentation zone; areas with a result surface attribute of -1 are siltation zones, indicating that island / reef coastline surface A is ocean and island / reef coastline surface B is land. Figure 4 The area represented in blue is the erosion zone; the area with a result surface attribute of 1 is the erosion zone, indicating that island / reef coastline surface A is land and island / reef coastline surface B is ocean. Figure 4 The areas are indicated in red. The areas of siltation and erosion are statistically analyzed, and the net rate of change is calculated. The formula is as follows: Net rate of change = (Siltation area - Erosion area) / Area of ​​island / reef coastline A × 100%.

[0059] Specifically, an example of overlay analysis (intersection inversion) is as follows: For the overlay analysis of 2025 and the previous year, the surface of 2025 is used as the basis for the analysis with the surface of the previous year 2024; for the overlay analysis of 2025 and the following year, the surface of 2026 is used as the basis for the analysis with the surface of the previous year 2025.

[0060] In summary, the embodiments of this invention, through automated detection methods and thorough calculation of the spatiotemporal changes of all island and reef coastlines, can quickly and automatically identify two types of years with significant changes in long-term time series and automatically identify erosion or siltation areas. Furthermore, this invention innovatively proposes a radial width change rate detection method for monitoring island and reef coastlines, achieving a "visual interpretation" effect to monitor local changes in all island and reef coastlines. It also involves taking the coastline positions from multiple calculations of the initial time phase and the coastline position information of all coastlines, and then using the mean value to analyze the change results.

[0061] Compared with the prior art, the present invention has at least the following beneficial effects: Existing technical problems: Traditional island and reef coastline monitoring methods require first generating a baseline, and then generating island and reef coastline cross-sections at fixed intervals based on the starting point. This method cannot comprehensively detect all locations where the island and reef coastline changes significantly.

[0062] Advantages of this invention: This invention eliminates the need to generate a baseline and uses a changing vector surface method to comprehensively monitor areas with significant changes in the coastline of islands and reefs. It fully monitors all local changes in the coastline of islands and reefs, increases the applicability of dynamic monitoring of the coastline of islands and reefs, and improves application efficiency and accuracy.

[0063] Existing technical problem: When calculating the spatiotemporal dynamic changes of island and reef coastlines using the baseline method, the net movement of the coastline and the endpoint rate only utilize the location information of the island and reef coastlines in the initial and final phases, while the irregular swaying and periodic fluctuations of the coastline in the intermediate process are ignored or filtered out.

[0064] Advantages of this invention: By calculating the initial shoreline position and shoreline position information of all shorelines, and then using the mean value analysis of the change results, this invention can effectively supplement the analysis of shoreline swaying and periodic band changes, and fully detect the spatiotemporal dynamic changes of island and reef shorelines through remote sensing.

[0065] like Figure 5 As shown, this embodiment of the invention also provides a spatiotemporal change monitoring device 900 for island and reef coastlines, which can implement the above-described method. This device may include: The first module 901 is used to acquire long-term multi-source remote sensing images of the target islands and reefs, and to obtain multi-temporal remote sensing images through preprocessing operations. The second module 902 is used to perform land-water separation based on multi-temporal remote sensing images using the normalized water index to obtain long-term island and reef coastlines; wherein, the long-term island and reef coastlines include island and reef coastlines of each temporal phase. The third module 903 is used to statistically analyze the changes in island and reef values ​​based on long-term island and reef coastlines, and to obtain a numerical trend map and a first time point; wherein, the island and reef values ​​include the island and reef perimeter and island and reef area, and the first time point represents the time point when the change in island and reef values ​​is greater than a first threshold. The fourth module 904 is used to detect radial width changes based on long-term island and reef coastlines through circumferential sampling, and obtain width change data. The width change data includes the starting angle, ending angle, intermediate angle, degree of change, and type of change of the target width change interval. The fifth module 905 is used to perform conditional judgment on the width change data and construct a target cross-section group in combination with the initial island and reef coastline; wherein, the initial island and reef coastline represents the island and reef coastline in the initial time phase, and the target cross-section group includes several cross-sections perpendicular to the initial island and reef coastline. The sixth module 906 is used to transform the change trends of all cross sections based on the intersection of the cross sections of the target cross section group and the long-term island and reef coastline, and then filter to obtain the second time point; wherein, the second time point represents the time point where the average rate of change of the change trend is greater than the second threshold. Module 7, 907, is used to obtain the net rate of change at the target time point based on the island and reef coastlines corresponding to the first and second time points through binarization overlay analysis.

