CN112784416A - Geometric optics-radiation transmission hybrid modeling method for row-seeding aquatic vegetation canopy reflection - Google Patents
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Abstract
The invention relates to a geometric optics-radiation transmission hybrid modeling method for row-sowing aquatic vegetation canopy reflection, which comprises the following steps: the aquatic vegetation with the characteristics of regular row geometric structure, row direction and row spacing is regarded as a rectangular box body which is uniformly distributed in the ridge rows and contains a certain gap, and a scene that vegetation canopies and water bodies are alternately and regularly arranged is formed in the direction vertical to the ridge rows; the model is coupled with a plant leaf spectrum model, a continuous medium aquatic vegetation canopy radiation transmission model, a wave water surface reflection model, a shallow water biological optical model and a porous geometric optical model, the reflectivity and the probability of each component in an observation field are respectively calculated, and the reflectivity of the whole aquatic vegetation canopy is obtained after weighting; the reflection spectrum characteristic and the reflection direction characteristic of the canopy of the aquatic vegetation are explored. The invention provides a new model tool and a technical method for the remote sensing monitoring of the physiological and biochemical parameters of the aquatic vegetation canopy, and simultaneously provides a scientific basis for the precise water and fertilizer regulation and control management of row-sowed crops.
Description
(I) in the field of technology
The invention relates to a geometric optics-radiation transmission hybrid modeling method for row-sowing aquatic vegetation canopy reflection, belongs to the field of optical remote sensing, and has important significance in wetland ecological research and crop quantitative monitoring application.
(II) background of the invention
The aquatic vegetation for sowing has a regular planting structure, the growing background of the aquatic vegetation is a shallow water area, the shallow water background is different from the soil background, one part of light incident on the water surface returns to an air medium through the reflection process of the water surface, the other part of incident light is transmitted into the water and interacts with the water body, dissolved matters and suspended matters in the water body, and finally escapes from the water surface through the attenuation effect and the scattering effect of the water body and the reflection process of the water bottom. Therefore, by researching the radiation transmission process of the aquatic vegetation, the row-seeding aquatic vegetation remote sensing model is constructed, the relation between the reflection spectrum characteristic and the two-way reflection characteristic of the aquatic vegetation canopy and solar radiation, vegetation structure parameters, water body parameters, water bottom reflection characteristic and observation geometry is scientifically known, information in data obtained by ground measurement and a satellite sensor can be more fully mined, and a more efficient and accurate new way is provided for quantitative application of monitoring, estimating, early warning, protecting and remote sensing of the aquatic vegetation. Meanwhile, the method has important significance for remote sensing monitoring of aquatic vegetation and inversion of water quality parameters of shallow water areas.
The reflection characteristics of an object are often described precisely by a Bidirectional Reflection Distribution Function (BRDF). The geometric optics-radiation transmission mixed modeling method for row-seeding aquatic vegetation canopy reflection is constructed by coupling the plant leaf spectrum model, the continuous medium aquatic vegetation canopy radiation transmission model, the wave water surface reflection model, the shallow water biological optical model and the porous geometric optical model, the method can efficiently and accurately simulate the reflection spectrum characteristic and the reflection direction characteristic of aquatic vegetation in vegetation remote sensing, and has important significance and application value for realizing remote sensing monitoring and parameter inversion of aquatic vegetation.
