CN114047185A - Visible light imaging device and monitoring method suitable for shallow sea coral reef underwater monitoring - Google Patents
Visible light imaging device and monitoring method suitable for shallow sea coral reef underwater monitoring Download PDFInfo
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Abstract
The invention belongs to the technical field of coral reef ecosystem monitoring, and discloses a visible light imaging device and a monitoring method suitable for shallow sea coral reef underwater monitoring, wherein the visible light imaging device comprises: the system comprises a master control platform, a spectrum camera, a solar descending irradiance measuring instrument, a depth sounding sonar and a water sample collecting device; the spectrum camera focal plane, the solar downlink irradiance measuring instrument focal plane and the depth sounding sonar detection device are positioned on a plane parallel to the sea level; the shooting direction of the spectrum camera is perpendicular to the sea level, and the solar downward irradiance measurement and measurement direction is opposite to the shooting direction of the spectrum camera. The imaging device arranged under water is used for imaging, so that the influence of solar reflection flare and the action of the wave lens is effectively avoided; by utilizing the spectrum of the seabed coral reef target and the solar downlink spectrum which are synchronously obtained, remote sensing reflectivity data of the coral reefs located in different depth sea areas are obtained through calculation, and imaging brightness difference caused by weakening of sunlight rays in different water depths is avoided.
Description
Technical Field
The invention belongs to the technical field of coral reef ecosystem monitoring, and particularly relates to a visible light imaging device and a monitoring method suitable for shallow sea coral reef underwater monitoring.
Background
At present, the purpose of monitoring a coral reef ecosystem is to discover and identify coral reefs, classify the types of the coral reefs on the basis of the coral reefs, and evaluate the health conditions of the coral reefs; the reflectivity spectrum identification and diagnosis method based on optical remote sensing is one of the main approaches for detecting, classifying and evaluating the coral reefs. The difficulty and the characteristics of the coral reef remote sensing monitoring are as follows: firstly, when a coral reef is observed, an imaging device arranged above a water surface of a satellite, an unmanned aerial vehicle or even a measuring ship is often influenced by sea air interface refraction and water surface reflection flare, and is also influenced by double influences of water radiation transmission and atmospheric radiation transmission, so that the image distortion, image pollution and spectrum distortion of an optical imaging result are caused; secondly, the depth of a true light layer of a region where most of coral reefs grow is large, and the region is distributed in a sea area which is shallow with the depth of about 20m above the true light layer, light rays of the region are good, but light ray energy is exponentially attenuated along with the increase of the depth, so that the problem that when optical measurement is carried out on the water surface, targets of the same type are in different water depth regions in the same image, and the targets have different reflectivities is caused; thirdly, the area where the coral reef is suitable for growing and densely growing is often the area where suspended particles, chlorophyll and nutrient substances are abundant, and the completely clean water quality condition cannot be achieved, so that the coral reef can be remotely monitored to a certain extent. Therefore, a coral reef underwater optical imaging device needs to be designed to solve various distortions and distortions of water surface imaging in coral reef remote sensing monitoring, overcome reflectivity errors caused by different water depths, and solve the problem of imaging quality reduction caused by light energy attenuation due to poor water quality conditions. For the monitoring requirement of the coral reef ecosystem, an underwater coral reef optical imaging device based on design and an image shot by the underwater coral reef optical imaging device are needed to develop a coral reef type identification and health assessment method.
For remote sensing monitoring of the coral reef ecosystem, the underwater imaging device has the potential of overcoming the technical problem of underwater target imaging. However, the current underwater optical imaging apparatus has not been able to effectively solve the above problems for reasons including: firstly, reflectivity spectrum imaging data which are crucial to coral reef detection, classification and evaluation cannot be effectively acquired, and secondly, absorption and scattering influences between a lens and a target due to water radiation transmission cannot be eliminated, and particularly, the signal-to-noise ratio of the imaging data is difficult to improve under the low-illumination condition due to the influence of water depth. Therefore, a new visible light imaging device and a monitoring method suitable for underwater monitoring of the shallow sea coral reefs are needed.
Through the above analysis, the problems and defects of the prior art are as follows:
(1) the existing imaging device arranged on the water surface of a satellite, an unmanned aerial vehicle or even a measuring ship often suffers from the influence of lens effect caused by sea-air interface refraction and flare caused by water surface reflection due to the existence of waves when the coral reef is observed, and simultaneously suffers from double influences of water radiation transmission and atmospheric radiation transmission, so that the image distortion, image pollution and spectrum distortion of an optical imaging result are caused.
