CN115019189A - Hyperspectral image change detection method based on NSST hidden Markov forest model - Google Patents
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Abstract
The invention discloses a hyperspectral image change detection method based on an NSST hidden Markov forest model, wherein the proposed three-dimensional hidden Markov forest model makes full use of the multidirectional correlation of HS images and improves the precision of the model; the accurate description of the space-spectrum information among the HS coefficients is realized by establishing a mixed Gaussian model, the strong correlation among the HS wave bands is fully utilized, the low-frequency sub-band space change information is referred to, the correlation between the high-frequency space sub-bands and the spectrum wave bands is combined, the transfer relation of the multi-time-phase hyperspectral image is further defined, the transfer relation and the correlation of the hidden state among time items are fully considered, the change condition of the ground features can be more accurately judged, and more precise ground surface change information is obtained.
Description
Technical Field
The invention relates to the field of hyperspectral remote sensing image processing, in particular to a hyperspectral image change detection method based on a NSST (Nonsubsampled shear wave Transform, NSST) Hidden Markov Forest model (HMF).
Background
In recent years, with the rapid development of Hyperspectral (HS) remote sensing technology and the continuous improvement of the demand for fine detection of surface changes, change detection technology based on Hyperspectral images is gradually emphasized and urgently needed for practical application. The multi-temporal hyperspectral image statistical model based on statistical modeling realizes the mining of the variation attribute by statistically modeling the pixel amplitude of the hyperspectral image or the difference image amplitude of the hyperspectral image. In the method, how to obtain a proper difference image, how to determine an accurate probability density statistical model and estimate parameters thereof, and how to improve the accuracy of change detection by using the correlation between pixels, the transfer characteristics and the like have yet to be deeply researched.
The traditional remote sensing spectrum image change detection method based on the statistical modeling theory is to determine the amplitude of a difference image by analyzing difference information among multi-temporal remote sensing images and further determine a proper threshold value to determine a change area. For example, the polar coordinate-based change vector analysis algorithm is to fit a difference image change region and a constant region respectively by using gaussian distributions with larger variance and smaller variance in mixed gaussian distributions, and then to determine the change region by applying bayesian theory. Rayleigh-Rice (RR) change detection algorithm theoretically analyzes probability distribution functions of a change region and a non-change region of the multi-temporal multispectral image difference image, RR distribution is adopted to fit the change region and the non-change region, and on the basis, the change detection process is realized by estimating model parameters by using an EM algorithm. At present, remote sensing image change detection methods based on statistical theory mostly aim at multispectral images, and probability density distribution of the multispectral images is used as prior distribution.
The hyperspectral image has more precise spectrum description and higher sparsity, so that statistical characteristics different from those of the multispectral image can be presented generally, meanwhile, strong correlation exists between multi-time-phase hyperspectral image spectrums in time, and researches on pixel distribution characteristics, difference image distribution characteristics and coefficient distribution characteristics under a transform domain are few. The existing method only analyzes the statistical characteristics of the pixel amplitude value generally, ignores the correlation of the generalized neighborhood, and is a very significant problem how to fully mine the correlation characteristics of the hyperspectral image and apply the correlation characteristics to the change detection of the hyperspectral image, so that the detection accuracy is improved and the algorithm efficiency is high.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides a hyperspectral image change detection method based on an NSST hidden Markov forest model.
The technical solution of the invention is as follows: a hyperspectral image change detection method based on an NSST hidden Markov forest model is carried out according to the following steps:
step 1, inputting a hyperspectral image H of T1 and T2 time phases T1 And H T2 The size is M × N × B, where M × N is the spatial size of each band image, and B is the number of bands;
step 2, for H T1 And H T2 Each wave band imageAndperforming non-down sampling shear wave transformation of Q scale with K directional sub-bands in each scale to obtainOf the low frequency sub-bandAnd high frequency sub-bandsOf the low frequency sub-bandAnd high frequency sub-bandsThe k is as{1,2,…,K};
Step 3, obtaining a low-frequency sub-band change detection graph CD by using a change vector analysis method L
Step 3.1 according to the formula (1), calculating a two-time phase hyperspectral image H T1 And H T2 Difference in total gray level of low frequency information | | Δ X therebetween L ||:
The i belongs to {1, 2, 3, …, M }, the j belongs to {1, 2, 3, …, N }, and the delta X belongs to {1, 2, 3, …, M }, the j belongs to {1, 2, 3, …, N }, the value of the delta X belongs to the field of the communication technology L (i, j) represents a two-time phase low frequency subband information gray scale difference value at the coordinate (i, j),andcoefficient values representing the low frequency subbands at the band b of the hyperspectral images T1 and T2 at coordinates (i, j), respectively;
step 3.2 according to formula (2), utilize total gray level difference | | Δ X L I and beta L Calculating to obtain a low-frequency sub-band transformation detection graph CD L :
Beta is the same as L Indicating the threshold, CD, determined by Otsu method L (i, j) is a low frequency subband change detection result value located at the coordinate (i, j);
step 4, constructing T1 and T2 time-phase high-frequency direction sub-bandsAndhidden Markov forest modelThe device is used for carrying out probability state amplitude modulation on the high-frequency subband coefficient;
step 4.1 according to the definition of formula (3), constructing general time phase T high-frequency direction sub-bandSet of hidden markov forest model parameters
The meaning of the parameters is as follows:
m and n are hidden states, the values of the hidden states are 1 or 0, and the hidden states represent changed states and unchanged states respectively;
high-frequency direction subband coefficients which are T time phase, b wave band, Q scale and k direction point (i, j) position;
is the root coefficient of sub-band in T time phase, b wave band, Q scale and k directionThe state probability of (2);
coefficient of T time phase, b-1 wave band, Q scale, k direction sub-band (i, j) positionProbability of state of (2), saidAnd divided into space dimensional state probabilitiesAnd spectral dimension state probabilityThe above-mentionedIs the sub-band coefficient of T time phase, b wave band, Q scale and k directionIs used to determine the spatial dimension parent coefficientProbability of state of (2), saidIs the sub-band coefficient of T time phase, b wave band, Q scale and k directionSpectral wiid ofThe state probability of (2);
is a T-phase space dimensional state transition probability, whereinTo representThe parent coefficients of the same (j, j) position in the previous dimension,the expression of (c) is:
the meaning is that in the k direction sub-band of the b wave band at the T phase, the parent coefficientHidden state variable ofWhen the value of (c) is equal to m or n, the child coefficientHidden state variable of (2)A conditional probability equal to m or n;
is the spectral dimension state transition probability;andsub-bands in T time phase, b wave band, Q scale and k directionThe node space dimension is hidden stateVariance and mean of time;
step 4.2, estimating the space dimension parameters in the formula (3) through the EM algorithm of the hidden Markov tree model, and continuously iterating and updating the parameters in the EM model to obtain a local optimal solution to obtain the space dimension parameters
Step 4.3 hiding the spectral dimension according to formula (4)And classifying the high-frequency direction subband coefficients:
the sigma T,b,Q,k Is the T time phase, b wave band, Q scale, k direction sub-band coefficient standard deviation, T T,b,Q,k Is a given threshold value for the value of the threshold,represents T time phase, b wave band, Q scale and k direction coefficientHidden states of spectral dimension change and unchanged;
step 4.4 according to the formula (5) and the formula (6), calculating the parent coefficient in the spectrum dimensionState probability ofCoefficient of sumState transition probability parameter of
The parameters have the following meanings:
y x y is the size of the neighborhood;
representing the paternal coefficientThe hidden state variable of (a) is,representing child coefficientsHidden state variables of (2);
is shown inA set of positions corresponding to state values m within a neighborhood y x y centered at the position,the number of coefficients in the neighborhood of 1;
andrespectively represent T time phase, b-1 wave band, Q scale and k direction father coefficientA spectral dimension state probability of m and n;
shows hidden state variables in T-phase, b-wave band and Q-scale k-direction sub-bandsWhen the value of (b) is equal to m or n, the hidden state variableA conditional probability equal to m or n;
step 4.5 according to the definitions of the formulas (7), (8) and (9), calculating the probability of the state of spatial dimension and spectral dimension change and unchangedAnd
the parameters have the following meanings:
is the sub-band coefficient of T time phase, b wave band, Q scale and k directionThe state probability of the space dimension of (1) is m or n;
is the sub-band coefficient of T time phase, b wave band, Q scale and k directionThe state probability of the spectral dimension of (1) is m or n;
ξ T a correlation metric coefficient of a b wave band and a b-1 wave band representing a T phase;
andpixel points at the positions of the hyperspectral images b and b-1 wave bands (i, j) respectively,andare respectively asAndmean value of (1), namely
Step 4.6, according to the construction process of the universal time phase T high-frequency direction sub-band hidden Markov range model in the steps 4.1-4.5, the T1 and T2 time phase high-frequency direction sub-bands shown in the formulas (10) and (11) can be constructedAndhidden Markov(s)Forest model
Step 5, according to the definitions of the formulas (12) and (13), calculating the probability of the changed and unchanged state of the current coefficient based on the time phase T1 and T2 space-spectrum dimensional joint correlationAnd
the parameters have the following meanings:
andrespectively T1 time phase, b wave band, Q scale, k direction sub-band coefficientState probabilities of change 1 and no change 0 of the spatial-spectral dimensional joint correlation;