Disclosure of the invention
The invention relates to a geometric optics-radiation transmission hybrid modeling method for row-sowing aquatic vegetation canopy reflection. The method comprises the following steps: the aquatic vegetation containing the water body background and having the characteristics of regular row geometric structure, row direction and row spacing is regarded as a rectangular box body which is uniformly distributed in the ridge rows and contains a certain gap, and a scene that aquatic vegetation canopies and the water body are alternately and regularly arranged is formed in the direction vertical to the ridge rows. The method comprises the following steps of coupling a model with a plant leaf reflectivity model, transmitting a continuous medium aquatic vegetation canopy radiation, uniformly distributing the aquatic vegetation model, a wave water surface reflection model, a shallow water biological optical model and a porous geometric optical model, calculating the reflectivity and the probability of each component respectively, weighting to obtain the reflectivity of the whole aquatic vegetation canopy, and further researching the reflection spectrum characteristic and the reflection direction characteristic of the aquatic vegetation canopy, wherein the method comprises the following specific steps:
a geometric optics-radiation transmission hybrid modeling method for row-seeding aquatic vegetation canopy reflection is characterized by comprising the following steps:
(1) the method comprises the following steps of (1) regarding aquatic vegetation canopies containing water body backgrounds and having characteristics of regular row geometric structures, row directions and row spacing as rectangular boxes which are uniformly distributed in ridge rows and contain certain gaps, and regarding the aquatic vegetation canopies and the water bodies among the ridge rows to be alternately and regularly arranged in a direction vertical to the ridge rows; because the reflectivity of different reflecting surfaces in a visual field is influenced by the interception condition of incident light besides the influence of materials, the whole scene is divided into 7 components which respectively comprise: planting a canopy component, a first type of illumination water surface component, a first type of shadow water surface component, a second type of illumination water surface component, a second type of shadow water surface component, an illumination water bottom component and a shadow water bottom component in the ridge;
(2) firstly, calculating the reflectivity and the transmittance of a single blade by using a continuous medium aquatic vegetation canopy radiation transmission model, inputting the reflectivity and the transmittance into a distribution medium aquatic vegetation canopy radiation transmission model, calculating the extinction coefficient and the scattering coefficient of an interline aquatic vegetation canopy by combining vegetation canopy structure parameters, water body parameters, water bottom parameters, incidence geometry and observation geometry parameters, and further obtaining the reflectivity R of the inline aquatic vegetation canopycanopy；
(3) Calculating the reflectivity of the water surface between lines by using a wave water surface reflection model, wherein the reflectivity comprises the reflectivity R of the first type of illumination water surfaceiw1First type shadow water surface reflectivity Rsw1The reflectivity R of the second kind of illumination water surfaceiw2Shadow water surface reflectance R of the second kindsw2；
(4) Using shallow water biological optical modelsCalculating the inter-row illumination water bottom reflectivity RibAnd shadow water bottom reflectivity Rsb；
(5) Converting a three-dimensional aquatic vegetation scene into a two-dimensional scene vertical to the row direction of ridges by utilizing the incident geometry, the observation geometry and the geometric relation of the row direction of the aquatic vegetation, and calculating the proportion of the occupied area of 7 components in the whole scene based on a porous geometric optical model;
(6) and finally, calculating the spectral reflectivity and the bidirectional reflectivity of the whole aquatic vegetation system according to the weighted sum of the reflectivity and the probability of the 7 components in the observation field.
The method for modeling row-seeding aquatic vegetation canopy reflection geometry optics-radiation transmission mixture as claimed in claim 1, wherein the method comprises the following steps: the aquatic vegetation canopy containing the water body background and having the characteristics of regular row geometric structure, row direction and row spacing in the step (1) is regarded as a rectangular box body which is uniformly distributed in rows and contains a certain gap, and is a scene in which the aquatic vegetation canopy and the water body between the rows are alternately and regularly arranged in the direction vertical to the ridge rows. For convenient calculation, the whole scene is divided into 7 components, which respectively comprise: planting a canopy component, a first type of illumination water surface component, a first type of shadow water surface component, a second type of illumination water surface component, a second type of shadow water surface component, an illumination water bottom component and a shadow water bottom component in the ridge.