(2) The depth of a true light layer of most regions where the coral reefs grow is large, the regions are distributed in sea areas with the upper layer of the true light layer being about 20m or less shallow, light in the regions is good, but with the increase of the depth, light energy is exponentially attenuated, and the problem that when coral reef optical remote sensing monitoring is carried out by an above-water method is caused, targets of the same type show different reflectivities in different water depth regions in the same image is solved.
(3) The area that the coral reef is suitable for growing and intensive growth often also is the abundant area of suspended particles, chlorophyll and nutrient substance, and not completely clean water quality condition can cause certain influence to coral reef remote sensing monitoring, leads to the formation of image quality to reduce.
(4) The existing underwater optical imaging device cannot effectively acquire reflectivity spectrum imaging data which are crucial to coral reef detection, classification and evaluation, cannot remove absorption and scattering influences between a lens and a target due to water radiation transmission, and particularly cannot improve the signal-to-noise ratio of the imaging data under a low-illumination condition due to water depth influence.
The difficulty in solving the above problems and defects is:
(1) the influence of lens effect and solar flare caused by waves is difficult to solve by the water imaging method, and the randomness and uncertainty of the interference information cause that the current correction method cannot ensure that the feature information of the coral reef is completely recovered and retained;
(2) the attenuation effect of electromagnetic waves in seawater radiation transmission is obvious and is strongly related to water quality conditions, and the imaging method on the water surface cannot be completed in the aspects of water depth measurement and water quality measurement, so that the coral reef imaging spectrum cannot be corrected, the imaging results of the similar coral reef bottom types at different depths are greatly different, and the obtained imaging results are distorted.
The significance of solving the problems and the defects is as follows:
the method breaks through a series of problems and defects in the traditional coral reef monitoring method above the water surface, solves the problems of distortion and pollution of visible light wave band electromagnetic waves containing coral reef information due to sea-air interface refraction and reflection, and realizes high-precision real-time correction of coral reef information attenuation caused by different water depths and water quality changes. The method really realizes high-fidelity imaging of the coral reef substrate type and the coral reef ecosystem below the water surface, further monitors the coral reefs and living reef building corals, provides unprecedented high-fidelity and distortion-free optical remote sensing imaging data for health assessment of the coral reef ecosystem, and has great significance for protecting the coral reef ecosystem in China and maintaining the safety of the coral island reef in China.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a visible light imaging device and a monitoring method suitable for underwater monitoring of a shallow sea coral reef.
The invention is realized in this way, a visible light imaging device suitable for shallow sea coral reef underwater monitoring, the visible light imaging device suitable for shallow sea coral reef underwater monitoring comprises: the system comprises a master control platform, a spectrum camera, a solar downlink irradiance measuring instrument, a depth sounding sonar and a water sample collecting device.
Wherein, the focal plane of the spectrum camera, the focal plane of the solar downward irradiance measuring instrument and the sounding sonar detection device are positioned on a plane parallel to the sea level; the shooting direction of the spectrum camera is perpendicular to the sea level, and the solar downward irradiance measurement and measurement direction is opposite to the shooting direction of the spectrum camera.
Further, the general control platform is used for providing integration space, power supply, control and data storage interaction for the spectral camera, the solar downlink irradiance measuring instrument, the depth sounding sonar and the water sample collecting device; the master control platform needs to be sealed and waterproof; the integrated direct-current power supply provides stable electric energy for the spectral camera, the solar downward irradiance measuring instrument, the depth sounding sonar and the water sample collecting device; the integrated control unit controls the switching and coordination of all internal devices and provides storage and reading services for data acquired by the integrated devices.
Further, the inside of the spectrum camera comprises a camera lens assembly, a CCD or CMOS optical recording array, a storage device and the like; the field angle phi of the camera should not be less than 40 degrees in air; the spectrum camera comprises characteristic wave bands with central wavelengths of 395nm, 430nm, 490nm, 517nm, 575nm, 600nm and 650nm, the wave bands are all the preferred wave bands for coral reef remote sensing observation, and at least 3 coral reef characteristic wave bands including 575nm, 600nm and 650nm are included; when the spectrum camera works, the lens of the spectrum camera is vertically downward to form a view field; the shooting mode of the spectrum camera during working is frame-type imaging.
Furthermore, the wave band of the solar downward irradiance measuring instrument is set to be the same as that of the spectrum camera, and the direction of the light receiving lens is vertical to the upward direction; when the solar downward irradiance measuring instrument works, the distance between a lens of the solar downward irradiance measuring instrument and the sea surface is more than or equal to 30 cm; the function of the solar downlink irradiance measuring instrument is to measure the remote sensing incident energy taking the sun as a light source and provide incident energy measurement for the remote sensing reflectivity calculation of the spectral camera measurement data; when the solar downlink irradiance measuring instrument works, synchronous data acquisition with the spectrum camera is realized through the control unit in the master control platform.
