A method for monitoring the growth of near-shore algae and a monitoring device therefor

Abstract

The present application provides a kind of nearshore algal growth condition monitoring method and its monitoring device, comprising: S1: at the slope shore of water body, water camera and underwater camera are configured, the viewfinder of water camera is directly opposite water body upper surface setting;Underwater camera is inserted into water body along the oblique direction of slope shore;S2: using water camera obtains first image, underwater camera obtains second image;And send to remote monitoring server;S3: remote monitoring server carries out spectral analysis to the first image and second image obtained, determines water bank line position, growing area of periphytic algae;S4: carry out water quality evaluation parameter calculation, obtain monitoring result.This scheme carries out spectral analysis and calculation to first image and second image, obtains the reproduction trend of alga in real time, and additionally provides a kind of specific monitoring device mechanical structure.

Description

Technical Field

[0001] This invention relates to the field of aquatic plant monitoring technology, and in particular to a method and device for monitoring the growth of nearshore algae. Background Technology

[0002] Attached algae are algae that grow or attach to the bottom, banks, aquatic plants, or other aquatic protrusions and floating objects. They are an important biological component and primary producer in aquatic ecosystems. Their growth locations are relatively fixed, their growth environments are diverse, and they are sensitive to changes in water quality. The death and surfacing of large numbers of attached algae has a significant impact on water quality, other aquatic organisms, and water-using equipment along waterways. Analyzing the growth of attached algae in water bodies and understanding their dynamic development trends is an indispensable part of ensuring water quality safety.

[0003] Chinese invention patent CN101980246B discloses a method for detecting the explosive reproduction of various algae and pests. It determines the reproductive status of algae and other organisms by acquiring image features. The method uses a color CCD camera and image acquisition card to acquire and store images at fixed times and locations. A computer image processing program converts the images into grayscale images and calculates one-dimensional and zero-dimensional Betty numbers to obtain a monthly variation curve of the average value. However, while cameras are effective at capturing microorganisms and algae on the water surface, their effectiveness in capturing underwater conditions is very limited, making it difficult to comprehensively and reliably reflect the real-time changes in algae and microorganisms within the water.

[0004] In conclusion, it is essential to provide a device and method for visual monitoring of algae, which can comprehensively and reliably obtain information on algae distribution on the water surface and underwater. Summary of the Invention

[0005] In view of this, the present invention proposes a method and device for real-time video monitoring of algal reproduction in water bodies and monitoring the growth of nearshore algae.

[0006] The technical solution of this invention is implemented as follows:

[0007] On the one hand, the present invention provides a method for monitoring the growth of nearshore algae, comprising the following steps:

[0008] S1: An above-water camera and an underwater camera are installed on the slope of the water body. The viewfinder of the above-water camera is set to face the surface of the water body. The underwater camera extends into the water body along the slope of the bank.

[0009] S2: Use a surface camera to acquire the first image and an underwater camera to acquire the second image; then send them to the remote monitoring server.

[0010] S3: The remote monitoring server performs spectral analysis on the first and second images to determine the location of the shoreline and the area where attached algae grow.

[0011] S4: Calculate water quality evaluation parameters and obtain monitoring results.

[0012] Based on the above technical solutions, preferably, the spectral analysis of the obtained first and second images in step S3 is performed using a method based on three spectral images: red, green, and blue.

[0013] Preferably, determining the shoreline location involves taking a number of pixels in the planar pixel coordinate system where the first image is located. The planar pixel coordinate system has a horizontal X-axis and a Y-axis perpendicular to the X-axis. A straight line is constructed along the X-axis, and the blue spectral value is taken along the constructed line and smoothed. The point where the blue spectral value of the constructed line changes abruptly is taken as the shoreline point. The shoreline is formed by fitting and smoothly connecting the shoreline points of the constructed line. An observation area containing the slope and water body is cut out along the extension direction of the shoreline. The observation area is rotated so that the shoreline is parallel to the X-axis or Y-axis of the planar pixel coordinate system.

