CN104699953A - Geometrical optics model of wetland aquatic vegetations - Google Patents

Abstract

The invention relates to a geometrical optics model of wetland aquatic vegetations. The establishment of the geometrical optics model comprises the following steps: inputting basic parameters of a scene, and taking a cylinder as a basic unit; dividing area components within a field of view into two parts above and below the water surface, and calculating the area of each component in the presence of only one basic unit; considering the number of the basic units, and calculating the area of each component within in the field of view through mutual occlusion; calculating the brightness of each component; only considering the transmission of the water surface, and calculating the weighted average of the brightness of all components within the field of view; superposing impacts of the water reflection, and calculating a bidirectional reflectance ratio of aquatic vegetation scenes. The geometrical optics model can achieve precise description of the directional reflectivity of aquatic vegetations under the conditions of different aquatic vegetation canopy parameters, the sun position, the observation position and the like, is an effective tool for analyzing the directional reflectivity of the aquatic vegetations and influencing factors. In addition, the geometrical optics model based on the structural morphology of vegetation canopies has the advantages of strong versatility, high calculation speed and the like.

Description

A kind of wetland aquatic vegetation geometric optical model

(1) art

The present invention relates to a kind of wetland aquatic vegetation geometric optical model, belong to remote optical sensing field, significant in the research of wetland remote sensing technology and aquatic vegetation Reflection Characteristic Analysis.

(2) background technology

Natural wetland aquatic vegetation can be divided into very water vegetation, swim vegetation and submerged vegetation three class according to its habit.The space distribution of aquatic vegetation often more complicated under state of nature, present the situation that different types of aquatic vegetation and water body are interspersed, and water body and dissimilar aquatic vegetation has different reflection characteristics more.Therefore the wetland Region under natural situation is typical non-homogeneous atural object often, needs the impact considering ground apparent bearing reflection characteristic when utilizing remote sensing image to carry out earth's surface information extraction.Relative water body, the water surface and aquatic vegetation have relatively high reflectivity and obvious direction reflection characteristic.Therefore, the direction reflection characteristic of scientific knowledge aquatic vegetation, has very important significance to the practical application such as classification, variation monitoring of aquatic vegetation.

The present invention uses for reference land vehicles canopy geometrical optics modeling method, propose a kind of disposal route considering water body and water surface impact, establish a kind of wetland aquatic vegetation geometric optical model, calculate aquatic vegetation direction reflection characteristic for correct in wetland remote sensing, the classification and the variation monitoring that realize aquatic vegetation have important scientific meaning and using value.

(3) summary of the invention

The present invention relates to a kind of wetland aquatic vegetation geometric optical model.Technical solution is: input scene basic parameter, using right cylinder as elementary cell; Area component in visual field is divided into more than the water surface and the following two parts of the water surface, calculates the area of each component when only having an elementary cell to exist; Consider number and the mutual area of each component in occlusion test visual field of elementary cell; Calculate the brightness of each component; The water surface only considers its transmission, calculates the weighted mean of each component intensities in visual field; The impact of superposition water-reflected, calculates the bidirectional reflectanD of aquatic vegetation scene.Its concrete steps are as follows:

1 one kinds of wetland aquatic vegetation geometric optical models.It is characterized in that comprising following steps:

(1) scene basic parameter is inputted, using right cylinder as elementary cell;

(2) the area component in visual field is divided into more than the water surface and the following two parts of the water surface, calculates the area of each component when only having an elementary cell to exist;

(3) number and the mutual area ratio of each component in occlusion test visual field of elementary cell is considered;

(4) brightness of each component is calculated;

(5) water surface only considers its transmission, calculates the weighted mean of each component intensities in visual field;

(6) superpose the impact of water-reflected, calculate the bidirectional reflectanD of aquatic vegetation scene.

2 require described a kind of wetland aquatic vegetation geometric optical model according to right 1, it is characterized in that: " the input scene basic parameter; using right cylinder as elementary cell " described in step (1), concrete computation process is as follows: input scene size, the depth of water, cylinder height, right cylinder bottom surface radius, right cylinder number, each cylindrical measure-alike and in scene stochastic distribution.

3 require described a kind of wetland aquatic vegetation geometric optical model according to right 1, it is characterized in that: " the area component in visual field being divided into more than the water surface and the following two parts of the water surface; calculate the area of each component when only having an elementary cell to exist " described in step (2), concrete computation process is as follows:

The first step: only consider a right cylinder, the area in visual field is divided into: illumination canopy waterborne, shade canopy waterborne, the illumination water surface, the shade water surface, Underwater Optical shine canopy, under water shade canopy, illumination is water-bed, shade is water-bed;

Second step: consider that the water surface is with upper part, calculates the area of illumination canopy waterborne, shade canopy waterborne, the illumination water surface, the shade water surface;

3rd step: consider that the water surface is with lower part, calculating Underwater Optical photograph canopy, under water shade canopy, the area that illumination is water-bed, shade is water-bed.

