CN108132096A - A kind of woods window solar radiation monitoring method based on laser radar - Google Patents
A kind of woods window solar radiation monitoring method based on laser radar Download PDFInfo
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Abstract
The invention discloses a kind of woods window solar radiation monitoring methods based on laser radar, include the following steps：Step 1：Woods window is identified based on laser radar ALS point cloud datas, to determine woods window edge；Step 2：Calculate the incident angular direction solar radiation total amount G in the part received above MODEL OVER COMPLEX TOPOGRAPHY lower canopyi；Step 3：Based on GiThe intensity of solar radiation Global of different location in woods window is calculatedgap.The woods window solar radiation monitoring method based on laser radar is easy to implement, and monitoring efficiency is high.
Description
Technical field
The present invention relates to a kind of woods window solar radiation monitoring methods based on laser radar.
Background technology
Nineteen forty-seven woods window (canopy gap) concept is put forward for the first time by Britain ecologist Watt, it refers mainly to forest community
Middle main storry is by human interference (selective cutting) or natural disturbance (disasters such as strong wind, snow, floods, mud-rock flow, insect pest) in storey shape
Into discontinuous woods void.Woods window is recurrent important Small and Medium Sized interference in forest community, is forest succession
One important stage, it is not only the driving factor of forest community succession, also in forest structure, species composition, dynamic and succession
In play an important role, it has also become one of current most active field of forest ecology research.
In the environment of forest land, solar radiation is divided into direct projection and scattering radiates, directly the just light above direct sunlight to canopy,
Scatter the light that just light beam scatters in atmosphere in different directions on canopy.Solar radiation is the most important ecological ring of woods window
One of border factor, illumination directly affect the physiological and ecological process of animals and plants, meanwhile, illumination also can be to woods window surface temperature, sky
Air humidity degree, the soil water, which grade, to be had an impact, so as to cause woods window environmental heterogeneity.Environmental heterogeneity determines gap regeneration,
It plays an important role in forest litterfall and During Succession.So the measurement of woods window solar radiation is that ecologist extremely pays close attention to
Problem, due to being influenced by gap size, gap shape, crown canopy height and the forest land gradient, slope aspect, woods window illumination is shown
Complicated special heterogeneity, position of sun moment variation in addition so that the measurement of solar radiation becomes very difficult.
The monitoring of traditional woods window solar radiation is divided into direct monitoring method and indirect photograph method.Direct monitoring method (such as illumination photometer)
The Lighting information of finite point can only be monitored, time-consuming and laborious, human cost is high.Indirect photograph method (such as fish eye lens image) although compared with
To be simple and quick, but when monitoring forest gap light environment heterogeneity, it is still desirable to shoot multiple hemisphere faces in woods window different location
Image.Above-mentioned two classes method to varying degrees there are heavy workload, process is tedious, destructive strong, the problems such as taking time and effort.
Airborne laser radar (Airborne Laser Scanning, ALS) is a kind of emerging active remote sensing technology,
The high-precision vegetation structure information of forest ecosystem, dimensional topography feature can be obtained on multiple space and time scales.ALS is to woods window
High precision monitor has great potential in understanding forest disturbance regime, update rule and inverting environmental parameters etc..
Studies in China focuses mostly on is carrying out forest biomass monitoring using ALS, and the measurement of woods window solar radiation is seldom related to.Cause
This, find it is a kind of it is quick, objective, accurate measure forest gap light environment method to woods window study it is extremely important, contribute to explain woods
The relationship of window species composition, bio-diversity and intensity of illumination special heterogeneity helps to disclose vegetation succession in control woods window
With the mechanism of species regeneration process, understanding exploitation China's forest is played an important role.
Therefore, it is necessary to design a kind of woods window solar radiation monitoring method based on laser radar.
Invention content
The technical problems to be solved by the invention are to provide a kind of woods window solar radiation monitoring method based on laser radar,
This method is the method for quick, objective, the accurate monitoring woods window intensity of illumination based on airborne laser radar, can overcome the disadvantages that existing skill
The technological gap of art middle forest window solar radiation monitoring method.
