CN111781147A - Remote sensing inversion model and method for chlorophyll a concentration of inland lake water body based on two wave bands - Google Patents
Remote sensing inversion model and method for chlorophyll a concentration of inland lake water body based on two wave bands Download PDFInfo
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 237
- 229930002868 chlorophyll a Natural products 0.000 title claims abstract description 158
- ATNHDLDRLWWWCB-AENOIHSZSA-M chlorophyll a Chemical compound C1([C@@H](C(=O)OC)C(=O)C2=C3C)=C2N2C3=CC(C(CC)=C3C)=[N+]4C3=CC3=C(C=C)C(C)=C5N3[Mg-2]42[N+]2=C1[C@@H](CCC(=O)OC\C=C(/C)CCC[C@H](C)CCC[C@H](C)CCCC(C)C)[C@H](C)C2=C5 ATNHDLDRLWWWCB-AENOIHSZSA-M 0.000 title claims abstract description 158
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- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 14
- 238000005259 measurement Methods 0.000 claims description 13
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Abstract
The invention provides a remote sensing inversion model of chlorophyll a concentration of inland lake water body based on two wave bands, which comprises the following steps: c10m*Index+nWherein C is the chlorophyll a concentration of the inland lake water body based on two wave bands;
wherein R is1Is the water body remote sensing reflectance R of inland lake water body at 678nm wave band2The remote sensing reflectance of the water body of the inland lake water body at the wavelength band of 724 nm; measuring chlorophyll a concentration C of inland lake water bodyChlaThe chlorophyll a concentration was calculated as follows: y ═ lg (C)Chla) (ii) a Determining a line between y and Index by using Excel software and taking y and Index as variables by adopting a least square methodEquation of property: and y is m × Index + n, and m and n are respectively a coefficient and a constant term in the linear equation. Related inversion methods are also provided. The remote sensing inversion model of the chlorophyll a concentration of the inland lake water body based on the two wave bands can reduce the error of a calculation result and improve the accuracy of the inversion model of the chlorophyll a concentration of the water body, and is ingenious in design, simple and convenient to calculate, easy to realize, low in cost and suitable for large-scale popularization and application.
Description
Technical Field
The invention relates to the technical field of inland lake water body environment monitoring, in particular to the technical field of inland lake water body chlorophyll a concentration measurement, and specifically relates to a remote sensing inversion model and method for inland lake water body chlorophyll a concentration based on two wave bands.
Background
Chlorophyll a is an important pigment for photosynthesis by phytoplankton (including algae and cyanobacteria). The chlorophyll a concentration is one of important parameters for estimating phytoplankton biomass and primary productivity of a lake ecosystem, and is also an important index for reflecting the water quality of the lake water environment and the eutrophication degree of the water body. The optical characteristics of the inland turbid water body are complex, and the rapid quantitative estimation of the concentration of chlorophyll a in the inland turbid water body becomes a difficult point by using remote sensing technologies such as hyperspectral technology, multispectral technology and the like.
The existing method for quantitatively inverting chlorophyll a by remote sensing mainly comprises an analysis method, a semi-empirical method and an empirical method, wherein chlorophyll a concentration information contained in various remote sensing data is extracted, and the chlorophyll a concentration is quantitatively calculated. The analytical method quantitatively inverts the chlorophyll a concentration through physical models such as bio-optics, radiation transmission and the like, parameters such as apparent optical characteristics and inherent optical characteristics of a water body need to be determined, while the water body components and optical characteristics of inland lakes are complex, and various parameters are difficult to accurately measure, so that the accuracy of inversion results is generally low; the chlorophyll a concentration is inverted by using a physical model of an analysis method for reference and determining partial operation parameters by a statistical analysis method through a semi-empirical method, the precision is good, the application is wide, but the constructed inversion model has certain space-time limitation; the empirical method quantitatively calculates the chlorophyll a concentration by establishing a statistical relationship between the remote sensing data and the ground actually-measured chlorophyll a concentration.
A great deal of research is carried out by the predecessors aiming at the inversion of the chlorophyll a concentration of the water body, and active progress is made. In many research results, the precision of the two-band-based band ratio model is considered to be higher than that of other models, such as a single-band model and a first-order differential model (segmentation floods, Zhang cypress, Liu dynasty, and the like. research on the relation between the spectral fluorescence peak characteristics of the dry lake water body and the chlorophyll a response [ J ]. the study on infrared and millimeter waves, 2006,25(5):355 + 359). In most researches, the ratio of two wave bands is used for constructing an exponential equation of chlorophyll a concentration by the constructed two-wave band model (a pyrogen wave. the optimal remote sensing wave band selection of the chlorophyll a of the Taihu lake water body based on the measured spectrum of the water surface and the model research [ D ]. Nanjing university of teachers, 2006). When the wave band ratio is used for constructing the chlorophyll a concentration inversion model, the calculation result is divergent for the water body with medium and low chlorophyll a concentration, the error is large, and further improvement and perfection are needed.
