CN107271372A - A kind of Apple Leaves chlorophyll remote sensing estimation method - Google Patents

A kind of Apple Leaves chlorophyll remote sensing estimation method Download PDF

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CN107271372A
CN107271372A CN201710408574.6A CN201710408574A CN107271372A CN 107271372 A CN107271372 A CN 107271372A CN 201710408574 A CN201710408574 A CN 201710408574A CN 107271372 A CN107271372 A CN 107271372A
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chlorophyll
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apple leaves
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常庆瑞
刘京
李粉玲
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Northwest A&F University
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    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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    • G01J3/28Investigating the spectrum
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28Investigating the spectrum
    • G01J3/2823Imaging spectrometer
    • G01J2003/2826Multispectral imaging, e.g. filter imaging

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Abstract

The invention discloses a kind of Apple Leaves chlorophyll remote sensing estimation method, Apple Leaves hyper spectral reflectance and corresponding chlorophyll relative content are synchronously obtained using SVC HR 1024i type bloom spectrometers and the chlorophyll meters of SPAD 502, correlation analysis is carried out to original spectrum reflectivity and first derivative spectrum, extract the Red-edge parameter of Apple Leaves spectrum, use traditional single argument regression algorithm, BP neural network and radial primary function network, and processing is optimized to artificial neural network, set up chlorophyll content inverse model.Work network model is compared traditional univariate model inversion accuracy and significantly improved, and radial primary function network pace of learning is fast, precision is high, and fitting result is relatively reliable, is a kind of chlorophyll content inverse model being worthy to be popularized.

Description

A kind of Apple Leaves chlorophyll remote sensing estimation method
Technical field
The invention belongs to agricultural technology field, it is related to a kind of Apple Leaves chlorophyll remote sensing estimation method.
Background technology
Vegetation chlorophyll content has preferable correlation with photosynthetic capacity, growth and development stage and nitrogen level, Have become a kind of means of effective evaluation vegetation growing way.Because the spectral reflectivity of green plants is green by leaf in visible light wave range Cellulose content influences, and is dominated by blade construction and cellulose etc. near infrared band is main, thus can with the reflectance spectrum of plant come Estimate pigment content.In recent years, high-spectrum remote-sensing is so that its spectral resolution is high, simple and effective and the advantages of non-destructive, into To monitor a developing direction of vegetation chlorophyll content.
Red side is due to that vegetation is multiple in blade interior near infrared band light in red spectral band absorption strong to chlorophyll Strong reflection formed by scattering, makes spectral reflectivity be steeply risen in 680~760nm intervals, the plant spectral of formation it is most aobvious Principal coordinates will.Correlation of the scholars on the one hand between chlorophyll and Red edge position is started with, and proposes " red side " to long wave direction Displacement reflects the increase of vegetation chlorophyll concentration;On the other hand the chlorophyll based on Red-edge parameter is built using statistical analysis to estimate Model is calculated, and precision evaluation is carried out to it.Influenceed by conditions such as field management, fertilising and weathers, scholars recognize tradition Statistical analysis technique estimation chlorophyll content precision of prediction is not high, it is necessary to build the estimation mould that a Stability and veracity has both Type;The plant chlorophyll based on Red-edge parameter, which is estimated, simultaneously carried out correlative study on the crops such as some corns, wheat, but in fruit Application on tree is relatively fewer.
It is a kind of non-linear relation between chlorophyll and spectral reflectance parameter, two kinds of parameters are with what kind of mathematical function relationship It is the important content for building Chlorophyll inversion model and its precision of prediction to set up contact, and scholars continuously attempt to various letters in recent years Number relation, wherein artificial neural network are a kind of effective means for handling complex nonlinear problem.With high spectrum resolution remote sensing technique Development, artificial neural network more and more be applied to high-spectrum remote-sensing research in.Such as utilize artificial nerve network model base Soil parameters is predicted in soil spectrum, preferable effect is achieved;Artificial nerve network model is set up based on EO-1 hyperion to predict Wheat, paddy rice, seeding corn and other crops biochemical parameter.Apple is the important industrial crops in the Northwest, and its yield accounts for national apple More than half of yield.Apple Leaves chlorophyll content is the important channel for monitoring apple production and liquid manure situation, using artificial Neutral net, which carries out the prediction of apple chlorophyll, has important theory and application value.