The technical solution of invention is as follows：
A kind of woods window solar radiation monitoring method based on laser radar, includes the following steps：
Step 1：Woods window is identified based on laser radar ALS point cloud datas, to determine woods window edge；
Step 2：Calculate the incident angular direction solar radiation total amount G in the part received above MODEL OVER COMPLEX TOPOGRAPHY lower canopyi；
Step 3：Based on GiThe intensity of solar radiation Global of different location in woods window is calculatedgap。
In step 1, identify that the model of woods window is as follows：
In formula, G (x, y)=1, it is woods window to represent the corresponding position of point (x, y)；X, y are respectively the abscissa of grid (x, y)
And ordinate, CHM (x, y) are the canopy height values on grid (x, y)；A is the discrimination threshold of canopy edge average height.Differentiate
Threshold value is determined by empirical value or on the spot sample investigation, if discrimination threshold is 5 meters.
In step 2：
Gi=Bi+Di；
In formula, GiFor the incident angular direction solar radiation total amount in part, Bi,DiThe respectively incident angular direction direct sunlight in part
Amount of radiation and amount of scatter radiation.
The calculation formula of part incidence angular direction beam radia amount is as follows：
Bi=In·δi·hillshade；δ in formulaiFor light part incidence angle, hillshade is massif shadow effect system
Number；Specifically, have：
Light part incidence angle：
Massif shadow effect coefficient：
Hillshade=(cos α cosSlop)+[sin α sinSlopcos (αs-Asp)]；
In formula Slop be landform the gradient, Asp be landform slope aspect (gradient refers to the inclined degree of slope surface, and slope aspect refers to
The direction of landform slope surface)；
δsFor declination angle, there is δs=23.45sin (360 ° of (284+N)/365), N is day of year (in 1 year in formula
Which day)；
L is geographic latitude；
hsFor solar hour angle.
Part incidence angular direction solar scattered radiation amount DiComputational methods it is as follows：
In view of surrounding massif the D in alpine terrain may be calculated to the influence of scattering lightiWhen, it is divided into incident angular direction
On without massif block δi＞ 0 and there is massif to block δi≤ 0 two kind of situation：
Variable declaration in formula：
(1) skyview is the vault of heaven ratio in the range of visible range；The parameter is calculated by ENVI softwares；
(2) hillshade is massif shadow factor；
Hillshade=(cos α cosSlope)+[sin α sinSlopecos (αs-Asp)]；
(3)IoFor extraatmospheric solar radiation quantity, Io=S0(1+0.0344cos (360 ° of N/365)), in formula, S0
For 1367 (w/m of solar radiation constant2), N is day of year (which day in 1 year).
(4)τbFor the penetrance of fair weather beam radia, τb=0.56 (e-0.65M+e-0.095M),
In formula, M is air quality coefficient, is specifically had, M=[1229+ (614sin α)2]1/2-614sinα
In formula, α is sun altitude；
(5)SoFor 1367 (w/m of solar radiation constant2)
(6)δiFor light part incidence angle, have：
δi=sin δs·(sinL·cosSlope-cosL·sinSlope·cosAsp)
+cosδscoshs·(cosL·cosSlope+sinL·sinSlope·cosAsp)
+cosδs·sinSlope·sinAsp·sinhs
Slope is the gradient of landform in formula；Asp is the slope aspect of landform；
δsFor declination angle, geographic latitudes of the L for region to be measured, hsFor solar hour angle；
(7)αsFor solar azimuth；
(8) Slope is terrain slope, and calculation formula refers to formula 11；
(9)DioFor initial local incidence angular direction solar scattered radiation intensity：
Dio=Io·τd·(cosSlop)2/2sinα。
Woods window solar radiation GlobalgapCalculation formula it is as follows：
Globalgap=crownshade (1-LPI)·Gi；
In formula, crownshade be woods window edge canopy generate shade, LPI be light beam penetrating coefficient, GiFor on canopy
Square solar radiation total amount；
Crownshade=(cos α cosSlopeDSM)+[sinα·sinSlopeDSM·cos(αs-AspDSM)]
In formula, SlopeDSMFor the gradient of Malabar Pied Hornbill model DSM, reflect the inclined degree of Malabar Pied Hornbill, AspDSMFor hat
The slope aspect of layer surface model DSM reflects the direction of Malabar Pied Hornbill.The gradient and slope aspect of DSM calculates reference formula 11；
α、αsFor sun altitude and azimuth.