andrespectively T2 time phase, b wave band, Q scale and k direction sub-band coefficientThe state probability of change 1 and no change 0 of the spatial-spectral dimension joint correlation;
ξ T1 and xi T2 Correlation metric coefficients of b-band and b-1 band at the time phases T1 and T2, respectively;
step 6, calculating the time phase coefficient of T1 according to the definitions of the formula (14) and the formula (15)Gaussian probability edge density function value ofAnd coefficient ofExpected probability of being a changing state
Step 7, calculating the time phase coefficient of T2 according to the definitions of the formula (16) and the formula (17)Edge density function value ofAnd coefficient ofExpected probability of being a changing state
Step 8, calculating the time phase direction templates D of T1 and T2 according to the definitions of the formula (18) and the formula (19) r Probability of region change state coefficient occupying change state coefficient in whole region
The parameters have the following meanings:
D r a 3 × 3 directional template;
is the time phase T1 toCoefficient-centered D r The expected probability of the state with the coefficient m equal to 1 in the region, i.e. theThe probability that the m-1 state coefficient occupies the whole direction area is equal to the probability of the 1 state coefficient;
is the time phase T2 toCoefficient-centered D r The state expectation probability of the in-region coefficient m being 1, that is, the probability that the in-region m being 1 state coefficient occupies the m being 1 state coefficient in the whole direction region;
step 9. high frequency subband coefficient for T1 and T2 phases according to the definitions of equations (20) and (21)Andcarrying out probability state amplitude modulation:
the parameters have the following meanings:
representing the coefficient ofPassing probabilityThe adjusted sub-band coefficient of the position in the k direction (i, j) of the Q scale of the phase b wave band at T1;
represents the coefficient ofPassing probabilityThe adjusted sub-band coefficient of the position in the k direction (i, j) of the Q scale of the phase b wave band at T2;
step 10, according to the definitions of the formula (22) and the formula (23), calculating the directional region energy of the T1 and the T2 based on the directional region
The parameters have the following meanings:
representation based on orientation template D r The direction region energy of the position coefficient in the k direction (i, j) of the Q scale of the phase b wave band at the internal T1;
representation based on orientation template D r The direction region energy of the position coefficient in the k direction (i, j) of the Q scale of the phase b wave band at the internal T2;
(u, v) is a 3X 3-directional template D centered on (i, j) r An inner position coordinate;
step 11, according to the definitions of the formula (22) and the formula (23), calculating the direction region entropy of the T1 and the T2 based on the direction region
The parameters have the following meanings:
representation based on orientation template D r The direction regional entropy of the position coefficient in the k direction (i, j) of the Q scale of the phase b wave band at the internal T1;
representation based on orientation template D r The direction regional entropy of the position coefficient in the k direction (i, j) of the Q scale of the b wave band at the internal T2 phase;
step 12, according to the definitions of the formula (24) and the formula (25), calculating the directional local correlation of the T1 and the T2 based on the region energy and the region entropy
The parameters have the following meanings:
andrespectively representing orientation-based templates D r The direction local correlation of the b-waveband Q-scale k direction (i, j) position coefficients of the inner T1 time phase and the T2 time phase based on the region energy and the region entropy;
andrespectively representing the mean values of the directional energy graphs of the b wave band Q scale k direction of the T1 time phase and the T2 time phase;
andrespectively representing direction entropy diagram mean values of b wave band Q scale k directions at the time phase T1 and the time phase T2;
step 13, calculating T1 and T2 high frequency direction sub-band change detection maps CD according to the definitions of the formula (26) and the formula (27) H_Q,k,T1 、CD H_Q,k,T2 ;
The parameters have the following meanings:
CD H_Q,k,T1 (i, j) and CD H_Q,k,T2 (i, j) respectively representing the detection coefficients of the high-frequency sub-bands in the Q scale k direction of the b wave band at the time phase of T1 and the high-frequency sub-bands at the time phase of T2 at the coordinates (i, j);
β H_Q,k,T1 and beta H_Q,k,T2 Respectively representing the high-frequency sub-bands in the Q scale k direction of the b wave band at the time phase of T1 and the time phase of T2 determined based on Otsu's methodA threshold value;
step 14, calculating the final high-frequency subband variation detection merging graph CD according to the definition of the formula (28) H :
CD H (i,j)=CD H_Q,k,T1 (i,j)+CD H_Q,k,T2 (i,j) (28)
The CD H (i, j) represents the coefficient at (i, j) in the two-time-phase high-frequency subband variation detection combined graph;
step 15, according to the definition of the formula (29), detecting the graph CD by using the low-frequency sub-band transform of the formula (2) L And (28) the high-frequency subband transform detection combined graph CD H Obtaining a final change detection map CD F :
The CD F (i, j) represents the final change detection graph CD F The element at (i, j) in (a) has a value of 1 indicating that a change has occurred, and a value of 0 indicating that no change has occurred.