Further, the depth sounding sonar is connected with the master control platform through a cable, and the direction of acoustic distance measurement is consistent with the direction of the spectrum camera; the depth sounding sonar has the function of measuring the distance between a scene target and the spectrum camera at the working moment of the spectrum camera and is used for carrying out water body radiation transmission correction on the spectrum energy received by the spectrum camera.
Further, when the position of the spectral camera is stable, before data recording is started or in a short time after data recording is finished, the water sample collecting device is opened, so that the water body is filled in the collecting device, and then the sealing valve is closed, so that water sample collection is finished; the water sample collecting device is used for collecting water samples near the shooting scene when the spectrum camera works, analyzing water quality parameters of the water at the position and at the moment, and performing water radiation transmission correction on the spectrum energy received by the spectrum camera by using the parameters.
Further, the spectrum camera, the solar downward irradiance measuring instrument and the depth sonar need to measure and record data at the same time during work.
Another object of the present invention is to provide a monitoring method of a visible light imaging device based on shallow sea coral reef underwater monitoring, which applies the visible light imaging device suitable for shallow sea coral reef underwater monitoring, wherein the monitoring method of the visible light imaging device based on shallow sea coral reef underwater monitoring comprises the following steps:
step one, the method is suitable for shallow sea coralThe visible light imaging device for underwater monitoring of the reef is completely arranged underwater; wherein, the h2The length of the observation lens is not less than 30cm, so that the observation lens of the solar descending irradiance measuring instrument is prevented from being exposed above the water surface due to sea surface fluctuation such as waves;
step two, when the coral reef is shot underwater, the distance from the coral reef is measured in real time by a depth sonar; wherein the distance h between the device and the seabed is more than h1；
Thirdly, when the visible light imaging device reaches a certain position in a sea area where the coral reefs are distributed, selecting a proper working depth according to measurement data obtained by a depth sonar;
fourthly, the master control platform stops moving and keeps static relative to the submarine coral reef target, and the water sample collecting device starts collecting water samples until the water samples are collected;
and step five, when the master control platform reaches and maintains a stable state again, the spectrum camera and the solar downward irradiance measuring instrument are started to work at the same time, the measured data are recorded at the same time, and data backup is carried out on the master control platform.
Further, the monitoring method of the visible light imaging device based on the shallow sea coral reef underwater monitoring further comprises the following steps:
the wavelength lambda light intensity recorded by the photosensitive element of the solar downward irradiance measuring instrument is EλoThe light intensity recorded by the light-sensitive element of the spectral camera is Eλ1：
In the formula (1), αλThe attenuation coefficient is the attenuation coefficient of light with the wavelength of lambda in a unit optical path in seawater, and the attenuation coefficient is obtained by water sample samples collected by a water sample collecting device through water quality analysis and the like.
Further, the monitoring method of the visible light imaging device based on the shallow sea coral reef underwater monitoring further comprises the following steps:
the seawater quality condition is assumed to be unchanged in a limited measurement space; rλFor subsea targets, e.g. coralReflectivity of reef or the like to light having a wavelength of lambda, and reflectivity R in the formula (1) is releasedλComprises the following steps:
when the spatial position of each pixel element in the field of view of the spectral camera is considered, formula (1) is changed to:
in the formula (3), (i, j) is a pixel coordinate in the image with the central pixel as an origin, and the number of the pixels in the column of the spectrum camera is N, then:
x＝(h2+((i*L/2N)2+(j*L/2N)2)1/2)1/2
(4)
equation (2) is then modified to the reflectance calculation equation relating to the spatial position of each pixel:
by combining all the technical schemes, the invention has the advantages and positive effects that: the invention provides a visible light imaging device and a monitoring method suitable for shallow sea coral reef underwater monitoring, which are oriented to the remote sensing monitoring and evaluation requirements of a tropical sea area shallow water coral reef ecosystem, utilize the luminous flux of a visible light spectrum section provided by solar downlink radiation, and simultaneously remove the attenuation of different wave band electromagnetic wave light paths caused by different water quality conditions according to the actually measured water quality environment parameters, thereby finally obtaining the reflectivity spectrum imaging data which are consistent to the same type of target under different seawater depth conditions; and developing coral reef detection, classification and health assessment methods based on the underwater optical reflectivity spectral imaging data of the coral reefs.
