CN107451413A - A kind of water body absorption coefficient bearing calibration and device - Google Patents
A kind of water body absorption coefficient bearing calibration and device Download PDFInfo
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Abstract
The invention discloses a kind of water body absorption coefficient bearing calibration and device, this method to include：The initial data of water body to collecting carries out data processing, the water body data after generation processing；Trip temperature and salinity amendment are entered to the water body data after the processing, obtain preliminary revised water body absorption coefficient and attenuation coefficient；According to revised water body absorption coefficient and attenuation coefficient structure exponential fitting equation group, scattering amplitude is calculated；The revised water body absorption coefficient and decay absorption are corrected according to the scattering amplitude, calculates and obtains water body target absorption coefficient.Solve the problems, such as that feux rouges and nearly feux rouges wave section overcorrect and correction are inaccurate by the present invention.
Description
Technical Field
The invention relates to the technical field of water absorption coefficients, in particular to an on-site second-class water absorption coefficient accurate correction method and device based on an E index fitting method.
Background
The water absorption coefficient is an important parameter for evaluating and detecting water quality and water ecological environment, and corresponding measurement and correction are required for obtaining the accurate water absorption coefficient by a precise optical instrument. The currently commonly used measuring instruments are 9-waveband absorption attenuation measuring instruments (AC 9 for short) developed and produced by WET Labs company in America, and with the increase of water color satellite wavebands and the requirement of water body hyperspectral research, the company has promoted an updated substitute product of AC9, namely an absorption attenuation spectrometer (ACS). The AC9 or ACS instrument has higher measurement precision on ocean water bodies and cleaner water bodies, the measurement cost is negligible compared with a laboratory measurement absorption method, and the instrument has the advantages of convenience in carrying and use and the like, and is a preferred instrument for measuring absorption and attenuation on the water color satellite calibration test site in the ocean optical measurement specification of the American aerospace agency at present.
However, as the instruments are widely used in the world, various problems are exposed, for example, various calibration parameters preset by instrument software are set by manufacturers according to the situation of limited water area types in the united states, but the complexity of high-absorption scattering water bodies in lakes and offshore places in China cannot be well solved, such as the scattering calibration problem of the AC9 or ACs instruments. Although various methods of scatter correction have been proposed in the prior art for AC9 or ACs instruments, such as Flat method, constant scaling factor method proposed by Kirk, scaling factor method proposed by zanevel (zanevel method for short), mcke method, and Boss method, etc. However, these correction methods have certain disadvantages, such as overcorrection of the red and near infrared bands; the Kirk correction method uses fixed 0.14 or 0.18 representatives for clear water and turbid water, but the lake and offshore water body components in nature vary greatly and are difficult to define and represent by fixed 0.18 or 0.14; the Boss method is not suitable for the second class of water bodies containing phytoplankton with different concentrations, such as offshore lakes, inland lakes and the like; the Mckee method relies on synchronous measurement of a backscattering instrument, the photon reflectivity of different absorption attenuation instruments needs to be known, many historical data have no synchronous backscattering data, the nine-waveband backscattering instrument Bb9 is complex in calibration, the empirical coefficients of the photon reflectivity of a flow tube of the absorption attenuation instrument are obviously different with time and specific instruments, and the old degree and the new degree hardly have fixed scattering efficiency values.
Therefore, the existing two types of water body absorption coefficient correction methods have the problem of over-correction of red light and near-red light outer wave bands, and further have the problem of inaccurate absorption coefficient correction.
Disclosure of Invention
Aiming at the problems, the invention provides a method and a device for correcting the water absorption coefficient, which solve the problems of over-correction and inaccurate correction of the red light and near-red light outer wave bands.
In order to achieve the above object, according to a first aspect of the present invention, there is provided a water body absorption coefficient correction method, including:
performing data processing on the acquired original data of the water body to generate processed water body absorption data;
correcting the temperature and salinity of the processed water body data to obtain a preliminarily corrected water body absorption coefficient and attenuation coefficient;
constructing an exponential fitting equation set according to the preliminarily corrected water absorption coefficient and attenuation coefficient, and calculating to obtain a scattering amplitude;
and correcting the corrected water body absorption coefficient and attenuation absorption according to the scattering amplitude, and calculating to obtain a water body target absorption coefficient.