[0066] It is understood that the content of the above method embodiments is applicable to the present device embodiments. The specific functions implemented by the present device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0067] This invention also provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the method described above. This electronic device can be any smart terminal, including tablet computers, in-vehicle computers, etc.

[0068] It is understood that the content of the above method embodiments is applicable to this device embodiment. The specific functions implemented by this device embodiment are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0069] like Figure 6 As shown, Figure 6 The hardware structure of an electronic device 1000 according to another embodiment is illustrated. The electronic device 1000 includes: The processor 1001 can be implemented using a general-purpose CPU (Central Processing Unit), microprocessor, application-specific integrated circuit (aSIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of the present invention. The memory 1002 can be implemented as a read-only memory (ROM), a static storage device, a dynamic storage device, or a random access memory (RaM). The memory 1002 can store the operating system and other application programs. When the technical solutions provided in the embodiments of this specification are implemented through software or firmware, the relevant program code is stored in the memory 1002 and is called and executed by the processor 1001. Input / output interface 1003 is used to implement information input and output; The communication interface 1004 is used to enable communication and interaction between this device and other devices. Communication can be achieved through wired means (such as USB, network cable, etc.) or wireless means (such as mobile network, WIFI, Bluetooth, etc.). Bus 1005 transmits information between various components of the device (e.g., processor 1001, memory 1002, input / output interface 1003, and communication interface 1004); The processor 1001, memory 1002, input / output interface 1003 and communication interface 1004 are connected to each other within the device via bus 1005.

[0070] The electronic device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0071] This invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method.

[0072] It is understood that the content of the above method embodiments is applicable to this storage medium embodiment. The specific functions implemented in this storage medium embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0073] This invention also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0074] It is understood that the content of the above method embodiments is applicable to the embodiments of this program product. The specific functions implemented by the embodiments of this program product are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0075] Memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs. Furthermore, memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, memory may optionally include memory remotely located relative to the processor, and these remote memories can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0076] The invention provides a method, apparatus, electronic device, storage medium, and program product for monitoring the spatiotemporal changes of island and reef coastlines. This method acquires long-term multi-source remote sensing images of target islands and reefs, processes them through preprocessing to obtain multi-temporal remote sensing images, and uses a normalized water index to perform land-water separation based on these images to obtain long-term island and reef coastlines. The long-term island and reef coastlines include coastlines from various temporal phases. Based on the long-term island and reef coastlines, changes in island and reef values ​​are statistically analyzed to obtain a numerical trend map and a first time point. Island and reef values ​​include the island and reef perimeter and area, and the first time point represents the time point when the change in island and reef values ​​exceeds a first threshold. Based on the long-term island and reef coastlines, radial width changes are detected through circumferential sampling to obtain the width. The data includes width variation data, which includes the starting angle, ending angle, intermediate angle, degree of change, and type of change of the target width variation range. Conditional judgments are made on the width variation data, and a target cross-section group is constructed in conjunction with the initial island / reef coastline. The initial island / reef coastline represents the island / reef coastline at the initial time phase, and the target cross-section group includes several cross-sections perpendicular to the initial island / reef coastline. Based on the intersections of the cross-sections in the target cross-section group with the long-term island / reef coastline, the variation trends of all cross-sections are transformed, and then a second time point is selected. The second time point represents the time point where the average rate of change of the variation trend is greater than a second threshold. Based on the island / reef coastlines corresponding to the first and second time points, the net rate of change of the target time point is obtained through binarization overlay analysis. This invention employs circumferential sampling to detect radial width changes, enabling precise identification of drastically changing cross-sectional locations along island and reef coastlines. This effectively avoids the problem of traditional equidistant sampling missing key change areas. Based on width change data conditions, a target cross-section group is constructed, ensuring the cross-section layout matches the actual dynamic characteristics of the coastline, significantly improving the monitoring accuracy of erosion and sedimentation spatial changes. Furthermore, by combining key time points from the first and second time points for binarized overlay analysis, key nodes of coastline changes and their net change rates can be effectively captured. This overcomes the shortcomings of existing methods that rely solely on sedimentation and erosion rates, lacking spatial details and annual change information. This provides more scientific and reliable data support for predicting island and reef coastline evolution trends and making ecological protection decisions.