Light beam transmission coefficient
Number (Ground Point cloud) and number (Ground Point cloud+canopy point cloud) represents unit area (such as 2m × 2m) respectively
Middle Ground Point cloud quantity is with putting cloud total amount；LPI is light beam transmission coefficient, which is combined with crownshade and calculates under crown canopy
The solar radiation of side, because what crownshade used for reference is massif shade calculation formula, it is impermeable that assumed condition is that massif blocks
Light, but really storey has certain translucency since density is not both to have hole, so utilizing the simulation of LPI coefficients
The translucency of canopy.On the other hand, theoretically LPI consider be vertical direction on unit area point cloud ratio, but due to reality
Often there are certain angle, the distributions of vegetation point cloud between at the top of the laser beam and canopy that airborne scanner emits in the operation of border
There may be certain deformation, so, the present invention proposes to optimize using neighbor analysis method (neighborhood analysis)
The calculating of LPI, contiguous range is by woods window edge wood height and laser beam flying angle-determining.
The LPI of target object (black unit in Fig. 5) is：
In formula, N is the number of grid cell in neighborhood.The LPI of target object is each grid cell in contiguous range
The mean value of LPI values.
Advantageous effect：
The woods window solar radiation monitoring method based on laser radar of the present invention, key point are as follows：
(1) above the canopy on the basis of the calculating of solar radiation total amount, according to the undulating state of Malabar Pied Hornbill model DSM,
Take the intensity of solar radiation that different location in woods window is calculated in canopy masking factor into account；(2) light based on laser point cloud is built
Beam penetrating coefficient model (LPI) improves solar radiation monitoring accuracy.
(1) the surface model DSM of canopy fluctuating situation can be accurately reflected by laser point cloud generation, uses for reference massif shade
The computational methods of (prior art) using sun altitude and azimuth, calculate the masking relationship between canopy, further according on canopy
Square solar radiation total amount can accurately calculate the intensity of solar radiation of different location in woods window.It can using digital complex demodulation
It calculates massif in traditional sense and covers relationship, on the basis of massif shade, DSM is recycled to estimate in small range scale and is preced with
The masking relationship of interlayer, this method are suitble to calculate the solar radiation of different size woods window, different location in complicated landform environment.
(2) canopy has hole, some light can be allowed to be transmitted to ground, so light transmission factor is produced in estimation by canopy
Seem very crucial during raw shadow region illumination.Laser beam can generate high density, high-precision cloud during penetrating canopy,
Fair weather available light irradiation canopy situation can be simulated.The present invention propose by Ground Point cloud quantity on unit of account area with
The ratio of point cloud total amount (the sum of canopy point cloud and Ground Point cloud) seeks light beam penetrating coefficient LPI, and using neighbor analysis method come
Optimize LPI.This method is easy to operate, calculating is accurate, not only can effectively avoid the systematic error as caused by cloud distribution distortion, and
It is and more much smaller than the computation complexity of traditional algorithm (such as Image Synthesis by Ray Tracing).
The woods window solar radiation monitoring method based on airborne laser radar of the present invention, has filled up prior art middle forest window too
The technological gap of positive Radiation monitoring method is a kind of measuring method of accurate, repeatable operation, can quickly measure fair weather feelings
Under condition in woods window any position intensity of solar radiation.
For the measure of woods window intensity of solar radiation, the prior art such as direct method of measurement and photograph method all can only be single
It is operated on the spot in sample prescription, when obtaining a wide range of sample prescription data, there are heavy workload, processes in varying degrees for conventional method
Tedious, the problems such as taking time and effort, and be difficult repetitive operation in a short time, include temporal-spatial heterogeneity error so as to cause result.
The present invention, by highdensity earth's surface and Vegetation canopy laser point cloud, calculates woods window model using airborne laser radar remote sensing technology
The solar radiation of interior different location is enclosed, breaks through the technical bottleneck of field survey, there is quick, accurate, repeatable operation,
And detection range is wide, has a good application prospect.