Preferably, the processing the acquired raw data of the water body to generate the processed water body absorption data includes:
acquiring original data of a water body;
performing data conversion on the original data to obtain physical quantity data corresponding to the original data;
and matching the temperature, salinity and depth information of the physical quantity data to obtain the processed water body absorption data.
Preferably, the correcting the temperature and salinity of the processed water body data to obtain the preliminarily corrected water body absorption coefficient and attenuation coefficient includes:
acquiring the on-site measurement water temperature T, salinity S and absorption coefficient a of the collected water bodym(lambda) and attenuation coefficient cm(λ)；
Analyzing and obtaining the temperature T of the instrument pure water in the processed water body data when the instrument pure water is calibratedrAnd salinity Sr；
According to the formulaCalculating to obtain the absorption coefficient after preliminary correction
According to the formulaCalculating to obtain the attenuation coefficient after preliminary correctionWherein,is a temperature variation factor of the absorption coefficient of pure water,andis the salinity variation factor of pure water absorption and attenuation, and lambda is the wavelength.
Preferably, the constructing an exponential fitting equation set according to the preliminarily corrected water absorption coefficient and attenuation coefficient, and calculating to obtain the scattering amplitude includes:
e index fitting is carried out on a wave band of a preset wavelength according to the preliminarily corrected water body absorption coefficient and attenuation coefficient to obtain a preliminarily corrected actually measured absorption curve, wherein the preset wavelength comprises 412nm, 440nm, 488nm, 510nm, 532nm, 555nm and 715 nm;
estimating to obtain the real absorption coefficient of the full wavelength of E index fitting according to the E index attenuation characteristic of the preliminarily corrected actually measured absorption curve
Construction of a set of exponential fitting equationsAnd combining the aboveIs substituted into the exponential fitting equation system, and the absorption coefficient of the wavelength at 440nm is calculated and obtainedSlope SdAnd an amplitude of scattering, wherein,is the sum of the absorption coefficients after the initial correctionThe attenuation coefficient after the initial correction is obtained.
Preferably, the step of correcting the primarily corrected water absorption coefficient and attenuation absorption according to the scattering amplitude to calculate and obtain a water target absorption coefficient includes:
according to the formulaAnd calculating to obtain a target absorption coefficient α (lambda) of the water body.
According to a second aspect of the present invention, there is provided a water body absorption coefficient correction apparatus, the apparatus comprising:
the data processing module is used for carrying out data processing on the acquired original data of the water body to generate processed water body absorption data;
the correction module is used for correcting the temperature and the salinity of the processed water body data to obtain a preliminarily corrected water body absorption coefficient and attenuation coefficient;
the calculation module is used for constructing an exponential fitting equation set according to the preliminarily corrected water absorption coefficient and attenuation coefficient, and calculating to obtain the scattering amplitude;
and the correction module is used for correcting the primarily corrected water body absorption coefficient and attenuation absorption according to the scattering amplitude, and calculating to obtain a water body target absorption coefficient.
Preferably, the data processing module includes:
the acquisition unit is used for acquiring and obtaining original data of the water body;
the conversion unit is used for carrying out data conversion on the original data to obtain physical quantity data corresponding to the original data;
and the matching unit is used for matching the temperature, salinity and depth information of the physical quantity data to obtain the processed water body absorption data.
Preferably, the correction module includes:
an acquisition unit for acquiring the on-site measured water temperature T, salinity S and absorption coefficient a of the acquired water bodym(lambda) and attenuation coefficient cm(λ)；
An analysis unit for analyzing and obtaining the temperature T of the instrument pure water calibration in the processed water body datarAnd salinity Sr；
A first correction unit for correcting the first correction value according to a formulaCalculating to obtain the absorption coefficient after preliminary correction
A second correction unit for correcting the first correction value according to the formulaCalculating to obtain the attenuation coefficient after preliminary correctionWherein,is a temperature variation factor of the absorption coefficient of pure water,andis the salinity variation factor of pure water absorption and attenuation, and lambda is the wavelength.