The content of the invention
It is an object of the invention to provide a kind of Apple Leaves chlorophyll remote sensing estimation method, this method utilizes SVC HR- 1024i type bloom spectrometers and SPAD-502 chlorophyll meters synchronously obtain Apple Leaves hyper spectral reflectance and corresponding chlorophyll phase To content, correlation analysis is carried out to original spectrum reflectivity and first derivative spectrum, the Red-edge parameter of Apple Leaves spectrum is extracted, Use traditional single argument regression algorithm, BP (Back Propagation) neutral nets and RBF (Radial Basis Function, RBF) network, and processing is optimized to artificial neural network, set up chlorophyll content inverse model.
Its concrete technical scheme is:
A kind of Apple Leaves chlorophyll remote sensing estimation method, comprises the following steps:
Step 1, spectroscopic data are determined
Blade is carried out using the portable bloom spectrometer of U.S.'s SCVHR 1024i types to diffuse the measure of modal data.Spectrum The wave-length coverage that instrument is determined is 350~2500nm, and port number is 1024, wherein 350~1000nm intervals spectral resolution is 1.4nm, 1000~1850nm interval spectral resolution are 3.8nm, and 1850~2500nm intervals spectral resolution is 2.4nm.Survey Fixed work is carried out indoors, is carried out every time before sample spectra measure, and instrumental correction, every group of blade are carried out using diffusing reflection reference plate 1 leaf is selected, first blade face is cleaned.Then spectroscopic assay is carried out.Each point, which is determined 2 times, averages as the light Measured value is composed, each blade takes 3~5 points, finally takes the average value of each point as the spectral value of the blade.
Step 2, measuring chlorophyll content
SPAD (the Soil Plant Analysis Development produced using Japanese KONICA MINOLTA companies Unit) the synchronous relative chlorophyll content to Apple Leaves of 502 chlorophyll meters carries out nondestructive measurement.In every leaf diverse location 10 SPAD values of upper measure, the SPAD values averaged as the leaf represent the chlorophyll content of the blade, and 500 are obtained altogether The SPAD values of blade.
Step 3, data processing
The processing software ViewSpec Pro 6.0 carried before data analysis using spectrometer are by the Apple Leaves of measure Spectroscopic data carries out resampling, and the setting sampling interval is 1nm.Spectroscopic data is carried out using Savitzky-Golay smothing filterings Pretreatment, it is 5 to set smooth points, and the first derivative spectra is tried to achieve by original spectrum, and blade is extracted from the first derivative spectra Red-edge parameter;
Step 4, model construction and accuracy test
Using unitary is linear, index, logarithm, multinomial and power function build chlorophyll content in leaf blades and every Red-edge parameter Common regression model, selection correlation is good, precision is high Red-edge parameter is used as independent variable, builds chlorophyll content estimation mould Type;The Red-edge parameter selected out builds the artificial neural network based on Red-edge parameter as the input vector of artificial neural network Model.
Further, in step 3, the Red-edge parameter of blade, including Red edge position, it is red in amplitude, it is red while area, coefficient of kurtosis And the coefficient of skewness.
Further, in step 3,286 groups of spectroscopic datas therein are have selected altogether and SPAD values are analyzed and researched.Modeled Cheng Zhong, 236 groups of random screening is used to model in 286 groups of data, and another 50 groups are used to verify.
Further, in step 4, two kinds of artificial neural network selection BP neural network and RBF neural.
Further, it is testing model precision in step 4, model predication value and measured value is subjected to regression fit, using logical The coefficient of determination (R2), root-mean-square error (RMSE), relative error (RE) verify model accuracy.