[0014] Further preferably, determining the algae growth area involves taking the red and green spectral values ​​of several pixels along a first preset direction within the observation area, plotting red-green spectral curves, and obtaining the red-green spectral difference curve for each pixel. The observation area is identified based on the following characteristics: 1) In the algae growth area, the red spectral values ​​of each pixel fluctuate, while the green spectral values ​​remain unchanged, forming a distinct red-green spectral difference change; 2) In algae-free water areas, the red spectrum is negatively correlated with water depth, while the green spectrum remains stable. In algae-free water areas, the red spectral difference curve gradually decreases as it rises along the slope of the water body; 3) In the slope area, the red, green, and blue spectra satisfy the gray-world assumption, with no significant difference in their mean values. In this area, the red-green spectral difference curve remains stable. The first preset direction is the horizontal length direction of the observation area.

[0015] After confirming the existence of algae-bearing areas within the observation region, a variable-slope oblique line fitting method was used to piecewise fit the red-green spectral difference curve, obtaining fitted oblique lines at both ends corresponding to the algae-free water area and the algae-bearing area. Because the red-green spectral difference in the algae-bearing area is significant, the slope of the oblique line in the algae-bearing area was increased to obtain a piecewise fitted oblique line. Where y represents a point on the difference curve of the red and blue spectra; x represents the horizontal coordinates of the image of the observation area; t represents the horizontal coordinates of the image of the observation area at the halfway point; k is the gain factor; a is the slope of the oblique line, a = (t3*t - t2*t4) / (t1*t - t2 - t2); and b is the offset of the oblique line, b = (t1*t4 - t2*t3) / (t1*t - t2*t2). The fitted oblique line divides the red-green spectral difference curve into two parts, upper and lower. The area above the fitted oblique line is the region with algae. The intersection of the fitted oblique line and the red-green spectral difference curve is the boundary of the algae. The higher the density of algae, the greater the deviation of the red-green spectral difference curve from the fitted oblique line.

[0016] More preferably, the calculation of water quality evaluation parameters in step S4 involves obtaining algal coverage area, algal growth height, and biomass, respectively.

[0017] The algae coverage area represents the area covered by algae within the observation region. N is the number of pixels in the algae-bearing growth area within the observation region. G Using a reference scale, the actual area S1 of a single pixel within the observation area is calculated. Then, the algae coverage area S within the observation area is... G Represented as S G =N G *S1, Because the slope of the water body forms an angle θ with the water surface, the actual algal coverage area also forms an angle θ with the water surface, and the actual algal coverage area S P Corrected to S by the included angle θ P =S G / cosθ;

[0018] The algae growth height represents the average height of algae growth. This is determined by real-time measurement of the second image (using a reference scale image and an underwater camera (3)) showing the algae covering the reference scale. The reference scale image and the second image are scanned vertically. Within the same vertical line, the height of the reference scale image is recorded as H1 pixels, and the height of the second image is recorded as H2 pixels. The height difference is H1-H2, which reflects the algae growth height H on the reference scale. G If the actual height of the reference scale is H0, then the algae growth height corresponding to the pixel difference between the reference scale image and the second image can be calculated.

[0019] Biomass refers to the mass of algae present in a unit area of ​​water within a given time period. The formula for calculating algal density is ρ. G =α+β(GRB), where ρ G Algae density, in mg / cm³ 2α is the density baseline coefficient; β is the adjustment coefficient; G is the green component value of the color; R is the red component value of the color; B is the baseline slope value; and M is the mass of the algae. G The calculation formula is M G =V G *ρ G V G This represents the volume of algae within a default 1 square meter observation area; the formula for calculating biomass PB is PB = M. G / S G .

[0020] On the other hand, the present invention also provides a nearshore algae growth monitoring device, comprising:

[0021] A pole is erected vertically at the top of the slope of the water body;

[0022] An underwater camera, positioned directly above the water body and fixed relative to a pole, is used to acquire the first image of the algae coverage area within its field of view;

[0023] An underwater camera, located below the surface of the water, is used to acquire a second image of the coverage area of ​​attached algae within its field of view;

[0024] The liftable platform is hinged at one end to the upright and at the other end to the underwater camera, and is used to adjust the depth of the underwater camera in the water along the extension direction of the slope.

[0025] The field controller is electrically connected to the above-water camera, the underwater camera, and the liftable platform, respectively. It is used to receive the first image and the second image and send them to the remote monitoring server, and selectively adjust the current position of the liftable platform. The remote monitoring server processes the first image and the second image according to the above-mentioned nearshore algae growth monitoring method.