Preferably, the calculation module includes:
the fitting unit is used for performing E-index fitting on a wave band of a preset wavelength according to the preliminarily corrected water body absorption coefficient and attenuation coefficient to obtain a preliminarily corrected actually-measured absorption curve, wherein the preset wavelength comprises 412nm, 440nm, 488nm, 510nm, 532nm, 555nm and 715 nm;
an estimating unit, configured to estimate a true absorption coefficient of the full wavelength of the E-exponential fitting according to the E-exponential decay characteristic of the preliminarily corrected actually measured absorption curve
A construction unit for constructing an exponential fitting equation setAnd combining the aboveIs substituted into the exponential fitting equation system, and the absorption coefficient of the wavelength at 440nm is calculated and obtainedSlope SdAnd an amplitude of scattering, wherein,is the sum of the absorption coefficients after the initial correctionThe attenuation coefficient after the initial correction is obtained.
Preferably, the correction module includes:
a calculation unit for calculating according to a formulaAnd calculating to obtain a target absorption coefficient α (lambda) of the water body.
Compared with the prior art, the method has the advantages that firstly, the acquired original data of the water body are subjected to primary processing and correction, and the corrected water body absorption coefficient and attenuation coefficient are obtained; and then E index fitting correction is carried out on the absorption coefficients of the two types of water bodies by adopting the first six bands and the last bands (412nm, 440nm, 488nm, 510nm, 532nm, 555nm and 715nm) of the nine-band absorption attenuation instrument, so that the influence of phytoplankton red light absorption peaks 650nm and 676nm in the two types of water bodies can be avoided, the traditional assumption that the near infrared band is zero is not adopted, the accurate absorption coefficients of the two types of water bodies are further obtained, and the problems of over-correction and inaccurate correction of red light and near red light external bands during correction of the absorption coefficients of the water bodies in the prior art are solved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for correcting a water absorption coefficient according to an embodiment of the present invention;
FIG. 2 is a flowchart illustrating data processing at step S11 in FIG. 1 according to an embodiment of the present invention;
FIG. 3 is a flowchart illustrating a coefficient correction process of step S12 in FIG. 1 according to an embodiment of the present invention;
FIG. 4 is a schematic flow chart of calculating scattering amplitude in step S13 of FIG. 1 according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a water absorption coefficient correction device according to a third embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terms "first" and "second," and the like in the description and claims of the present invention and the above-described drawings are used for distinguishing between different objects and not for describing a particular order. Furthermore, the terms "comprising" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not set forth for a listed step or element but may include steps or elements not listed.
Example one
Referring to fig. 1, a method for correcting an absorption coefficient of a water body according to an embodiment of the present invention includes the following steps:
s11, carrying out data processing on the acquired original data of the water body to generate processed water body absorption data;
it should be noted that, in the embodiment of the present invention, the raw data of the water body is collected by a 9-waveband absorption attenuation measuring instrument (abbreviated as AC9) developed and produced by WET Labs corporation of usa or an absorption Attenuation Spectrometer (ACs) which is an upgraded substitute product of AC9, because the AC9/ACs instrument has higher measurement accuracy for the ocean water body and cleaner water body, the measurement cost is negligible compared with a laboratory absorption measurement method, and the instrument has many advantages of convenient carrying and use, etc., and is a preferred instrument for measuring the absorption and attenuation in the water color satellite calibration inspection field in the current ocean optical measurement specification of the american space agency. It is representative to use both instruments for data acquisition. The inland lakes, reservoirs and other water bodies and offshore water bodies are two types of water bodies, a large number of phytoplanktons often exist, most of the existing water body absorption coefficient correction methods are not suitable for the offshore and inland lakes and other two types of water bodies containing phytoplanktons with different concentrations, and correction is always relatively difficult by means of synchronous measurement of another optical instrument (such as a backscattering instrument or a PSICAM), so in order to highlight the advantages of the invention, the water body selected in the embodiment of the invention is the two types of water bodies.
