阅读说明：本技术 一种基于高光谱目标探测数据的动态解混方法 (Hyperspectral target detection data-based dynamic unmixing method ) 是由 巩晋南 施天俊 智喜洋 胡建明 鲍广震 张鹏飞 于 2021-06-29 设计创作，主要内容包括：本发明公开了一种基于高光谱目标探测数据的动态解混方法,所述方法包括如下步骤：步骤1：提取高光谱目标探测数据中目标所在混合像元光谱数据,构建混合像元时序矩阵；步骤2：基于高光谱目标探测数据估计目标所在场景的光谱曲线；步骤3：基于步骤1筛选的谱段,以步骤2估计的场景光谱作为先验信息,对步骤1中获取的混合像元矩阵进行动态解混,得到真实的目标光谱。该方法可以实现对亚像元目标在不同场景下高光谱探测数据的光谱动态解混,获取更准确的有利于后续目标识别等应用的光谱特性。(The invention discloses a dynamic unmixing method based on hyperspectral target detection data, which comprises the following steps: step 1: extracting mixed pixel spectrum data of a target in the hyperspectral target detection data, and constructing a mixed pixel time sequence matrix; step 2: estimating a spectral curve of a scene where the target is located based on the hyperspectral target detection data; and step 3: and (3) based on the spectrum band screened in the step (1), taking the scene spectrum estimated in the step (2) as prior information, and performing dynamic unmixing on the mixed pixel matrix obtained in the step (1) to obtain a real target spectrum. The method can realize the spectrum dynamic unmixing of the hyperspectral detection data of the sub-pixel target in different scenes, and obtain more accurate spectral characteristics which are beneficial to the application of subsequent target identification and the like.)

1. A dynamic unmixing method based on hyperspectral target detection data is characterized by comprising the following steps:

step 1: extracting mixed pixel spectrum data of a target in the hyperspectral target detection data, and constructing a mixed pixel time sequence matrix;

step 2: estimating a spectral curve of a scene where the target is located based on the hyperspectral target detection data;

and step 3: and (3) based on the spectrum band screened in the step (1), taking the scene spectrum estimated in the step (2) as prior information, and performing dynamic unmixing on the mixed pixel matrix obtained in the step (1) to obtain a real target spectrum.

2. The hyperspectral target detection data-based dynamic unmixing method according to claim 1 is characterized in that the specific steps of the step 1 are as follows:

on the basis of obtaining the target position through detection data prior, the spectrum r of the mixed pixel position where each scene target is located is directly extracted_jCombining to obtain a mixed pixel timing matrix R which isAnd h is multiplied by n dimensional matrix, wherein h and n respectively represent the number of spectral segments and the number of scenes.

3. The hyperspectral target detection data-based dynamic unmixing method according to claim 1 is characterized in that the specific steps of the step 2 are as follows:

(1) performing superpixel segmentation based on simple linear iterative clustering;

(2) and carrying out scene spectrum estimation based on the spatial distance weight.

4. The hyperspectral target detection data-based dynamic unmixing method according to claim 3 is characterized in that the specific steps of the step (1) are as follows:

(a) initializing superpixel centers

For the hyperspectral data with the number of wave bands of h, each pixel corresponds to an h + 2-dimensional vector V_jThe spectral information and the spatial position of each wave band are jointly defined and written as follows:

in the formula, V_jRepresenting a characterization vector of the jth pixel based on the spectral information and the spatial position; r is_j＝[r_1j,...,r_hj]^TSpectral dimension information of j pixel in each spectral band, wherein r_1j-r_hjRespectively representing the spectral information of the jth pixel from the 1 st spectral band to the h spectral band; [ m ] of_j,n_j]^TIs the position of the jth pixel element in a space coordinate system, wherein m_jAnd n_jRespectively is the spatial coordinate position of the jth pixel element in the x and y directions; symbol T represents vector transposition;a real number space representing h +2 dimensions;

generating P super-pixel mean value points through the step distance omega according to given parameters;

by super-pixelThe super-pixel can also pass through an h + 2-dimensional vector C_iAnd (3) characterization:

in the formula, C_iA characterization vector representing the ith superpixel based on spectral information and spatial location;for the spectral information of the ith super-pixel in each spectral band, the average of the pixel spectral data contained in the super-pixel is calculated, wherein r_1i-r_hiRespectively representing the spectral information of the ith super pixel from the 1 st spectral band to the h-th spectral band;is the position of the ith super pixel in a space coordinate system, whereinAndthe spatial coordinate positions of the ith super pixel in the x direction and the y direction respectively; symbol T represents vector transposition;a real number space representing h +2 dimensions;

in order to avoid selecting edges, noise and abnormal points as clustering centers, replacing the initial center with the minimum gradient position in a 3 x 3 area around the initial center;