Compared with prior art, beneficial effects of the present invention:
What is behaved oneself best in the univariate model that the present invention is set up is Red edge position, coefficient of kurtosis and the coefficient of skewness, correlation Coefficient is all higher than 0.7;These three variables are chosen as the input variable of artificial neural network, BP neural network optimal models is set up Predicted value and measured value between the linear regression coefficient of determination to be linear between 0.916, RBF neural network forecasts value and measured value It is 0.939 to return the coefficient of determination, and precision of prediction is up to 96.57%.Artificial network's model compares traditional univariate model inverting essence Degree is significantly improved, and radial primary function network pace of learning is fast, precision is high, and fitting result is relatively reliable, is that one kind is worthy to be popularized Chlorophyll content inverse model.
Brief description of the drawings
Fig. 1 is the correlation of chlorophyll content and original spectrum and first derivative spectrum;
Fig. 2 is the Apple Leaves chlorophyll content inverse model based on the coefficient of skewness;
Fig. 3 is the comparison of Apple Leaves inverse model measured value based on the coefficient of skewness and predicted value;
Fig. 4 is the comparison of optimal BP neural network model actual measurement value and predicted value;
Fig. 5 is the comparison of optimal RBF neural network model measured value and predicted value.
Embodiment
Technical scheme is described in more detail with specific embodiment below in conjunction with the accompanying drawings.
1 materials and methods
1.1 research area's overviews
Selection Baoji, Shaanxi province city Fufeng County Xing Lin towns orchard is research object, and the ground is located at 34 ° 19 ' 02 "~34 ° 23 ' 33 " between N, 107 ° 54 ' 45 "~108 ° 02 ' 40 " E, 470~570m of height above sea level, continental semi-moist monsoon climate, the four seasons point are belonged to It is bright, annual sunshine 2134.3h, 12.4 DEG C of average temperature of the whole year, mean annual precipitation 591.9mm.It is richness that orchard, which is located at fruit variety, Scholar.It is in April, 2015-September to gather the date, and the florescence (April 27) of corresponding fruit tree, young fruit period (May 30), fruit are swollen respectively Big phase (July 6), fruit color phase (August 5 days), fructescence (September 11 days).According to research area's distribution situation, in garden Selection is representative, growth is uniform, the age of tree is close and the apple tree without pest and disease damage is sampled point, and 25 fruit trees are chosen altogether and are made For research sample.In random method when taking blade sample, every fruit tree takes leaf color to have 4 groups of blades of notable difference, every group of collection 4 Piece leaf, each issue of collection, 100 groups of leaves, gathers 500 groups of blades, carries out spectrum and measuring chlorophyll content altogether.
1.2 determine project and method
1.2.1 spectroscopic data is determined
Blade is carried out using the portable bloom spectrometer of U.S.'s SCVHR 1024i types to diffuse the measure of modal data.Spectrum The wave-length coverage that instrument is determined is 350~2500nm, and port number is 1024, wherein 350~1000nm intervals spectral resolution is 1.4nm, 1000~1850nm interval spectral resolution are 3.8nm, and 1850~2500nm intervals spectral resolution is 2.4nm.Survey Fixed work is carried out indoors, is carried out every time before sample spectra measure, and instrumental correction, every group of blade are carried out using diffusing reflection reference plate 1 leaf is selected, first blade face is cleaned.Then spectroscopic assay is carried out.Each point, which is determined 2 times, averages as the light Measured value is composed, each blade takes 3~5 points, finally takes the average value of each point as the spectral value of the blade.
1.2.2 measuring chlorophyll content
SPAD (the Soil Plant Analysis Development produced using Japanese KONICA MINOLTA companies Unit) the synchronous relative chlorophyll content to Apple Leaves of 502 chlorophyll meters carries out nondestructive measurement.Numerous studies show, blade Greenness (SPAD) value has significant correlation with chlorophyll content, and SPAD values can be directly as sign chlorophyll concentration Relative value.10 SPAD values are determined on every leaf diverse location, the SPAD values averaged as the leaf represent the blade Chlorophyll content, altogether obtain 500 blades SPAD values.