The method for modeling row-seeding aquatic vegetation canopy reflection geometry optics-radiation transmission mixture as claimed in claim 1, wherein the method comprises the following steps: in the step (2), "calculating the reflectivity and transmittance of a single blade by using a plant blade spectrum model and inputting the reflectivity and transmittance to a continuous medium aquatic vegetation canopy radiation transmission model, calculating the extinction coefficient and scattering coefficient of the inline aquatic vegetation canopy by combining the vegetation canopy structure parameter, the water body parameter, the water bottom parameter, the illumination geometric parameter and the observation geometric parameter, and further obtaining the spectrum reflectivity and the bidirectional reflectivity of the inline aquatic vegetation canopy", the specific calculation process is as follows:
the first step is as follows: dividing a single leaf into a plurality of layers according to the plant leaf spectrum model, and calculating the spectrum reflectivity and the transmittance of the single leaf;
the second step is that: dividing the aquatic vegetation canopy in each ridge row into an emergent aquatic vegetation canopy VE, a water-air interface I, a submerged vegetation canopy VS and a soil layer S, and calculating the extinction coefficient and scattering coefficient of the aquatic vegetation by utilizing a continuous medium aquatic vegetation canopy radiation transmission model and combining the reflectivity and transmittance of a single blade, the structure parameters of the aquatic vegetation canopy, water body parameters, water bottom parameters, incident geometry and observation geometric conditions so as to obtain the reflectivity of the whole aquatic vegetation canopy;
the top reflectivity of the emergent aquatic vegetation canopy calculated by the continuous medium aquatic vegetation canopy radiation transmission model can be expressed as:
wherein
Representing a reflectivity matrix that takes into account the underlying soil and submerged vegetation layers;
representing a reflectivity matrix that takes into account underwater vegetation, soil, and water-air interfaces;
representing a canopy top reflectivity matrix that takes into account underlying surface soil, submerged vegetation layers, water-air interfaces, and emergent water vegetation layers; where R represents the reflectance, T represents the transmittance, the subscripts b represents the bottom of the layer, T represents the top of the layer, d represents the down flux, and u represents the up flux.
4 according to claim 1The geometric optics-radiation transmission hybrid modeling method for row-seeding aquatic vegetation canopy reflection is characterized by comprising the following steps of: step (3) calculating the specular reflectivity of the water surface between the rows by using a wave water surface reflection model, wherein the specular reflectivity comprises the first-class illumination water surface reflectivity Riw1First type shadow water surface reflectivity Rsw1The reflectivity R of the second kind of illumination water surfaceiw2Shadow water surface reflectance R of the second kindsw2The calculation process is as follows:
the first step is as follows: calculating the first type of water surface reflectivity and the second type of water surface reflectivity by using a simplified wave water surface reflection model, taking the water surface as the geometry of micro surface elements with different gradients by using a Cox-Munk model, and firstly calculating the BRDF of the wave water surface as follows:
wherein r (ω) is the Fresnel reflectivity at the incident angle ω when the water surface is calm, and p (z)x,zy) As a function of the probability distribution of the surface gradient of the wave, zx,zyIs a micro bin coordinate system, thetanThe zenith angle direction of the normal line of the wavy surface element with specular reflection, thetasAt the zenith angle of the sun, thetaoFor observing zenith angles, sigma is a water surface roughness factor;
the second step is that: the BRDF based on the wave water surface can calculate the contribution value of the solar direct light to the reflectivity of the vegetation canopy as follows:
wherein beta is the proportion of the incident irradiance of the solar direct light in the scene to the total incident irradiance, phisIs the sun azimuth angle, phioFor observing azimuth angle, calculating hemispherical space for sky scattered light of all same-polarity hemispherical spacesThe contribution value of the scattered light of the sky to the reflectivity of the vegetation canopy is as follows:
the third step: for the first type of illumination water surface reflectivity, the incident energy sources are direct solar light and sky scattered light of a hemispherical space, so the first type of illumination water surface reflectivity is the common contribution of the direct solar light and the sky scattered light of the hemispherical space, and is expressed as:
Riw1＝Riw,dir+Riw,diff
the first type of shadow surface components are low light areas due to occlusion by vegetation canopies, the incident energy sources are direct light passing through the canopies gaps and scattered light from the sky, so the reflectivity of the first type of shadow surface is expressed as:
similarly, the reflectivity of the second type of illumination water surface is as follows:
the reflectivity of the shadow water surface of the second type is as follows:
in the formula
The crown layer gap ratio in the solar incidence direction,
The crown layer gap ratio in the observation direction,
The two-way gap probability of the sun direction and the observation direction is considered at the same time.