(b) calculating the distance between each pixel and the center of the super-pixel, and updating the center of the super-pixel

Searching pixels which are close to the initial central point in distance and similar in spectrum with the initial central point, classifying the pixels and the central point into one class, then recalculating a clustering center for the clustered pixels, then continuously searching similar pixels around, and continuously iterating until convergence;

(c) merging isolated points

And (4) allocating the connected component with the undersized area to the nearest super-pixel class through a neighborhood connected algorithm.

5. The method according to claim 4, wherein the relationship between the step distance ω and the number P of the super-pixel mean points and the total number N of the pixels is expressed as:

6. the method according to claim 4, wherein the distance between each pixel and the center of a super pixel is calculated as follows:

in the formula, D_jiMeasuring the similarity degree of the ith super pixel and the jth pixel element; d_xMeasuring the spectral similarity of the ith super pixel and the jth pixel element, whereinFor spectral information vector characterization of the ith superpixel, r_jRepresenting the spectrum information vector of the jth pixel; d_mnMeasuring the Euclidean space distance between the ith super pixel and the jth pixel element, wherein m_jAnd n_jThe spatial coordinate positions of the jth pixel element in the x and y directions respectively,andthe spatial coordinate positions of the ith super pixel in the x direction and the y direction respectively; parameter omega_sTo adjust the weight between spatial distance and spectral similarity;representing a real number space in h +2 dimensions.

7. The method according to claim 3, wherein the scene spectrum estimation formula is as follows:

r_e＝∑_ijα_ijr_ij；

in the formula, r_eFor the scene spectrum to be estimated, r_ijTo use for the estimated neighborhood spectrum, α_ijAnd (i, j) and (a, b) are respectively the spatial coordinates of the neighborhood pixels and the pixels to be estimated.

8. The hyperspectral target detection data-based dynamic unmixing method according to claim 1 is characterized in that the specific steps of step 3 are as follows:

(1) setting a sparsity constraint weight matrix;

(2) and performing target spectrum unmixing through an iterative optimization algorithm.

9. The hyperspectral target detection data-based dynamic unmixing method according to claim 8 is characterized in that the specific steps of the step (1) are as follows:

combining weighted L for the case of targets in multi-scene aliasing₁Regularization constraint constrains sparsity of end element distribution, and a final solution model of target spectrum unmixing is expressed as:

s.t.E≥0,A≥0

wherein R, E, A represents the mixed pixel timing matrix, the end-member spectrum matrix and the abundance matrix respectively,is a scalar quantity, called penalty factor, for controlling the weight of the regularization term in the cost function,is a weight matrix, | is a point-by-symbol, | | · | |_FIs the F norm of the matrix, | · | | non-woven phosphor_FIs a 1 norm of a matrix, 1_mAnd 1_nRespectively an m x m identity matrix and an n x n identity matrix,in order to obtain the values of E and A under the condition of minimum right formula, the constraint condition to be met is shown after s.t.

10. The hyperspectral target detection data-based dynamic unmixing method according to claim 8 is characterized in that in the step (2), when the non-negative matrix decomposition is realized by a multiplicative iteration method, the specific steps are as follows:

(a) initializing iteration parameters

Initializing an end-member spectrum matrix E and an abundance matrix A;

(b) updating iterative parameters

Updating and iterating the end-member spectrum matrix E and the abundance matrix A according to the following formula:

E←E.*(RA^T)./EAA^T；

A←A.*(E^TR)./(E^TEA+λW)。

Technical Field

The invention belongs to the technical field of target detection and identification, and relates to a dynamic unmixing method based on hyperspectral target detection data.