The invention effectively solves the influence of solar reflection flare and wave lens action during the above-water imaging through the imaging of the underwater spectrum camera; by utilizing the spectrum of the seabed coral reef target and the solar downlink spectrum which are synchronously obtained, the remote sensing reflectivity data of the coral reefs in different depth sea areas can be obtained through calculation, and the imaging brightness difference caused by the attenuation of the sunlight in different water depths is avoided.
According to the invention, the distance between the spectrum camera and the submarine coral reef target obtained through real-time measurement and the water sample analysis data obtained through the water sample collecting device can be used for effectively correcting the influence of reflected light of the submarine target on radiation transmission of a light path water body, improving the accuracy of remote sensing reflectivity data and enhancing the imaging quality. Meanwhile, the measurement height, namely the distance between the spectral camera and the coral reef target, can be adjusted only according to different water depth conditions of the coral reef distribution area, all data acquisition processes can be automatically completed, and the method is convenient to operate, safe and reliable.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a structural arrangement diagram of a visible light imaging device suitable for underwater monitoring of shallow sea coral reefs provided by an embodiment of the invention;
in the figure: 1. a spectral camera; 2. a solar downward irradiance measuring instrument; 3. sounding sonar; 4. a water sample collection device; 5. a master control platform; 6. a solar downward irradiance measuring instrument photosensitive element; 7. a spectral camera light sensing element.
Fig. 2 is a flow chart of a monitoring method of the visible light imaging device based on shallow sea coral reef underwater monitoring provided by the embodiment of the invention.
Fig. 3 is a diagram illustrating the effect of reflectivity spectrum changes before and after correction of water bodies in different coral reef areas according to an embodiment of the present invention. (a) In the step before the reef, the coverage rate of the coral reef is about 15 percent, and the water depth is about 7 m; (b) the coral reef coverage rate of the coral deposition area is about 35 percent, and the water depth is about 13 m.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following 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.
Aiming at the problems in the prior art, the invention provides a visible light imaging device and a monitoring method suitable for underwater monitoring of shallow sea coral reefs, and the invention is described in detail below by combining with the attached drawings.
As shown in fig. 1, a visible light imaging device suitable for underwater monitoring of shallow sea coral reefs provided by the embodiment of the present invention includes: the system comprises a master control platform, a spectrum camera, a solar downlink irradiance measuring instrument, a depth sounding sonar and a water sample collecting device.
Wherein, the focal plane of the spectrum camera, the focal plane of the solar downward irradiance measuring instrument and the sounding sonar detection device are positioned on a plane parallel to the sea level; the shooting direction of the spectrum camera is perpendicular to the sea level, and the solar downward irradiance measurement and measurement direction is opposite to the shooting direction of the spectrum camera.
As shown in fig. 2, the monitoring method of the visible light imaging device based on shallow sea coral reef underwater monitoring provided by the embodiment of the invention comprises the following steps:
s101, completely placing the visible light imaging device suitable for the shallow sea coral reef underwater monitoring under water; wherein, the h2Not less than 30 cm;
s102, when the coral reef is shot underwater, the distance between the coral reef and the coral reef is measured in real time by a depth sonar; wherein the distance h between the device and the seabed target is more than h1；
S103, when the visible light imaging device reaches a certain position in a sea area where coral reefs are distributed, selecting a proper working depth according to measurement data obtained by a depth finding sonar;
s104, the master control platform stops moving and keeps static relative to a submarine coral reef target, and the water sample collecting device starts collecting water samples until the water sample collecting is finished;
and S105, under the condition that the master control platform is kept stable, the spectrum camera and the solar downward irradiance measuring instrument are started to work at the same time, the measured data are recorded at the same time, and data backup is carried out on the master control platform.
The technical solution of the present invention will be further described with reference to the following examples.
Example 1
The invention aims to provide a coral reef underwater optical spectrum imaging device, which aims to meet the requirements of remote sensing monitoring and evaluation of a tropical sea area shallow water coral reef ecosystem, utilizes luminous flux of a visible spectrum section provided by solar downlink radiation, and simultaneously removes attenuation of electromagnetic wave light paths of different wave bands caused by different water quality conditions according to actually measured water quality environment parameters so as to finally obtain reflectivity spectrum imaging data which are consistent to the same type of targets under different seawater depth conditions. And developing coral reef detection, classification and health assessment methods based on the underwater optical reflectivity spectral imaging data of the coral reefs.