The method for modeling row-seeding aquatic vegetation canopy reflection geometry optics-radiation transmission mixture as claimed in claim 1, wherein the method comprises the following steps: the step (4) of calculating the underwater reflectivity R of the interline illumination by using the shallow water biological optical modelibAnd the underwater reflectivity R of the interline shadowsb", the specific calculation process is as follows:
solving the radiation energy intensity of the reflectivity of the water body components, wherein the transmission of the water surface, the attenuation of the water body, the scattering of the water body and the reflection process of the water bottom surface need to be considered; the refraction effect of the water body needs to be considered on the light transmission path; for the water bottom components, the optical shallow water model is used to calculate the out-of-water reflectivity exhibited by the water bottom components. The shallow water biological optical model is a semi-analytical reflectivity model, and the BRDF of the radiance transmitted out of the water surface at the water bottom and the incident irradiance on the water surface is calculated:
and t (theta) is the transmittance generated on the water surface when the included angle between the light ray direction in the air and the water surface is theta, and is calculated by a Fresnel formula. Gamma is the reflection coefficient under the water surface; r isdIs the irradiance reflectivity, rho, under the water surfacebIs the water bottom reflectivity.
Due to RibThe energy of (A) is constituted by direct solar light transmitted into water and sky scattered light of a hemispherical space, RsbIs constructed as sky scattered light in a hemispherical space. Then R isibContribution value and R of sky scattered light in middle hemisphere space to reflectivitysbAre equal. For sky scattered light in isotropic hemisphere space, RsbIs a hemispherical incident space RLeeMultiplied by the proportion of sky scattered light in the hemispherical space:
Ribcontribution R of medium direct light to reflectivityib,dirCan be directly derived from the Lee model as:
Rib,dir＝β·RLee(θs,φs,θo,φo,ρb,Hw)
in the formula, thetasIs the zenith angle of the sun, phisIs the sun azimuth angle, θoTo observe zenith angle, phioFor observation of azimuth angle, ρbIs the water bottom reflectivity, HwThe depth of water, the reflectance at the bottom of the illuminated water is:
Rib＝Rsb+Rib,dir
the method for modeling row-seeding aquatic vegetation canopy reflection geometry optics-radiation transmission mixture as claimed in claim 1, wherein the method comprises the following steps: in the step (5), "the three-dimensional aquatic vegetation scene is converted into a two-dimensional scene perpendicular to the ridge row direction by using the incident geometry, the observation geometry and the geometric relationship of the aquatic vegetation row direction, and the proportion of the occupied area of 7 components in the field of view is calculated based on the porous geometric optical model", and the specific calculation process is as follows:
along (theta)s,φs) Or (theta)o,φo) Height H of canopy above water2Length of projection L in the direction perpendicular to the rowskComprises the following steps:
wherein k is s or o, θkFor the zenith angle of the sun or the observation zenith angle,
the absolute value of the difference between the azimuth angle of the sun or the observation azimuth angle and the azimuth angle of the row direction; compared with the projection length on water, the horizontal projection length on the water bottom is longer and is equal to the canopy H above the water surface in value2Horizontal projection length and water surfaceLower canopy H1Sum of horizontal projection lengths of LkwComprises the following steps:
in order to solve the problem of mutual overlapping of projections during observation of a large zenith angle, a parameter n is introducedkRepresenting the complete number of lines traversed by the projection, LKThe remaining projection length.
nk＝int(L/S)
Lk＝L-nkS
In the formula, L is the length of horizontal projection, and S is the length of one row sowing period for row sowing of the aquatic vegetation.
The method for modeling row-seeding aquatic vegetation canopy reflection geometry optics-radiation transmission mixture as claimed in claim 1, wherein the method comprises the following steps: the step (6) of calculating the bi-directional reflectivity of the whole aquatic vegetation system according to the weighted sum of the reflectivity and the probability of the 7 components in the observation field comprises the following specific calculation processes:
R＝RcanopyPcanopy+Riw1Piw1+Rsw1Psw1+Riw2Piw2+Rsw2Psw2+RibPib+RsbPsb
compared with the prior art, the invention has the advantages that:
(1) in the field of vegetation remote sensing, a general model capable of scientifically and effectively describing reflection spectrum characteristics and two-way reflection characteristics of aquatic vegetation sowed under a water body background is absent at present, the geometric optics-radiation transmission hybrid modeling method developed for aquatic vegetation sowed in shallow water areas has remarkable innovativeness, and a more efficient and accurate new way is provided for monitoring, estimating, early warning and protecting the aquatic vegetation sowed in shallow water areas and inverting biophysical parameters.