[0026] Preferably, the liftable platform (4) includes a first link (41), a second link (42), and a sliding part (43). One end of the first link (41) is hinged to the surface of the upright (1) in the axial extension direction, and the other end of the first link (41) extends outward in the direction away from the upright (1). One end of the second link (42) is slidably connected to the end of the first link (41) away from the upright (1), and the other end of the second link (42) is hinged to the sliding part (43). The sliding part (43) is slidably connected to the slope bank and fixedly connected to the underwater camera (3). The first link (41) rotates relative to the axial extension direction of the upright (1) and drives the second link (42) and the sliding part (43) to change their posture.

[0027] More preferably, a reference scale is also provided in the water body, with one end of the reference scale fixed at the bottom of the water body and the other end extending vertically upward along the vertical direction; the side surface of the reference scale is set facing the underwater camera (3).

[0028] More preferably, the sliding part (43) is also provided with a supplementary light, and the light-emitting part of the supplementary light is positioned facing the side surface of the reference scale.

[0029] More preferably, the sliding part (43) is also provided with a cleaning device for cleaning the viewfinder of the underwater camera (3).

[0030] The present invention provides a method and device for monitoring nearshore algal growth, which, compared with the prior art, has the following advantages:

[0031] (1) This solution adopts a real-time image-based processing method, which does not require water quality sampling. It makes full use of the spectral characteristics of water and algae to perform quantitative analysis. The liftable platform can adjust the position of the underwater camera according to the height of the liquid surface, which can more accurately reflect the actual situation of aquatic algae reproduction.

[0032] (2) By using image segmentation and constructing oblique lines, we can better distinguish the abrupt changes in the red-green spectral difference curve, indicate the areas where algae may exist, and further obtain water quality information to provide reliable data support for water monitoring. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the layout of a method and device for monitoring nearshore algae growth according to the present invention.

[0035] Figure 2 This is a structural block diagram of a method and device for monitoring nearshore algae growth according to the present invention.

[0036] Figure 3 This is a flowchart of the method steps for monitoring nearshore algae growth and the monitoring device of the present invention;

[0037] Figure 4 The present invention relates to a method and device for monitoring nearshore algae growth, and presents the reflectance curves of plants and water bodies at different wavelengths and the absorption rate of water to light bands.

[0038] Figure 5 This is an example of a comparison of visible light and near-infrared images of a method and device for monitoring nearshore algae growth according to the present invention.

[0039] Figure 6 This is a schematic diagram of the attached algae growth area of ​​the nearshore algae growth monitoring method and monitoring device of the present invention;

[0040] Figure 7 This is a second image example including a reference scale, illustrating the nearshore algae growth monitoring method and monitoring device of the present invention.

[0041] Figure 8 This is a schematic diagram illustrating the calculation of the elevation of attached algae in a method and device for monitoring nearshore algal growth according to the present invention.

[0042] Figure 9 This is a schematic diagram of the spectral analysis of the shoreline in the first image of a waterborne camera, representing the method and device for monitoring nearshore algae growth according to the present invention.

[0043] Figure 10 This invention relates to a method and device for monitoring the growth of nearshore algae, which describes the spectral characteristics of the algal growth region. Detailed Implementation

[0044] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0045] like Figure 1 Combination Figure 2 As shown, on one hand, the present invention provides a nearshore algae growth monitoring device, including a pole 1, a surface camera 2, an underwater camera 3, a liftable platform 4, and a field controller 5 installed on site.

[0046] The pole 1 is set vertically at the top of the slope of the water body; the slope is set at a certain angle to the water body.

[0047] The underwater camera 2 is located directly above the water body and is fixed relative to the pole 1. It is used to acquire the first image of the algae coverage area within the field of view. The underwater camera 2 is also used to acquire a top view of the water body or bank below, i.e., the first image. The underwater camera is installed on the top of the pole at the monitoring site, above the shoreline, and has rotation, tilt, and zoom functions.

[0048] The underwater camera 3 is located below the water surface and is used to acquire a second image of the algae coverage area within the field of view.

[0049] The liftable platform 4 is hinged to the upright 1 at one end and connected to the underwater camera 3 at the other end. It is used to adjust the depth of the underwater camera 3 in the water along the extension direction of the slope to adapt to changes in the water surface.

