CN104699952B - A kind of wetland aquatic vegetation canopy BRDF Monte Carlo models - Google Patents
A kind of wetland aquatic vegetation canopy BRDF Monte Carlo models Download PDFInfo
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Abstract
The present invention relates to a kind of wetland aquatic vegetation canopy BRDF Monte Carlo models.Its step is as follows：Canopy structural parameter according to input generates aquatic vegetation scene；Uniform lattice is divided the space into, secondary data structure is set up；Set up rough water scattering direction look-up table；By celestial sphere according to angularly or waiting solid angle to be divided into some regions；The light attached bag of given quantity is followed the trail of in aquatic vegetation water body coupled system；The directional reflectance ratio of total weight calculation aquatic vegetation of photon is received according to each region.The distribution character of the energy of the invention preferably canopy structure element of simulation different type aquatic vegetation, the accurate simulation of aquatic vegetation direction reflection characteristic under the conditions of different canopy layers structural parameters, water constituent concentration etc. is realized, is the powerful for studying incident solar radiation and aquatic vegetation canopy interaction mechanism.In addition the present invention is a kind of three-dimensional computer simulation model, has the advantages that computational accuracy is high, strong applicability, and can partly substitute field trial carries out contrast verification with other kinds of aquatic vegetation canopy reflectance model.
Description
(1) art
The present invention relates to a kind of wetland aquatic vegetation canopy BRDF Monte Carlo models, belong to optical remote sensing field, wet
Ground remote sensing technology research and remote sensing radiation transmission Analysis on Mechanism aspect are significant.
(2) background technology
Wetland aquatic vegetation can be divided into according to its habit：Very water vegetation, swim vegetation and the class of submerged vegetation three.Phase
To water body and land vehicles, aquatic vegetation region water body can influence each other with the reflected signal of Vegetation canopy, therefore aquatic vegetation
Canopy can show some unique reflectance signatures, and this is that traditional land vehicles canopy model or water model are difficult to essence
Really describe.The spectral reflection characteristic of scientific knowledge aquatic vegetation and two to reflection characteristic, supervise by the remote sensing to aquatic vegetation region
The application such as survey, water quality parameter inverting has very important significance.
Aquatic vegetation region is interspersed due to different types of vegetation and water body, but the little water-bed many mud of depth,
Therefore, it is difficult to set foot in, field trial has many difficulties with investigation.Additionally, the reflectance spectrum of aquatic vegetation is subject to water body and vegetation
The influence of canopy, needs the auxiliary parameter of measurement more in experiment, uncertainty is also than larger.Due to aquatic vegetation reflectance spectrum
Situ measurement it is relatively difficult, and the experimental error that causes such as non-uniform Distribution of aquatic vegetation is difficult to accurate description,
The research of radiation transmission mechanism and direction reflection characteristic in aquatic vegetation is relatively fewer.Existing a small amount of aquatic vegetation canopy mould
Type often employs various simplified process methods, and lacks the model checking of system.
Monte Carlo model based on atural object scene as a kind of computer model, the modeling of Vegetation canopy with test
It is widely used in card.This Monte Carlo model both can more truly reflect the characteristic of atural object, with higher
Precision；Its parameter can be controlled again, and with respect to field trial, uncertainty is small.Therefore be usually used in radiative transfer model etc. other
The contrast verification of canopy model.But the Monte Carlo model for being directed to aquatic vegetation is seldom seen in report.
The present invention scatters the direction look-up table simulated waves water surface using the triangular vane of random distribution using the water surface, adopts
With the accelerated method of uniform lattice, a kind of wetland aquatic vegetation canopy BRDF Monte Carlo models are built, in wetland remote sensing
The direction reflection characteristic of aquatic vegetation is computed correctly, research and the direction reflection characteristic of aquatic vegetation radiation transmission mechanism is realized
Analysis has important Research Significance.