(2) The invention can solve the problem that when the traditional uniform canopy radiation transmission model is used for simulating row seeding crops, the row effect is ignored, and the system deviation occurs when the observation zenith angle is more than 40 degrees. Meanwhile, the invention overcomes the problem of low simulation precision of the traditional rice model because the influence of the water background is neglected. Compared with the traditional vegetation model, the vegetation model has the advantages of clear physical concept, strong universality, convenience in calculation, high speed and reliable precision guarantee.
(IV) description of the drawings
FIG. 1 is a process flow of the present invention.
(V) detailed description of the preferred embodiments
In order to better illustrate the geometric optics-radiation transmission hybrid modeling method for row-sowing aquatic vegetation canopy reflection, which is related by the invention, the model of the invention is used for testing and analyzing, and good effects are obtained, and the specific implementation method is as follows:
(1) the aquatic vegetation canopies in the rows are regarded as rectangular box bodies which are uniformly distributed in the rows and contain certain gaps, and the scene that the aquatic vegetation canopies and water bodies in the rows are alternately and regularly arranged in the direction vertical to the ridge rows is formed. The whole scene is divided into 7 components, which respectively comprise: planting a canopy component, a first type of illumination water surface component, a first type of shadow water surface component, a second type of illumination water surface component, a second type of shadow water surface component, an illumination water bottom component and a shadow water bottom component in the ridge;
(2) calculating the reflectivity and the transmittance of a single blade based on the plant blade spectrum model, and calculating the spectral reflectivity and the bidirectional reflectivity of the inline aquatic vegetation canopy through the continuous medium aquatic vegetation canopy radiation transmission model by combining the reflectivity and the transmittance of the single blade, the vegetation canopy structure parameter, the water body parameter, the water bottom parameter, the incident geometry and the observation geometry parameter;
(3) calculating the reflectivity of the water surface between rows in the aquatic vegetation scene according to the wave water surface reflection model, and meanwhile calculating the first-class illumination water surface reflectivity, the first-class shadow water surface reflectivity, the second-class illumination water surface reflectivity and the second-class shadow water surface reflectivity by combining the canopy clearance rates in different directions;
(4) giving water body components such as chlorophyll concentration, suspended particulate matter concentration, colored soluble organic matter concentration and water body turbidity parameter, and calculating out the out-of-water reflectivity expressed by the illumination water bottom and shadow water bottom according to a shallow water optical model;
(5) converting a three-dimensional aquatic vegetation scene into a two-dimensional scene vertical to the ridge row direction by utilizing the incident geometry, the observation geometry and the geometric relation of the aquatic vegetation row direction, and calculating to obtain the proportion of the occupied area of 7 components in the whole scene based on a porous geometric optical model;
(6) and finally, calculating the spectral reflectivity and the bidirectional reflectivity of the whole aquatic vegetation system according to the weighted sum of the reflectivity and the probability of the 7 components in the field of view.