In the embodiment of the invention, the data processing adopts an AC9/ACS instrument provided by WET Labs company, the method is also explicitly stated in ocean optical specifications of satellite water color remote sensor authenticity check of the National Aeronautics and Space Administration (NASA), and the specific data processing comprises two aspects of data conversion and information matching, so that the original data is more conveniently ensured in the subsequent processing process.
S12, correcting the temperature and salinity of the processed water body data to obtain a primarily corrected water body absorption coefficient and attenuation coefficient;
in particular, since the AC9/ACs instrument uses pure water at a temperature and salinity (typically, salinity of 0PSU at calibration) that is generally different from the temperature and salinity measured on site, the variations in temperature and salinity cause variations in the absorption and attenuation coefficients, and thus, the original coefficients need to be corrected.
S13, constructing an exponential fitting equation set according to the preliminarily corrected water absorption coefficient and attenuation coefficient, and calculating to obtain a scattering amplitude;
it can be understood that the absorption coefficients based on the absorption of the non-pigment particles and the absorption of yellow substances in the main bodies of the two types of water bodies are E exponential attenuation, the phytoplankton absorption coefficient is close to accord with the E exponential attenuation except for the absorption peak, and the spectrum of the total absorption coefficient of the three elements also basically follows the rule of the E exponential attenuation, so that an exponential fitting equation is constructed based on the E exponential attenuation in the invention, and the scattering amplitude is obtained through calculation.
S14, correcting the primarily corrected water absorption coefficient and attenuation absorption according to the scattering amplitude, and calculating to obtain a water target absorption coefficient.
According to the technical scheme disclosed by the embodiment of the invention, firstly, the acquired original data of the water body is subjected to primary processing and correction to obtain a corrected water body absorption coefficient and a corrected attenuation coefficient; and then E index fitting correction is carried out, the influence of phytoplankton red light absorption peaks 650nm and 676nm in the second class of water body can be avoided when the wave band is selected, and the accurate absorption coefficient of the second class of water body is obtained without the assumption that the traditional near infrared wave band is zero, so that the problems of over correction and inaccurate correction of red light and near red light outer wave bands when the water body absorption coefficient is corrected in the prior art are solved.
Example two
Referring to the first embodiment of the present invention and the specific process from S11 to S14 described in fig. 1, referring to fig. 2, the step S11 performs data processing on the acquired raw data of the water body to generate processed water body absorption data, and specifically includes:
s111, acquiring original data of the water body;
s112, performing data conversion on the original data to obtain physical quantity data corresponding to the original data;
it can be understood that the field measurement device for the inherent optical characteristics of the water body needs to be calibrated more strictly, the original data of the water body acquired by the AC9/ACs instrument is signal data, and the conversion of the measured physical quantity of the original data according to the calibration data can be completed by loading the calibration file through the acquisition software system WetView software provided by the instrument manufacturer, so that the original data file is converted into data with physical significance.
And S113, matching the temperature, salinity and depth information of the physical quantity data to obtain the processed water body absorption data.
Depth-temperature-salinity (CTD) information was matched to each recorded AC9/ACs instrument data using synchronized timeline information. That is, since the CTD information collection device has a different sampling frequency than the AC9/ACs device, the CTD data is differentiated based on the time axis information.
After the preliminary processing is performed on the data, temperature and salinity correction needs to be performed, referring to fig. 3, the step S12 performs temperature and salinity correction on the processed water body data to obtain an absorption coefficient and an attenuation coefficient of the water body after the preliminary correction, which specifically includes:
s121, acquiring the on-site measured water temperature T, salinity S and absorption coefficient a of the collected water bodym(lambda) and attenuation coefficient cm(λ)；
S122, analyzing and obtaining the temperature T of the instrument pure water in the processed water body data when the instrument pure water is calibratedrAnd salinity Sr；
S123, according to the formulaCalculating to obtain the absorption coefficient after preliminary correction
S124, according to the formulaCalculating to obtain the attenuation coefficient after preliminary correctionWherein,is a temperature variation factor of the absorption coefficient of pure water,andis the salinity variation factor of pure water absorption and attenuation, and lambda is the wavelength.