In order to achieve the purpose, the invention adopts the technical scheme that:
an underwater spectral imaging device and a monitoring method suitable for monitoring a shallow sea coral reef ecosystem. The method comprises the following steps: the system comprises a master control platform, a spectrum camera, a solar downlink irradiance measuring instrument, a depth sounding sonar and a water sample collecting device. The spectrum camera focal plane, the solar downlink irradiance measuring instrument focal plane and the depth sounding sonar detection device are positioned on a plane parallel to the sea level; the shooting direction of the spectrum camera is perpendicular to the sea level, and the solar downward irradiance measurement and measurement direction is opposite to the shooting direction of the spectrum camera.
The master control platform is used for providing integration space, power supply, control and data storage interaction for the spectral camera, the solar downlink irradiance measuring instrument, the depth sounding sonar and the water sample collecting device. The master control platform needs to be sealed and waterproof; the integrated direct-current power supply provides stable electric energy for the spectral camera, the solar downward irradiance measuring instrument, the depth sounding sonar and the water sample collecting device; the integrated control unit controls the switching and coordination of all internal devices and provides storage and reading services for data acquired by the integrated devices.
The spectrum camera internally comprises a camera lens assembly, a CCD or CMOS optical recording array, a storage device and the like. The field angle Φ of the camera should be no less than 40 ° in air. The spectral camera comprises characteristic wave bands with central wavelengths of 395nm, 430nm, 490nm, 517nm, 575nm, 600nm, 650nm and the like, the wave bands are all the preferable wave bands for the coral reef remote sensing observation, and at least comprises 3 coral reef characteristic wave bands of 575nm, 600nm, 650nm and the like. When the spectrum camera works, the lens of the spectrum camera is vertically downward to form a view field. The shooting mode of the spectral camera during working is frame-type imaging.
The solar downward irradiance measuring instrument has the same wave band setting as the spectral camera, and the light receiving lens is vertical upwards. When the solar downward irradiance measuring instrument works, the distance between a lens of the solar downward irradiance measuring instrument and the sea surface is not less than 30 cm. The function of the solar downlink irradiance measuring instrument is to measure the remote sensing incident energy taking the sun as a light source and provide incident energy measurement for the remote sensing reflectivity calculation of the spectral camera measurement data. When the solar downlink irradiance measuring instrument works, synchronous data acquisition with the spectrum camera is realized through the control unit in the master control platform.
The sounding sonar is connected with a master control platform through a cable, and the direction of acoustic distance measurement is consistent with the direction of the spectrum camera. The function of the sounding sonar is to measure the distance between the scene target and the spectrum camera at the working moment of the spectrum camera, and is used for carrying out water radiation transmission correction on the spectrum energy received by the spectrum camera.
When the position of the spectrum camera is stable, the water sample collecting device is opened in a short time before data recording is started or after data recording is finished, so that the water sample collecting device is filled with water, and then the sealing valve is closed to finish water sample collection. The water sample collecting device is used for collecting water samples near the shooting scene when the spectrum camera works, analyzing water quality parameters of the water at the position and at the moment, and performing water radiation transmission correction on the spectrum energy received by the spectrum camera by using the parameters.
The spectrum camera, the solar downward irradiance measuring instrument and the depth sonar need to measure and record data at the same time during work.
The invention effectively solves the influence of solar reflection flare and wave lens action during the above-water imaging through the imaging of the underwater spectrum camera; the invention utilizes the spectrum of the submarine coral reef target and the solar downlink spectrum which are synchronously acquired, and can obtain the remote sensing reflectivity data of the coral reefs in the sea areas at different depths through calculation, thereby avoiding the imaging brightness difference caused by the attenuation of the sunlight at different water depths;
according to the invention, the distance between the spectrum camera and the submarine coral reef target is obtained through real-time measurement, and the water sample analysis data is obtained through the water sample collecting device, so that the influence of the reflected light of the submarine target on the absorption scattering of the middle water body of the light receiving path can be effectively corrected, the accuracy of remote sensing reflectivity data is improved, and the imaging quality is improved; according to the method, the measurement height, namely the distance between the spectral camera and the coral reef target, is adjusted only according to different water depth conditions of the coral reef distribution area, and all data acquisition processes can be automatically completed. The operation is convenient, safe and reliable.
Example 2
Fig. 1 shows a structural arrangement diagram of the present invention.
The device of the invention is completely arranged under water when in use, and in order to ensure that the solar descending irradiance measuring instrument does not expose out of the water surface or be not influenced by sea surface waves in the whole measuring process 2, as shown in figure 1, h in the figure2Should not be less than 30 cm.