Claims (7)
1. A geometric optics-radiation transmission hybrid modeling method for row-seeding aquatic vegetation canopy reflection is characterized by comprising the following steps:
(1) the method comprises the following steps of (1) regarding aquatic vegetation canopies containing water body backgrounds and having characteristics of regular row geometric structures, row directions and row distances as rectangular boxes which are uniformly distributed in ridges and contain certain gaps, and regarding the aquatic vegetation canopies containing the water body backgrounds and having the characteristics of regular row geometric structures, row directions and row distances as a scene in which the vegetation canopies and water bodies among the ridges are alternately and regularly arranged in a direction vertical to the row directions of the; because the reflectivity that different reflection planes show in the visual field still is influenced by the interception condition to incident ray except that being influenced by the material, so according to incident energy source difference and the transmission path difference of reflection ray with the whole scene of observing divide into 7 components, include respectively: planting a canopy component, a first type of illumination water surface component, a first type of shadow water surface component, a second type of illumination water surface component, a second type of shadow water surface component, an illumination water bottom component and a shadow water bottom component in the ridge;
(2) firstly, calculating the reflectivity and the transmittance of a single blade by using a plant blade spectrum model, inputting the reflectivity and the transmittance into a uniformly distributed medium aquatic vegetation canopy radiation transmission model, and calculating the extinction coefficient and the scattering coefficient of the inline aquatic vegetation canopy by combining the vegetation canopy structure parameter, the water body parameter, the water bottom parameter, the incidence geometry and the observation geometry parameter so as to obtain the reflectivity of the inline aquatic vegetation canopy;
(3) calculating the reflectivity of the water surface between the rows by using a wave water surface reflection model, wherein the reflectivity comprises a first type of illumination water surface reflectivity, a first type of shadow water surface reflectivity, a second type of illumination water surface reflectivity and a second type of shadow water surface reflectivity;
(4) calculating the underwater reflectivity of the interline illumination and the interline shadow by using the shallow water biological optical model;
(5) converting a three-dimensional aquatic vegetation scene into a two-dimensional scene vertical to the ridge row direction by utilizing the incident geometry, the observation geometry and the geometric relation of the aquatic vegetation row direction, and calculating the proportion of the occupied area of 7 components in the whole view field based on a porous geometric optical model;
(6) and finally, calculating the spectral reflectivity and the bidirectional reflectivity of the whole aquatic vegetation system according to the weighted sum of the reflectivity and the probability of the 7 components in the observation field.
2. The method for modeling row-seeding aquatic vegetation canopy reflection geometry optics-radiation transmission mixing of claim 1, wherein the method comprises the following steps: regarding the aquatic vegetation canopy containing the water body background and having the characteristics of regular row geometric structure, row direction and row spacing as a rectangular box body which is uniformly distributed in the ridge rows and contains a certain gap, and regarding the scene that the aquatic vegetation canopy and the water body between the rows are alternately and regularly arranged in the direction vertical to the ridge rows in the step (1); for convenient calculation, the whole scene is divided into 7 components, which respectively comprise: planting a canopy component, a first type of illumination water surface component, a first type of shadow water surface component, a second type of illumination water surface component, a second type of shadow water surface component, an illumination water bottom component and a shadow water bottom component in the ridge; wherein, the components of the planted canopy in the ridge are row-sowing aquatic vegetation which is uniformly distributed in rows, and the incident energy sources are direct solar light and sky scattered light of a hemispherical space; the first kind of illumination water surface is an interline water surface which is not shielded by a canopy in the incident direction and the observation direction, and the incident energy source is direct solar light and sky scattered light of a hemispherical space; the first kind of shadow water surface is a low illumination area formed by being shielded by a canopy, and refers to an interline water surface which is shielded by the canopy in the incident direction and is not shielded by the canopy in the observation direction, and the incident energy sources of the first kind of shadow water surface are direct solar light passing through a gap between the canopies and sky scattered light in a hemispherical space; the second kind of illumination water surface is an interline water surface which is not shielded by a canopy in the sun direction and is shielded by the canopy in the observation direction, and the incident energy sources of the second kind of illumination water surface are direct solar light and sky scattered light in a hemispherical space; the second type of shadow water surface is an interline water surface which is shielded by the canopy in the incident direction and the observation direction, the incident energy sources are direct solar light passing through the canopy gap and sky scattered light in a hemispherical space, and the influence of the two-way gap rate of the canopy, namely the probability that photons pass through the canopy without being intercepted, needs to be considered in calculation.