Background

The hyperspectral images have the advantages of high spectral resolution, integrated atlas and the like, so that accurate target identification becomes possible, and if the target spectral features can be accurately extracted, the targets such as ships and airplanes in the scene can be accurately identified on models by means of matching with a spectral library and the like. However, due to the factors of low spatial resolution of the hyperspectral detector, small target size and the like, the target may not occupy one pixel. The spectral signals generated by such sub-pixel targets will also be mixed with the signals of the scene. The sub-pixel target does not have textural features, so that physical form information cannot be directly extracted to achieve the purpose of detection and identification. Therefore, in order to realize target identification through spectrum matching, the spectrum information in the mixed pixel must be unmixed through a signal processing mode to break through the spatial resolution limit of the detector, so that the identification capability of the weak and small moving targets is improved. In order to obtain spectral characteristics and distribution conditions of different substances in a hyperspectral image, the traditional unmixing method needs to unmix the whole image in a spatial domain plane. An important task of the hyperspectral imaging system oriented to detection and identification is to acquire the radiation characteristics of moving targets such as ships and airplanes. Different types of moving objects exhibit spectral characteristics that differ significantly from the scene due to differences in reflection, radiation, etc. characteristics from the scene, these spectral regions being referred to as fingerprint spectral regions of the object. Fingerprint spectrum segments are the core of different types of object recognition. Therefore, the dynamic unmixing for detection and identification mainly focuses on the extraction of a target spectral curve and the extraction precision of a fingerprint spectral band, so that time domain information needs to be introduced, that is, mixed pixel spectral data where targets in different scenes are located is extracted to form a time domain spectral signal, so as to achieve spectral unmixing of pixels where the targets are located.

Therefore, the dynamic unmixing of the hyperspectral detection data is based on the prior of the target detection position, the hyperspectral data at different moments or under different scenes is introduced, the pixels of the sub-pixel targets are unmixed in a targeted manner to obtain more accurate target spectral features, and support can be provided for the subsequent application of spectral data such as feature extraction, target identification and the like.

Disclosure of Invention

The invention provides a dynamic unmixing method based on hyperspectral target detection data, which aims at the problems that accurate target spectral characteristics are difficult to extract due to aliasing of a sub-pixel target and a scene spectrum. The method can realize the spectrum dynamic unmixing of the hyperspectral detection data of the sub-pixel target in different scenes, and obtain more accurate spectral characteristics which are beneficial to the application of subsequent target identification and the like.

The purpose of the invention is realized by the following technical scheme:

a dynamic unmixing method based on hyperspectral target detection data comprises the following steps:

step 1: extracting mixed pixel spectrum data of a target in the hyperspectral target detection data, and constructing a mixed pixel time sequence matrix;

step 2: estimating a spectral curve of a scene where the target is located based on the hyperspectral target detection data;

and step 3: and (3) based on the spectrum band screened in the step (1), taking the scene spectrum estimated in the step (2) as prior information, and performing dynamic unmixing on the mixed pixel matrix obtained in the step (1) to obtain a real target spectrum.

Compared with the prior art, the invention has the following advantages:

(1) the invention provides a hyperspectral target dynamic unmixing idea oriented to detection application. According to a traditional unmixing method for a whole image, the spectral characteristics and the distribution condition of different substances in a hyperspectral image are obtained by performing airspace global unmixing on a single scene; the hyperspectral dynamic unmixing oriented to detection application can more specifically and efficiently acquire the fingerprint spectrum characteristics of a restored target by locally unmixing the mixed pixels of the sub-pixel targets in multiple scenes, and provide support for subsequent operations of spectrum data such as characteristic extraction, target identification and the like.

(2) The invention provides a dynamic unmixing method based on hyperspectral exploration data. Based on detection prior of the target in different scenes, information which is beneficial to unmixing in the hyperspectral target detection data is fully extracted through methods such as mixed pixel time sequence matrix construction and scene spectrum estimation, and unmixing is carried out on pixels where the sub-pixel target is located through nonnegative matrix decomposition so as to obtain accurate target spectrum characteristics.

(3) The invention fully extracts the information which is beneficial to unmixing in the aliasing data through a series of preprocessing operations. Obtaining data beneficial to realizing dynamic unmixing through constructing a mixed pixel time sequence matrix; and the prior information is introduced through scene spectrum estimation to improve the convergence rate and the de-mixing precision of the dynamic de-mixing.