Compared with the prior art, the invention has the following advantages: firstly, compared with an image processing method of a hidden Markov tree model based on multi-scale transformation, the hidden Markov tree model can simultaneously describe the edge statistical characteristics and the joint statistical characteristics of a multi-scale geometric analysis sub-band, and can only describe the transmission relationship of a two-dimensional image through a tree structure, but the three-dimensional hidden Markov forest model provided by the invention fully utilizes the multi-direction correlation of HS images, and improves the precision of the model; secondly, compared with other traditional change detection methods, the NSST-HMF method provided by the invention realizes accurate description of space-spectrum information among HS coefficients by establishing a mixed Gaussian model, makes full use of strong correlation among HS wave bands, not only refers to low-frequency subband space change information, but also combines the correlation between high-frequency space subbands and spectrum wave bands, further defines the transfer relation of multi-time-phase hyperspectral images, fully considers the transfer relation and correlation of a hidden state among time items, can more accurately distinguish ground feature change conditions, and obtains more precise ground surface change information.
Drawings
FIG. 1 is a schematic diagram of an overall detection process according to an embodiment of the present invention.
FIG. 2 is a graph comparing the results of the Wetland Agricultural Area change test according to the present invention and the prior art.
Detailed Description
The invention discloses a hyperspectral image change detection method based on an NSST hidden Markov forest model, which is shown in figure 1 and is carried out according to the following steps:
step 1, inputting a hyperspectral image H of T1 and T2 two time phases T1 And H T2 The size is M × N × B, where M × N is the spatial size of each band image, and B is the number of bands;
step 2, for H T1 And H T2 Each wave band imageAndperforming non-subsampled shear wave transform (NSST) of Q scale with K directional sub-bands per scale to obtainOf the low frequency sub-bandAnd high frequency sub-bandsOf the low frequency sub-bandAnd high frequency sub-bandsThe K belongs to {1, 2, …, K };
step 3, obtaining a low-frequency sub-band change detection graph CD by using a change vector analysis method L
Step 3.1 according to the formula (1), calculating a two-time phase hyperspectral image H T1 And H T2 Difference in total gray level of low frequency information | | Δ X therebetween L ||:
The i belongs to {1, 2, 3, …, M }, the j belongs to {1, 2, 3, …, N }, and the delta X belongs to {1, 2, 3, …, M }, the j belongs to {1, 2, 3, …, N }, the value of the delta X belongs to the field of the communication technology L (i, j) represents a two-time phase low frequency subband information gray scale difference value at the coordinate (i, j),andcoefficient values representing the low frequency subbands at the band b of the hyperspectral images T1 and T2 at coordinates (i, j), respectively;
step 3.2 according to formula (2), utilize total gray level difference | | Δ X L | | and β L Calculating to obtain a low-frequency sub-band transformation detection graph CD L :
Beta is the same as L Indicating the threshold, CD, determined by Otsu method L (i, j) is a low frequency subband change detection result value located at the coordinate (i, j);
step 4, constructing T1 and T2 time-phase high-frequency direction sub-bandsAndhidden Markov forest modelFor performing probability state amplitude on high-frequency subband coefficientsValue modulation;
step 4.1 according to the definition of formula (3), constructing general time phase T high-frequency direction sub-bandSet of hidden markov forest model (HMF) parameters
The meaning of the parameters is as follows:
m and n are hidden states, the values of the m and n are 1 or 0, and the m and n respectively represent changed states and unchanged states;
high-frequency direction subband coefficients which are T time phase, b wave band, Q scale and k direction point (i, j) position;
is the root coefficient of sub-band in T time phase, b wave band, Q scale and k directionThe state probability of (2);
coefficient of T time phase, b-1 wave band, Q scale, k direction sub-band (i, j) positionProbability of state of (2), saidAnd is divided into spatial dimension state probabilityAnd spectral dimensional state probabilityThe above-mentionedIs the sub-band coefficient of T time phase, b wave band, Q scale and k directionIs used to determine the spatial dimension parent coefficientProbability of state of (2), saidIs the sub-band coefficient of T time phase, b wave band, Q scale and k directionSpectral wiid ofThe state probability of (2);
is a T-phase space dimension state transition probability, whereinTo representThe parent coefficients of the same (i, j) position in the previous dimension,the expression of (a) is:
the meaning is that in the k direction sub-band of the b wave band at the T phase, the parent coefficientHidden state variable of (2)When the value of (d) is equal to m or n, the child coefficientHidden state variable ofA conditional probability equal to m or n;
is the spectral dimension state transition probability;andsub-bands in T time phase, b wave band, Q scale and k directionThe node space dimension is hidden stateVariance and mean of time;
step 4.2, estimating the space dimension parameters in the formula (3) through an EM algorithm of a hidden Markov tree model (HMF), and continuously iteratively updating the parameters in the EM model to obtain a local optimal solution and obtain the space dimension parameters
Step 4.3 hiding the spectral dimension state according to formula (4)And classifying the high-frequency direction subband coefficients:
the sigma T,b,Q,k Is the T time phase, b wave band, Q scale, k direction sub-band coefficient standard deviation, T T,b,Q,k Is a given threshold value for the value of the threshold,represents T time phase, b wave band, Q scale and k direction coefficientA hidden state of spectral dimension change and no change;
step 4.4 according to the formula (5) and the formula (6), calculating the parent coefficient in the spectrum dimensionState probability ofCoefficient of sumState transition probability parameter of
The parameters have the following meanings:
y x y is the size of the neighborhood;
representing the paternal coefficientThe hidden state variable of (a) is,representing child coefficientsA hidden state variable of (a);
is shown inA set of positions corresponding to state values m within a neighborhood y x y centered at the position,the number of coefficients in the neighborhood of 1;
andrespectively represent T time phase, b-1 wave band, Q scale and k direction father coefficientSpectral dimension state probabilities of m and n;
expressed in the T time phase, b wave band and Q scale k powerInto subbands, hidden state variablesWhen the value of (d) is equal to m or n, the hidden state variableA conditional probability equal to m or n;
step 4.5 according to the definitions of the formulas (7), (8) and (9), calculating the probability of the state of spatial dimension and spectral dimension change and unchangedAnd(Note: these two state probabilities are collectively referred to as state probabilities in the HMF parameter set model):
The parameters have the following meanings:
is the sub-band coefficient of T time phase, b wave band, Q scale and k directionThe state probability of the space dimension of (1) is m or n;
is the sub-band coefficient of T time phase, b wave band, Q scale and k directionThe state probability of the spectral dimension of (1) is m or n;
ξ T a correlation metric coefficient of a b wave band and a b-1 wave band representing a T phase;
andpixel points at the positions of the hyperspectral images b and b-1 wave bands (i, j) respectively,andare respectively asAndmean value of (i) i.e. having
Step 4.6, according to the construction process of the hidden Markov process model of the universal time phase T high-frequency direction sub-band in the steps 4.1-4.5, the T1 and T2 time phase high-frequency direction sub-bands shown in the formulas (10) and (11) can be constructedAndhidden Markov forest model
Step 5, according to the definitions of the formulas (12) and (13), calculating the probability of the changed and unchanged state of the current coefficient based on the time phase T1 and T2 space-spectrum dimensional joint correlationAnd
the parameters have the following meanings:
andrespectively T1 time phase, b wave band, Q scale and k direction sub-band coefficientOf joint correlations in the space-spectral dimensionState probability of 1 change, 0 no change;
andrespectively T2 time phase, b wave band, Q scale, k direction sub-band coefficientThe state probability of change 1 and no change 0 of the spatial-spectral dimension joint correlation;
ξ T1 and xi T2 Correlation metric coefficients of b-band and b-1 band at T1 and T2 phases, respectively (see equation (8));
step 6, calculating the time phase coefficient of T1 according to the definitions of the formula (14) and the formula (15)Gaussian probability edge density function value ofAnd coefficient ofExpected probability of being a changing state
Step 7, calculating the time phase coefficient of T2 according to the definitions of the formula (16) and the formula (17)Edge density function value ofAnd coefficient ofExpected probability of being a changing state
Step 8, calculating the time phase direction templates D of T1 and T2 according to the definitions of the formula (18) and the formula (19) r Probability of region change state coefficient occupying change state coefficient in whole region
The parameters have the following meanings:
D r representing a 3 × 3 directional template in size;
is the time phase T1 toCoefficient-centered D r The state expectation probability of the coefficient m ═ 1 in the region, that is, the probability that the state coefficient m ═ 1 in the region occupies the state coefficient m ═ 1 in the whole direction region;