When the device of the invention shoots the coral reef underwater, the distance between the device and the coral reef is measured in real time by a 3-depth sonar, in order to ensure that the device is not damaged by touching the bottom and can measure and obtain an image with proper width, the distance h between the device and the seabed as shown in figure 1 is at least more than h1。
According to the device shown in the figure 1, after a sea area where coral reefs are distributed reaches a certain position, a proper depth is selected according to measurement data obtained by a 3-depth-measuring sonar, and 5, the master control platform stops moving and keeps static relative to a seabed coral reef target; and then 4, starting to collect the water sample by the water sample collecting device until the water sample collecting is finished.
And under the condition that the 5 master control platform maintains a stable state, the 1 spectrum camera and the 2 solar downward irradiance measuring instrument are started to work at the same time, the measured data are recorded at the same time, and data backup is carried out on the 5 master control platform.
At this time, the light intensity of the wavelength lambda recorded by the photosensitive element of the 6-sun downward irradiance measuring instrument is Eλ0And 7 the light intensity recorded by the light-sensitive element of the spectral camera is Eλ1At this time:
in the formula (1), αλThe attenuation coefficient of light with the wavelength of lambda in the seawater per unit optical path is obtained by water quality analysis and the like of a water sample collected by a 4 water sample collecting device, and the seawater quality condition is assumed to be unchanged in a limited measurement space range; rλThe reflectivity R in the formula (1) is released for the reflectivity of submarine objects such as coral reef and the like to light with the wavelength of lambdaλComprises the following steps:
when considering the spatial position of each pixel within the 1-spectral camera field of view as shown in FIG. 1, equation (1) can be written as:
in the formula (3), (i, j) is a pixel coordinate in the image with the central pixel as an origin, and the number of the pixels in the column of the 1 spectrum camera is N, then:
x＝(h2+((i*L/2N)2+(j*L/2N)2)1/2)1/2
(4)
equation (2) is then modified to the reflectance calculation equation relating to the spatial position of each pixel:
in the sea area with coral reefs, the following specific characteristics are provided: firstly, the water quality condition is generally a water body, namely a water body with chlorophyll as a main water quality element type, but on a coral reef disc which develops in islands and sandbars, suspended particulate matters in the water body are water quality elements which cannot be ignored due to the influences of hydrological conditions such as tides and waves and the substrate condition of coral sand distribution, so that the backscattering of water body radiation transmission caused by the suspended particulate matters must be considered, and the content of soluble organic salt and the spectral absorption caused by the content of the soluble organic salt can be disregarded; secondly, the coral reefs are mostly distributed in shallow sea areas of the true sunlight layer of the tropical sea area, and are most densely and abundantly distributed according to the depth of water of 20m, underwater illumination conditions are good in the sea areas and the depth of water, and an additional active light source is not needed to be erected during coral reef image shooting; thirdly, the area of the coral reef on the coral reef where the coral reef grows well is generally high in water mobility, particularly at the position in front of the coral reef disc reef, high-speed sea current can form sea waves at broken wave bands of slopes in front of the reef, the slopes in front of the reef are also the positions where the coral reef is distributed densely, and under the condition, the underwater depth of the solar downward irradiance measuring instrument is required to be placed in deeper water according to wave conditions.
The method is characterized in that reflected light energy of the coral reef and solar downward light energy are synchronously observed in shallow sea water, and changes of coral reef light in radiation transmission in sea water caused by absorption and scattering are corrected, so that a reflectivity spectrum image of a coral reef distribution area is obtained. The key link for acquiring the high-quality coral reef reflectivity spectrum image is to correct the radiation transmission influence of the coral reef observation light in seawater, and whether the correction can be realized is related to the feasibility of the method.
Obtaining a reflectivity image R as shown in formula (2)λThe key point of (1) is to obtain the attenuation coefficient alpha of light in seawater of the coral reef monitoring areaλAnd αλ＝f(a(λ)，bb(λ)) can be obtained from the water quality analysis parameters obtained by the water quality acquisition device mounted in the present invention. Wherein a (λ) is the total absorption coefficient at wavelength λ, bb(λ) is the backscattering coefficient at wavelength λ.
For more convenient experimental derivation and understanding, equation (2) can be further rewritten as:
R(λ)＝Rt(λ)-Rw(λ)
wherein R ist(lambda) is obtained by calculation according to the measured values of the solar descending irradiance measuring instrument and the spectrum camera, and the following key is to calculate the reflectivity influence of the water body, namely to remove Rw(lambda). And R isw(λ) is again a (λ) and bb(λ) is used. In the near-shore water body with chlorophyll and suspended particles as main water quality conditions, Rw(λ) can be expressed as:
wherein, H is the optical path of the light of the monitoring target in the seawater.