(3) content of the invention
The present invention relates to a kind of wetland aquatic vegetation canopy BRDF Monte Carlo models.Technical solution is：According to defeated
The canopy structural parameter generation aquatic vegetation scene for entering；Uniform lattice is divided the space into, secondary data structure is set up；Set up ripple
The unrestrained water surface scatters direction look-up table；By celestial sphere according to angularly or waiting solid angle to be divided into some regions；In aquatic vegetation-water
The light attached bag of given quantity is followed the trail of in body coupled system；Total weight calculation aquatic vegetation of photon is received according to each region
Directional reflectance ratio.It is comprised the following steps that：
A kind of 1 wetland aquatic vegetation canopy BRDF Monte Carlo models.It is characterized in that comprising the steps of：
(1) canopy structural parameter according to input generates aquatic vegetation scene, and specific calculating process is as follows：
The first step：Scene is layered according to aquatic vegetation type, plant leaf blade is replaced with equilateral triangle, according to input
Scene size, leaf area index, the blade length of side, scene hierarchical information calculate every layer of number of medium Leaf；
Second step：According to the Leaf angle inclination distribution parameter of input, the cumulative probability of blade Leaf inclination is calculated according to SAIL models
Distribution function；
3rd step：Random generation blade center-of-gravity station, leaf is generated according to Leaf inclination cumulative distribution function in scene
Piece Leaf inclination, can calculate three coordinates on summit of blade, blade normal vector data afterwards；
(2) uniform lattice is divided the space into, secondary data structure is set up, specific calculating process is as follows：
The first step：Relation according to grid number and the number of blade calculates grid number and ruler for drawing grids on three directions of x, y, z
It is very little；
Second step：According to the minimum value and maximum of blade coordinate on three directions of x, y, z, each grid and position are set up
In the mapping relations of blade therein numbering；
(3) rough water scattering direction look-up table is set up, its calculating process is as follows：
The first step：Celestial sphere is divided with 1 ° of azimuthal separation according to 1 ° of zenith angular spacing；
Second step：According to rough water two to scatter distributions function, wherein scattering includes two kinds of processes of reflection and transmission,
And law of conservation of energy
In the case of calculating different incidence angles, the distribution of rough water emanated energy, wherein, θs、Respectively incident zenith
Angle and azimuth；θo、Respectively view zenith angle and azimuth；F for rough water distribution of bi directional reflectance function or two to
Transmission distribution function, the span of incidence zenith angle is 0 ° to 180 °, wherein 0 ° represents straight up, it is incident from water,
180 ° represent straight down, incident from air；
3rd step：The emanated energy distribution that will be calculated is normalized and deletes less increment, sets up emanated energy
Cumulative distribution function；
(4) by celestial sphere according to angularly or waiting solid angle to be divided into some regions；Specific calculating process is as follows：According to research
By upper half spherical space according to equiangularly spaced or wait three-dimensional angular spacing to be divided the need for problem；
(5) the light attached bag of given quantity is followed the trail of in aquatic vegetation-water body coupled system；Specific calculating process is as follows：
The first step：The initial position of random generation incident photon at the top of scene, the original incident direction of photon is according to straight
Ratio, solar direction and the skylight distributed model for penetrating light and diffused light determine；
Second step：Photon is propagated in the grid that step (2) is set up, and is entered with the triangular vane in current grid
Row is intersecting to be judged：Next grid is continued to move to if photon does not intersect with all blades in current grid；If photon with
Blade in current grid intersects, then find and the nearest intersection point in photon current location, and reflectivity, transmitance according to blade
And absorption coefficient calculates the change of the exit direction after photon is intercepted by blade and weight；When photon passes through the water surface, according to step
Suddenly the rough water scattering direction look-up table set up in (3) determines the exit direction of photon；When the surrounding of photon spread to scene
During border, the offside that photon moves to current border face is proceeded to propagate；Assuming that water-bed is lambert's body, when photon spread is arrived
When water-bed, weight change and the reflection direction of photon are calculated according to water-bed reflectivity；
3rd step：It is handled as follows when photon is less than given threshold value from scene top outgoing or weight：For preceding
Person is, it is necessary to the exit direction according to photon determines the region of its upper half spherical space for falling into；For the latter, it is necessary to true using wheel disc
Determine followed by the weight for increasing current photon and continue tracking, be also off the tracking of current photon and generate a new light
Son；
(6) directional reflectance ratio of total weight calculation aquatic vegetation of photon is received according to each region, was specifically calculated
Journey is as follows：The reflectivity of exit direction can be expressed as
R=π Wo/(dΩoWs)
Wherein, d ΩoIt is the project stereoscopic angle in exit direction correspondence celestial sphere region, WsIt is total weight of incident photon, is seeing
The total weight of outgoing photon surveyed in the corresponding region of direction is Wo。
Present invention advantage compared with prior art is：
(1) academic circles at present lacks for aquatic vegetation (very water vegetation, the vegetation that swims, submerged vegetation) direction reflection characteristic
Monte Carlo model, the present invention filled up the blank in this field, and can be used for aquatic vegetation radiative transfer model etc.