[0077] The embodiments described in this invention are for the purpose of more clearly illustrating the technical solutions of the embodiments of this invention, and do not constitute a limitation on the technical solutions provided by the embodiments of this invention. As those skilled in the art will know, with the evolution of technology and the emergence of new application scenarios, the technical solutions provided by the embodiments of this invention are also applicable to similar technical problems.

[0078] Those skilled in the art will understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of the present invention, and may include more or fewer steps than shown, or combine certain steps, or different steps.

[0079] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0080] Those skilled in the art will understand that all or some of the steps in the methods disclosed above, as well as the functional modules / units in the systems and devices, can be implemented as software, firmware, hardware, or suitable combinations thereof.

[0081] The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and spirit of the present invention should be within the scope of the claims of the present invention.

Claims

1. An atoll shoreline spatio-temporal change monitoring method, characterized in that, The method includes the following steps: Long-term multi-source remote sensing images of the target islands and reefs are acquired, and multi-temporal remote sensing images are obtained through preprocessing operations. Based on the multi-temporal remote sensing images, land and water are separated using the normalized water index to obtain long-term island and reef coastlines; wherein, the long-term island and reef coastlines include island and reef coastlines of each temporal phase. Based on the changes in island and reef values ​​statistically analyzed over a long time series, a numerical trend map and a first time point are obtained; wherein, the island and reef values ​​include the island and reef perimeter and the island and reef area, and the first time point represents the time point when the change in the island and reef values ​​is greater than a first threshold. Based on the long-term island and reef coastline, radial width change is detected through circumferential sampling to obtain width change data; wherein, the width change data includes the starting angle, ending angle, intermediate angle, degree of change, and type of change of the target width change interval; The width change data is conditionally determined and a target cross-section group is constructed in combination with the initial island and reef coastline; wherein, the initial island and reef coastline represents the island and reef coastline in the initial time phase, and the target cross-section group includes several cross-sections perpendicular to the initial island and reef coastline. Based on the intersection of the target cross section group and the long-term island and reef coastline, the change trends of all cross sections are transformed, and then a second time point is selected; wherein, the second time point represents the time point where the average rate of change of the change trend is greater than a second threshold. Based on the island and reef coastlines corresponding to the first and second time points, the net rate of change at the target time point is obtained through binarization overlay analysis. The step of obtaining long-term island and reef coastlines by performing land-water segmentation using the normalized water index based on the multi-temporal remote sensing images includes the following steps: The initial phase is taken as the first phase; Atmospheric top reflectance is extracted from the first temporal corresponding remote sensing image in the multi-temporal remote sensing image; wherein, the atmospheric top reflectance includes the first atmospheric top reflectance in the green band and the second atmospheric top reflectance in the near-infrared band; Based on the atmospheric top reflectivity, the water index image of the first time phase is obtained by processing with the normalized water index. Based on the water index image, the water body and land are segmented using the Otsu threshold segmentation algorithm to obtain the island and reef coastline in the first time phase. The next time phase of the first time phase is taken as the first time phase, and the step of extracting the atmospheric top reflectance from the remote sensing image corresponding to the first time phase in the multi-time phase remote sensing image is returned to be executed until all time phases are traversed, and the long-time series island and reef coastline is obtained.

2. The method of claim 1, wherein, The process of obtaining a numerical trend map and a first time point based on the changes in island and reef coastal statistics over a long period of time includes the following steps: Based on the quantization of the island and reef coastline in each time phase of the long-term island and reef coastline, the island and reef perimeter and island and reef area corresponding to each time phase are obtained. The initial phase is taken as the second phase; The next phase after the second phase is taken as the third phase; The perimeter change value of the third time phase is obtained by quantifying the perimeter of the islands and reefs corresponding to the second time phase, and the area change value of the third time phase is obtained by quantifying the area of ​​the islands and reefs corresponding to the second time phase. If the change in perimeter is greater than the first perimeter threshold and / or the change in area is greater than the first area threshold, the time point corresponding to the third time is taken as the first candidate time point. The third phase is used as the second phase, and the process returns to the step of using the next phase of the second phase as the third phase, until all phases have been traversed. The numerical trend chart is obtained by summarizing and converting the perimeter change values ​​and area change values ​​corresponding to all times. The first time point is obtained by summing all the first candidate time points.