1.3 data processing
The processing software ViewSpec Pro 6.0 carried before data analysis using spectrometer are by the Apple Leaves of measure Spectroscopic data carries out resampling, and the setting sampling interval is 1nm.Using Savitzky-Golay (SG) smothing filtering to spectroscopic data Pre-processed, it is 5 to set smooth points.The first derivative spectra is tried to achieve by original spectrum, leaf is extracted from the first derivative spectra The Red-edge parameter of piece, including Red edge position, it is red in amplitude, it is red while area, coefficient of kurtosis and the coefficient of skewness (table 1).
The definition of the Red-edge parameter of table 1 and algorithm
Table1 Definition and algorithm of red edge parameter
R (λ) is the spectral reflectivity of any wavelength;R ' (λ) is the corresponding derivative spectrum of any wavelength;E (X) is vector X Desired value, μ be vector X average value, σ for vector X standard deviation.
R(λ)is the spectral reflectance of any wavelength,R′(λ)is the corresponding first derivative spectra.E(X)is the expected value of vector X, μis the average value of vector X,σis the standard deviation of vector X.
Due to the measurement result error of some samples is larger or spectroscopic data is weak value, the present invention have selected it altogether In 286 groups of spectroscopic datas and SPAD values analyzed and researched.In modeling process, 236 groups of use of random screening in 286 groups of data In modeling, another 50 groups are used to verify.
1.4 model constructions and accuracy test
Using unitary is linear, index, logarithm, multinomial and power function build chlorophyll content in leaf blades and every Red-edge parameter Common regression model, selection correlation is good, precision is high Red-edge parameter is used as independent variable, builds chlorophyll content estimation mould Type;The Red-edge parameter selected out builds the artificial neural network based on Red-edge parameter as the input vector of artificial neural network Model.
Artificial neural network selects two kinds of BP neural network and RBF neural.BP neural network is a kind of multilayer feedforward Neutral net, the network is mainly characterized by before signal to transmission, error back propagation.Forward direction transmission in, input signal from Input layer is successively handled through hidden layer, until one layer of neuron state under the influence of output layer, each layer of neuron state.Such as Fruit output layer cannot get desired output, then be transferred to backpropagation, network weight and threshold value be adjusted according to predicated error, so that BP Neural network prediction output constantly approaches desired output.BP neural network is made up of input layer, hidden layer and output layer, hidden layer The number of plies and nodes have large effect to BP neural network precision of prediction;RBF (RBF, Radical Basic Function) it is a kind of hyperspace interpolation technique, the same BP neural network of structure, basic thought is as hidden unit with RBF " base " constitutes implicit sheaf space, and hidden layer enters line translation to input vector, and it is empty that the pattern input data of low-dimensional is transformed into higher-dimension In, make the linear separability in higher dimensional space of the nonlinear problem in lower dimensional space, spreading coefficient SPREAD selection is to knot Fruit has certain influence.
For testing model precision, model predication value and measured value are subjected to regression fit, using the general coefficient of determination (R2), root-mean-square error (RMSE), relative error (RE) verify model accuracy.
2 results and analysis
The correlation of 2.1 Apple Leaves chlorophyll contents and original spectrum and first derivative spectrum
Correlation analysis is carried out with Apple Leaves chlorophyll content to original spectrum and first derivative spectrum at each wavelength (Fig. 1), it can be seen that Apple Leaves chlorophyll and original spectrum reflectivity are in 0.01 pole in 400nm~760nm wave-length coverages It is significantly correlated, since coefficient correlation after 700nm reduce, to 810nm at coefficient correlation close to 0, i.e., from ripple later 810nm Section hardly reflects chlorophyll information;Coefficient correlation is between -0.8 in 520nm~620nm, 695nm~725nm wave-length coverages Between~-0.9, maximum is reached at 554nm, is 0.899.Apple Leaves chlorophyll content exists with the first derivative spectra Extremely notable negative correlation is reached in 435nm~550nm, 675nm~710nm wave-length coverages, 555nm~670nm, 715nm~ Reach extremely notable positive correlation in 890nm wavelength bands, after 890nm in wavelength band coefficient correlation be gradually reduced and fluctuate compared with Greatly, wherein 575nm~585nm, coefficient correlation is higher than 0.9 in 725nm~765nm wavelength bands, and maximum is reached at 733nm Value, is 0.921.Compared with primary light spectrum, first derivative spectrum value and chlorophyll content correlation are higher.