Description of the drawings
Fig. 1 is canopy laser point cloud and earth's surface laser point cloud schematic diagram；
Fig. 2 is sun altitude and azimuth schematic diagram；
Fig. 3 is LPI schematic diagrames on 2m × 2m unit areas；
Fig. 4 covers relation schematic diagram for laser beam and woods window edge wood canopy；
Fig. 5 calculates LPI schematic diagrames for neighbor analysis；
Fig. 6 is region Malabar Pied Hornbill model DSM schematic diagrames to be measured；
Fig. 7 is zone digit elevation model DEM schematic diagrames to be measured；
Fig. 8 identifies schematic diagram for region woods window to be measured；
Region woods window solar radiation to be measured calculates result schematic diagram (sun altitude when Fig. 9 is 7 days 11 June in 2016
70.23 °, 102.092 ° of azimuth)；
Region woods window solar radiation to be measured calculates result schematic diagram (sun altitude when Figure 10 is 7 days 16 June in 2016
41.40 °, 276.24 ° of azimuth)；
Figure 11 is the Linear Fit Chart of this method and field investigation result；
Specific embodiment
The present invention is described in further details below with reference to the drawings and specific embodiments：
Embodiment 1：Such as Fig. 1~11, the present invention monitors fair weather situation using airborne laser radar (ALS) point cloud data
The solar radiation of different location in lower woods window, while take the influence of complicated landform, canopy form and light transmittance into account, improve monitoring essence
Degree.The first step differentiates woods window using ALS point cloud datas, determines woods window edge；；Second step, according to sun altitude and azimuth
Estimate intensity of solar radiation under fair weather situation in region to be measured, with reference to digital complex demodulation, calculate under MODEL OVER COMPLEX TOPOGRAPHY
The direct sunlight and amount of scatter radiation received above canopy；Third walks, and according to the undulating state of Malabar Pied Hornbill model DSM, cares for
And the intensity of solar radiation of different location in woods window is calculated in canopy masking relationship and light beam penetrating coefficient.
1st, the woods window based on ALS point cloud datas differentiates
The ALS data refer to the remotely-sensed data by fixed wing aircraft or the acquisition of UAV flight's laser scanner, with point
Cloud format stores.Each point cloud includes X, Y, Z coordinate value and echo strength information.Utilize existing Remote Sensing Data Processing software
The Environment for Visualizing Images (ENVI, v5.3) set the correct projected coordinate system of point cloud data
System, measurement unit is rice.
Woods window identification model：
In formula, G (x, y)=1, it is woods window to represent the corresponding position of point (x, y)；X, y are respectively the abscissa of grid (x, y)
And ordinate, CHM (x, y) are the canopy height values on grid (x, y)；A is the discrimination threshold of canopy edge average height, by passing through
It tests value or sample investigation on the spot determines, if discrimination threshold is 5 meters.
CHM is the difference of Malabar Pied Hornbill model and earth's surface elevation model, i.e.,：
CHM (x, y)=DSM (x, y)-DEM (x, y)； (2)
DSM is Malabar Pied Hornbill model in formula, and DEM is digital elevation model.
First, original point cloud is divided into canopy point cloud using adaptive irregular triangle network filtering method (prior art)
With Ground Point cloud (Fig. 1).Canopy point cloud is interpolated to DSM using kriging analysis method (prior art), instead apart from weights interpolation
Ground Point cloud interpolation is generated DEM by method (prior art).The feature of density in view of cloud and canopy characterization, setting DSM and
DEM has identical raster resolution.
Secondly, difference operation is carried out to DSM and DEM using remote sensing image processing software ENVI, obtains canopy height grid
MODEL C HM, and the binary map G (x, y) of woods window and Fei Lin windows is carried out according to the height threshold a of woods window edge canopy on this basis
Classification.
Then, woods window recognition result is post-processed, to improve accuracy of identification, using ENVI softwares in G (x, y) two-value
Morphologic filtering operation is carried out on the basis of figure, determines final woods window range.Vectoring operations finally are carried out to woods window range, are obtained
To the polygon polar plot of woods window edge.
2nd, fair weather mountain area intensity of solar radiation is estimated
Theoretically speaking reach the solar radiation total amount of earth's surface by the direct sunlight of the incident angular direction in part, scattering and
Earth surface reflection is formed.Actually woods window is mostly distributed in the higher forest land of afforestation rate, reflection of the earth's surface to solar radiation
Very little in order to improve computational efficiency, when calculating solar radiation total amount above woods window canopy, only considers the incident angular direction in part
Direct sunlight and scattering two parts, i.e.,：
Gi=Bi+Di (3)
In formula, GiFor the incident angular direction solar radiation total amount in part, Bi,DiRespectively direct sunlight and amount of scatter radiation.
(1) the incident angular direction beam radia in part calculates：
Bi=Io·τb·δi·hillshade (4)
In formula, I0For extraatmospheric solar radiation quantity, τbFor the penetrating in atmosphere of beam radia in fair weather
Rate, δiFor light part incidence angle, hillshade is massif shadow factor.(above-mentioned parameter is calculated by formula 5-12)
Io=S0·(1+0.0344cos(360°·N/365)) (5)
In formula, S0For 1367 (w/m of solar radiation constant2), N is day of year (which day in 1 year).