Therefore, it is desirable to provide a remote sensing inversion model of chlorophyll a concentration of inland lake water body based on two wave bands, which can reduce error of calculation results and improve accuracy of the inversion model of chlorophyll a concentration of the water body.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide a remote sensing inversion model of chlorophyll a concentration of inland lake water body based on two wave bands, which can reduce the error of calculation results, improve the accuracy of the inversion model of the chlorophyll a concentration of the water body and is suitable for large-scale popularization and application.
The invention also aims to provide a remote sensing inversion model of the chlorophyll a concentration of the inland lake water body based on two wave bands, which has the advantages of ingenious design, simple and convenient calculation, easy realization and low cost and is suitable for large-scale popularization and application.
The invention also aims to provide a remote sensing inversion method of the chlorophyll a concentration of the water body of the inland lake based on two wave bands, which can reduce the error of a calculation result, improve the inversion accuracy of the chlorophyll a concentration of the water body and is suitable for large-scale popularization and application.
The invention also aims to provide a remote sensing inversion method of the chlorophyll a concentration of the inland lake water body based on two wave bands, which has the advantages of ingenious design, simple and convenient operation and low cost, and is suitable for large-scale popularization and application.
In order to achieve the above object, in a first aspect of the present invention, there is provided a two-band-based remote sensing inversion model for chlorophyll a concentration in a water body of an inland lake, which is characterized in that the two-band-based remote sensing inversion model for chlorophyll a concentration in a water body of an inland lake is:
C＝10m*Index+n，
wherein C is the chlorophyll a concentration of the inland lake water body based on two inverted wave bands;
wherein R is1Is the remote sensing reflectance ratio R of the inland lake water body at 678nm waveband2The remote sensing reflectance of the water body of the inland lake water body at the wavelength band of 724 nm;
m and n are determined as follows:
measuring the chlorophyll a concentration C of the inland lake water bodyChla：
The chlorophyll a concentration was calculated as follows:
y＝lg(CChla)；
determining a linear equation between y and Index by using Excel software and taking y and Index as variables by using a least square method:
y＝m*Index+n
wherein m and n are coefficients and constant terms in the linear equation, respectively.
Preferably, the water body remote sensing reflectance is calculated by adopting the following equation:
Rrs＝(Lsw-rsky*Lsky)/(Lp*π/ρp)，
wherein Rrs is the remote sensing reflectance of the water body; l isswThe water body spectrum data of the inland lake water body; r isskyThe air-water surface reflectivity of the inland lake water body is 0.022-0.028, and r is measured on a calm water surfaceskyThe value of r is 0.022, and r is obtained at the wind speed of 5m/sskyThe value is 0.025, and the value is 0.026-0.028 at the wind speed of 10 m/s; l isskyDiffuse scattered light for the sky of the inland lake water body; l ispIs the reflected light of the standard plate; rhopIs the reflectance of the standard plate.
Preferably, the chlorophyll-a concentration CChlaThe following methods were used for the measurements:
collecting a water sample of the inland lake water body, filtering the water sample by using filter paper to obtain a filter paper sample, extracting the filter paper sample by using a chlorophyll a extraction solution, centrifuging, taking a supernatant, and measuring the absorbance E of the supernatant at 665nm and 750nm665And E750Adding acid, and measuring absorbance A of the supernatant at 665nm and 750nm665And A750Calculating the chlorophyll a concentration C of the inland lake water body by using the following formulaChla：
Wherein, V1Is the volume of the chlorophyll-a extraction solution, V2Is the volume of the water sample.
Preferably, m is-0.0818 and n is 0.8514.
In a second aspect of the invention, the invention provides a remote sensing inversion method of chlorophyll a concentration of inland lake water body based on two wave bands, which is characterized by comprising the following steps:
(1) measuring the remote sensing reflectance of the inland lake water body;
(2) measuring the chlorophyll a concentration C of the inland lake water bodyChla：
(3) Calculating the two-band Index of the chlorophyll-a concentration:
wherein R is1Is the remote sensing reflectance ratio R of the water body at the 678nm wave band2The remote sensing reflectance of the water body at the wavelength of 724 nm;
(4) determining the two-band inverse model of chlorophyll a concentration using least squares
The chlorophyll a concentration was calculated as follows:
y＝lg(CChla)；
determining a linear equation between y and Index by using Excel software and taking y and Index as variables by using a least square method:
y＝m*Index+n
wherein m and n are respectively a coefficient and a constant term in the linear equation;
finally, obtaining the two-waveband inversion model:
C＝10m*Index+n，
wherein C is the chlorophyll a concentration of the inland lake water body based on two wave bands.
