A kind of adaptive Gauss low-pass filtering algorithm for organic matter in black soil information extraction
Technical field
The invention belongs to information extraction technology fields, and in particular to a kind of for the adaptive of organic matter in black soil information extraction
Gassian low-pass filter algorithm.
Background technique
China's black soil of Northeast China is rich in organic matter, and introducing Airborne Hyperspectral data can provide for Scientific evaluation black earth geological measuring
New technological means.In the organic matter in black soil content identification based on high-spectral data, spectroscopic data is interpreted as reflection black earth
The energy profile of component content target electromagnetic radiation characteristic, this processing merely depict the Spectral Properties of atural object Energy distribution
Property, it is a kind of method of black earth list Pixel Analysis, the black earth Limited information that can be extracted.It is passed to grasp remote sensing optical system information
Rule is passed, from the frequency domain channel matrix derivation of remote sensing optical system, imaging system frequency domain is believed from the angle analysis of frequency domain
It ceases Transfer Parameters and carries out numerical value calculating, research achievement plays reference role to the design of remote sensing optical system.
Conventional method is to carry out the characterization of the energy expression of blackland pixel spectrum and frequency-domain spectrum energy to separate place
Original spectral data cannot be redistributed to another space, can not reflect the change of energy in spatial domain picture by reason, this processing
Law, so that the space characteristics such as the tone of black earth, texture, trend and boundary fail to participate in soil property assessment, assessment knot
Fruit is often not a comprehensive black earth characteristic set, limits the precision of organic matter in black soil information extraction.
Therefore, there is an urgent need on the basis of analyzing black earth spectrum signature, design a kind of adaptive Gauss low-pass filtering calculation
Method achievees the purpose that blackland classification classification by gradually excluding the data of different-energy grade.Joint blackland EO-1 hyperion picture
Member spatial context information and spectral information classify to EO-1 hyperion pixel, break through image spatial information break through tradition by
The performance bottleneck of pixel spectra classification, charts for organic matter in black soil and provides support, with a wide range of precise to solve existing method
Drawback.
Summary of the invention
It is a kind of for the adaptive of organic matter in black soil information extraction the purpose of the present invention is in view of the drawbacks of the prior art, providing
Answer Gassian low-pass filter algorithm.
The technical scheme is that
A kind of adaptive Gauss low-pass filtering algorithm for organic matter in black soil information extraction, comprising the following steps:
Step 1: blackland EO-1 hyperion pre-processes;
Radiant correction locates high-spectral data using the FLAASH algorithm based on MODTRAN4+ radiative transfer model in advance
Reason.Needed when calculating metadata include observation field angle, sun angle, sea level on the average, Atmospheric models, aerosol type and
Visibility range;Geometric correction realizes that inertial navigation system and positioning system have recorded each on machine using airborne 510 system of POS
The location parameter X, Y, Z and attitude parameter Roll, Pitch, Heading of pixel will be sat by the GPS time of each frame image
Mark is assigned to the picture dot;
Step 2: frequency domain converts;
Original blackland high-spectral data is subjected to frequency domain conversion, generates frequency domain data;
Step 3: adaptive Gaussian mixture model;
In conjunction with the interpolated data of organic prime number evidence known in black earth geographical space, the gaussian filtering that design can be adaptive
Device, so that selecting different σ on the basis of retaining black earth image local feature, realizing the classification of original image;This process
In, it is constantly compared with ground analysis data, interative computation, is required until meeting classification;
Step 4: grading extraction;
A kind of adaptive Gauss low-pass filtering algorithm is designed, by gradually excluding the data of different-energy grade, is realized black
The purpose of soil content of organic matter classification classification;
Step 5: organic matter extracts result;
The organic matter of each rank content is subjected to composite mapping, the Airborne Hyperspectral for forming the content of organic matter extracts knot
Fruit;By overall accuracy and the highest parameter setting σ of Kappa coefficient1=0.5, ε1=1.1 are applied to the operation of blackland organic matter
In, after classification, according to Ground analysis data, the content of organic matter of each rank is provided, obtains the sky of organic matter in black soil content
Between distribution situation.