It should be noted that the AC9/ACS instrument uses the temperature T of pure water for calibrationrAnd salinity Sr(during calibration, the salinity of pure water is usually 0PSU) is different from the water temperature T and the salinity S which are measured on site, the absorption and attenuation coefficients are changed due to the change of the temperature and the salinity, and the temperature and the salinity are corrected by adopting a formula (1) and a formula (2) respectively.
In the formula,andrespectively the preliminary absorption coefficient and attenuation coefficient after temperature and salinity correction, am(lambda) and cm(lambda) is temperature andthe absorption coefficient and the attenuation coefficient measured before salinity correction,is a temperature variation factor of the absorption coefficient of pure water,andis the salinity variation factor of pure water absorption and attenuation, and lambda is the wavelength. The salinity of the water bodies of the fresh water lakes and reservoirs is extremely low and is generally ignored (0 PSU).
The AC9 temperature correction corresponds to the lake and ocean using the change factors for pure water and salinity as described in Pegau (1997), respectively, and the ACs uses the change factors provided in Sullivan (2006) collectively.
After obtaining the absorption coefficient and the attenuation coefficient after the preliminary correction of the temperature and the salinity, E-exponential correction is required, referring to fig. 4, the step S13 constructs an exponential fitting equation set according to the absorption coefficient and the attenuation coefficient of the water body after the preliminary correction, and obtains the scattering amplitude by calculation, which specifically includes:
s131, performing E-index fitting on a wave band of a preset wavelength according to the preliminarily corrected water body absorption coefficient and attenuation coefficient to obtain a preliminarily corrected actually measured absorption curve, wherein the preset wavelength comprises 412nm, 440nm, 488nm, 510nm, 532nm, 555nm and 715 nm;
s132, estimating and obtaining a real absorption coefficient of the full wavelength of E exponential fitting according to the E exponential decay characteristic of the preliminarily corrected actually-measured absorption curve
S133, constructing an exponential fitting equation setAnd combining the aboveIs substituted into the exponential fitting equation system, and the absorption coefficient of the wavelength at 440nm is calculated and obtainedSlope SdAnd an amplitude of scattering, wherein,is the sum of the absorption coefficients after the initial correctionThe attenuation coefficient after the initial correction is obtained.
Specifically, it can be understood that: e-exponential fitting is carried out on the wave band of the preset wavelength to obtain an actually measured absorption curve after preliminary temperature and salinity correction, and according to the E-exponential attenuation characteristic of the absorption curve, the real absorption coefficient of the preset wavelength at 440nm is presetAnd fitting the true absorption coefficient of the full wavelength by E indexWherein the preset wavelengths comprise 412nm, 440nm, 488nm, 510nm, 532nm, 555nm and 715 nm;
construction of a set of exponential fitting equationsAnd combining the aboveIs substituted into the exponential fitting equation system, and the absorption coefficient of the wavelength at 440nm is calculated and obtainedSlope SdAnd the scattering amplitude.
Specifically, the absorption coefficient α is based on the absorption coefficient of non-pigment particles occupying the main body in the second class of water bodyNAPAnd yellow substance absorption coefficient αCDOMThe absorption coefficients of the three elements are E exponential decay, the absorption coefficients of the phytoplankton are close to the E exponential decay except the absorption peak, and the total absorption coefficient spectrum of the three elements basically follows the rule of the E exponential decay. Assuming that the water body absorption spectrum is dominated by inorganic particle (NAP) and yellow matter absorption, its spectral characteristics appear to decay approximately E-exponential with wavelength. The variable ratio coefficient method (Zaneveld method for short) proposed in Zaneveld of the related art: the data of one reference band is used to determine the proportion of the scattering coefficient that should be subtracted from the result, the scattering coefficient b can be obtained by subtracting the absorption coefficient a from the attenuation coefficient c, and the correction algorithm is based on three assumptions: absorbing the portion of the scattered light not collected by the instrument, independent of wavelength; the scattered light part collected by the attenuation instrument is independent of the wavelength; there is a reference wavelength and the absorption of particulate matter other than water is negligible. But neglects the influence of phytoplankton in water, and the correction is inaccurate. Based on the fact that a certain proportion of scattering is removed from an absorption coefficient in a Zaneveld method to realize correction, the amplitude of the scattering is a wavelength independent quantity, and an on-site measured spectrum after temperature and salinity correction is carried outIndirect fitting to obtain the true total absorption:
or
In generalNo scatter correction process is performed.