The contrast verification of other canopy models, with significant novelty.
(2) present invention represents blade in Vegetation canopy using triangle, it is contemplated that blade optical characteristics, rough water with
The influence of the optical activity component in water body, compared to radiative transfer model, model of the invention closer to real surface scene,
By simulating communication process calculated direction reflectivity of the radiation in aquatic vegetation canopy and water body, with reliable precision.
(4) illustrate
Fig. 1 is techniqueflow chart of the invention.
(5) specific embodiment
In order to a kind of wetland aquatic vegetation canopy BRDF Monte Carlo models of the present invention are better described, using this
The model of invention be tested with analysis, achieve good effect, specific implementation method is as follows：
(1) canopy structural parameter according to input generates aquatic vegetation scene；
(2) uniform lattice is divided the space into, secondary data structure is set up；
(3) rough water scattering direction look-up table is set up；
(4) by celestial sphere according to angularly or waiting solid angle to be divided into some regions；
(5) the light attached bag of given quantity is followed the trail of in aquatic vegetation-water body coupled system；
(6) directional reflectance ratio of total weight calculation aquatic vegetation of photon is received according to each region.
Experimental result as shown in Fig. 2 be based on model of the invention, can be with Quantitative Discussion Leaf angle inclination distribution, incidence zenith angle
Etc. factor to influence from aquatic vegetation two to reflection characteristic.
Claims (1)
1. a kind of wetland aquatic vegetation canopy BRDF Monte Carlo models, it is characterised in that comprise the steps of：
(1) canopy structural parameter according to input generates aquatic vegetation scene, and specific calculating process is as follows：
The first step：Scene is layered according to aquatic vegetation type, plant leaf blade is replaced with equilateral triangle, according to the scene of input
Size, leaf area index, the blade length of side, scene hierarchical information calculate every layer of number of medium Leaf；
Second step：According to the Leaf angle inclination distribution parameter of input, the cumulative probability for calculating blade Leaf inclination according to SAIL models is distributed
Function；
3rd step：Random generation blade center-of-gravity station, blade and blade is generated according to Leaf inclination cumulative distribution function in scene
Inclination angle, can calculate three coordinates on summit of blade, blade normal vector data afterwards；
(2) uniform lattice is divided the space into, secondary data structure is set up, specific calculating process is as follows：
The first step：Relation according to grid number and the number of blade calculates grid number and lattice dimensions on three directions of x, y, z；
Second step：According to the minimum value and maximum of blade coordinate on three directions of x, y, z, set up each grid and be located at it
In blade numbering mapping relations；
(3) rough water scattering direction look-up table is set up, its calculating process is as follows：
The first step：Celestial sphere is divided with 1 ° of azimuthal separation according to 1 ° of zenith angular spacing；
Second step：According to rough water two to scatter distributions function, wherein scattering includes two kinds of processes of reflection and transmission, and energy
Amount law of conservation
In the case of calculating different incidence angles, the distribution of rough water emanated energy, wherein, θs、Respectively incidence zenith angle and side
Parallactic angle；θo、Respectively view zenith angle and azimuth；F is the distribution of bi directional reflectance function of rough water or two to transmission point
Cloth function, the span of incidence zenith angle is 0 ° to 180 °, wherein 0 ° represents straight up, incident from water, 180 ° of expressions
Straight down, it is incident from air；
3rd step：The emanated energy distribution that will be calculated is normalized and deletes less increment, sets up the tired of emanated energy
Product probability-distribution function；