The step 1 the following steps are included:
Step 1.1 radiant correction
Calculate the received pixel spectral radiance at bloom spectrum sensor:
In formula, L is the received global radiation brightness of sensor;ρ is pixel surface reflectivity;ρeFor average surface around pixel
Reflectivity;S is atmosphere spherical albedo;LαFor atmospheric backscatter radiance;A, B is the coefficient of atmosphere and geometrical condition;Side
The mechanism of method is using the atmospheric radiation transmission based on MODTRAN4+;
Step 1.2 geometric correction
The GPS time that each frame image is had recorded in original image generates a time tag after radiant correction
File * .att file is recorded, the GPS time of each frame image is had recorded in this document, which is included in POS system
In the period of destination file, by the time compare and coordinate projection transformation be obtained with each frame image attitude data and
Position data carries out geometric correction to image;
The step 2 the following steps are included:
Step 2.1 establishes basic Filtering Model
In frequency domain, basic Filtering Model are as follows:
G (u, v)=H (u, v) F (u, v)
In formula, F (u, v) is the Fourier transformation image filtered;H (u, v) is filter transform function;After decaying
Smoothed out image G (u, v) is generated after high-frequency information.
The foundation of step 2.2 gauss low frequency filter
Transform of spatial domain can be turned to the gauss low frequency filter of frequency domain are as follows:
In formula, D (u, v) is the distance away from transformation origin, and d is the degree of Gaussian curve extension, i.e. cutoff frequency.Design one
Kind adaptive Gaussian mixture model device automatically selects different d according to the black earth content characteristics for being smoothed image, so that after treatment
Result images in obtain the organic matter data of corresponding content.
The step 3 the following steps are included:
The expression of step 3.1 Gaussian smoothing
Assuming that the Gaussian smoothing of black earth image is indicated with following formula:
I0(x, y)=Id(x,y)+ed(x,y)
In formula, for the pixel at (x, y), I0(x, y) is the gray value of original high-spectral data, Id(x, y) is cut-off
Low pass gray value under frequency d, εd(x, y) is the residual values under cutoff frequency d.
Step 3.2 realizes process from the algorithm for being suitable for gaussian filtering
Input: black earth Hyperspectral imaging x=(x1,x2,…,xi)∈Rd×i, filtering content of organic matter rank C ∈ (1,2,3,
4,5), black earth image classification set ξ={ 1,2 ..., n }, training set Tm={ (x1,c1),…,(xm,cm)}∈(Rd×ξ)m,
In, c ∈ ξ and m represent the quantity of training sample;
A): input training set constructs gauss low frequency filter, carries out classification pixel-by-pixel to EO-1 hyperion black earth image and obtains just
Beginning classification results c;
B): being face domain information by ground chemical examination data interpolating, be as a result expressed as class probability graph ξn, n=1,2 ..., N;
C): initial cutoff frequency d is carried out to Hyperspectral imaging x1It calculates, obtains initial variance σ1With residual values ε1;
D): if d1=dbest then
E): extracted information meets a certain rank content of organic matter section, then is denoted as c1
F): end
G): else
H): d1'=d1++;
I): initial cutoff frequency d is carried out to Hyperspectral imaging x1' calculate, obtain new variances sigma1' and residual values ε1';
J): until, extracted information meets a certain rank content of organic matter section, then is denoted as c1;
K): inverse transformation being carried out to high-spectral data x, removes respective pixel in airspace, generates x ';
L): end
M): initial cutoff frequency d is carried out to Hyperspectral imaging x '2It calculates, obtains initial variance σ2With residual values ε2;
N): d~m step is repeated, until generating c1、c2、c3、c4And c5
Output: content of organic matter classification results c=(c1,c2,…,ci), each pixel i is endowed one in classification results
A label ci∈ξ
The step 4 the following steps are included:
Step 4.1 calculates cutoff frequency d
Design a kind of method for calculating cutoff frequency d, reach can smooth black earth high-spectral data realize classification classification and
It is able to maintain the purpose closest with laboratory values.
Design a kind of calculation method based on energy function:
In formula, c is constant term, is determined according to the organic matter analysis data of sampled point;σ is variance;ε is residual values.
Step 4.2 smoothsort and details keep principle
It obtains, in the case where c is known constant item, optimal cutoff frequency d needs variances sigma as big as possible, and high-spectral data is become
It is changed to more smooth data.And residual epsilon must as small as possible, i.e., the reflection after gaussian filtering, at original pixels (x, y)
Rate value amplitude of variation is the smaller the better.In this way, establishing a kind of synthesis gaussian filtering method in the factor content of organic matter, reach
Smoothsort and the balance for keeping minutia.