is the time phase T2 toCoefficient-centered D r The state expectation probability of the in-region coefficient m being 1, that is, the probability that the in-region m being 1 state coefficient occupies the m being 1 state coefficient in the whole direction region;
step 9. high frequency subband coefficient for T1 and T2 phases according to the definitions of equations (20) and (21)Andcarrying out probability state amplitude modulation:
the parameters have the following meanings:
represents the coefficient ofPassing probabilityThe adjusted T1 phase b band Q-dimension k-direction (i,j) subband coefficients of a position;
representing the coefficient ofPassing probabilityThe adjusted sub-band coefficient of the position in the k direction (i, j) of the Q scale of the phase b wave band at T2;
step 10, according to the definitions of the formula (22) and the formula (23), calculating the directional region energy of the T1 and the T2 based on the directional region
The parameters have the following meanings:
representation based on orientation template D r The direction region energy of the position coefficient in the k direction (i, j) of the Q scale of the phase b wave band at the internal T1;
representation based on orientation template D r The direction region energy of the position coefficient in the k direction (i, j) of the Q scale of the phase b wave band at the internal T2;
(u, v) is a 3X 3-directional template D centered on (i, j) r An inner position coordinate;
step 11. according to the formula (22) and the formula (23)Defining, calculating orientation region entropy for T1 and T2 based on orientation regions
The parameters have the following meanings:
representation based on orientation template D r The direction regional entropy of the position coefficient in the k direction (i, j) of the Q scale of the phase b wave band at the internal T1;
representation based on orientation template D r The direction regional entropy of the position coefficient in the k direction (i, j) of the Q scale of the b wave band at the internal T2 phase;
step 12, according to the definitions of the formula (24) and the formula (25), calculating the directional local correlation of the T1 and the T2 based on the region energy and the region entropy
The parameters have the following meanings:
andrespectively representing orientation-based templates D r The direction local correlation of the b-waveband Q-scale k direction (i, j) position coefficients of the inner T1 time phase and the T2 time phase based on the region energy and the region entropy;
andrespectively representing the mean values of the directional energy maps in the Q-scale k direction of the b wave band of the T1 time phase and the T2 time phase;
andrespectively representing direction entropy diagram mean values of b wave band Q scale k directions at the time phase T1 and the time phase T2;
step 13, calculating T1 and T2 high frequency direction sub-band change detection maps CD according to the definitions of the formula (26) and the formula (27) H_Q,k,T1 、CD H_Q,k,T2 ;
The parameters have the following meanings:
CD H_Q,k,T1 (i, j) and CD H_Q,k,T2 (i, j) respectively representing the detection coefficients of the high-frequency sub-bands in the Q scale k direction of the b wave band at the time phase of T1 and the high-frequency sub-bands at the time phase of T2 at the coordinates (i, j);
β H_Q,k,T1 and beta H_Q,k,T2 Respectively representing the thresholds determined by Otsu method based on the high-frequency sub-band in the b wave band Q scale k direction of the T1 time phase and the T2 time phase;
step 14, calculating the final high-frequency subband variation detection merging graph CD according to the definition of the formula (28) H :
CD H (i,j)=CD H_Q,k,T1 (i,j)+CD H_Q,k,T2 (i,j) (28)
The CD H (i, j) represents the coefficient at (i, j) in the two-time phase high frequency subband change detection combination graph;
step 15, according to the definition of formula (29), detecting the graph CD by using the low frequency subband transform of formula (2) L And (28) the high-frequency subband transform detection combined graph CD H Obtaining a final change detection map CD F :
The CD F (i, j) represents the final change detection graph CD F The element in (i, j) in (a) has a value of 1 indicating that the element is changed, and a value of 0 indicating that the element is not changed.
FIG. 2 shows a comparison of the results of the Wetland Agricultural Area change test in the present embodiment with those in the prior art, and NSST-HMF is an embodiment of the present invention.
The objective evaluation index pair table is shown below for the Wetland Agricultural Area change test.
Methods | OA_CHG | OA_UN | OA | Kappa |
MAD | 0.864 | 0.076 | 0.618 | -0.071 |
ED | 0.611 | 0.867 | 0.787 | 0.492 |
CVA | 0.617 | 0.868 | 0.790 | 0.499 |
PCDA | 0.788 | 0.796 | 0.793 | 0.548 |
NSST-HMF | 0.828 | 0.938 | 0.879 | 0.759 |
From the above comparison, it can be seen that the overall performance index of the inventive example (NSST-HMF) is superior to that of the prior art.