The 2.2 Apple Leaves chlorophyll content single argument appraising models based on Red-edge parameter
Corresponding Red-edge parameter is extracted from the first derivative spectra of original spectrum.These Red-edge parameters and plant it is various Physical and chemical parameter is closely related, and the factor such as chlorophyll content, vegetation coverage, canopy structure, leaf area index, biomass is all The change of Red edge position and amplitude can be caused, the present invention only does related divide to the chlorophyll content of blade aspect with Red-edge parameter Analysis, as a result as shown in table 2.
Coefficient correlation between the Red-edge parameter of table 2 and Apple Leaves chlorophyll content
Table2 Correlation coefficients between red edge parameter and chlorophyll content of apple leaf
* represents that correlation reaches the pole level of signifiance
indicates high significance at 0.01 level
From table 2, the correlation of Apple Leaves chlorophyll content and five kinds of Red-edge parameters reaches the pole level of signifiance. The more commonly used Red edge position, it is red in amplitude, it is red while three parameters of area in, Red edge position with chlorophyll content horizontal relationship most To be close, coefficient correlation reaches 0.799, and it is red in amplitude and it is red while area coefficient correlation it is relatively low, this and previous karyotype studies one Cause.It is that, in order to preferably describe the distribution of crest, the degree of bias is reflection data distribution pair to introduce coefficient of kurtosis and the coefficient of skewness The statistic of title property, kurtosis is the statistic for the intensity for reflecting data near average, and coefficient of kurtosis is same with the coefficient of skewness Chlorophyll content in leaf blades is in extremely notable positive correlation, and it is feasible that chlorophyll content appraising model is set up with this.By comparing, with Correlation level is foundation, selection Red edge position, coefficient of kurtosis and coefficient of skewness inverting chlorophyll content in leaf blades, sets up single argument Linear processes chlorophyll content appraising model.
Apple Leaves chlorophyll content single argument estimation models and assay of the table 3 based on Red-edge parameter
Table 3 Estimation models and test results of single variable for chlorophyll content in apple leaf based on red edge parameter
Institute's established model and its precision such as table 3, all model coefficient correlations of foundation are all higher than 0.7, correlation considerably beyond The confidential interval upper limit, reaches extremely significantly correlated level.The model set up based on Red edge position, coefficient correlation is led to more than 0.8 The error and the result of comparison model are crossed, it is larger and root-mean-square error and relative error are smaller for standard with coefficient correlation, it is many Although a formula model coefficient correlation is maximum, error is also very big, so the advantage of unitary linear model and logarithmic model is bigger;And The result error is more than modeling error, illustrates that the suitability of model has much room for improvement.Set up based on coefficient of kurtosis and the coefficient of skewness Model (because coefficient of kurtosis and coefficient of skewness part trend data contain null value, therefore logarithm and power function model can not be set up), phase Relation number reached between 0.7-0.8, it is extremely significantly correlated, wherein, model and the result of the multinomial model in foundation In all behave oneself best, and the result coefficient correlation and error level all close to modeling accuracy, illustrate that model stability is preferable. Overall apparently the model set up based on the coefficient of skewness is behaved oneself best, and accuracy is higher than other two Red-edge parameters, and the result Coefficient correlation is more than 0.86, and error is also minimum, and Model suitability is good.From coefficient of skewness inverting Apple Leaves leaf The multinomial inverse model (Fig. 2) of chlorophyll contents, is verified to model, comparison such as Fig. 3 of measured value and predicted value, equation Regression coefficient reaches 0.8598, and the coefficient of determination is 0.8715, and both correlations are high.