Preferably, in the step (1), the step of measuring the remote sensing reflectance of the water body of the inland lake water body specifically includes:
measuring the water body spectrum data L of the inland lake water bodyswAnd the sky diffuse scattered light L of the inland lake water bodyskyAnd reflected light L of the standard platepAnd calculating the water body remote sensing reflectance:
Rrs＝(Lsw-rsky*Lsky)/(Lp*π/ρp)，
wherein Rrs is the remote sensing reflectance of the water body; r isskyThe air-water surface reflectivity of the inland lake water body is 0.022-0.028, and r is measured on a calm water surfaceskyThe value of r is 0.022, and r is obtained at the wind speed of 5m/sskyThe value is 0.025, and the value is 0.026-0.028 at the wind speed of 10m/s, rhopIs the reflectance of the standard plate.
More preferably, in the step (1), the measurement is performed by using a portable geophysical spectrometer, the portable geophysical spectrometer uses a lens with a field angle of 25 °, the measurement is performed by using a measurement method above the water surface, and the observation geometry of the measurement method above the water surface is set as follows: phi (v135 °, v 40 °, the standard board is a standard white board with a reflectivity of 10%.
Preferably, in the step (2), the chlorophyll a concentration C of the inland lake water body is measuredChlaThe method specifically comprises the following steps:
collecting the inland lakeFiltering a water sample of a pool body by using filter paper to obtain a filter paper sample, extracting the filter paper sample by using a chlorophyll a extraction solution, centrifuging, taking a supernatant, and measuring the absorbance E of the supernatant at 665nm and 750nm665And E750Adding acid, and measuring absorbance A of the supernatant at 665nm and 750nm665And A750Calculating the chlorophyll a concentration C of the inland lake water body by using the following formulaChla：
Wherein, V1Is the volume of the chlorophyll-a extraction solution, V2Is the volume of the water sample.
More preferably, in the step (2), the filter paper is Whatman GF/F filter paper, the chlorophyll a extraction solution is 90% ethanol, the extraction is carried out by soaking and leaching at 4 ℃ in the dark for 8 hours, the acid is 1mol/L hydrochloric acid solution, the addition amount of the hydrochloric acid solution is 1-2 drops, and the time of the acid addition treatment is 1 minute.
Preferably, in the step (4), m is-0.0818 and n is 0.8514.
The invention has the following beneficial effects:
1. the remote sensing inversion model of the chlorophyll a concentration of the inland lake water body based on two wave bands is as follows: c10m *Index+nWherein C is the chlorophyll a concentration of the inland lake water body based on two wave bands;
wherein R is1Is the water body remote sensing reflectance R of inland lake water body at 678nm wave band2The remote sensing reflectance of the water body of the inland lake water body at the wavelength band of 724 nm; measuring chlorophyll a concentration C of inland lake water bodyChlaThe chlorophyll a concentration was calculated as follows: y ═ lg (C)Chla) (ii) a Using Excel software, using y and Index as variables, using least squares method,determine the linear equation between y and Index: and y is m × Index + n, and m and n are coefficients and constant terms in a linear equation respectively, so that the method can reduce calculation result errors, improve the accuracy of an inversion model of the chlorophyll a concentration of the water body, and is suitable for large-scale popularization and application.
2. The remote sensing inversion model of the chlorophyll a concentration of the inland lake water body based on two wave bands is as follows: c10m *Index+nWherein C is the chlorophyll a concentration of the inland lake water body based on two wave bands;
wherein R is1Is the water body remote sensing reflectance R of inland lake water body at 678nm wave band2The remote sensing reflectance of the water body of the inland lake water body at the wavelength band of 724 nm; measuring chlorophyll a concentration C of inland lake water bodyChlaThe chlorophyll a concentration was calculated as follows: y ═ lg (C)Chla) (ii) a Determining a linear equation between y and Index by using Excel software and taking y and Index as variables by using a least square method: and y is m × Index + n, and m and n are coefficients and constant terms in a linear equation respectively, so the method has the advantages of ingenious design, simple and convenient calculation, easy realization and low cost, and is suitable for large-scale popularization and application.