The estimated absorption coefficient after the scattering correction is assumed to beAt this timeIs a true value, i.e. the amount of E-exponential fit at 440nm of α (λ), which decays E-exponentially with wavelength λ, but the slope S in the corresponding spectrumdIs unknown, at a wavelength of 440nmComprises the following steps:
substituting equation (4) into equation (3) yields:
solving the first six wave bands and the last wave band (412nm, 440nm, 488nm, 510nm, 532nm, 555nm and 715nm) by using a nonlinear least square method, wherein wave bands 650nm and 676nm near the absorption characteristic peaks of chlorophyll a and b red light are not used in the process, fitting the actually measured absorption curve to the maximum extent, and solving α (440) (m)-1)、Sd(nm-1) α (λ) is finally obtained by fitting, α (λ), α (λ) found using equation (3) is in fact αpg(λ), i.e. particulate matter absorption αp(lambda) and yellow matter absorption αgThe sum of (lambda).
Although the Boss correction method in the prior art uses the first 7 wave bands of AC9 for fitting, avoids correction of temperature and salinity extreme values, can reduce the absorption influence of salinity on the near-infrared wave band of the absorption coefficient, the method is only suitable for water bodies with inorganic particles as main materials, the seventh wave band of 650nm is sensitive to the chlorophyll b absorption peak in phytoplankton, the tail of the measured absorption coefficient is warped, and the fitting is greatly influenced.
According to the technical scheme disclosed by the second embodiment of the invention, firstly, physical quantity data conversion and CTD information interpolation are carried out on the acquired original data, because the invention aims at correcting the absorption coefficient obtained by an AC9/ACS instrument, and the two instruments use the temperature and salinity of pure water to carry out calibration and the temperature and salinity of a water body measured on site are different, the absorption and attenuation coefficients are influenced, so that the processed data need to be corrected, and finally, E index fitting correction is carried out by utilizing the front 6 wave bands and the last wave bands (412nm, 440nm, 488nm, 510nm, 532nm, 555nm and 715nm) of the instruments, so that the influence of 650nm and 676nm of phytoplankton red light absorption peaks in the water body of the second class and the error that a near infrared wave band (such as 715nm) is supposed to be 0 can be avoided well, and accurate absorption coefficients of the water body of the second class are obtained, thereby solving the problems of overcorrection and correction of inaccurate red light and near infrared wave bands during the correction of the absorption coefficients in the water.
EXAMPLE III
Corresponding to the water absorption coefficient correction methods disclosed in the first and second embodiments of the present invention, a third embodiment of the present invention further provides a water absorption coefficient correction device, and referring to fig. 5, the device includes:
the data processing module 1 is used for carrying out data processing on the acquired original data of the water body to generate processed water body absorption data;
the correction module 2 is used for correcting the temperature and salinity of the processed water body data to obtain a primarily corrected water body absorption coefficient and attenuation coefficient;
the calculation module 3 is used for constructing an exponential fitting equation set according to the preliminarily corrected water absorption coefficient and attenuation coefficient, and calculating to obtain the scattering amplitude;
and the correction module 4 is used for correcting the primarily corrected water absorption coefficient and attenuation absorption according to the scattering amplitude, and calculating to obtain a water target absorption coefficient.
Correspondingly, the data processing module 1 comprises:
the acquisition unit 11 is used for acquiring and obtaining original data of the water body;
a conversion unit 12, configured to perform data conversion on the original data to obtain physical quantity data corresponding to the original data;
and the matching unit 13 is used for matching the temperature, salinity and depth information of the physical quantity data to obtain the processed water body absorption data.