The paper delivered according to researchers such as Kreith in internal authority periodical is as a result, fair weather beam radia
Penetrance can be reduced to：
τb=0.56 (e-0.65M+e-0.095M) (6)
In formula, M is air quality coefficient, is specifically had,
M=[1229+ (614sin α)2]1/2-614sinα (7)
In formula, α is sun altitude.
Sun altitude and azimuth (Fig. 2) are calculated：
α=arcsin (sinLsin δs+cosL·cosδs coshs) (8)
δ in formulasFor declination angle, geographic latitudes of the L for region to be measured, hsFor solar hour angle.
Light part incidence angle：
δi=sin δs·(sinL·cosSlope-cosL·sinSlope·cosAsp)
+cosδscoshs·(cosL·cosSlope+sinL·sinSlope·cosAsp)
+cosδs·sinSlope·sinAsp·sinhs (10)
The gradients of the Slope for landform in formula, slope aspects of the Asp for landform, specific formula for calculation：
Asp=Slopesn/Slopewe (11)
In formula, slopeweFor the gradient of X-direction on digital complex demodulation, slopesnLadder for Y direction on DEM
Degree；0~90 ° of gradient value range.
| e5 | e2 | e6 |
| e1 | e | e3 |
| e8 | e4 | e7 |
For the data of upper table, have：
E and e1-e8 represents the height value of 9 different locations in the grid of 3 × 3 sizes, and cellsize is big for grid
It is small, i.e. raster resolution, such as 2 meters.
Massif shadow factor：
Hillshade=(cos α cosSlope)+[sin α sinSlopecos (αs-Asp)] (12)
(2) the incident angular direction solar scattered radiation in part calculates：
The paper delivered according to researchers such as Gates in internal authority periodical is as a result, the part incidence angular direction sun dissipates
Penetrate radiation and scattering transmittance τd, terrain slope Slope, sun altitude α are related：
Dio=Io·τd·(cos Slop)2/2sinα (13)
In formula, IoFor extraatmospheric solar radiation quantity (referring to formula 5),
τd=0.271-0.294 τb (14)
When calculating amount of scatter radiation in alpine terrain, incidence may be divided into the influence of scattering light in view of surrounding massif
On angular direction δ is blocked without massifi＞ 0 and there is massif to block δi≤ 0 two kind of situation：
Skyview is the vault of heaven ratio in the range of visible range in formula, can be calculated by ENVI softwares.
3rd, the solar radiation of woods window calculates
The calculating of woods window solar radiation is considered as the light transmittance of canopy form, canopy top solar radiation total amount and canopy
Etc. factors influence, i.e.,：
Globalgap=crownshade(1-LPI)·Gi (16)
In formula, crownshade be woods window edge canopy generate shade, LPI be light beam penetrating coefficient, GiFor on canopy
Square solar radiation total amount.
Crownshade=(cos α cosSlopeDSM)+[sinα·sinSlopeDSM·cos(αs-AspDSM)] (17)
In formula, SlopeDSMFor the gradient of Malabar Pied Hornbill model DSM, reflect the inclined degree of Malabar Pied Hornbill, AspDSMFor hat
The slope aspect of layer surface model DSM reflects the direction of Malabar Pied Hornbill, specific to calculate reference formula 11.α、αsFor sun altitude and
Azimuth.
What crownshade was used for reference is massif shade calculation formula, and assumed condition is that shield portions are light tight, but crown canopy
Layer has certain translucency, the present invention simulates the translucency of canopy using LPI coefficients due to the difference of density.LPI light beams are saturating
It penetrates coefficient and refers to sunray and the ability that canopy reaches earth's surface is penetrated (including direct projection and scattering), in airborne laser radar application,
LPI obtains LPI (Fig. 3) by Ground Point cloud quantity in unit of account area (2m × 2m) with putting the ratio of cloud total amount, i.e.,：
LPI value ranges are (0,1), and 0 expression light beam is blocked completely by canopy, and effect is as light beam is by opaque object
It blocks；1 expression light beam is not influenced by canopy or vegetation component, can directly be irradiated to ground.