The 2.3 Apple Leaves chlorophyll content estimations based on BP neural network
The present invention sets up BP neural network using MATLAB 11.0, and output layer is Apple Leaves chlorophyll content, input layer For Red edge position, coefficient of kurtosis and the coefficient of skewness.BP neural network is trained using training data, makes network that there is predictive ability, The plan of BP neural network is analyzed with the model prediction output valve trained, and by comparison model prediction output and desired output Conjunction ability.Influence of the node in hidden layer, network type of BP neural network to model accuracy is very big, and table 4 and table 5 are respectively not With the precision and assay of nodes and network classification estimation models.
The different node in hidden layer BP neural network estimation models of table 4 and assay
Table 4 Estimation models and test results of BP neural network model with different node of hidden layer
As can be seen from Table 4, the precision of BP neural network increases afterwards as the increase of node in hidden layer presents first to reduce Trend, when nodes are 5, the coefficient of determination of model is maximum, and error is minimum, and the result accuracy is high, and model performance is steady It is fixed.
The heterogeneous networks classification BP neural network estimation models of table 5 and assay
Table 4 Estimation models and test results of BP neural network model with different network type
As can be seen from Table 5, the more single hidden layer BP neural network of double hidden layer BP neural networks, the coefficient of determination is improved, Relative error and root-mean-square error reduce, and precision of prediction increases, but amplitude is little.Contrast nodes for 4 and 5 it is double implicit Layer estimation models, consider from neural network accuracy and on the training time, and nodes behave oneself best for 4 double hidden layer models, and The result Stability and veracity is all very high, is optimal BP neural network Apple Leaves chlorophyll content estimation models.With This model is estimated that the relation (Fig. 4) between predicted value and measured value is fine in each value area prediction effect, is a kind of leaf The effective ways of green plain lossless estimation.
The 1.5 Apple Leaves chlorophyll content appraising models based on RBF neural
RBF neural is built using the newrbe functions in MATLAB 11.0, Apple Leaves chlorophyll content is as defeated Outgoing vector, Red edge position, coefficient of kurtosis, the coefficient of skewness are as output vector, and spreading coefficient SPREAD values are set to acquiescence, use RBF Neural network model studies the inverting relation of Red-edge parameter and chlorophyll content.Drawn by model construction, training and inspection As a result, the training pattern coefficient of determination is 0.943, and relative error is 4.41%, and root-mean-square error is 2.825, and testing model is determined Coefficient is 0.909, and root-mean-square error is 2.500, and relative error is 4.25%, has higher stability than BP neural network. Be less than the general principle of the typical range between input vector according to SPREAD values, determine SPREAD values should be set to [0, 1] between, the RBF neural network model estimation result such as table 6 of different SPREAD values.
The lower RBF neural estimation models of the difference SPREAD of table 6 values and assay
Table 4 Estimation models and test results of RBF neural network model with different SPREAD value
As can be seen from Table 6, SPREAD values are smaller, coefficient of determination increase, and root-mean-square error and relative error gradually subtract Small, the model of foundation is more accurate;But when SPREAD values are less than after 0.6, the result precise decreasing illustrates that network performance becomes Difference, occurred in that adaptation, so determining when SPREAD values are 0.6, the RBF neural of foundation is estimation Apple Leaves The best model of chlorophyll content, the coefficient of determination reaches 0.955, and side is 2.517 with error, and relative error is 3.69%, and Prediction effect accuracy is high, and model stability is good.Fig. 5 is that the optimal Apple Leaves chlorophyll content based on RBF drawn out is estimated Survey the 1 of model predication value and measured value:1 graph of a relation, comparison diagram 3 and Fig. 4 are visible, compared with conventional model and BP neural network model, RBF network degrees of fitting are higher, and with speed faster, the characteristics of algorithm is easy.