(4) by celestial sphere according to angularly or waiting solid angle to be divided into some regions；Specific calculating process is as follows：According to studying a question
The need for by upper half spherical space according to equiangularly spaced or wait three-dimensional angular spacing to be divided；
(5) the light attached bag of given quantity is followed the trail of in aquatic vegetation-water body coupled system；Specific calculating process is as follows：
The first step：The initial position of random generation incident photon at the top of scene, the original incident direction of photon is according to direct light
Ratio, solar direction and skylight distributed model with diffused light determine；
Second step：Photon is propagated in the grid that step (2) is set up, and carries out phase with the triangular vane in current grid
Hand over and judge：Next grid is continued to move to if photon does not intersect with all blades in current grid；If photon with it is current
Blade in grid intersects, then find and the nearest intersection point in photon current location, and reflectivity according to blade, transmitance and suction
Receive the change that coefficient calculates the exit direction after photon is intercepted by blade and weight；When photon passes through the water surface, according to step (3)
The rough water scattering direction look-up table of middle foundation determines the exit direction of photon；When the surrounding border of photon spread to scene
When, the offside that photon moves to current border face is proceeded to propagate；Assuming that water-bed is lambert's body, when photon spread to the bottom
When, weight change and the reflection direction of photon are calculated according to water-bed reflectivity；
3rd step：It is handled as follows when photon is less than given threshold value from scene top outgoing or weight：For the former, need
The region of its upper half spherical space for falling into is determined according to the exit direction of photon；For the latter, it is necessary to determine to connect using wheel disc
It is to increase the weight of current photon and continue tracking to get off, and is also off the tracking of current photon and generates a new photon；
(6) directional reflectance ratio of total weight calculation aquatic vegetation of photon is received according to each region, specific calculating process is such as
Under：The reflectivity of exit direction can be expressed as
R=π Wo/(dΩoWs)
Wherein, d ΩoIt is the project stereoscopic angle in exit direction correspondence celestial sphere region, WsIt is total weight of incident photon, in observation side
It is W to the total weight of outgoing photon in corresponding regiono。
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| CN105118083B (en) * | 2015-08-11 | 2018-03-16 | 浙江大学 | A kind of Photon Mapping method for drafting of unbiased |
| CN105841804B (en) * | 2016-03-17 | 2018-02-02 | 北京大学 | A kind of vegetation two contributes the acquisition methods of item to sexual reflex primary scattering |
| CN105891120A (en) * | 2016-03-23 | 2016-08-24 | 中国科学院遥感与数字地球研究所 | Urban dense grassland radiation direction characteristic simulation method |
| CN108196266B (en) * | 2017-12-29 | 2021-07-02 | 中山大学 | Vegetation canopy three-dimensional radiation transmission simulation method based on Lidar data |
| CN109740180B (en) * | 2018-11-30 | 2021-02-02 | 北京航空航天大学 | Sparse aquatic vegetation canopy direction reflectivity simulation method based on geometric optical model |
| CN114528728B (en) * | 2022-01-20 | 2024-05-28 | 北京航空航天大学 | Monte Carlo computer simulation method for canopy reflection of aquatic vegetation in line sowing |
| CN114529618B (en) * | 2022-02-23 | 2024-05-28 | 北京航空航天大学 | Aquatic vegetation canopy reflection modeling method based on radiance |
| CN114547896B (en) * | 2022-02-25 | 2023-05-09 | 北京航空航天大学 | Total reflection spectrum radiation transmission modeling method for wetland aquatic vegetation canopy |
| CN114549763B (en) * | 2022-02-28 | 2024-05-28 | 北京航空航天大学 | Wetland aquatic vegetation canopy reflection modeling method based on photon mapping |
| CN115526924B (en) * | 2022-11-29 | 2023-06-23 | 湖南长理尚洋科技有限公司 | Monte Carlo simulated hydrologic environment modeling method and system |
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