Theoretically, what LPI calculated consideration is the point cloud ratio of vertical direction on unit area, but due to machine in practical operation
Often there are certain angles between carrying at the top of the laser beam and canopy of scanner transmitting, and there may be one for the distribution of vegetation point cloud
Fixed deformation.So it is proposed that optimize the calculating of LPI using neighbor analysis method (neighborhood analysis).Through
It counts, the average height of woods window edge wood is 20 meters in region to be measured, 15 ° of the scanning angle average out to of laser beam, canopy masking
Horizontal distance for 5.36 meters (Fig. 4), since the raster resolution that we set is 2 meter, so unilateral masking distance is equivalent to 3
A grid cell length.Build as a result, 7 × 7 grid Square Neighborhoods (1 unit of target object, side respectively have 3 units) with
The LPI of target object is calculated, as shown in figure 5, the LPI of target object (black unit in Fig. 5) is：
In formula, N is the number of grid cell in neighborhood.The LPI of target object is each grid cell in contiguous range
The mean value of LPI values.
Illustrate the application of the present invention below by way of specific example：
Study area's overview：
Research ground be located at Northeast of Hunan Fu Shou mountain forest (28 ° 3 ' 00 " -28 ° 32 ' 30 " N, 113 ° 41 ' 15 " -
113 ° 45 ' 00 " E), it is located in Luoxiao mountain range and connects Yunshan Mountain offshoot, topography is high in the south and low in the north, more than 1200 rice of mean sea level, and mean inclination is
The landforms of hills and mountains overlapping are presented in 22-27 degree.12.1 DEG C of average temperature of the whole year, year sunshine 1500 hours, 217 days frost-free periods.Mainly
Vegetation pattern is typical Mid-subtropical Evergreen Broadleaved Forests, upper layer trees seeds mainly have China fir, Pinus taiwanesis, Qinggang oak, bitter sweet oak,
Sassafrases, Alnus Trabeculosa, hickory nut and Fagaceae.
The sample investigation of woods window on the spot uses hemisphere face image method, and forest gap area is determined according to fish eye lens projection theory；
Gap border trees height is measured using angle gauge method or telescopic height finder；Differential GPS or total station survey woods window center height above sea level and
Position.Woods window density is 12.77/hm in region-2, account for area of woods 11.27%；The high mean value difference of forest gap area, Border tree
For 85.06m2And 20.33m, it is mostly compared with small area, edge effect unnoticeably woods window in region.
Field investigation method：
The sample prescription of 80 30m × 30m in permanent sample plot is set, the position of each sample prescription is determined with differential GPS, each
At sample prescription center and diagonal quartile hemisphere face woods is obtained with the external fish eye lens of digital camera (wide-angle is 183 °, orthographic projection)
Image is preced with, image direction is overlapped with magnetic north direction.With Gap Light Analyzer (GLA, V2.0, image processing software) to hat
Layer photo is analyzed and woods window solar radiation total amount is calculated, and measurement unit is w/m2.Investigation work selection day in June current year
It is carried out under the sunny situation of gas, control time section is Beijing time 6：00 to 18：00, it is primary per measuring every other hour, then sum
Calculate total intensity of solar radiation.40 are used as training sample data in 80 sample prescription data, remaining 40 as verification sample
Notebook data.
Airborne laser radar data：
Airborne laser radar data ALS obtains the time as summer in 2016, and sunny and partly cloudy weather is selected to fly, according to
Situations such as testing geographic coverage and Terrain Elevation, gradient designs a plurality of course line along topography.Airborne lidar system is
ALTM2050, average 15 °, measurement accuracy ± 20mm of laser beam flying angle, average spot size 15cm, point cloud density for 2~
10/m2.Using the projection coordinate of ENVI software set laser point cloud datas for Mercator projection (UTM) mode, reference ellipsoid
For WGS84, code name 38 is projected, laser radar data is with a cloud storage form record (table 1).
1 laser point cloud storage format of table, each laser point correspond to a line record
Based on the method for the present invention to studying area's woods window solar radiation monitoring process：
(1) the woods window based on ALS point cloud datas differentiates
Using the projection coordinate of ENVI software set laser point cloud datas for Mercator projection (UTM) mode, reference ellipsoid
For WGS84, determine projection code name for north 38 by the longitude and latitude in region to be measured.Utilize adaptive irregular triangle network filtering technique root
Original point cloud is divided into canopy point cloud and Ground Point cloud according to height value, using raster interpolation method respectively to canopy point cloud and earth's surface
Point cloud interpolation generation DSM (Fig. 6) and DEM (Fig. 7) grating image, and the raster resolution for setting DSM and DEM is all 2 meters.It utilizes
ENVI softwares carry out grid difference operation to DSM and DEM, generate the canopy height MODEL C HM of 2 meters of resolution ratio.