(4) The invention transplants and improves the non-negative matrix decomposition, which is a static unmixing algorithm mainly aiming at the whole image, and combines a series of preprocessing operations such as mixed pixel time sequence matrix construction, scene spectrum estimation and the like to realize higher unmixing precision on the sub-pixel target, so that the unmixed target spectrum has certain identifiability.

Drawings

FIG. 1 is a flow chart of a dynamic unmixing method based on hyperspectral exploration data;

FIG. 2 is an example of weight matrix setting selection in a non-negative matrix factorization approach;

FIG. 3 is a use case construction process for testing a dynamic unmixing method;

fig. 4 is a comparison of the spectrum unmixed based on the present invention and the actual spectrum.

Detailed Description

The technical solution of the present invention is further described below with reference to the accompanying drawings, but not limited thereto, and any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be covered by the protection scope of the present invention.

The invention provides a dynamic unmixing method based on hyperspectral exploration data, which comprises the following specific implementation steps as shown in figure 1:

step 1: and extracting mixed pixel spectrum data of the target in the hyperspectral target detection data, and constructing a mixed pixel time sequence matrix. The method comprises the following specific steps:

on the basis of obtaining the target position through detection data prior, the spectrum r of the mixed pixel position where each scene target is located is directly extracted_jAnd combining to obtain a mixed pixel time sequence matrix R. The matrix is an h multiplied by n dimensional matrix, wherein h and n respectively represent the number of spectral segments and the number of scenes.

Step 2: and estimating a spectral curve of a scene where the target is located based on the hyperspectral target detection data, and using the spectral curve as prior information for later dynamic unmixing. The method comprises the following specific steps:

(1) superpixel segmentation based on simple linear iterative clustering

The simple linear iterative clustering is performed by two adjustable parameters, namely the number P of super pixels and a measurement weight omega_sAnd controlling, namely controlling the number of the superpixels by using the former and controlling the weight occupied by the spectral similarity and the spatial distance in the iteration of the algorithm by using the latter. The algorithm comprises the following specific steps:

(a) initializing superpixel centers

For the hyperspectral data with the number of wave bands of h, each pixel corresponds to an h + 2-dimensional vector V_jThe spectral information and the spatial position of each wave band are jointly defined and written as follows:

in the formula, V_jRepresenting a characterization vector of the jth pixel based on the spectral information and the spatial position; r is_j＝[r_1j,...,r_hj]^TSpectral dimension information of j pixel in each spectral band, wherein r_1j-r_hjRespectively representing the spectral information of the jth pixel from the 1 st spectral band to the h spectral band; [ m ] of_j,n_j]^TIs the position of the jth pixel element in a space coordinate system, wherein m_jAnd n_jRespectively is the spatial coordinate position of the jth pixel element in the x and y directions; symbol T represents vector transposition;real null representing h +2 dimensionsAnd (3) removing the solvent.

According to given parameters, P super-pixel mean value points are generated through the step distance omega, and the relation between the step distance omega and the number P of the super-pixel mean value points and the total number N of the pixels can be approximately expressed as:

the superpixel can also pass through an h + 2-dimensional vector C by the pixel information contained in the superpixel_iAnd (3) characterization:

in the formula, C_iA characterization vector representing the ith superpixel based on spectral information and spatial location;for the spectral information of the ith super-pixel in each spectral band, the average of the pixel spectral data contained in the super-pixel is calculated, wherein r_1i-r_hiRespectively representing the spectral information of the ith super pixel from the 1 st spectral band to the h-th spectral band;is the position of the ith super pixel in a space coordinate system, whereinAndthe spatial coordinate positions of the ith super pixel in the x direction and the y direction respectively; symbol T represents vector transposition;representing a real number space in h +2 dimensions. To avoid selecting edges, noise and outliers as cluster centers, the initial center is replaced with the minimum position of gradient in the 3 x 3 region around the initial center。

(b) Calculating the distance between each pixel and the center of the super-pixel, and updating the center of the super-pixel

Pixels that are close in distance and spectrally similar to the point are searched around the initial center point, which is classified as the center point. Then, the clustering center of the clustered pixels is recalculated, and then similar pixels around are continuously searched, and iteration is continued until convergence.