The beneficial effects of the present invention are:
First is that adaptive Gauss low-pass filtering algorithm not only makes smooth region pixel classifications precision improvement, while making score
Field content of organic matter edge detection in grade result is more accurate.Plot smothing filtering can effectively combine the space of image
With spectral information, on the basis of effectively removing salt-pepper noise caused by similar conventional sorting methods, so that black earth in classification results
The profile on ground and true blackland plot profile are almost the same;
Second is that compared to traditional hyperspectral classification algorithm, this chapter propose frequency domain and extraction algorithm computational efficiency compared with
Height can quickly calculate the result data of each grade after clear content of organic matter grade;Frequency domain method is from new angle
High-spectral data is described and is characterized, on the basis of solution high-spectral data is uncertain, this following method may energy
The restraining factors such as traditional atmospheric correction and radiant correction are enough broken through, completely new method is brought.
Specific embodiment
The present invention is further introduced below with reference to embodiment:
Spatially and spectrally information reference data can will be used as simultaneously to realize in the classification of black earth Hyperspectral Image Classification
The adaptive Gauss low-pass filtering algorithm (Adv of organic matter in black soil content information is added in frequency domain combining classifiers for target
Gauss filter)。
The core concept of the algorithm is that one of foundation can carry out energy conversion to high spectrum image, realizes that energy is low
The Gaussian low pass wave pattern for just extracting (or excluding) reach black by gradually excluding the data of different-energy grade
The purpose of land classification classification.When Gauss model is smoothed image, Gaussian function determines filtering by calculating variances sigma
As a result.In conjunction with the interpolated data of organic prime number evidence known in black earth geographical space, the Gaussian filter that design can be adaptive makes
It obtains on the basis of retaining black earth image local feature, selects different σ, realize the classification of original image.
A kind of adaptive Gauss low-pass filtering algorithm for organic matter in black soil information extraction, comprising the following steps:
Step 1: blackland EO-1 hyperion pre-processes;
Radiant correction locates high-spectral data using the FLAASH algorithm based on MODTRAN4+ radiative transfer model in advance
Reason.Needed when calculating metadata include observation field angle, sun angle, sea level on the average, Atmospheric models, aerosol type and
Visibility range;Geometric correction realizes that inertial navigation system and positioning system have recorded each on machine using airborne 510 system of POS
The location parameter X, Y, Z and attitude parameter Roll, Pitch, Heading of pixel will be sat by the GPS time of each frame image
Mark is assigned to the picture dot;
Step 2: frequency domain converts;
Original blackland high-spectral data is subjected to frequency domain conversion, generates frequency domain data;
Step 3: adaptive Gaussian mixture model;
In conjunction with the interpolated data of organic prime number evidence known in black earth geographical space, the gaussian filtering that design can be adaptive
Device, so that selecting different σ on the basis of retaining black earth image local feature, realizing the classification of original image;This process
In, it is constantly compared with ground analysis data, interative computation, is required until meeting classification;
Step 4: grading extraction;
A kind of adaptive Gauss low-pass filtering algorithm is designed, by gradually excluding the data of different-energy grade, is realized black
The purpose of soil content of organic matter classification classification;
Step 5: organic matter extracts result;
The organic matter of each rank content is subjected to composite mapping, the Airborne Hyperspectral for forming the content of organic matter extracts knot
Fruit;By overall accuracy and the highest parameter setting σ of Kappa coefficient1=0.5, ε1=1.1 are applied to the operation of blackland organic matter
In, after classification, according to Ground analysis data, the content of organic matter of each rank is provided, obtains the sky of organic matter in black soil content
Between distribution situation.