3. The method of claim 1, wherein, The method of detecting radial width changes based on the long-term island and reef coastline through circumferential sampling to obtain width change data includes the following steps: Initialize the first angle; The radial distance extremes for all time phases are extracted from the long-time island reef coastline along the first angle; wherein, the radial distance extremes include the minimum radial distance and the maximum radial distance; The radial width variation value of the first angle is determined based on the difference between the maximum radial distance and the minimum radial distance; Based on a preset angle step size, the first angle is incremented, and the process returns to the step of extracting the radial distance extreme values ​​of all time phases from the long-time island reef coastline along the direction of the first angle, until a circumferential sampling is completed, and the radial width change value of all sampled angles is obtained. Initialize the second angle; The two adjacent angles that are spaced apart from the second angle by the preset angle step size are successively used as the third angle and the fourth angle; The gradient of the second angle is obtained by performing first derivative and absolute value operations based on the radial width change value of the third angle, the radial width change value of the fourth angle, and the preset angle step size; The second derivative is calculated based on the radial width change value of the second angle, the radial width change value of the third angle, the radial width change value of the fourth angle, and the preset angle step size to obtain the curvature of the second angle. Based on the preset angle step size, the second angle is incremented, and the process returns to the step of taking the two adjacent angles that are separated from the second angle by the preset angle step size as the third angle and the fourth angle in turn, until the circumferential sampling is completed, so as to obtain the changing gradient and the changing curvature of all sampled angles. The gradient mean and gradient standard deviation are obtained by calculating the gradient changes based on all sampling angles, and the gradient threshold is obtained by converting the gradient mean and gradient standard deviation. The target width variation range is determined based on the continuous angular range where the gradient change is greater than the gradient threshold; Based on the angle range included in each target width variation interval, the starting angle, the ending angle, and the intermediate angle of the corresponding target width variation interval are determined; The degree of change of the corresponding target width variation interval is determined based on the maximum change gradient of all sampling angles in each target width variation interval; Based on the curvature of the change in the intermediate angle of each target width change interval, the change type of the corresponding target width change interval is determined by mapping positive and negative cases.

4. The method of claim 1, wherein, The process of determining the width variation data based on conditions and constructing a target cross-section group in conjunction with the initial island / reef coastline includes the following steps: The average perimeter of the islands and reefs is obtained by averaging the perimeters of the islands and reefs across all time periods. The angle difference and interval angle are determined by mapping the numerical range of the average perimeter of the islands and reefs. Extract the first intersection point along the intermediate angle for each of the target width variation intervals from the initial island / reef coastline; Based on the direction of each first intersection point perpendicular to the initial island / reef coastline, a perpendicular line is constructed as a cross section, and then the first cross section group is obtained by summing them up. Based on the difference between the ending angle and the starting angle corresponding to the target width change interval, determine the angle difference for each target width change interval; If there exists an angle difference greater than the angle difference, extract the second intersection point of the target width variation range along the direction of the starting angle and the ending angle from the initial island / reef coastline; Based on each of the second intersection points, a perpendicular line is constructed in the direction perpendicular to the initial island / reef coastline to form a cross section, and then the two cross section groups are obtained by summing them up. If the second cross-section group is not empty, the second cross-section group is used as the candidate cross-section group; otherwise, the first cross-section group is used as the candidate cross-section group. In the region where the initial island / reef coastline is located between adjacent cross-sections in the candidate cross-section group, a perpendicular line to the initial island / reef coastline is constructed as a cross-section according to the interval angle, and then the third cross-section group is obtained. The target cross-section group is obtained by summing the candidate cross-section group and the third cross-section group.