4 require described a kind of wetland aquatic vegetation geometric optical model according to right 1, it is characterized in that: " the considering number and the mutual area ratio of each component in occlusion test visual field of elementary cell " described in step (3), its computation process is as follows: the first step: the area ratio on calculating illumination ground

$K_g=e^{-\mathrm{\λ}({\mathrm{\Γ}}_s+{\mathrm{\Γ}}_o-O)}=e^{\mathrm{\λ\Γ}}$

Wherein, a unit is respectively Γ along direction of illumination and observed ray at the area of ground cast shadow _swith Γ _o, O is the overlapping area of two shades, and Γ is the union of two shades, and λ is the number of the elementary cell on unit area.

Second step: the area ratio calculating illumination canopy component

$K_c=\mathrm{\β}(\mathrm{\λ}{\mathrm{\Γ}}_c-f\·\mathrm{\λ}{\mathrm{\Γ}}_o)+(1-\mathrm{\β})\frac{{\mathrm{\Γ}}_c}{\mathrm{\Γ}}(1-K_g)$

Wherein, β is the weight that unit center position distributes at vertical direction, and value is from completely random 0 to highly identical 1.F is for covering coefficient.

3rd step: the area ratio on computational shadowgraph canopy and shade ground

$\left\{\begin{array}{c}{K}_t=e^{-\mathrm{\λ}{\mathrm{\Γ}}_c}-e^{-\mathrm{\λ}{\mathrm{\Γ}}_o}\\ K_z=1-K_g-K_c-K_t\end{array}\right.$

Wherein, K _tfor the area ratio of shade canopy, K _zfor the area ratio on shade ground.

5 require described a kind of wetland aquatic vegetation geometric optical model according to right 1, it is characterized in that: " the calculating the brightness of each component " described in step (4), concrete computation process is as follows: the brightness of the above canopy part of the water surface is input parameter, the brightness of the illumination water surface calculates according to rough water reflection model, and the brightness of the following component of the water surface needs the impact considering water surface transmission and water body decay.

6 require described a kind of wetland aquatic vegetation geometric optical model according to right 1, it is characterized in that: " water surface only considers its transmission; calculate the weighted mean of each component intensities in visual field " described in step (5), concrete computation process is as follows: when not considering water-reflected, and the brightness that sensor receives can be expressed as

L0＝CK _c+TK _t+C _wK _cw+T _wK _tw+G _wK _gw+Z _wK _zw

Wherein, C, T, C _w, T _w, G _w, Z _wbe illumination canopy waterborne respectively, shade canopy waterborne and Underwater Optical when considering water surface transmission and water body decay be according to canopy, under water shade canopy, illumination is water-bed and shade is water-bed brightness.These brightness are multiplied with the area ratio in each comfortable visual field and sue for peace.

7 require described a kind of wetland aquatic vegetation geometric optical model according to right 1, it is characterized in that: " impact of superposition water-reflected; calculate the bidirectional reflectanD of aquatic vegetation scene " described in step (6), concrete computation process is as follows: by calculate in step (5) do not consider water-reflected time the impact of brightness superposition water-reflected

L＝L0+GK _g+ZK _z

Wherein, G, Z are the brightness of the illumination water surface and the shade water surface respectively, be multiplied in the brightness be added to again when not considering water-reflected respectively, namely obtain the reflectivity of whole scene with respective area ratio.

The present invention's advantage is compared with prior art:

(1) academic circles at present lacks the geometric optical model describing aquatic vegetation direction reflection characteristic, and the present invention has filled up the blank in this field, has significant novelty, has enriched Vegetation canopy remote sensing theoretical.

(2) the present invention uses for reference land vehicles canopy geometric optical model, consider the impact of the water surface and water body, compared to one dimension radiative transfer model, contemplated by the invention uncontinuity and the heterogeneity on earth's surface, clear physics conception, highly versatile, convenience of calculation.

(4) accompanying drawing explanation

Fig. 1 is techniqueflow chart of the present invention.Fig. 2 is the schematic diagram of illumination shade, observation shade and shade overlapping area in step (2).Fig. 3 is under different elementary cell number, solar zenith angle, the depth of water, unit size condition, and the aquatic vegetation two calculated based on model of the present invention is to reflection characteristic.

(5) embodiment

In order to a kind of wetland aquatic vegetation geometric optical model that the present invention relates to is described better, utilize model of the present invention to carry out testing and analyzing, achieve good effect, specific implementation method is as follows:

(1) scene basic parameter is inputted, using right cylinder as elementary cell;

(2) the area component in visual field is divided into more than the water surface and the following two parts of the water surface, calculates the area of each component when only having an elementary cell to exist;

(3) number and the mutual area ratio of each component in occlusion test visual field of elementary cell is considered;

(4) brightness of each component is calculated;

(5) water surface only considers its transmission, calculates the weighted mean of each component intensities in visual field;

(6) superpose the impact of water-reflected, calculate the bidirectional reflectanD of aquatic vegetation scene.