2 discuss
By analyzing related pass between Apple Leaves original spectrum and first derivative spectrum and chlorophyll content in the present invention System, first derivative spectrum correlation is higher than original spectrum, consistent with previous karyotype studies, analyzes its reason, it may be possible to utilize micro- Point technology reduces the influence of background noise, therefore the correlation of differential smoothing and vegetation Physiological And Biochemical Parameters is more preferable.From differential light The Red edge position that is extracted in spectrum, it is red in amplitude, it is red while three parameters of area in, Red edge position with chlorophyll content horizontal relationship most To be close, red side is the most distinctive marks of plant spectral, when chlorophyll content increase, and Red edge position can be inclined to long wave direction Move, when chlorophyll content is reduced, Red edge position then changes round about, Red edge position is red side regional change most fast ripple Section, thus Red edge position it is redder in amplitude and it is red while area it is more sensitive to chlorophyll content reacting condition, be a kind of effective Chlorophyll content indicates parameter.
Introduce the chlorophyll content appraising model stability and precision of the two parameters foundation of coefficient of kurtosis and the coefficient of skewness all Higher than the model set up based on Red edge position, it may be possible to by the information content that coefficient of kurtosis and the coefficient of skewness are included is bigger.Cause The overall variation of spectral shape in the range of red side can be embodied in itself for coefficient of kurtosis and the coefficient of skewness, and spectral shape changes Just because of caused by the change of chlorophyll content, so coefficient of kurtosis and the coefficient of skewness can also be used as estimation leaf chlorophyll The parameter of content.Multinomial model is better than other models in institute's established model, and this is probably due to every Red-edge parameter and chlorophyll More complicated non-linear relation is there is between content, linear relationship is difficult to reflection, and it is essential.
Artificial neural network is a kind of effective means for handling complex nonlinear problem, high, non-linear with concurrency Mapping ability is strong, self-learning capability and the features such as strong adaptive ability so that neutral net has very strong unascertained information Disposal ability.It is of the invention to be found by analyzing two kinds of artificial nerve network models of BP and RBF compared with traditional univariate model, Neural network model has higher Stability and veracity, and can solve the problem that while there are multiple independents variable and multiple because becoming The problem of amount, a kind of feasible method for estimating chlorophyll content in leaf blades can be used as.BP neural network algorithm is substantially control The difference of reality output and desired output, is repeated using input sample forward-propagating and error back propagation this process, right A kind of supervised learning algorithm that each layer connection weight of network and the threshold value of each node are successively adjusted from the front to the back.So BP is neural Network performance depends on primary condition, and convergence rate is slow, and less stable, learning process is easily absorbed in local minimum, and randomness By force, BP neural network precision is made to be affected.And RBF networks overcome the shortcoming of feedforward neural network (such as BP neural network), It should determine that, exported independent of the good characteristic such as initial weight and pace of learning be fast with Adaptation of structure, can be at utmost Ground approaches actual measured value.But at the same time it is noted that adjusting SPREAD values and network structure, in order to avoid cause over-fitting.
3 conclusions
The present invention using apple in Shaanxi province as subjects, to Apple Leaves original spectrum reflectivity, first derivative spectrum and Its Red-edge parameter has carried out correlation analysis with chlorophyll content, sets up traditional single argument regression model based on Red-edge parameter, uses Red edge position, coefficient of kurtosis, the coefficient of skewness set up chlorophyll content BP neural network model and RBF network appraising models, and compare The precision of more several models, draws to draw a conclusion:
(1) original spectrum is compared, first derivative spectrum and chlorophyll content correlation are higher, and maximum is reached at 733nm Value 0.921;In Apple Leaves Red-edge parameter, Red edge position, coefficient of kurtosis and the coefficient of skewness and chlorophyll content correlation compared with Good, the coefficient of determination is above 0.7.
(2) simulation precision of multinomial model is most in the single argument regression model that Red-edge parameter and chlorophyll content are set up Height, by comparing, the multinomial model set up based on the coefficient of skewness is the best-estimated model, and the result coefficient of determination is 0.872, root-mean-square error is 4.631, and relative error is 8.81%.