Correspondingly, the modification module 2 includes:
an acquisition unit 21 for acquiring the on-site measured water temperature T, salinity S and absorption coefficient a of the acquired water bodym(lambda) and attenuation coefficient cm(λ)；
An analysis unit 22 for analyzing and obtaining the temperature T of the instrument pure water calibration in the processed water body datarAnd salinity Sr；
A first correction unit 23 for correcting the first correction according to the formula
Calculating to obtain the absorption coefficient after preliminary correction
A second correction unit 24 for correcting the second correction according to the formula
Calculating to obtain the attenuation coefficient after preliminary correctionWherein,is a temperature variation factor of the absorption coefficient of pure water,andis the salinity variation factor of pure water absorption and attenuation, and lambda is the wavelength.
Correspondingly, the computing module 3 includes:
the fitting unit 31 is configured to perform E-index fitting on a waveband of a preset wavelength according to the preliminarily corrected water absorption coefficient and attenuation coefficient to obtain a preliminarily corrected actually measured absorption curve, where the preset wavelength includes 412nm, 440nm, 488nm, 510nm, 532nm, 555nm, and 715 nm;
an estimating unit 32, configured to estimate a true absorption coefficient of the full wavelength of the E-exponential fitting according to the E-exponential decay characteristic of the preliminarily corrected actually measured absorption curve
A construction unit 33 for constructing a system of exponential fitting equationsAnd combining the aboveIs substituted into the exponential fitting equation system, and the absorption coefficient of the wavelength at 440nm is calculated and obtainedSlope SdAnd an amplitude of scattering, wherein,is the sum of the absorption coefficients after the initial correctionThe attenuation coefficient after the initial correction is obtained.
Specifically, the correction module 4 includes:
a calculation unit 40 for calculating according to the formulaAnd calculating to obtain a target absorption coefficient α (lambda) of the water body.
In the third embodiment of the invention, the original data acquired by the instrument is processed by the data processing module, so that the data meets the requirement of subsequent fitting processing, then the original absorption coefficient and attenuation coefficient are corrected by the correction module according to the calibration value of the temperature and salinity during the calibration of pure water of the instrument, an exponential fitting equation set is constructed in the calculation module, the scattering amplitude is calculated and obtained, and finally scattering correction is carried out in the correction module to obtain the corrected absorption coefficient.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A method for correcting the absorption coefficient of a water body is characterized by comprising the following steps:
performing data processing on the acquired original data of the water body to generate processed water body absorption data;
correcting the temperature and salinity of the processed water body data to obtain a preliminarily corrected water body absorption coefficient and attenuation coefficient;
constructing an exponential fitting equation set according to the preliminarily corrected water absorption coefficient and attenuation coefficient, and calculating to obtain a scattering amplitude;
and correcting the preliminarily corrected water body absorption coefficient and attenuation coefficient according to the scattering amplitude, and calculating to obtain a water body target absorption coefficient.
2. The method of claim 1, wherein the processing the collected raw data of the body of water to generate processed water absorption data comprises:
acquiring original data of a water body;
performing data conversion on the original data to obtain physical quantity data corresponding to the original data;
and matching the temperature, salinity and depth information of the physical quantity data to obtain the processed water body absorption data.
3. The method according to claim 1, wherein the correcting the temperature and salinity of the processed water body data to obtain the preliminarily corrected absorption coefficient and attenuation coefficient of the water body comprises:
acquiring the on-site measurement water temperature T, salinity S and absorption coefficient a of the collected water bodym(lambda) and attenuation coefficient cm(λ)；
Analyzing and obtaining the temperature T of the instrument pure water in the processed water body data when the instrument pure water is calibratedrAnd salinity Sr；
According to the formulaCalculating to obtain the absorption coefficient after preliminary correction
According to the formulaCalculating to obtain the attenuation coefficient after preliminary correctionWherein,is a temperature variation factor of the absorption coefficient of pure water,andis the salinity variation factor of pure water absorption and attenuation, and lambda is the wavelength.