The step 1 the following steps are included:
Step 1.1 radiant correction
Calculate the received pixel spectral radiance at bloom spectrum sensor:
In formula, L is the received global radiation brightness of sensor;ρ is pixel surface reflectivity;ρeFor average surface around pixel
Reflectivity;S is atmosphere spherical albedo;LαFor atmospheric backscatter radiance;A, B is the coefficient of atmosphere and geometrical condition;Side
The mechanism of method is using the atmospheric radiation transmission based on MODTRAN4+;
Step 1.2 geometric correction
The GPS time that each frame image is had recorded in original image generates a time tag after radiant correction
File * .att file is recorded, the GPS time of each frame image is had recorded in this document, which is included in POS system
In the period of destination file, by the time compare and coordinate projection transformation be obtained with each frame image attitude data and
Position data carries out geometric correction to image;
The step 2 the following steps are included:
Step 2.1 establishes basic Filtering Model
In frequency domain, basic Filtering Model are as follows:
G (u, v)=H (u, v) F (u, v)
In formula, F (u, v) is the Fourier transformation image filtered;H (u, v) is filter transform function;After decaying
Smoothed out image G (u, v) is generated after high-frequency information.
The foundation of step 2.2 gauss low frequency filter
Transform of spatial domain can be turned to the gauss low frequency filter of frequency domain are as follows:
In formula, D (u, v) is the distance away from transformation origin, and d is the degree of Gaussian curve extension, i.e. cutoff frequency.Design one
Kind adaptive Gaussian mixture model device automatically selects different d according to the black earth content characteristics for being smoothed image, so that after treatment
Result images in obtain the organic matter data of corresponding content.
The step 3 the following steps are included:
The expression of step 3.1 Gaussian smoothing
Assuming that the Gaussian smoothing of black earth image is indicated with following formula:
I0(x, y)=Id(x,y)+ed(x,y)
In formula, for the pixel at (x, y), I0(x, y) is the gray value of original high-spectral data, Id(x, y) is cut-off
Low pass gray value under frequency d, εd(x, y) is the residual values under cutoff frequency d.
Step 3.2 realizes process from the algorithm for being suitable for gaussian filtering
Input: black earth Hyperspectral imaging x=(x1,x2,…,xi)∈Rd×i, filtering content of organic matter rank C ∈ (1,2,3,
4,5), black earth image classification set ξ={ 1,2 ..., n }, training set Tm={ (x1,c1),…,(xm,cm)}∈(Rd×ξ)m,
In, c ∈ ξ and m represent the quantity of training sample;
A): input training set constructs gauss low frequency filter, carries out classification pixel-by-pixel to EO-1 hyperion black earth image and obtains just
Beginning classification results c;
B): being face domain information by ground chemical examination data interpolating, be as a result expressed as class probability graph ξn, n=1,2 ..., N;
C): initial cutoff frequency d is carried out to Hyperspectral imaging x1It calculates, obtains initial variance σ1With residual values ε1;
D): if d1=dbest then
E): extracted information meets a certain rank content of organic matter section, then is denoted as c1
F): end
G): else
H): d1'=d1++;
I): initial cutoff frequency d is carried out to Hyperspectral imaging x1' calculate, obtain new variances sigma1' and residual values ε1';
J): until, extracted information meets a certain rank content of organic matter section, then is denoted as c1;
K): inverse transformation being carried out to high-spectral data x, removes respective pixel in airspace, generates x ';
L): end
M): initial cutoff frequency d is carried out to Hyperspectral imaging x '2It calculates, obtains initial variance σ2With residual values ε2;
N): d~m step is repeated, until generating c1、c2、c3、c4And c5
Output: content of organic matter classification results c=(c1,c2,…,ci), each pixel i is endowed one in classification results
A label ci∈ξ
The step 4 the following steps are included:
Step 4.1 calculates cutoff frequency d
Design a kind of method for calculating cutoff frequency d, reach can smooth black earth high-spectral data realize classification classification and
It is able to maintain the purpose closest with laboratory values.
Design a kind of calculation method based on energy function:
In formula, c is constant term, is determined according to the organic matter analysis data of sampled point;σ is variance;ε is residual values.
Step 4.2 smoothsort and details keep principle
It obtains, in the case where c is known constant item, optimal cutoff frequency d needs variances sigma as big as possible, and high-spectral data is become
It is changed to more smooth data.And residual epsilon must as small as possible, i.e., the reflection after gaussian filtering, at original pixels (x, y)
Rate value amplitude of variation is the smaller the better.In this way, establishing a kind of synthesis gaussian filtering method in the factor content of organic matter, reach
Smoothsort and the balance for keeping minutia.