3. The invention discloses a remote sensing inversion method of chlorophyll a concentration of inland lake water body based on two wave bands, which comprises the following steps: measuring the remote sensing reflectance of the inland lake water body; measuring chlorophyll a concentration C of inland lake water bodyChla(ii) a Calculating the two-band Index of the chlorophyll a concentration:
wherein R is1Is the remote sensing reflectance ratio R of the water body at the 678nm wave band2The remote sensing reflectance of the water body at the wavelength band of 724 nm; the chlorophyll a concentration was calculated as follows: y ═ lg (C)Chla) (ii) a Determining a linear equation between y and Index by using Excel software and taking y and Index as variables by using a least square method: y is m Index+ n, where m and n are the coefficient and constant terms in the linear equation, respectively; finally, obtaining a two-band inversion model: c10m*Index+nAnd C is the inverted inland lake water body chlorophyll a concentration based on two wave bands, so that the method can reduce the error of a calculation result, improve the inversion accuracy of the chlorophyll a concentration of the water body, and is suitable for large-scale popularization and application.
4. The invention discloses a remote sensing inversion method of chlorophyll a concentration of inland lake water body based on two wave bands, which comprises the following steps: measuring the remote sensing reflectance of the inland lake water body; measuring chlorophyll a concentration C of inland lake water bodyChla(ii) a Calculating the two-band Index of the chlorophyll a concentration:
wherein R is1Is the remote sensing reflectance ratio R of the water body at the 678nm wave band2The remote sensing reflectance of the water body at the wavelength band of 724 nm; the chlorophyll a concentration was calculated as follows: y ═ lg (C)Chla) (ii) a Determining a linear equation between y and Index by using Excel software and taking y and Index as variables by using a least square method: y is m Index + n, where m and n are coefficients and constant terms in a linear equation, respectively; finally, obtaining a two-band inversion model: c10m*Index+nAnd C is the inverted two-waveband-based inland lake water body chlorophyll a concentration, so that the method is ingenious in design, simple and convenient to operate, low in cost and suitable for large-scale popularization and application.
These and other objects, features and advantages of the present invention will become more fully apparent from the following detailed description, the accompanying drawings and the claims, and may be realized by means of the instrumentalities, devices and combinations particularly pointed out in the appended claims.
Drawings
Fig. 1 is a geometrical diagram of a spectrometer for observing above water surface according to an embodiment of the remote sensing inversion method of chlorophyll a concentration in inland lake water based on two wave bands.
FIG. 2 is a flow diagram of model construction for the embodiment shown in FIG. 1.
FIG. 3 is a graph of the band Index of the embodiment shown in FIG. 1 plotted against the logarithm of the chlorophyll a concentration.
FIG. 4 is a diagram illustrating the results of model verification for the embodiment shown in FIG. 1.
Detailed Description
The invention provides a two-band-based remote sensing inversion model of chlorophyll a concentration in water bodies of inland lakes aiming at the defects of the existing band ratio model, and provides the two-band-based remote sensing inversion model of chlorophyll a concentration in water bodies of inland lakes, wherein the two-band-based remote sensing inversion model of the chlorophyll a concentration in the water bodies of the inland lakes is as follows:
C＝10m*Index+n，
wherein C is the chlorophyll a concentration of the inland lake water body based on two inverted wave bands;
wherein R is1Is the remote sensing reflectance ratio R of the inland lake water body at 678nm waveband2The remote sensing reflectance of the water body of the inland lake water body at the wavelength band of 724 nm;
m and n are determined as follows:
measuring the chlorophyll a concentration C of the inland lake water bodyChla：
The chlorophyll a concentration was calculated as follows:
y＝lg(CChla)；
determining a linear equation between y and Index by using Excel software and taking y and Index as variables by using a least square method:
y＝m*Index+n
wherein m and n are coefficients and constant terms in the linear equation, respectively.
The water body remote sensing reflectance can be measured by any suitable method, and preferably, the water body remote sensing reflectance is calculated by the following equation:
Rrs＝(Lsw-rsky*Lsky)/(Lp*π/ρp)，
wherein Rrs is the remote sensing reflectance of the water body; l isswThe water body spectrum data of the inland lake water body; r isskyThe air-water surface reflectivity of the inland lake water body is 0.022-0.028, and r is measured on a calm water surfaceskyThe value of r is 0.022, and r is obtained at the wind speed of 5m/sskyThe value is 0.025, and the value is 0.026-0.028 at the wind speed of 10 m/s; l isskyDiffuse scattered light for the sky of the inland lake water body; l ispIs the reflected light of the standard plate; rhopIs the reflectance of the standard plate.