Claims (7)

1. a wetland aquatic vegetation geometric optical model.It is characterized in that comprising following steps:

(1) scene basic parameter is inputted, using right cylinder as elementary cell;

(2) the area component in visual field is divided into more than the water surface and the following two parts of the water surface, calculates the area of each component when only having an elementary cell to exist;

(3) number and the mutual area ratio of each component in occlusion test visual field of elementary cell is considered;

(4) brightness of each component is calculated;

(5) water surface only considers its transmission, calculates the weighted mean of each component intensities in visual field;

(6) superpose the impact of water-reflected, calculate the bidirectional reflectanD of aquatic vegetation scene.

2. require described a kind of wetland aquatic vegetation geometric optical model according to right 1, it is characterized in that: " the input scene basic parameter; using right cylinder as elementary cell " described in step (1), concrete computation process is as follows: input scene size, the depth of water, cylinder height, right cylinder bottom surface radius, right cylinder number, each cylindrical measure-alike and in scene stochastic distribution.

3. require described a kind of wetland aquatic vegetation geometric optical model according to right 1, it is characterized in that: " the area component in visual field being divided into more than the water surface and the following two parts of the water surface; calculate the area of each component when only having an elementary cell to exist " described in step (2), concrete computation process is as follows:

The first step: only consider a right cylinder, the area in visual field is divided into: illumination canopy waterborne, shade canopy waterborne, the illumination water surface, the shade water surface, Underwater Optical shine canopy, under water shade canopy, illumination is water-bed, shade is water-bed;

Second step: consider that the water surface is with upper part, calculates the area of illumination canopy waterborne, shade canopy waterborne, the illumination water surface, the shade water surface respectively;

3rd step: consider that the water surface is with lower part, calculates Underwater Optical respectively according to canopy, under water shade canopy, illumination is water-bed, shade is water-bed area.

4. require described a kind of wetland aquatic vegetation geometric optical model according to right 1, it is characterized in that: " the considering number and the mutual area ratio of each component in occlusion test visual field of elementary cell " described in step (3), its computation process is as follows: the first step: the area ratio on calculating illumination ground

$K_g=e^{-\mathrm{\λ}({\mathrm{\Γ}}_s+{\mathrm{\Γ}}_o-O)}=e^{-\mathrm{\λ\Γ}}$

Wherein, a unit is respectively Γ along direction of illumination and observed ray at the area of ground cast shadow _swith Γ _o, O is the overlapping area of two shades, and Γ is the union of two shades, and λ is the number of the elementary cell on unit area.

Second step: the area ratio calculating illumination canopy component

$K_c=\mathrm{\β}({\mathrm{\λ\Γ}}_c-f\·{\mathrm{\λ\Γ}}_o)+(1-\mathrm{\β})\frac{{\mathrm{\Γ}}_o}{\mathrm{\Γ}}(1-K_g)$

Wherein, β is the weight that unit center position distributes at vertical direction, and value is from completely random 0 to highly identical 1.F is for covering coefficient.

3rd step: the area ratio on computational shadowgraph canopy and shade ground

$\left\{\begin{array}{c}{K}_t=e^{-\mathrm{\λ}{\mathrm{\Γ}}_c}-e^{-{\mathrm{\λ\Γ}}_o}\\ K_z=1-K_g-K_c-K_t\end{array}\right.$

Wherein, K _tfor the area ratio of shade canopy, K _zfor the area ratio on shade ground.

5. require described a kind of wetland aquatic vegetation geometric optical model according to right 1, it is characterized in that: " the calculating the brightness of each component " described in step (4), concrete computation process is as follows: the brightness of the above canopy part of the water surface is input parameter, the brightness of the illumination water surface calculates according to rough water reflection model, and the brightness of the following component of the water surface needs the impact considering water surface transmission and water body decay.

6. require described a kind of wetland aquatic vegetation geometric optical model according to right 1, it is characterized in that: " water surface only considers its transmission; calculate the weighted mean of each component intensities in visual field " described in step (5), concrete computation process is as follows: when not considering water-reflected, and the brightness that sensor receives can be expressed as

L0＝CK _c+TK _t+C _wK _cw+T _wK _tw+G _wK _gw+Z _wK _zw

Wherein, C, T, C _w, T _w, G _w, Z _wbe illumination canopy waterborne respectively, shade canopy waterborne and Underwater Optical when considering water surface transmission and water body decay be according to canopy, under water shade canopy, illumination is water-bed and shade is water-bed brightness.These brightness are multiplied with the area ratio in each comfortable visual field and sue for peace.

7. require described a kind of wetland aquatic vegetation geometric optical model according to right 1, it is characterized in that: " impact of superposition water-reflected; calculate the bidirectional reflectanD of aquatic vegetation scene " described in step (6), concrete computation process is as follows: by calculate in step (5) do not consider water-reflected time the impact of brightness superposition water-reflected

L＝L0+GK _g+ZK _z

Wherein, G, Z are the brightness of the illumination water surface and the shade water surface respectively, be multiplied in the brightness be added to again when not considering water-reflected respectively, namely obtain the reflectivity of whole scene with respective area ratio.