Claims (1)
1. A hyperspectral image change detection method based on an NSST hidden Markov forest model is characterized by comprising the following steps:
step 1, inputting a hyperspectral image H of T1 and T2 two time phases T1 And H T2 The size is M × N × B, where M × N is the spatial size of each band image, and B is the number of bands;
step 2, for H T1 And H T2 Each wave band image ofAndb belongs to {1, 2, …, B }, and non-down sampling shear wave transformation of Q scale with K direction sub-bands in each scale is obtainedOf the low frequency sub-bandAnd high frequency sub-bandsOf the low frequency sub-bandAnd high frequency sub-bandsThe K belongs to {1, 2, …, K };
step 3, obtaining a low-frequency subband change detection graph CD by using a change vector analysis method L
Step 3.1 according to the formula (1), calculating a two-time phase hyperspectral image H T1 And H T2 Difference in total gray level of low frequency information | | Δ X therebetween L ||:
The i belongs to {1, 2, 3, …, M }, i belongs to {1, 2, 3, …, N }, and delta X belongs to L (i, j) represents a two-time phase low frequency subband information gray scale difference value at the coordinate (i, j),andcoefficient values representing the low frequency subbands at the band b of the hyperspectral images T1 and T2 at coordinates (i, j), respectively;
step 3.2 according to formula (2), utilize total gray level difference | | Δ X L I and beta L Calculating to obtain a low-frequency sub-band transformation detection graph CD L :
Beta is the same as L Indicating the threshold, CD, determined by Otsu method L (i, j) is the low frequency subband variation detection result value located at coordinate (i, j);
step 4, constructing T1 and T2 time-phase high-frequency direction sub-bandsAndhidden Markov forest model of K e {1, 2, …, K }The device is used for carrying out probability state amplitude modulation on the high-frequency subband coefficient;
step 4.1 according to the definition of formula (3), constructing general time phase T high-frequency direction sub-bandSet of hidden markov forest model parameters
The meaning of the parameters is as follows:
m and n are hidden states, the values of the m and n are 1 or 0, and the m and n respectively represent changed states and unchanged states;
high-frequency direction subband coefficients which are T time phase, b wave band, Q scale and k direction point (i, j) position;
is the sub-band root coefficient of T time phase, b wave band, Q scale and k directionState probability of (2);
coefficient of T time phase, b-1 wave band, Q scale, k direction sub-band (i, j) positionState probability of (2), saidAnd divided into space dimensional state probabilitiesAnd spectral dimension state probabilityThe above-mentionedIs the sub-band coefficient of T time phase, b wave band, Q scale and k directionIs used to determine the spatial dimension parent coefficientProbability of state of (2), saidIs the sub-band coefficient of T time phase, b wave band, Q scale and k directionSpectral wiid ofThe state probability of (2);
is a T-phase space dimensional state transition probability, whereinTo representThe parent coefficients of the same (i, j) position in the previous dimension,the expression of (c) is:
the meaning is that in the b wave band k direction sub-band in T time phase, the father coefficientHidden state variable ofWhen the value of (d) is equal to m or n, the child coefficientHidden state variable ofA conditional probability equal to m or n;
is the spectral dimension state transition probability;andrespectively a T time phase, a b wave band, a Q scale and a k direction sub-bandThe node space dimension is hidden stateVariance and mean of time;
step 4.2 estimating the space dimension parameter in the formula (3) by the EM algorithm of the hidden Markov tree model, and continuously iteratingThe parameters in the EM model are updated to obtain the local optimal solution and the space dimension parameters
Step 4.3 hiding the spectral dimension according to formula (4)And (3) classifying the high-frequency direction subband coefficients:
the sigma T,b,Q,k Is the T time phase, b wave band, Q scale, k direction sub-band coefficient standard deviation, T T,b,Q,k Is a given threshold value for the value of the threshold,represents T time phase, b wave band, Q scale and k direction coefficientHidden states of spectral dimension change and unchanged;
step 4.4 according to the formula (5) and the formula (6), calculating the parent coefficient in the spectrum dimensionState probability ofSum coefficientState transition probability parameter of
The parameters have the following meanings:
y x y is the size of the neighborhood;
representing the paternal coefficientThe hidden state variable of (a) is,representing child coefficientsHidden state variables of (2);
is shown inA set of positions corresponding to state values m within a neighborhood y x y centered at the position,the number of coefficients in the neighborhood of 1;
andrespectively represent T time phase, b-1 wave band, Q scale and k direction father coefficientSpectral dimension state probabilities of m and n;
shows hidden state variables in T-phase, b-wave band and Q-scale k-direction sub-bandsWhen the value of (d) is equal to m or n, the hidden state variableA conditional probability equal to m or n;
step 4.5 according to the definitions of the formulas (7), (8) and (9), calculating the probability of the state of space dimension and spectrum dimension change and no changeAnd
the parameters have the following meanings:
is T time phase, b wave band, Q scale, k direction sub-band coefficientThe state probability of the space dimension of (1) is m or n;
is T time phase, b wave band, Q scale, k direction sub-band coefficientThe state probability of the spectral dimension of (1) is m or n;
ξ T a correlation metric coefficient of a b wave band and a b-1 wave band representing a T phase;
andrespectively the pixel points at the positions of the hyperspectral images b and b-1 wave bands (i, j),andare respectively asAndmean value of (i) i.e. having
Step 4.6, according to the construction process of the universal time phase T high-frequency direction sub-band hidden Markov range model in the steps 4.1-4.5, the T1 and T2 time phase high-frequency direction sub-bands shown in the formulas (10) and (11) can be constructedAndhidden Markov forest model of K e {1, 2, …, K }