[0050] The field controller 5 is electrically connected to the surface camera 2, underwater camera 3, and the liftable platform 4, respectively. It receives the first and second images and sends them to the remote monitoring server, and selectively adjusts the current position of the liftable platform 4. Both the surface camera 2 and underwater camera 3 are controlled by the field controller 5. The monitoring server's computer can remotely obtain video images from the two cameras, analyze the characteristics, growth changes, and biomass of the algae, and achieve automatic online remote monitoring and extraction and storage of quantitative image data, achieving real-time and accurate results. Furthermore, the nearshore algae growth monitoring device is equipped with a battery pack, solar panels, and chargers and inverters to ensure the system can operate continuously for two days in cloudy or rainy conditions. The top of the nearshore algae growth monitoring device is also equipped with a lightning arrester, which connects to an underground grounding network via wires to conduct lightning into the ground, thus ensuring the normal operation of the equipment and the safety of operators during lightning strikes.

[0051] Compared to ordinary water bodies, aquatic plants such as attached algae and aquatic grasses exhibit significant differences in reflectivity at different wavelengths. Figure 3 As shown, the reflectance of ordinary water bodies is generally uniform across the entire visible light spectrum (450-700nm), but weaker in the blue band. Aquatic plants, containing chlorophyll, exhibit strong reflectance in the green band (500-600nm) and weaker reflectance in the red band (600-700nm) and blue band (450-500nm). Based on the similarity in reflectance spectral characteristics between algae and aquatic plants, the following analytical criteria are derived: The weak reflectance of water bodies in the blue band distinguishes them from the shoreline and determines the shoreline location. The uniform and stable reflectance of water bodies in the red and green bands, compared to the strong reflectance of algae in the green band and weak reflectance in the red band, determines the growth area of ​​algae. Furthermore, a greater difference in reflectance between the red and green bands indicates a higher chlorophyll content, suggesting a higher density and greater biomass of algae. However, considering that phytoplankton also contain chlorophyll, they may interfere with the reflectance spectral characteristics of algae. However, the slope of the main canal where this monitoring system is installed is uniform, and the green spectral characteristics of phytoplankton will increase relatively smoothly with the increase of water depth, while attached algae will only form a locally fluctuating green reflectance spectrum in the nearshore zone.

[0052] When different building materials and other debris exist on a slope, its image features satisfy the well-known gray-world hypothesis in the field of computer vision. According to the gray-world hypothesis, when other materials and debris exist on a slope, the average reflectance of these objects tends to be close to gray, that is, the average value of the red, green and blue components tends to be close to the gray value, thus causing a relatively synchronous change in the red and green spectrum.

[0053] like Figure 1 As shown, to better adjust the position of the underwater camera 3 below the water surface, the liftable platform 4 includes a first connecting rod 41, a second connecting rod 42, and a sliding part 43. One end of the first connecting rod 41 is hinged to the surface of the upright 1 in the axial extension direction, and the other end of the first connecting rod 41 extends outward away from the upright 1. One end of the second connecting rod 42 is slidably connected to the end of the first connecting rod 41 away from the upright 1, and the other end of the second connecting rod 42 is hinged to the sliding part 43. The sliding part 43 is slidably connected to the slope bank and fixedly connected to the underwater camera 3. The first connecting rod 41 rotates relative to the axial extension direction of the upright 1, causing the second connecting rod 42 and the sliding part 43 to change their attitude. When the first connecting rod 41 rotates clockwise relative to the upright, it causes the second connecting rod 42 to rotate and causes the sliding part 43 to approach the slope bank surface along the slope bank's inclination direction. Conversely, when the first connecting rod 41 rotates counterclockwise relative to the upright, the sliding part 43 moves away from the slope bank. The second link 42 can extend and retract relative to the first link, adjusting the length of the second link 42 and the sliding part 43 extending beyond the first link 41, thereby allowing the underwater camera 3 to enter different underwater depths.

[0054] To confirm the vertical variation of algae in the water, a reference scale is installed within the water body. One end of the reference scale is fixed to the bottom of the water body, and the other end extends vertically upwards; the side surface of the reference scale is positioned facing the underwater camera 3. Of course, as... Figure 1 As shown, the reference scale can also be set perpendicular to the slope.