5. The method of claim 1, wherein, The process of converting the intersection points of the target cross-section group with the long-term island and reef coastline to obtain the changing trends of all cross-sections, and then filtering out the second time point, includes the following steps: Initialize the number of valid years, and take the next time phase after the initial time phase as the fourth time phase; The first section of the target section group is taken as the quantized section; The intersection of the quantized section with the island and reef coastline of the initial time phase is taken as the third intersection point, and the intersection of the quantized section with the island and reef coastlines of all time phases from the initial time phase to the fourth time phase is taken as the fourth intersection point. The sum of the differences between each of the fourth intersection points and the third intersection point is used as the numerator, and the number of valid years minus one is used as the denominator to calculate the average rate of change of the quantized section in the fourth time phase. If the average rate of change is greater than the second threshold, the fourth time phase will be used as the second candidate time point; Take the next section of the target section group as the quantized section, and return to execute the step of taking the intersection of the quantized section and the island reef coastline of the initial time phase as the third intersection point, until all sections of the target section group have been traversed. The number of valid years is incremented, the next time phase of the fourth time phase is taken as the fourth time phase, and the step of taking the first section of the target section group as the quantization section is returned to be executed until all time phases have been traversed. The change trend is obtained by summing the average rate of change of the target cross-section group in all time phases, and the second time point is obtained by summing all the second candidate time points.

6. The method of claim 1, wherein, The net rate of change at the target time point is obtained by binarizing and overlaying the island and reef coastlines based on the corresponding time phases of the first and second time points, including the following steps: The target time point is determined based on the union of the first time point and the second time point; The phase corresponding to the first time point in the target time point is taken as the fifth time phase; The phase preceding the fifth phase is taken as the sixth phase; The island and reef coastlines in the fifth time phase are binarized and assigned values ​​to obtain the first island and reef coastline surface. The island and reef coastlines in the sixth time phase are binarized and assigned values ​​to obtain the second island and reef coastline surface. By subtracting the coastline of the second island from the coastline of the first island, the siltation zone and the erosion zone are determined based on the positive or negative values ​​of each region. The net rate of change in the fifth time phase is obtained by subtracting the area of ​​the erosion zone from the area of ​​the siltation zone, and using the area of ​​the island and reef coastline in the fifth time phase as the denominator. The next time point in the target time point is taken as the fifth time point, and the process returns to the step of taking the previous time point of the fifth time point as the sixth time point, until all time points of the target time point have been traversed.

7. An atoll shoreline spatio-temporal change monitoring device, characterized in that, The apparatus for implementing the method of claim 1 includes: The first module is used to acquire long-term multi-source remote sensing images of the target islands and reefs, and to obtain multi-temporal remote sensing images through preprocessing operations. The second module is used to perform land-water segmentation based on the multi-temporal remote sensing images using the normalized water index to obtain long-term island and reef coastlines; wherein, the long-term island and reef coastlines include island and reef coastlines of each temporal phase. The third module is used to obtain a numerical trend map and a first time point based on the changes in island and reef values ​​according to the long-term island and reef coastline statistics; wherein, the island and reef values ​​include the island and reef perimeter and island and reef area, and the first time point represents the time point when the change in the island and reef values ​​is greater than a first threshold. The fourth module is used to detect radial width changes based on the long-term island and reef coastline through circumferential sampling to obtain width change data; wherein, the width change data includes the starting angle, ending angle, intermediate angle, degree of change, and type of change of the target width change interval; The fifth module is used to perform conditional determination on the width change data and construct a target cross-section group in combination with the initial island and reef coastline; wherein, the initial island and reef coastline represents the island and reef coastline in the initial time phase, and the target cross-section group includes several cross-sections perpendicular to the initial island and reef coastline. The sixth module is used to transform the change trends of all cross sections based on the intersection of the cross sections of the target cross section group and the long-term island and reef coastline, and then filter to obtain the second time point; wherein, the second time point represents the time point where the average rate of change of the change trend is greater than the second threshold. The seventh module is used to obtain the net rate of change at the target time point based on the island and reef coastlines corresponding to the first and second time points through binarization overlay analysis.

8. An electronic device, comprising: The electronic device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the method according to any one of claims 1 to 6.

9. A computer program product, characterised in that, The computer program product includes a computer program that, when executed by a processor, implements the method according to any one of claims 1 to 6.

Images