The differentiation of woods window range is carried out on CHM using woods window identification model (formula 1), rule of thumb with on-site inspection knot
Fruit sets woods window edge canopy height threshold value a as 5 meters, generates the binary map of woods window and Fei Lin window ranges.Existed using ENVI softwares
Morphologic filtering operation is carried out on the basis of G (x, y) binary map, (2 meters of small―gap suture between forest is eliminated using " corrosion " algorithm
Within) or crown canopy in small " cavity ", restore to obtain true storey gap using " expansion " algorithm, determine final woods window model
(Fig. 8) is enclosed, carries out " grid conversion vector " operation on this basis, sketches the contours and preserve the polygon polar plot of woods window edge.
(2) fair weather mountain area solarimeter is calculated
Solar radiation total amount above complicated landform environment middle forest window canopy, measurement unit w/m are calculated according to formula (3)2。
Terrain slope and slope aspect are calculated on the basis of DEM using ENVI softwares, with reference to the geographic latitude in region to be measured, position of sun, mountain
The factors such as body shade calculate the beam radia of the incident angular direction in part according to formula (4)~formula (15) and scattering radiate,
Solar radiation time-space distribution graph above the entire region canopy to be measured of generation.
(3) solar radiation of woods window calculates
Above the canopy calculated according to step (2) based on solar radiation total amount, fully consider that canopy masking is influenced and is preced with
Layer light transmittance calculates solar radiation in the range of woods window according to formula (16), generates woods window sun spoke in entire region to be measured
Penetrate the time-space distribution graph (Fig. 9,10) of intensity.Based on Malabar Pied Hornbill model DSM, calculated according to formula (17) by canopy form
Caused by shade.According to formula (18) unit of account area (2m × 2m) inner light beam transmission coefficient LPI, entire region to be measured is generated
LPI grating images.In order to reduce the systematic error caused by cloud distribution, optimize according to formula (19) and neighbor analysis method
The value of LPI.
(4) result verification
Expert data statistical analysis software Statistical Product and Service Solutions (SPSS,
V19) to 7 days 6 June in 2016：00~18：The estimation of solar radiation total amount (is tested with field investigation result in 00 period woods window
Demonstrate,prove sample) carry out linear fit precision analysis (Figure 11).It is verified respectively according to different location in gap size and woods window, profit
Compare laser radar estimation and the difference (table 2) of field investigation result in the case of 4 kinds with paired-samples T-test (paired t-test).
According to field investigation sample prescription position, area is set separately>200m2It is great Lin windows, area≤200m2For holt window, position in woods window
It puts and is divided into woods window center area and marginal zone.
2 this method of table and field investigation results contrast
X is field investigation value, and y is this method estimated value.
Woods window intensity of solar radiation difference normal distribution conspicuousness Sig. >=0.05 illustrates have using paired-samples T-test method
Statistical significance.The null hypothesis of paired-samples T-test is that the distribution of intensity of illumination difference meets average value for 0 t distributions, holt window,
The two-sided significance P of great Lin windows and woods window center is both greater than 0.05 (table 2), and Monitoring by Lidar is too in the case of illustrating this 3 kinds
Significant difference is not present with field investigation result in positive radiation intensity, and the intensity of illumination of woods window edge monitors and field investigation result
There is notable difference.From the point of view of opposite root-mean-square error, the monitoring result of the intensity of solar radiation of great Lin windows and woods window center is better than
Holt window and woods window edge.From the point of view of regression equation and related coefficient, the result of Monitoring by Lidar and the result of field investigation
Being proportionate property, but underestimate there are a degree of.In summary it analyzes, the woods window solar radiation that this method measures has higher
Precision, available for quickly measuring different size of woods window, in woods window different location luminous environment.
By showing that woods window edge wood species and average height and laser point cloud are close to the data analysis of 40 verification samples
Degree all has an impact light beam transmissivity LPI, and then may influence final monitoring result.So it should increase in practical operation
The Duplication of flight air strips pays attention to the small data of more options laser scanning angle to improve a cloud to improve cloud density
The precision of LPI.