[0055] To better capture images below the water surface, a supplementary light is also provided on the sliding part 43. The light-emitting part of the supplementary light is positioned facing the side surface of the reference scale, and the supplementary light is used for supplementary illumination. To prevent underwater debris from obscuring the viewfinder of the underwater camera 3, a cleaning device can be further provided on the sliding part 43. The cleaning device is used to clean the viewfinder of the underwater camera 3.

[0056] Vegetation exhibits significant reflectivity in the near-infrared region around 840nm. The substantial difference in reflectivity between water and attached algae in the near-infrared band allows for clear differentiation of their boundaries in near-infrared images, thus determining the algae's growth area. However, this method only considers the water's reflectance spectrum, neglecting its absorption spectrum. The absorption spectrum refers to the degree to which different wavelengths of light are absorbed as they pass through water. The absorption intensity varies considerably across different wavelengths. Since attached algae grow in near-shore underwater environments, determining how many wavelengths of light of interest can penetrate the water and reach their growth area, and how much reflected light can exit the water and enter the camera, are prerequisites for subsequent spectral analysis. Figure 4 As shown, the absorption spectrum of water exhibits a significant trough in the visible light band between 400-600 nm, indicating that light waves in this band can easily penetrate the water surface, while light waves in other bands are strongly absorbed by the water and thus have difficulty penetrating the water body. This means that when performing spectral analysis of attached algae images, using the visible light band, i.e., the absorption spectrum in the 400-750 nm range, makes it easier to obtain underwater images. Infrared spectra, however, have difficulty penetrating water. In the near-infrared band, the longer the wavelength, the stronger the absorption by the water, and the lower the chance of obtaining clear underwater images.

[0057] To investigate the combined effects of strong reflection by plants in the near-infrared band, forming near-infrared bright images, and strong absorption of near-infrared bands by water, forming near-infrared dark images, experimental imaging was conducted using an infrared camera, a visible light color camera, and filters of different wavelengths for comparison. In the experiment, a piece of intact moss was peeled from the shore as a plant block to represent algae, and visible light and near-infrared images of it placed on a dry surface on the water were captured as the initial state for the experiment. Figure 5 The image shows a comparison of visible light and near-infrared images for different algae located at different depths above, below, and above the water surface. It is evident that when algae or aquatic plants are at a certain depth underwater, near-infrared spectral images become indistinguishable from the environment. Due to the strong absorption of infrared light by water, near-infrared spectral images, while suitable for analyzing vegetation on land, are unsuitable for analyzing underwater plant targets. Therefore, this scheme employs a method based on red, green, and blue spectral images for spectral analysis.

[0058] This invention also provides a method for monitoring nearshore algal growth, which specifically includes the following steps:

[0059] S1: Configure the aforementioned nearshore algae growth monitoring device. The structure of the monitoring device is referenced below. Figure 1 and Figure 2 As shown.

[0060] S2: Use surface camera 2 to acquire the first image and underwater camera 3 to acquire the second image; field controller 5 sends the first and second images to the remote monitoring server.

[0061] S3: The remote monitoring server performs spectral analysis on the first and second images to determine the location of the shoreline and the area where attached algae grow.

[0062] Step S3 describes performing spectral analysis on the obtained first and second images. This spectral analysis is performed using a method based on the red, green, and blue spectral images, the characteristics of which have been discussed above.

[0063] Specifically, determining the shoreline location involves taking a planar pixel coordinate system containing the first image. This system has a horizontal X-axis and a Y-axis perpendicular to the X-axis. Several pixels are randomly selected within this system, and a straight line is constructed along the X-axis. Blue spectral values ​​are taken along this line and smoothed. Points where the blue spectral values ​​of the constructed line change abruptly are designated as shoreline points. These shoreline points are fitted and smoothly connected to form the shoreline. An observation area containing the slope and water body is then cut along the shoreline's extension direction. This observation area is rotated so that the shoreline is parallel to either the X-axis or Y-axis of the planar pixel coordinate system. Since the camera's observation position and angle along the shoreline are fixed, the actual water level can be calculated from the pixel distances in the image. The calculations of parameters such as coverage and growth area in the following text are based on this. Figure 9 As shown, Figure 9 The left figure has a horizontal X-axis and a vertical Y-axis constructed at the top. A horizontal construction line is chosen; this construction line is... Figure 9 The upper left straight line segment deviating from the X-axis is used to obtain the blue spectrum values ​​of the pixels corresponding to this constructed line. These values ​​are then smoothed to create a curve. Points where the gradient of the smoothed blue spectrum curve significantly increases are the waterfront points. Repeating this process to obtain multiple waterfront points and then smoothly connecting them forms the waterfront area. Figure 9 The sloping shoreline in the left image; the observation area along the shoreline, including a portion of the slope and water body, is... Figure 9 The rectangle in the left image is rotated and aligned to ensure the observation area has orthogonal edges, thus obtaining... Figure 9 The image on the right is the result of automatic rotation and cropping.