The chlorophyll a concentration CChlaCan be measured by any suitable method, preferably, the chlorophyll-a concentration CChlaThe following methods were used for the measurements:
collecting a water sample of the inland lake water body, filtering the water sample by using filter paper to obtain a filter paper sample, extracting the filter paper sample by using a chlorophyll a extraction solution, centrifuging, taking a supernatant, and measuring the absorbance E of the supernatant at 665nm and 750nm665And E750Adding acid, and measuring absorbance A of the supernatant at 665nm and 750nm665And A750Calculating the chlorophyll a concentration C of the inland lake water body by using the following formulaChla：
Wherein, V1Is the volume of the chlorophyll-a extraction solution, V2Is the volume of the water sample.
m and n can be any suitable values, preferably m is-0.0818 and n is 0.8514.
The invention also provides a remote sensing retrieval method of chlorophyll a concentration of inland lake water body based on two wave bands, which comprises the following steps:
(1) measuring the remote sensing reflectance of the inland lake water body;
(2) measuring the chlorophyll a concentration C of the inland lake water bodyChla：
(3) Calculating the two-band Index of the chlorophyll-a concentration:
wherein R is1Is the remote sensing reflectance ratio R of the water body at the 678nm wave band2The remote sensing reflectance of the water body at the wavelength of 724 nm;
(4) determining the two-band inverse model of chlorophyll a concentration using least squares
The chlorophyll a concentration was calculated as follows:
y＝lg(CChla)；
determining a linear equation between y and Index by using Excel software and taking y and Index as variables by using a least square method:
y＝m*Index+n
wherein m and n are respectively a coefficient and a constant term in the linear equation;
finally, obtaining the two-waveband inversion model:
C＝10m*Index+n，
wherein C is the chlorophyll a concentration of the inland lake water body based on two wave bands.
In the step (1), the step of measuring the remote water body reflectance of the inland lake water body may specifically include any suitable method, and preferably, in the step (1), the step of measuring the remote water body reflectance of the inland lake water body specifically includes:
measuring the water body spectrum data L of the inland lake water bodyswAnd the sky diffuse scattered light L of the inland lake water bodyskyAnd reflected light L of the standard platepAnd calculating the water body remote sensing reflectance:
Rrs＝(Lsw-rsky*Lsky)/(Lp*π/ρp)，
wherein Rrs is the remote sensing reflectance of the water body; r isskyThe air-water surface reflectivity of the inland lake water body is 0.022-0.028, and r is measured on a calm water surfaceskyThe value of r is 0.022, and r is obtained at the wind speed of 5m/sskyThe value is 0.025, and the value is 0.026-0.028 at the wind speed of 10m/s, rhopIs the reflectance of the standard plate.
In the step (1), the measurement may be performed by any suitable spectrometer, the measurement may be performed by any suitable method, the standard plate may be any suitable standard plate, and preferably, in the step (1), the measurement is performed by a portable terrestrial object spectrometer, the portable terrestrial object spectrometer uses a lens with an angle of view of 25 °, the measurement is performed by a measurement method above the water surface, and an observation geometry of the measurement method above the water surface is set as: phi (v135 °, v 40 °, the standard board is a standard white board with a reflectivity of 10%.
In the step (2), the chlorophyll a concentration C of the inland lake water body is measuredChlaThe step (2) may specifically include any suitable method, and preferably, in the step (2), the measurement of the chlorophyll a concentration C of the inland lake water bodyChlaThe method specifically comprises the following steps:
collecting a water sample of the inland lake water body, filtering the water sample by using filter paper to obtain a filter paper sample, extracting the filter paper sample by using a chlorophyll a extraction solution, centrifuging, taking a supernatant, and measuring the absorbance E of the supernatant at 665nm and 750nm665And E750Adding acid, and measuring absorbance A of the supernatant at 665nm and 750nm665And A750Calculating the chlorophyll a concentration C of the inland lake water body by using the following formulaChla：
Wherein, V1Is the volume of the chlorophyll-a extraction solution, V2Is the volume of the water sample.
In the step (2), the filter paper may be any suitable filter paper, the chlorophyll-a extraction solution may be any suitable chlorophyll-a extraction solution, the acid may be any suitable acid, and more preferably, in the step (2), the filter paper is Whatman GF/F filter paper, the chlorophyll-a extraction solution is 90% ethanol, the extraction is soaking and leaching at 4 ℃ in the dark for 8 hours, the acid is 1mol/L hydrochloric acid solution, the addition amount of the hydrochloric acid solution is 1-2 drops, and the time of the acid addition treatment is 1 minute.
In the step (4), m and n may be any suitable values, and preferably, in the step (4), m is-0.0818, and n is 0.8514.
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention.