3. The method for modeling row-seeding aquatic vegetation canopy reflection geometry optics-radiation transmission mixing of claim 1, wherein the method comprises the following steps: the method comprises the following steps that in the step (2), the continuous medium aquatic vegetation canopy radiation transmission model is used for calculating the reflectivity and the transmittance of a single blade, the reflectivity and the transmittance are input into the continuous medium aquatic vegetation canopy radiation transmission model, the extinction coefficient and the scattering coefficient of the inline aquatic vegetation canopy are calculated by combining the vegetation canopy structure parameter, the water body parameter, the water bottom parameter, the incidence geometry and the observation geometry parameter, and further the spectral reflectivity and the bidirectional reflectivity of the inline aquatic vegetation canopy are calculated, and the specific calculation process is as follows:
the first step is as follows: dividing a single leaf into a plurality of layers according to a continuous plant leaf spectrum model, and further calculating the spectrum reflectivity and transmittance of the single leaf;
the second step is that: dividing the aquatic vegetation canopy in the row into an emergent water vegetation layer VE, a water-air interface I, a submerged vegetation layer VS and a soil layer S; calculating extinction coefficient and scattering coefficient of the whole aquatic vegetation by using a continuous medium aquatic vegetation canopy radiation transmission model and combining the reflectivity and transmittance of a single blade, the aquatic vegetation canopy structure parameters, the water body parameters, the water bottom parameters, the incident geometry and the observation geometry conditions, and further obtaining the spectral reflectivity and the two-way reflectivity of the whole vegetation canopy;
the top reflectivity of the emergent aquatic vegetation canopy calculated by the continuous medium aquatic vegetation canopy radiation transmission model is as follows:
wherein
Representing a reflectivity matrix that accounts for flooding of the vegetation layer and the underlying soil layer;
representing a reflectivity matrix that takes into account the water-air interface, the submerged vegetation layer, and the underlying soil layer;
representing a canopy top reflectivity matrix that considers an emergent water vegetation layer, a water-air interface, a submerged vegetation layer, and an underlying surface soil layer; where R represents the reflectance, T represents the transmittance, the subscripts b represents the bottom of the layer, T represents the top of the layer, d represents the down flux, and u represents the up flux.
4. The method for modeling row-seeding aquatic vegetation canopy reflection geometry optics-radiation transmission mixing of claim 1, wherein the method comprises the following steps: step (3) calculating the reflectivity of the water surface between lines by using a wave water surface reflection model, wherein the reflectivity comprises the reflectivity R of the first type of illumination water surfaceiw1First type shadow water surface reflectivity Rsw1The reflectivity R of the second kind of illumination water surfaceiw2Shadow water surface reflectance R of the second kindsw2Which calculatesThe process is as follows:
the first step is as follows: calculating the first type of light surface reflectivity and the first type of shadow surface reflectivity by using a simplified wave water surface reflection model, taking the water surface as the geometry of micro surface elements with different gradients by using a Cox-Munk model, and firstly calculating the BRDF of the wave water surface as follows:
wherein r (ω) is the Fresnel reflectivity at the incident angle ω when the water surface is calm, and p (z)x,zy) As a function of the probability distribution of the surface gradient of the wave, zx,zyIs a micro bin coordinate system, thetanThe zenith angle direction of the normal line of the wavy surface element with specular reflection, thetasAt the zenith angle of the sun, thetaoIn order to observe the zenith angle, sigma is a water surface roughness factor to describe the fluctuation degree of the water surface, and the wind speed W is replaced as the input of a water surface reflectivity model;
the second step is that: the BRDF based on the wave water surface can calculate the contribution value of the solar direct light to the reflectivity of the vegetation canopy:
wherein beta is the proportion of the incident irradiance of the solar direct light in the scene to the total incident irradiance, phisIs the sun azimuth angle, phioIn order to observe the azimuth angle, the contribution value of the sky scattered light of the hemispherical space to the vegetation canopy reflectivity is calculated:
the third step: for the first type of light surface reflectivity, the incident energy sources are direct solar light and sky scattered light in the hemispherical space, i.e. single scattering contribution and multiple scattering contribution, so the first type of light surface reflectivity is the common contribution of the direct solar light and the sky scattered light in the hemispherical space, and is expressed as:
Riw1＝Riw,dir+Riw,diff
the first type of shadow surface component is a low light level area generated by occlusion of the canopy, the incident energy source is direct light passing through the gap of the canopy and scattered light from the sky, so the reflectivity of the first type of shadow surface is expressed as:
similarly, the reflectivity of the second type of illumination water surface is as follows:
the reflectivity of the shadow water surface of the second type is as follows:
in the formula
The crown layer gap ratio in the solar incidence direction,
The crown layer gap ratio in the observation direction,
The two-way gap probability of the sun direction and the observation direction is considered at the same time.