[0064] like Figure 10As shown, determining the algae-bearing growth area involves taking the red and green spectral values ​​of several pixels along a first preset direction within the observation area, plotting red-green spectral curves, and obtaining the red-green spectral difference curve for each pixel. The observation area is identified based on the following characteristics: 1) In the algae-bearing growth area, the red spectral values ​​of each pixel fluctuate, while the green spectral values ​​remain unchanged, forming a distinct red-green spectral difference change; 2) In algae-free water areas, the red spectrum is negatively correlated with water depth, while the green spectrum remains stable. In algae-free water areas, the red spectral difference curve gradually decreases as it rises along the slope of the water body; 3) In the slope area, the red, green, and blue spectra satisfy the gray-world assumption, with no significant difference in their mean values, and the red-green spectral difference curve remains stable in this area. As a preferred implementation, the point at 1 / 2 of the horizontal direction of the image along the obtained green and red spectral difference curves can be reasonably considered as the boundary between algae-free and algae-bearing water areas. The first preset direction selected here is the horizontal length direction of the observation area. Figure 9 After the image on the right is automatically rotated and cropped, the range of the difference between the red and green spectra is used as the vertical axis, and a horizontal tangent line perpendicular to the vertical axis is used as the horizontal axis. The difference curve between the green and red spectra of each pixel on the horizontal tangent line is obtained. The difference curve between the green and red spectra of each pixel on the horizontal tangent line is then fitted to construct a straight line.

[0065] Specifically, after confirming the existence of algae-bearing areas within the observation region, a variable-slope oblique line fitting method was used to piecewise fit the red-green spectral difference curve, obtaining fitted oblique lines at both ends corresponding to the algae-free water area and the algae-bearing area. Because the red-green spectral difference in the algae-bearing area is significant, the slope of the oblique line in the algae-bearing area was increased to obtain a piecewise fitted oblique line. Where y represents a point on the difference curve of the red and blue spectra; x represents the horizontal coordinates of the image of the observation area; t represents the horizontal coordinates of the image of the observation area at the halfway point; k is the gain factor; a is the slope of the oblique line, a = (t3*t - t2*t4) / (t1*t - t2 - t2); and b is the offset of the oblique line, b = (t1*t4 - t2*t3) / (t1*t - t2*t2). The fitted oblique line divides the red-green spectral difference curve into upper and lower parts. The area above the fitted oblique line represents the region with algae growth. The intersection of the fitted oblique line and the red-green spectral difference curve marks the boundary of the algae. The higher the algae density, the greater the deviation of the red-green spectral difference curve from the fitted oblique line. Algae-bearing areas are represented in green, and algae-free areas in black. Different shades of green are assigned based on the magnitude of the red-green difference, with brighter greens for areas of greater difference. Drawing algae-bearing growth areas on different images allows for a relatively accurate correspondence with actual conditions. Figure 6 This diagram illustrates how an RGB original image can be drawn as a region for the growth of attached algae.

[0066] S4: Calculate water quality evaluation parameters and obtain monitoring results.

[0067] The water quality assessment parameters are calculated by obtaining 1) algal coverage area, 2) algal growth height and 3) biomass.

[0068] 1) Algae coverage area represents the area covered by algae within the observation region. N is the number of pixels in the algae-bearing growth area within the observation region. G Using a reference scale, the actual area S1 of a single pixel within the observation area is calculated. Then, the algae coverage area S within the observation area is... G Represented as S G =N G *S1, Because the slope of the water body forms an angle θ with the water surface, the actual algal coverage area also forms an angle θ with the water surface, and the actual algal coverage area S P Corrected to S by the included angle θ P =S G / cosθ.