Examples
The remote sensing inversion method for the chlorophyll a concentration of the inland lake water body based on the two wave bands adopts the water body optical characteristics and the water body component information collected by the Hongze lake, and the 40 sampling points are uniformly distributed and completely cover the whole lake area of the Hongze lake. The Hongze lake is one of five freshwater lakes in China, has the average water depth of 5.62m, has great influence on the resuspension of sediments at the bottom of the lake by the wind and waves on the surface of the lake, belongs to a high-turbidity water body, and is a typical inland class II water body. The data of 40 sampling points are divided into 2 parts by a random method, wherein the data of 30 sampling points is used for constructing a model, and the data of 10 sampling points is used for model inspection.
1. And (4) measuring the water body spectrum.
And measuring the water body spectrum by using the portable surface feature spectrometer and the standard plate to obtain the remote sensing reflectance Rrs. The measurement method above the water surface is adopted, the observation geometry is shown in figure 1, and the current typical observation geometry is adopted: Φ v is 135 ° and v is 40 °. When measuring the water body spectrum, recording the single integral value of the spectrum, not adopting the average value, and recording the spectrum value of 15 times of tests, wherein the measuring time spans the wave period (the measuring time is 2-5 minutes). The spectrometer uses a lens with a 25 degree field angle and a standard white board with a reflectivity of 10%. Respectively measuring water body spectral data, sky diffuse scattering light and reflected light of a standard plate, and calculating a water body remote sensing reflectance Rrs:
Rrs＝(Lsw-rsky*Lsky)/(Lp*π/ρp)
wherein Rrs is the water body remote sensing reflectance, LswWater spectral data measured for a spectrometer, rskyThe reflectivity of the surface of the gas and water is 0.0245, LskyIs diffusely scattered light from the sky, LpIs the reflected light of the standard plate, ppThe reflectance of the standard plate used in this example was 10%.
2. And (4) measuring the concentration of chlorophyll a in the water body.
When the water body spectral data are measured, 200ml of water sample is synchronously collected, Whatman GF/F filter paper is used for filtering, the filtered filter paper is folded in half, and is placed into aluminum foil paper for wrapping, and the wrapped filter paper is frozen and stored in a refrigerator at the temperature of minus 20 ℃. Extracting filter paper sample with 90% hot ethanol solution at 75 deg.C, soaking and extracting at 4 deg.C in dark for 8 hr, centrifuging, collecting supernatant, measuring with 722 spectrophotometer, and recording absorbance E at 665nm and 750nm665And E750Then adding 1-2 drops of 1mol/L hydrochloric acid solution into a common rubber-tipped pipette, and recording the absorbances A at 665nm and 750nm after 1 minute665And A750The chlorophyll a concentration was calculated using the formula:
wherein, CChlaThe chlorophyll a concentration (ug/L), E665、E750The absorbances at 665nm and 750nm before adding acid, A665、A750The absorbance at 665nm and 750nm after adding acid, V1Is the volume (ml) of a 90% hot ethanol solution, V2Is the volume (L) of the water sample.
3. Model construction
The spectral data and chlorophyll a concentration data of 30 sampling points obtained at random are used for constructing a model.
(1) Calculating the two-band Index of the chlorophyll a concentration:
wherein R is1Is the water body remote sensing reflectivity at 678nm, R2The remote sensing reflectivity of the water body at 724nm is obtained.
(2) Two-band inversion model for determining chlorophyll a concentration by using least square method
The measured chlorophyll-a concentration was calculated as follows:
y＝lg(CChla)
the linear relationship between y and the parameter Index was determined using the least squares method using Microsoft's (Microfot) form processing software (Excel) with y and parameter Index as variables, resulting in the following model:
y＝-0.0818*Index+0.8514
at the same time, R of the model2The results are shown in fig. 3, 0.9248.
Finally, a chlorophyll a concentration inversion model based on two wave bands is obtained as follows:
C＝10m*Index+n
wherein C is the concentration of chlorophyll a in the water body of inversion, and Index is the Index calculated by remote sensing reflectance at the positions of 678nm and 724nm of wave bands.
4. Model inspection
The measured data of 10 sampling points used for model verification in this embodiment are shown in table 1.
Table 1 measured data of sampling points for model test (n ═ 10)
Obtaining a predicted value of the chlorophyll a concentration by using the remote sensing reflectance at the 678nm and 724nm in the 10 sampling point data according to the constructed model calculation, analyzing the relation between the predicted value and the measured value in Excel software, and obtaining the result shown in FIG. 4, wherein R of the model is2＝0.8678。
Therefore, the invention provides a two-waveband chlorophyll a inversion model of inland lake water chlorophyll a concentration based on remote sensing hyperspectral data, improves the two-waveband chlorophyll a inversion model aiming at the defects of a waveband ratio model based on actually measured water spectral data and field collected chlorophyll a concentration data, provides a new two-waveband semi-analytical model, can overcome the defect that the error of the two-waveband ratio model in the water inversion result of the chlorophyll a concentration too large or the chlorophyll a concentration too small, fully utilizes the chlorophyll a concentration information contained in the characteristic waveband data, and improves the inversion model precision of the chlorophyll a concentration of the water.