Distance measure D_jiIntegrating the spectral information and the spatial position information, and measuring the distance between the jth pixel element and the ith super pixel, wherein the definition is shown as the following formula:

in the formula, D_jiMeasuring the similarity degree of the ith super pixel and the jth pixel element; d_xMeasuring the spectral similarity of the ith super pixel and the jth pixel element, whereinFor spectral information vector characterization of the ith superpixel, r_jRepresenting the spectrum information vector of the jth pixel; d_mnMeasuring the Euclidean space distance between the ith super pixel and the jth pixel element, wherein m_jAnd n_jThe spatial coordinate positions of the jth pixel element in the x and y directions respectively,andrespectively is the ith superThe spatial coordinate position of the pixel in the x and y directions; parameter omega_sTo adjust the weight between spatial distance and spectral similarity;representing a real number space in h +2 dimensions.

(c) Merging isolated points

There may be isolated points in a super-pixel that belong to other super-pixels. In order to improve the segmentation effect, connected components with too small areas are allocated to the nearest super-pixel class through a neighborhood connected algorithm.

(2) Scene spectrum estimation based on spatial distance weight

When the rest pixels in the super-pixels are used for estimating the scene spectrum of the target, the weight of each neighborhood pixel is inversely proportional to the spatial distance between the neighborhood pixel and the position of the target, and the weighting coefficient is shown as the following formula:

in the formula, (i, j) and (a, b) are respectively the spatial coordinates of the neighborhood pixels and the pixels to be estimated.

The scene spectrum at the pixel where the target is located can be estimated by performing weighted average according to the following formula:

r_e＝∑_ijα_ijr_ij；

in the formula, r_eFor the scene spectrum to be estimated, r_ijIs the neighborhood spectrum used for estimation.

And step 3: and (3) based on the spectrum band screened in the step (1), the scene spectrum estimated in the step (2) is used as prior information, and the mixed pixel matrix obtained in the step (1) is unmixed through unmixing methods such as nonnegative matrix decomposition based on sparsity constraint, so that a real target spectrum is obtained. The method comprises the following specific steps:

(1) setting sparsity constraint weight matrix

Combining weighted L for the case of targets in multi-scene aliasing₁Regularization constraints constrain sparsity of end-member distributionsThe solution model for the beam, final target spectrum unmixing can be expressed as:

wherein R, E, A represents the mixed pixel timing matrix, the end-member spectrum matrix and the abundance matrix respectively,is a scalar quantity, called penalty factor, for controlling the weight of the regularization term in the cost function,is a weight matrix, | is a point-by-symbol, | | · | |_FIs the F norm of the matrix, | · | | non-woven phosphor_FIs a 1 norm of a matrix, 1_mAnd 1_nRespectively an m x m identity matrix and an n x n identity matrix,in order to obtain the values of E and A under the condition of minimum right formula, the constraint condition to be met is shown after s.t.

For the abundance value corresponding to each element of the weight matrix, the larger the weight value, the easier the iteration to 0. For each column of the abundance matrix, only the abundance values of the target spectrum and the current scene spectrum should have values, and the abundance values of the remaining scene spectra should be 0. Here, λ W is merged, a weight of 0 is set for an element for which a value should exist, and the same weight value ω ∈ [0,1] is set for an element for which 0 should exist. For example, for aliased data where there are objects in three scenes, each scene containing two frames, the weight matrix setting is as shown in FIG. 2.

(2) Target spectrum unmixing by iterative optimization algorithm

Taking a multiplicative iteration method as an example to realize non-negative matrix decomposition, the method specifically comprises the following steps:

(a) initializing iteration parameters

And initializing an end member spectrum matrix E and an abundance matrix A, wherein the end member spectrum matrix can be initialized by the estimated scene spectrum and a random number, and the end member spectrum matrix can be initialized by the random number.

(b) Updating iterative parameters

The formula for updating and iterating the end-element spectrum matrix E and the abundance matrix A is as follows:

E←E.＊(RA^T)./EAA^T；

A←A.*(E^TR)./(E^TEA+λW)。

by using the target spectrum mixing test sample constructed based on fig. 3, the spectrum curve after unmixing obtained through the above specific steps is shown in fig. 4, and it can be seen that a more accurate target spectrum unmixing result can be obtained through the dynamic unmixing method based on hyperspectral sounding data provided by the invention.