Here, the total absorption coefficient a (λ) and the backscattering coefficient b at the wavelength λb(lambda) can be obtained by measuring the water sample collected by the water sample collecting device, and the water sample is used as a water body radiation transmission parameter in a limited local space range to participate in radiation transmission correction of the coral reef observation spectrum. The size of the local space can be determined by measuring the water absorption scattering parameters through collecting water samples on site and developing the spatial heterogeneity of the absorption scattering characteristics.
As shown in fig. 3, for the results before and after the spectral water body radiation transmission correction shown by using the discrete spectrum of the on-site measurement, the simulated common optical remote sensor band settings generally include 4 spectral bands, i.e., a blue band, a green band, a red band, and a near-infrared band with central wavelengths of 490nm, 575nm, 650nm, and 835nm, respectively. As can be easily seen from fig. 3, in water, due to the absorption effect of water molecules on electromagnetic waves, the near-infrared band cannot be propagated in water, and therefore, underwater optical observation can only use electromagnetic waves in the range from blue light to red light. In the water body correction result of the upper graph, on one hand, the spectrum reflectivity after correction is obviously improved, and on the other hand, for the coral deposition area with larger water depth, the spectrum improvement amplitude of the reflectivity is higher than that of the reef front step with shallower water depth.
In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When used in whole or in part, can be implemented in a computer program product that includes one or more computer instructions. When loaded or executed on a computer, cause the flow or functions according to embodiments of the invention to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, the computer instructions may be transmitted from one website site, computer, server, or data center to another website site, computer, server, or data center via wire (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL), or wireless (e.g., infrared, wireless, microwave, etc.)). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server, a data center, etc., that includes one or more of the available media. The usable medium may be a magnetic medium (e.g., floppy Disk, hard Disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., Solid State Disk (SSD)), among others.
The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. The utility model provides a visible light image device suitable for monitoring under shallow sea coral reef, a serial communication port, visible light image device suitable for monitoring under shallow sea coral reef includes: the system comprises a master control platform, a spectrum camera, a solar descending irradiance measuring instrument, a depth sounding sonar and a water sample collecting device;
wherein, the focal plane of the spectrum camera, the focal plane of the solar downward irradiance measuring instrument and the sounding sonar detection device are positioned on a plane parallel to the sea level; the shooting direction of the spectrum camera is perpendicular to the sea level, and the solar downward irradiance measurement and measurement direction is opposite to the shooting direction of the spectrum camera.
2. The visible light imaging device suitable for shallow sea coral reef underwater monitoring as claimed in claim 1, wherein the master control platform is used for providing integration space, power supply, control and data storage interaction for a spectral camera, a solar downlink irradiance measuring instrument, a depth sounding sonar and a water sample collecting device; the master control platform needs to be sealed and waterproof; the integrated direct-current power supply provides stable electric energy for the spectral camera, the solar downward irradiance measuring instrument, the depth sounding sonar and the water sample collecting device; the integrated control unit controls the switching and coordination of all internal devices and provides storage and reading services for data acquired by the integrated devices.
3. The visible light imaging device suitable for the underwater monitoring of the shallow sea coral reef in accordance with claim 1, wherein the spectrum camera internally comprises a camera lens assembly, a CCD or CMOS optical recording array, a storage device and the like; the field angle phi of the camera should not be less than 40 degrees in air; the spectrum camera comprises characteristic wave bands with central wavelengths of 395nm, 430nm, 490nm, 517nm, 575nm, 600nm and 650nm, the wave bands are all the preferred wave bands for coral reef remote sensing observation, and at least 3 coral reef characteristic wave bands including 575nm, 600nm and 650nm are included; when the spectrum camera works, the lens of the spectrum camera is vertically downward to form a view field; the shooting mode of the spectrum camera during working is frame-type imaging.
4. The visible light imaging device suitable for shallow sea coral reef underwater monitoring as claimed in claim 1, wherein the solar downward irradiance measuring instrument has the same wave band setting as the spectral camera and the receiving lens is vertically upward; when the solar downward irradiance measuring instrument works, the distance between a lens of the solar downward irradiance measuring instrument and the sea surface is more than or equal to 30 cm; the function of the solar downlink irradiance measuring instrument is to measure the remote sensing incident energy taking the sun as a light source and provide incident energy measurement for the remote sensing reflectivity calculation of the spectral camera measurement data; when the solar downlink irradiance measuring instrument works, synchronous data acquisition with the spectrum camera is realized through the control unit in the master control platform.