Compared with the prior art, the invention has the following advantages:
(1) the two-waveband semi-analytical model is suitable for inversion of chlorophyll a concentration of a water body of an inland lake, and fully utilizes information contained in characteristic wavebands 678nm and 724nm of chlorophyll a on the basis of comprehensively considering information of all waveband ranges of hyperspectrum according to an actually measured water body remote sensing reflectance and the chlorophyll a concentration;
(2) a new algorithm is used, a two-band model is constructed based on information contained in chlorophyll a characteristic bands of 678nm and 724nm, the chlorophyll a concentration inversion model precision of the medium-low concentration chlorophyll a water body smaller than 60ug/L and the R of the model are improved2Above 0.85;
(3) the two-waveband semi-analytical model provided by the invention is simple and convenient to calculate, makes full use of waveband data containing the richest chlorophyll a concentration, and is suitable for remote sensing quantitative inversion of chlorophyll a concentrations in inland lakes in different areas and in different seasons.
In conclusion, the remote sensing inversion model of the chlorophyll a concentration of the inland lake water body based on the two wave bands can reduce the error of a calculation result and improve the accuracy of the inversion model of the chlorophyll a concentration of the water body, and is ingenious in design, simple and convenient to calculate, easy to realize, low in cost and suitable for large-scale popularization and application.
It will thus be seen that the objects of the invention have been fully and effectively accomplished. The functional and structural principles of the present invention have been shown and described in the embodiments, and the embodiments may be modified without departing from the principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the claims.
Claims (10)
1. The remote sensing inversion model of the chlorophyll a concentration of the water body of the inland lake based on two wave bands is characterized in that the remote sensing inversion model of the chlorophyll a concentration of the water body of the inland lake based on two wave bands is as follows:
C＝10m*Index+n，
wherein C is the chlorophyll a concentration of the inland lake water body based on two inverted wave bands;
wherein R is1Is the remote sensing reflectance ratio R of the inland lake water body at 678nm waveband2The remote sensing reflectance of the water body of the inland lake water body at the wavelength band of 724 nm;
m and n are determined as follows:
measuring the chlorophyll a concentration C of the inland lake water bodyChla：
The chlorophyll a concentration was calculated as follows:
y＝lg(CChla)；
determining a linear equation between y and Index by using Excel software and taking y and Index as variables by using a least square method:
y＝m*Index+n
wherein m and n are coefficients and constant terms in the linear equation, respectively.
2. The remote sensing inversion model of chlorophyll a concentration of inland lake water based on two wave bands of claim 1, wherein the remote sensing reflectance of water is calculated by using the following equation:
Rrs＝(Lsw-rsky*Lsky)/(Lp*π/ρp)，
wherein Rrs is the remote sensing reflectance of the water body; l isswThe water body spectrum data of the inland lake water body; r isskyThe air-water surface reflectivity of the inland lake water body is 0.022-0.028, and r is measured on a calm water surfaceskyThe value of r is 0.022, and r is obtained at the wind speed of 5m/sskyThe value is 0.025, and the value is 0.026-0.028 at the wind speed of 10 m/s; l isskyDiffuse scattered light for the sky of the inland lake water body; l ispIs the reflected light of the standard plate; rhopIs the reflectance of the standard plate.
3. The remote sensing inversion model of chlorophyll a concentration of inland lake water based on two wave bands of claim 1, wherein the chlorophyll a concentration CChlaThe following methods were used for the measurements:
collecting a water sample of the inland lake water body, filtering the water sample by using filter paper to obtain a filter paper sample, extracting the filter paper sample by using a chlorophyll a extraction solution, centrifuging, taking a supernatant, and measuring the absorbance E of the supernatant at 665nm and 750nm665And E750Adding acid, and measuring absorbance A of the supernatant at 665nm and 750nm665And A750Calculating the chlorophyll a concentration C of the inland lake water body by using the following formulaChla：
Wherein, V1Is the volume of the chlorophyll-a extraction solution, V2Is the volume of the water sample.
4. The remote sensing inversion model of chlorophyll a concentration in inland lake water based on two wave bands of claim 1, wherein m is-0.0818 and n is 0.8514.