(3) BP neural network and RBF nerve nets are built using Red edge position, coefficient of kurtosis and the coefficient of skewness as input variable Two kinds of models of network carry out inverting to Apple Leaves chlorophyll content, and model accuracy is higher than traditional single argument regression model;After optimization The RBF neural network model the result coefficient of determination be 0.939, root-mean-square error is 2.009, and relative error is 3.44%, Pace of learning is fast, precision is high, and fitting result is reliable, is the best model for estimating Apple Leaves chlorophyll content.
The foregoing is only a preferred embodiment of the present invention, protection scope of the present invention not limited to this, any ripe Those skilled in the art are known in the technical scope of present disclosure, the letter for the technical scheme that can be become apparent to Altered or equivalence replacement are each fallen within protection scope of the present invention.

Claims (5)

1. a kind of Apple Leaves chlorophyll remote sensing estimation method, it is characterised in that comprise the following steps:
Step 1, spectroscopic data are determined
Blade is carried out using the portable bloom spectrometer of U.S.'s SCVHR 1024i types to diffuse the measure of modal data;Spectrometer is surveyed Fixed wave-length coverage is 350~2500nm, and port number is 1024, wherein 350~1000nm intervals spectral resolution is 1.4nm, 1000~1850nm interval spectral resolution are 3.8nm, and 1850~2500nm intervals spectral resolution is 2.4nm;Survey Fixed work is carried out indoors, is carried out every time before sample spectra measure, and instrumental correction, every group of blade are carried out using diffusing reflection reference plate 1 leaf is selected, first blade face is cleaned;Then spectroscopic assay is carried out;Each point, which is determined 2 times, averages as the light Measured value is composed, each blade takes 3~5 points, finally takes the average value of each point as the spectral value of the blade;
Step 2, measuring chlorophyll content
The synchronous relative chlorophyll to Apple Leaves of SPAD502 chlorophyll meters produced using Japanese KONICA MINOLTA companies Content carries out nondestructive measurement;10 SPAD values of measure on every leaf diverse location, the SPAD values averaged as the leaf, The chlorophyll content of the blade is represented, the SPAD values of 500 blades are obtained altogether;
Step 3, data processing
The processing software ViewSpec Pro 6.0 carried before data analysis using spectrometer are by the Apple Leaves spectrum of measure Data carry out resampling, and the setting sampling interval is 1nm;Spectroscopic data is located in advance using Savitzky-Golay smothing filterings Reason, it is 5 to set smooth points, and the first derivative spectra is tried to achieve by original spectrum, and the red side of blade is extracted from the first derivative spectra Parameter;
Step 4, model construction and accuracy test
Using unitary is linear, index, logarithm, multinomial and power function build the general of chlorophyll content in leaf blades and items Red-edge parameter Logical regression model, the selection Red-edge parameter that correlation is good, precision is high builds chlorophyll content appraising model as independent variable;Discriminate The Red-edge parameter selected builds the artificial nerve network model based on Red-edge parameter as the input vector of artificial neural network.
2. Apple Leaves chlorophyll remote sensing estimation method according to claim 1, it is characterised in that in step 3, blade Red-edge parameter, including Red edge position, it is red in amplitude, it is red while area, coefficient of kurtosis and the coefficient of skewness.
3. Apple Leaves chlorophyll remote sensing estimation method according to claim 1, it is characterised in that in step 3, altogether selection 286 groups of spectroscopic datas therein and SPAD values are analyzed and researched;In modeling process, the random screening 236 in 286 groups of data Group is used to model, and another 50 groups are used to verify.
4. Apple Leaves chlorophyll remote sensing estimation method according to claim 1, it is characterised in that in step 4, artificial god Two kinds of BP neural network and RBF neural are selected through network.
5. Apple Leaves chlorophyll remote sensing estimation method according to claim 1, it is characterised in that in step 4, to examine Model accuracy, carries out regression fit, using general coefficient of determination R by model predication value and measured value2, root-mean-square error RMSE, relative error RE verify the accuracy of model.
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