5. The method for modeling row-seeding aquatic vegetation canopy reflection geometry optics-radiation transmission mixing of claim 1, wherein the method comprises the following steps: the step (4) of calculating the underwater reflectivity R of the interline illumination by using the shallow water biological optical modelibAnd the underwater reflectivity R of the interline shadowsb", the specific calculation process is as follows:
solving the energy intensity of the reflectivity of the water body components, wherein the transmission of the water surface, the attenuation of the water body, the scattering of the water body and the reflection process of the water bottom surface need to be considered; the refraction effect of the water body needs to be considered on the light transmission path; for the water bottom component, the optical shallow water model is used to calculate the reflection contribution of the water bottom component due to RibThe energy of (A) is constituted by direct solar light transmitted into water and sky scattered light of a hemispherical space, RsbIs formed as sky scattered light of a hemispherical space, RibContribution value and R of sky scattered light in middle hemisphere space to reflectivitysbEquality, R for sky scattered light of isotropic hemisphere spacesbIs a hemispherical incident space RLeeMultiplied by the proportion of sky scattered light in the hemispherical space:
Ribcontribution R of medium direct light to reflectivityib,dirThe method can be calculated by a shallow water biological optical model to obtain:
Rib,dir＝β·RLee(θs,φs,θo,φo,ρb,Hw)
in the formula, thetasIs the zenith angle of the sun, phisIs the sun azimuth angle, θoTo observe zenith angle, phioFor observation of azimuth angle, ρbIs the water bottom reflectivity, HwThe depth of water, the reflectance at the bottom of the illuminated water is:
Rib＝Rsb+Rib,dir
6. the method for modeling row-seeding aquatic vegetation canopy reflection geometry optics-radiation transmission mixing of claim 1, wherein the method comprises the following steps: the step (5) of converting the three-dimensional aquatic vegetation scene into a two-dimensional scene perpendicular to the ridge row direction by using the geometric relationship between the observation geometry and the aquatic vegetation row direction, and calculating the proportion of the occupied area of 7 components in the scene based on the improved porous geometric optical model comprises the following specific calculation processes:
along (theta)s,φs) Or (theta)o,φo) Height H of canopy above water2Length of projection L in the direction perpendicular to the rowskComprises the following steps:
wherein k is s or o, θkFor the zenith angle of the sun or the observation zenith angle,
the absolute value of the difference between the azimuth angle of the sun or the observation azimuth angle and the azimuth angle of the row direction; compared with the projection length on water, the horizontal projection length on the water bottom is longer and is equal to the canopy H above the water surface in value2Horizontal projection length and canopy H below water surface1Sum of horizontal projection lengths of LkwComprises the following steps:
in order to solve the problem of mutual overlapping of projections during observation of a large zenith angle, a parameter n is introducedkRepresenting the complete number of lines traversed by the projection, LKFor the remaining length of the projection to be,
nk＝int(L/S)
Lk＝L-nkS
in the formula, L is the length of horizontal projection, and S is the length of one row sowing period for row sowing of the aquatic vegetation.
7. The method for modeling row-seeding aquatic vegetation canopy reflection geometry optics-radiation transmission mixing of claim 1, wherein the method comprises the following steps: the step (6) of calculating the bi-directional reflectivity of the whole aquatic vegetation system according to the weighted sum of the reflectivity and the probability of the 7 components in the observation field comprises the following specific calculation processes:
R＝RcanopyPcanopy+Riw1Piw1+Rsw1Psw1+Riw2Piw2+Rsw2Psw2+RibPib+RsbPsb
in the formula, R represents the scene reflectivity, and P is the area ratio of each component in the observation field.
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