5. The visible light imaging device suitable for underwater monitoring of the shallow sea coral reef according to claim 1, wherein the depth sonar is connected with a master control platform through a cable, and the direction of the acoustic distance measurement is consistent with the shooting direction of the spectral camera; the depth sounding sonar has the function of measuring the distance between a scene target and the spectrum camera at the working moment of the spectrum camera and is used for carrying out water body radiation transmission correction on the spectrum energy received by the spectrum camera.
6. The visible light imaging device suitable for underwater monitoring of shallow sea coral reefs of claim 1, wherein the water sample collection device, when the position of the spectral camera is stable, opens a valve of the water sample collection device to fill the collection device with water before starting to record data or within a short time after completing data recording, and then closes a sealing valve to complete water sample collection; the water sample collecting device is used for collecting water samples near the shooting scene when the spectrum camera works, analyzing water quality parameters of the water at the position and at the moment, and performing water radiation transmission correction on the spectrum energy received by the spectrum camera by using the parameters.
7. The visible light imaging device suitable for shallow sea coral reef underwater monitoring of claim 1, wherein the spectral camera, the solar downward irradiance measuring instrument and the depth sonar need to measure and record data at the same time during work.
8. The monitoring method of the visible light imaging device based on the shallow sea coral reef underwater monitoring comprises the following steps:
completely placing the visible light imaging device suitable for the shallow sea coral reef underwater monitoring under water; the h2 is not less than 30cm, so that the observation lens of the solar descending irradiance measuring instrument is prevented from being exposed above the water surface due to sea surface fluctuation such as waves;
step two, when the coral reef is shot underwater, the distance from the coral reef is measured in real time by a depth sonar; wherein the distance h between the device and the seabed is more than h1；
Thirdly, when the visible light imaging device reaches a certain position in a sea area where the coral reefs are distributed, selecting a proper working depth according to measurement data obtained by a depth sonar;
fourthly, the master control platform stops moving and keeps static relative to the submarine coral reef target, and the water sample collecting device starts collecting water samples until the water samples are collected;
and step five, under the condition that the master control platform is kept stable, the spectrum camera and the solar downward irradiance measuring instrument are started to work at the same time, the measured data are recorded at the same time, and data backup is carried out on the master control platform.
9. The monitoring method of the visible light imaging device based on the shallow sea coral reef underwater monitoring as claimed in claim 8, wherein the monitoring method of the visible light imaging device based on the shallow sea coral reef underwater monitoring further comprises:
the wavelength lambda light intensity recorded by the photosensitive element of the solar downward irradiance measuring instrument is Eλ0The light intensity recorded by the light-sensitive element of the spectral camera is Eλ1：
In the formula (1), αλThe attenuation coefficient is the attenuation coefficient of light with the wavelength of lambda in a unit optical path in seawater, and the attenuation coefficient is obtained by water sample samples collected by a water sample collecting device through water quality analysis and the like.
10. The monitoring method of the visible light imaging device based on the shallow sea coral reef underwater monitoring as claimed in claim 8, wherein the monitoring method of the visible light imaging device based on the shallow sea coral reef underwater monitoring further comprises:
the seawater quality condition is assumed to be unchanged in a limited measurement space; rλThe reflectivity R in the formula (1) is released for the reflectivity of submarine objects such as coral reef and the like to light with the wavelength of lambdaλComprises the following steps:
when the spatial position of each pixel element in the field of view of the spectral camera is considered, formula (1) is changed to:
in the formula (3), (i, j) is a pixel coordinate in the image with the central pixel as an origin, and the number of the pixels in the column of the spectrum camera is N, then:
x＝(h2+((i*L/2N)2+(j*L/2N)2)1/2)1/2
(4)
equation (2) is then modified to the reflectance calculation equation relating to the spatial position of each pixel:
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| CN114397253A (en) * | 2022-03-22 | 2022-04-26 | 中国海洋大学 | Water absorption coefficient measuring device based on natural light |
| CN114814071A (en) * | 2022-06-17 | 2022-07-29 | 武汉正元环境科技股份有限公司 | Water quality detection method based on ion chromatography |
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| CN114397253A (en) * | 2022-03-22 | 2022-04-26 | 中国海洋大学 | Water absorption coefficient measuring device based on natural light |
| CN114397253B (en) * | 2022-03-22 | 2022-06-24 | 中国海洋大学 | Water absorption coefficient measuring device based on natural light |
| CN114814071A (en) * | 2022-06-17 | 2022-07-29 | 武汉正元环境科技股份有限公司 | Water quality detection method based on ion chromatography |
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