Claims (7)
1. a kind of woods window solar radiation monitoring method based on laser radar, which is characterized in that include the following steps：
Step 1：Woods window is identified based on laser radar ALS point cloud datas, to determine woods window edge；
Step 2：Calculate the incident angular direction solar radiation total amount G in the part received above MODEL OVER COMPLEX TOPOGRAPHY lower canopyi；
Step 3：Based on GiThe intensity of solar radiation Global of different location in woods window is calculatedgap。
2. the woods window solar radiation monitoring method according to claim 1 based on laser radar, which is characterized in that step 1
In, identify that the model of woods window is as follows：
In formula, G (x, y)=1, it is woods window to represent the corresponding position of point (x, y)；X, y are respectively the abscissa of grid (x, y) and indulge
Coordinate, CHM (x, y) are the canopy height values on grid (x, y)；A is the discrimination threshold of canopy edge average height.
3. the woods window solar radiation monitoring method according to claim 1 based on laser radar, which is characterized in that step 2
In：
Gi=Bi+Di；
In formula, GiFor the incident angular direction solar radiation total amount in part, Bi,DiThe respectively incident angular direction beam radia in part
Amount and amount of scatter radiation.
4. the woods window solar radiation monitoring method according to claim 3 based on laser radar, which is characterized in that part enters
The calculation formula of firing angle direction beam radia amount is as follows：
Bi=In·δi·hillshade；δ in formulaiFor light part incidence angle, hillshade is massif shadow effect coefficient；
Specifically, have：
Light part incidence angle：
Massif shadow effect coefficient：
Hillshade=(cos α cos Slop)+[sin α sin Slopcos (αs-Asp)]；
In formula Slop be landform the gradient, Asp be landform slope aspect (gradient refers to the inclined degree of slope surface, and slope aspect refers to landform
The direction of slope surface)；
δsFor declination angle, there is δs=23.45sin (360 ° of (284+N)/365), N is day of year in formula；
L is geographic latitude；
hsFor solar hour angle.
5. the woods window solar radiation monitoring method according to claim 3 based on laser radar, which is characterized in that part enters
Firing angle direction solar scattered radiation amount DiComputational methods it is as follows：
In view of surrounding massif the D in alpine terrain may be calculated to the influence of scattering lightiWhen, it is divided on incident angular direction without mountain
Body blocks δi＞ 0 and there is massif to block δi≤ 0 two kind of situation：
Variable declaration in formula：
(1) skyview is the vault of heaven ratio in the range of visible range；
(2) hillshade is massif shadow factor；
Hillshade=(cos α cos Slope)+[sin α sin Slopecos (αs-Asp)]；
(3)IoFor extraatmospheric solar radiation quantity, Io=S0(1+0.0344cos (360 ° of N/365)), in formula, S0For too
Positive 1367 (w/m of radiation constant2), N is day of year (which day in 1 year).
(4)τbFor the penetrance of fair weather beam radia, τb=0.56 (e-0.65M+e-0.095M),
In formula, M is air quality coefficient, is specifically had, M=[1229+ (614sin α)2]1/2-614sinα
In formula, α is sun altitude；
(5)SoFor 1367 (w/m of solar radiation constant2)
(6)δiFor light part incidence angle, have：
Slope is the gradient of landform in formula；Asp is the slope aspect of landform；
δsFor declination angle, geographic latitudes of the L for region to be measured, hsFor solar hour angle；
(7)αsFor solar azimuth；
(8) Slope is terrain slope；
(9)DioFor initial local incidence angular direction solar scattered radiation intensity：
Dio=Io·τd·(cos Slop)2/2sinα。
6. according to woods window solar radiation monitoring method of the claim 1-5 any one of them based on laser radar, feature exists
In woods window solar radiation GlobalgapCalculation formula it is as follows：
Globalgap=crownshade(1-LPI)·Gi；
In formula, crownshade be woods window edge canopy generate shade, LPI be light beam penetrating coefficient, GiFor the sun above canopy
Radiation amount；
Crownshade=(cos α cos SlopeDSM)+[sinα·sin SlopeDSM·cos(αs-AspDSM)]
In formula, SlopeDSMFor the gradient of Malabar Pied Hornbill model DSM, reflect the inclined degree of Malabar Pied Hornbill, AspDSMFor canopy table
The slope aspect of surface model DSM reflects the direction of Malabar Pied Hornbill；
α、αsFor sun altitude and azimuth.
7. the woods window solar radiation monitoring method according to claim 6 based on laser radar, which is characterized in that
In formula, number (Ground Point cloud) and number (Ground Point cloud+canopy point cloud) represent respectively unit area (such as 2m ×
Ground Point cloud quantity is with putting cloud total amount in 2m)；
The LPI of target object is：
In formula, N is the number of grid cell in neighborhood.The LPI of target object is each grid cell LPI values in contiguous range
Mean value.
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