5. A remote sensing inversion method of chlorophyll a concentration of inland lake water based on two wave bands is characterized by comprising the following steps:
(1) measuring the remote sensing reflectance of the inland lake water body;
(2) measuring the chlorophyll a concentration C of the inland lake water bodyChla：
(3) Calculating the two-band Index of the chlorophyll-a concentration:
wherein R is1Is the remote sensing reflectance ratio R of the water body at the 678nm wave band2The remote sensing reflectance of the water body at the wavelength of 724 nm;
(4) determining the two-band inverse model of chlorophyll a concentration using least squares
The chlorophyll a concentration was calculated as follows:
y＝lg(CChla)；
determining a linear equation between y and Index by using Excel software and taking y and Index as variables by using a least square method:
y＝m*Index+n
wherein m and n are respectively a coefficient and a constant term in the linear equation;
finally, obtaining the two-waveband inversion model:
C＝10m*Index+n，
wherein C is the chlorophyll a concentration of the inland lake water body based on two wave bands.
6. The remote sensing inversion method of chlorophyll a concentration in water body of inland lake based on two wave bands as claimed in claim 5, wherein in said step (1), said step of measuring remote sensing reflectance of water body of inland lake specifically comprises:
measuring the water body spectrum data L of the inland lake water bodyswAnd the sky diffuse scattered light L of the inland lake water bodyskyAnd reflected light L of the standard platepAnd calculating the water body remote sensing reflectance:
Rrs＝(Lsw-rsky*Lsky)/(Lp*π/ρp)，
wherein Rrs is the remote sensing reflectance of the water body; r isskyThe air-water surface reflectivity of the inland lake water body is 0.022-0.028, and r is measured on a calm water surfaceskyThe value is 0.022, at 5 m-At the wind speed of s, rskyThe value is 0.025, and the value is 0.026-0.028 at the wind speed of 10m/s, rhopIs the reflectance of the standard plate.
7. The remote sensing inversion method of chlorophyll a concentration in inland lake water based on two wave bands as claimed in claim 6, wherein in said step (1), said measurement is performed by using a portable geophysical spectrometer, said portable geophysical spectrometer uses a lens with an angle of view of 25 °, said measurement is performed by using a measurement method above water surface, and the observation geometry of said measurement method above water surface is set as: phi (v135 °, v 40 °, the standard board is a standard white board with a reflectivity of 10%.
8. The remote sensing inversion method for chlorophyll a concentration in water body of inland lake according to claim 5, wherein in said step (2), said measuring chlorophyll a concentration C in water body of inland lakeChlaThe method specifically comprises the following steps:
collecting a water sample of the inland lake water body, filtering the water sample by using filter paper to obtain a filter paper sample, extracting the filter paper sample by using a chlorophyll a extraction solution, centrifuging, taking a supernatant, and measuring the absorbance E of the supernatant at 665nm and 750nm665And E750Adding acid, and measuring absorbance A of the supernatant at 665nm and 750nm665And A750Calculating the chlorophyll a concentration C of the inland lake water body by using the following formulaChla：
Wherein, V1Is the volume of the chlorophyll-a extraction solution, V2Is the volume of the water sample.
9. The two-band-based remote sensing inversion method for chlorophyll a concentration in inland lake water bodies according to claim 8, wherein in the step (2), the filter paper is Whatman GF/F filter paper, the chlorophyll a extraction solution is 90% ethanol, the extraction is carried out by soaking and leaching at 4 ℃ in the dark for 8 hours, the acid is 1mol/L hydrochloric acid solution, the addition amount of the hydrochloric acid solution is 1-2 drops, and the time of the acid addition treatment is 1 minute.
10. The remote sensing inversion method of chlorophyll a concentration in inland lake water based on two wave bands of claim 5, wherein in the step (4), m is-0.0818, and n is 0.8514.
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| CN112881293A (en) * | 2021-01-08 | 2021-06-01 | 浙江工商大学 | Inland lake clean water body chlorophyll a concentration inversion method based on high-grade first satellite |
| CN115080905A (en) * | 2022-06-07 | 2022-09-20 | 昆明理工大学 | Remote sensing inversion method for chlorophyll a concentration of plateau lake |
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| CN112362812A (en) * | 2020-11-10 | 2021-02-12 | 淮阴师范学院 | Remote sensing inversion model and method for rice leaf chlorophyll carotenoid content ratio based on Lars algorithm |
| CN112881293A (en) * | 2021-01-08 | 2021-06-01 | 浙江工商大学 | Inland lake clean water body chlorophyll a concentration inversion method based on high-grade first satellite |
| CN115080905A (en) * | 2022-06-07 | 2022-09-20 | 昆明理工大学 | Remote sensing inversion method for chlorophyll a concentration of plateau lake |
| CN115080905B (en) * | 2022-06-07 | 2024-05-17 | 昆明理工大学 | Remote sensing inversion method for chlorophyll a concentration in plateau lake |
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