[0069] Another indicator for evaluating algal cover area is coverage, which refers to the algal cover area within a 1-square-meter observation area by default, and the total area of ​​the observation area within a 1-square-meter area by default. The value of coverage is [0, 1].

[0070] 2) Algae growth height, representing the average height of algae growth, is determined by real-time measurement of the algae covering the reference scale image and a second image taken by underwater camera 3. The reference scale image and the second image are scanned vertically. Within the same vertical line, the height of the reference scale image is recorded as H1 pixels, and the height of the base scale in the second image is recorded as H2 pixels. The height difference is H1-H2, which reflects the algae growth height H on the reference scale. G If the actual height of the reference scale is H0, then the algae growth height corresponding to the pixel difference between the reference scale image and the second image can be calculated. like Figure 7 and Figure 8 As shown, Figure 7 The algae cover a certain height on the side surface of the reference scale in the image, causing its bottom boundary to become blurred. The difference between the initial height H1 of the base scale and the height H2 of the reference scale in the second image is the pixel height difference of the algae covering the reference scale, which can then be converted into the actual height.

[0071] 3) Biomass refers to the mass of algae present in a unit area of ​​water within a certain time unit. The formula for calculating algae density is ρ. G=α+β(GRB), where ρ G Algae density, in mg / cm³ 2 α is the density baseline coefficient; β is the adjustment coefficient; G is the green component value of the color; R is the red component value of the color; B is the baseline slope value; and M is the mass of the algae. G The calculation formula is M G =V G *ρ G V G This represents the volume of algae within a default 1 square meter observation area; the formula for calculating biomass PB is PB = M. G / S G .

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for monitoring nearshore algal growth, characterized in that, Includes the following steps: S1: An above-water camera (2) and an underwater camera (3) are installed on the slope of the water body. The viewfinder of the above-water camera (2) is set facing the upper surface of the water body; the underwater camera (3) extends into the water body along the slope of the bank. S2: Use the surface camera (2) to acquire the first image and the underwater camera (3) to acquire the second image; and send them to the remote monitoring server; S3: The remote monitoring server performs spectral analysis on the first and second images to determine the location of the shoreline and the area where attached algae grow. Step S3 describes performing spectral analysis on the obtained first and second images, which is done using a method based on the red, green, and blue spectral images. Determining the shoreline location involves using a planar pixel coordinate system containing the first image, where the planar pixel coordinate system has a horizontal direction. X axis and perpendicular to X Axial direction Y Axis, taking any number of pixels in the planar pixel coordinate system and along X A straight line is constructed along the axis. Blue spectral values ​​are taken along this line and smoothed. Points where the blue spectral values ​​of the constructed line change abruptly are designated as shoreline points. Several shoreline points are fitted and smoothly connected to form a shoreline. An observation area containing slopes and water is cut along the extension direction of the shoreline. This observation area is then rotated so that the shoreline aligns with the planar pixel coordinate system. X shaft or Y The axes are parallel; The algae-bearing growth area is defined by taking the red and green spectral values ​​of several pixels along a first preset direction within the observation area, plotting red-green spectral curves, and obtaining the red-green spectral difference curve for each pixel. The observation area is identified based on the following characteristics: 1) In the algae-bearing growth area, the red spectral values ​​of each pixel fluctuate, while the green spectral values ​​remain unchanged, forming a distinct red-green spectral difference change; 2) In algae-free water areas, the red spectrum is negatively correlated with water depth, while the green spectrum remains stable. In algae-free water areas, the red spectral difference curve gradually decreases as it rises along the slope of the water body; 3) In the slope area, the red, green, and blue spectra satisfy the gray-world assumption, with no significant difference in their mean values. In this area, the red-green spectral difference curve remains stable. The first preset direction is the horizontal length direction of the observation area. After confirming the existence of algae-bearing areas within the observation region, a variable-slope oblique line fitting method was used to piecewise fit the red-green spectral difference curve, obtaining fitted oblique lines at both ends corresponding to the algae-free water area and the algae-bearing area. Because the red-green spectral difference in the algae-bearing area is significant, the slope of the oblique line in the algae-bearing area was increased to obtain a piecewise fitted oblique line. ,in y Points on the curve representing the difference between the red and blue spectra; x Represents the horizontal coordinates of the image over the observed area; t The coordinates of the image of the measured area at the horizontal halfway point; k As a gain factor; a The slope of the sloping line. , b This represents the offset of the diagonal line. , ; , , The fitted oblique line divides the red-green spectral difference curve into two parts, upper and lower. The area above the fitted oblique line is the area with algae. The intersection of the fitted oblique line and the red-green spectral difference curve is the boundary of the algae. The higher the density of algae, the greater the deviation of the red-green spectral difference curve from the fitted oblique line. S4: Calculate water quality evaluation parameters and obtain monitoring results.