4. The method according to claim 3, wherein the step of constructing an exponential fitting equation system according to the preliminarily corrected water body absorption coefficient and attenuation coefficient, and calculating to obtain the scattering amplitude comprises the following steps:
e index fitting is carried out on a wave band of a preset wavelength according to the preliminarily corrected water body absorption coefficient and attenuation coefficient to obtain a preliminarily corrected actually measured absorption curve, wherein the preset wavelength comprises 412nm, 440nm, 488nm, 510nm, 532nm, 555nm and 715 nm;
estimating to obtain the real absorption coefficient of the full wavelength of E index fitting according to the E index attenuation characteristic of the preliminarily corrected actually measured absorption curve
Construction of a set of exponential fitting equationsAnd combining the aboveIs substituted into the exponential fitting equation system, and the absorption coefficient of the wavelength at 440nm is calculated and obtainedSlope SdAnd an amplitude of scattering, wherein,is the sum of the absorption coefficients after the initial correctionThe attenuation coefficient after the initial correction is obtained.
5. The method according to claim 4, wherein the correcting the preliminarily corrected water body absorption coefficient and attenuation absorption according to the scattering amplitude, and calculating to obtain a water body target absorption coefficient comprises:
according to the formulaAnd calculating to obtain a target absorption coefficient α (lambda) of the water body.
6. A water absorption coefficient correction device, characterized in that, the device includes:
the data processing module is used for carrying out data processing on the acquired original data of the water body to generate processed water body absorption data;
the correction module is used for correcting the temperature and the salinity of the processed water body data to obtain a preliminarily corrected water body absorption coefficient and attenuation coefficient;
the calculation module is used for constructing an exponential fitting equation set according to the preliminarily corrected water absorption coefficient and attenuation coefficient, and calculating to obtain the scattering amplitude;
and the correction module is used for correcting the primarily corrected water body absorption coefficient and attenuation absorption according to the scattering amplitude, and calculating to obtain a water body target absorption coefficient.
7. The apparatus of claim 6, wherein the data processing module comprises:
the acquisition unit is used for acquiring and obtaining original data of the water body;
the conversion unit is used for carrying out data conversion on the original data to obtain physical quantity data corresponding to the original data;
and the matching unit is used for matching the temperature, salinity and depth information of the physical quantity data to obtain the processed water body absorption data.
8. The apparatus of claim 6, wherein the modification module comprises:
an acquisition unit for acquiring the on-site measured water temperature T, salinity S and absorption coefficient a of the acquired water bodym(lambda) and attenuation coefficient cm(λ)；
An analysis unit for analyzing and obtaining the temperature T of the instrument pure water calibration in the processed water body datarAnd salinity Sr；
A first correction unit for correcting the first correction value according to a formulaCalculating to obtain the absorption coefficient after preliminary correction
A second correction unit for correcting the first correction value according to the formulaCalculating to obtain the attenuation coefficient after preliminary correctionWherein,is a temperature variation factor of the absorption coefficient of pure water,andis the salinity variation factor of pure water absorption and attenuation, and lambda is the wavelength.
9. The apparatus of claim 8, wherein the computing module comprises:
the fitting unit is used for performing E-index fitting on a wave band of a preset wavelength according to the preliminarily corrected water body absorption coefficient and attenuation coefficient to obtain a preliminarily corrected actually-measured absorption curve, wherein the preset wavelength comprises 412nm, 440nm, 488nm, 510nm, 532nm, 555nm and 715 nm;
an estimating unit, configured to estimate a true absorption coefficient of the full wavelength of the E-exponential fitting according to the E-exponential decay characteristic of the preliminarily corrected actually measured absorption curve
A construction unit for constructing an exponential fitting equation setAnd combining the aboveIs substituted into the exponential fitting equation system, and the absorption coefficient of the wavelength at 440nm is calculated and obtainedSlope SdAnd an amplitude of scattering, wherein,is the sum of the absorption coefficients after the initial correctionThe attenuation coefficient after the initial correction is obtained.
10. The apparatus of claim 9, wherein the correction module comprises:
a calculation unit for calculating according to a formulaAnd calculating to obtain a target absorption coefficient α (lambda) of the water body.
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