Step 5, according to the definitions of the formulas (12) and (13), calculating the probability of the changed and unchanged state of the current coefficient based on the time phase T1 and T2 space-spectrum dimensional joint correlationAnd
the parameters have the following meanings:
andrespectively T1 time phase, b wave band, Q scale and k direction sub-band coefficientState probabilities of change 1 and no change 0 of the spatial-spectral dimensional joint correlation;
andrespectively T2 time phase, b wave band, Q scale and k direction sub-band coefficientThe state probability of change 1 and no change 0 of the spatial-spectral dimension joint correlation;
ξ T1 and xi T2 Correlation metric coefficients of b-band and b-1 band at the time phases T1 and T2, respectively;
step 6, calculating the time phase coefficient of T1 according to the definitions of the formula (14) and the formula (15)Gaussian probability edge density function value ofAnd coefficient ofExpected probability of being a changing state
Step 7, calculating the time phase coefficient of T2 according to the definitions of the formula (16) and the formula (17)Edge density function value ofAnd coefficient ofExpected probability of being a changing state
Step 8, calculating the time phase direction templates D of T1 and T2 according to the definitions of the formula (18) and the formula (19) r Probability of region change state coefficient occupying change state coefficient in whole region
The parameters have the following meanings:
D r representing a 3 × 3 directional template in size;
is the time phase T1 toCoefficient-centered D r The state expectation probability of the in-region coefficient m being 1, that is, the probability that the in-region m being 1 state coefficient occupies the m being 1 state coefficient in the whole direction region;
is the time phase T2 toCoefficient-centered D r The state expectation probability of the in-region coefficient m being 1, that is, the probability that the in-region m being 1 state coefficient occupies the m being 1 state coefficient in the whole direction region;
step 9. high frequency subband coefficient for T1 and T2 phases according to the definitions of equations (20) and (21)Andcarrying out probability state amplitude modulation:
the parameters have the following meanings:
represents the coefficient ofPassing probabilityThe adjusted sub-band coefficient of the position in the k direction (i, j) of the Q scale of the phase b wave band at T1;
representing the coefficient ofPassing probabilityThe adjusted sub-band coefficient of the position in the k direction (i, j) of the Q scale of the phase b wave band at T2;
step 10, according to the definitions of the formula (22) and the formula (23), calculating the directional region energy of the T1 and the T2 based on the directional region
The parameters have the following meanings:
representation based on orientation template D r The direction region energy of the position coefficient in the k direction (i, j) of the Q scale of the phase b wave band at the internal T1;
representation based on orientation template D r The direction region energy of the position coefficient in the k direction (i, j) of the Q scale of the phase b wave band at the internal T2;
(u, v) is a 3X 3-directional template D centered on (i, j) r An inner position coordinate;
step 11, according to the definitions of the formula (22) and the formula (23), calculating the direction region entropy of the T1 and the T2 based on the direction region
The parameters have the following meanings:
representation based on orientation template D r The direction regional entropy of the position coefficient in the k direction (i, j) of the Q scale of the b wave band at the internal T1 phase;
representation based on orientation template D r The direction regional entropy of the position coefficient in the k direction (i, j) of the Q scale of the b wave band at the internal T2 phase;
step 12, according to the definitions of the formula (24) and the formula (25), calculating the directional local correlation of the T1 and the T2 based on the region energy and the region entropy
The parameters have the following meanings:
andrespectively representing orientation-based templates D r The direction local correlation of the b-waveband Q-scale k direction (i, j) position coefficients of the inner T1 time phase and the T2 time phase based on the region energy and the region entropy;
andrespectively representing the mean values of the directional energy graphs of the b wave band Q scale k direction of the T1 time phase and the T2 time phase;
andrespectively representing direction entropy diagram mean values of b wave band Q scale k directions at the time phase T1 and the time phase T2;
step 13, calculating T1 and T2 high frequency direction sub-band change detection maps CD according to the definitions of the formula (26) and the formula (27) H_Q,k,T1 、CD H_Q,k,T2 ;
The parameters have the following meanings:
CD H_Q,k,T1 (i, j) and CD H_Q,k,T2 (i, j) respectively representing the detection coefficients of the high-frequency sub-bands in the Q scale k direction of the b wave band at the time phase of T1 and the high-frequency sub-bands at the time phase of T2 at the coordinates (i, j);
β H_Q,k,T1 and beta H_Q,k,T2 Respectively representing the threshold values of the b wave band Q scale k direction high-frequency sub-band determined by the Otsu method in the T1 time phase and the T2 time phase;
step 14, calculating the final high-frequency subband variation detection merging graph CD according to the definition of the formula (28) H :
CD H (i,j)=CD H_Q,k,T1 (i,j)+CD H_Q,k,T2 (i,j) (28)
The CD H (i, j) represents the coefficient at (i, j) in the two-time-phase high-frequency subband variation detection combined graph;
step 15 according to formula (29)By definition, the detection of the graph CD is performed using the low frequency subband transform of equation (2) L And (28) the high-frequency subband transform detection combined graph CD H Obtaining a final change detection map CD F :
The CD F (i, j) represents the final change detection graph CD F The element at (i, j) in (a) has a value of 1 indicating that a change has occurred, and a value of 0 indicating that no change has occurred.
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