2. The method for monitoring nearshore algal growth according to claim 1, characterized in that, Step S4 involves calculating water quality evaluation parameters, which includes obtaining algal coverage area, algal growth height, and biomass. Algal coverage area represents the area covered by algae within the observation region. It is calculated by counting the number of pixels in the algal growth area within the observation region. N G The actual area of ​​a single pixel within the observation area is calculated using a reference scale. S 1 The algal coverage area within the observation area S G Represented as Because the slope of the water body forms an angle with the water surface The actual area covered by algae also forms an angle with the water surface. Actual algae coverage area S P Through the included angle Revised to ; The algae growth height represents the average height of algae growth. It is determined by real-time measurement of the second image of algae covering the reference scale using a reference scale image and an underwater camera (3). The reference scale image and the second image are scanned with a vertical line. The scale height of the reference scale image within the same vertical line is recorded as... H 1 The height of the scale bar in the second image is denoted as pixels. H 2 pixels, height difference is H 1 -H 2 This reflects the height of algal growth on the baseline. H G Let the actual height of the reference scale be H 0 Then, the algae growth height corresponding to the pixel difference between the baseline image and the second image can be calculated. ; Biomass refers to the mass of algae present per unit area of ​​water within a given time period. The formula for calculating algae density is: ,in Algae density, in mg / cm³ 2 ; This is the density reference coefficient; This is the adjustment coefficient; G This represents the green component value of the color; R The red component value of the color; B The baseline slant value; the mass of algae. The calculation formula is: , This represents the volume of algae within a default 1 square meter observation area; biomass. The calculation formula is: .

3. A device for monitoring nearshore algal growth, characterized in that, include: A pole (1) is erected vertically on the top of the slope of the water body; The underwater camera (2) is located directly above the water body and is fixed relative to the pole (1) to acquire the first image of the algae coverage area within the field of view; An underwater camera (3) is located below the surface of the water body and is used to acquire a second image of the coverage area of ​​attached algae within the field of view; The liftable platform (4) is hinged to the pole (1) at one end and connected to the underwater camera (3) at the other end, and is used to adjust the depth of the underwater camera (3) in the water along the extension direction of the slope. The field controller (5) is electrically connected to the above-water camera (2), the underwater camera (3) and the liftable platform (4) respectively, and is used to receive the first image and the second image and send them to the remote monitoring server, and selectively adjust the current position of the liftable platform (4); the remote monitoring server processes the first image and the second image in accordance with the nearshore algae growth monitoring method according to any one of claims 1-2.

4. The nearshore algae growth monitoring device according to claim 3, characterized in that, The liftable platform (4) includes a first link (41), a second link (42), and a sliding part (43). One end of the first link (41) is hinged to the surface of the upright (1) in the axial extension direction. The other end of the first link (41) extends outward in the direction away from the upright (1). One end of the second link (42) is slidably connected to the end of the first link (41) away from the upright (1). The other end of the second link (42) is hinged to the sliding part (43). The sliding part (43) is slidably connected to the slope bank and fixedly connected to the underwater camera (3). The first link (41) rotates relative to the axial extension direction of the upright (1) and drives the second link (42) and the sliding part (43) to change their posture.

5. The nearshore algae growth monitoring device according to claim 4, characterized in that, A reference scale is also provided in the water body. One end of the reference scale is fixed at the bottom of the water body, and the other end extends vertically upward along the vertical direction. The side surface of the reference scale is set facing the underwater camera (3).

6. The nearshore algae growth monitoring device according to claim 5, characterized in that, The sliding part (43) is also provided with a supplementary light, and the light-emitting part of the supplementary light is set facing the side surface of the reference scale.

7. The nearshore algae growth monitoring device according to claim 4, characterized in that, The sliding part (43) is also provided with a cleaning device, which is used to clean the viewfinder of the underwater camera (3).

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