Hyperspectral Imaging Seminar HI Sensor Fusion

Report
Noa Privman Horesh
December 2012
Many uses for fusion:
 Visualization – fuse between bands
 Sharpening - fusion between hyperspectaral
image and panchromatic image
 Detection and classification - fusion
between hyperspectaral image and
panchromatic/ FOPEN SAR / LIDAR image
Visualization
In lecture 3 – Displaying of Hyperspectral
Images on RGB Displays we saw several
algorithms:
1BT Based Band Selection
Principal Components Analysis
(PCA)
Spectral Weighting Envelopes
Visualization – cont’
 Another method for getting better
visualization - hierarchical fusion based on
vector quantization and bilateral filtering.
Hierarchical Fusion Using Vector
Quantization for Visualization of
Hyperspectral Images
 A typical hyperspectral image data set in
remote sensing contains a few hundred
images to be fused into a single image (for
grayscale) or three images (for RGB).
 Fusing all the bands together requires
heavy calculation and a lot of memory
Visualization - Hierarchical Fusion
 For the hyperspectral image cube of
dimensions (X*Y *N), vector quantization (V
Q) based fusion is applied across a contiguous
subset of dimensions (X*Y*P) to generate B =
N/P different fused images at the first stage of
hierarchy
 In the subsequent levels of hierarchy,
contiguous images are grouped together in a
smaller subset and fused using ’bilateral
filtering’.
Visualization - Hierarchical Fusion –
cont’
 Images I1 to IN from N contiguous bands are
organized into Group1 to GroupB, using
uniform grouping. So each group has P =
N/B images each of size X*Y .
 First stage - Each group is individually fused
using Vector quantization
Fused using Vector quantization
 Vector Quantization used to compress the
information and manipulate the data in a
way that maintain the most important
features.
 Each image Ik is divided into sub-blocks of
size mxm giving rise to (XxY )/m2 image
blocks.
 In a given group there are IVn = (XxYxP)/(m2)
image sub- blocks.
Generate first code-vector
 Convert these image vectors to one
dimensional vectors each of size m2 and
generate a cluster (matrix) S of size IVnx m2
 The first code-vector (CV (1,1)) of the codebook size 1, can be computed by finding the
column wise average of the entire cluster as
follows:
Generate code book
 The code-vector (CV (1,1)) is then split into
two code-vectors by adding and subtracting
a tolerance ε, in order to double the codebook size:
Generate code book – cont’
 The original cluster S is divided into two
clusters – S1 and S2 based on the distortion
D1(2,1)and D1(2,2) with respect to the codevectors
 Comparing the values D1(2,1) (k) and D1(2,2)(k)
the image vectors of the cluster S is grouped
into two sub-clusters S1 and S2 such that
and
Generate code book – cont’
 The quality of the code-book is enhanced by
updating existing code-vectors through
calculating the mean of the image-vectors
in each sub-cluster S1 and S2.
 The code-vectors are updated to the new
code-vectors.
 The corresponding distortions are
calculated for the complete image vector set
S to get updated sub-clusters S1 and S2.
Generate code book – cont’
 The update repeated until the vector sum of
the distortion in the current level is
significantly less than the distortion in the
previous level
 Now we have n code-vectors, each of size
m2, in the code-book (size nxm2).
Fused using Vector quantization
 Each image Ii rearrange to a matrix of size
(XxY/m2, m2).
 The rearranged image is now compared with
all the n code-vectors with respect to MSE
 The MSE values of all the P images for a
given sub-block position with all the codevectors are then added.
 The code-vector CVi that gives the
minimum sum of MSE values is selected as
the ith sub-block of the fused image IF
Hierarchical Fusion - vector
quantization
 At the end of first stage fusion, there are B
fused images (I1,1 to I1,B) which are the input
images for second level of hierarchy.
Fusion using Bilateral Filtering
 bilateral filtering is used only from the
second hierarchical level following the
redundancy removal in the first stage
through Vector quantization.
A bilateral filter
 A bilateral filter is an edge-preserving
and noise reducing smoothing filter.
 The intensity value at each pixel in an image
is replaced by a weighted average of intensity
values from nearby pixels.
 This weight is based on a Gaussian
distribution.
 This preserves sharp edges by systematically
looping through each pixel and according
weights to the adjacent pixels accordingly.
Fusion using Bilateral Filtering
 Compute the bilateral filtered image:
 Calculate the weight at each pixel (x, y) for
each image:
Fusion using Bilateral Filtering
 The fused Image of the hyperspectral cube
subset IF is given by
The 1st and the 81st image of the urban image
cube (Palo Alto) from Hyperion dataset
Results
(a)
(b)
(c)
Sharpening
 Combine the high spatial and the high
spectral resolutions in order to obtain the
complete and accurate description of the
observed scene.
 The following method will be describe:
 Unmixing-based constrained nonnegative
matrix factorization (UCNMF)
Unmixing-based constrained
nonnegative matrix factorization
Nonnegative matrix factorization
(NMF) for hyperspectral unmixing
 The hyperspectral data is a 3D-array
 V ∈ RL×K store the original hyperspectral
data.
 V = WH + N
 W ∈ RL×S - the spectral signature matrix
 H ∈ RS×K is the abundance matrix
Nonnegative matrix factorization
(NMF) for hyperspectral unmixing –
cont’
 To unmix the hyperspectral data, NMF could
be conducted:
Euc(W, H) 
1
2
V  WH
2

V


2
1
i


WH
ij
j
 Minimize the square of the Euclidean
distance between V and WH
ij 
2
Unmixing-based constrained
nonnegative matrix factorization
(UCNMF) for image fusion
 After creating the abundance matrix, the
weighted fusion method is adopted.
min F(W, H) 
1
V  WH
2
2
s .t ., W  0 , H  0
 Therefore, we have the fused data Vf :
Vf = W(αH + (1 − α)P)
Preserve the spectral information
of the original hyperspectral image
 The fuse image does not hold the same
spectral quality as the original hyperspectral
image causing spectral distortion .
 Constraint function:
V    V
k
S
f
i 1



2
fi
2
V
i

V
,
fi V
i
 Which is equivalent to:

2

   tr V V . * V V   tr V V . * V V 
SV
T
f
f
T
f
T
f
T
Final Fusion model
min J(W, H) = F(W, H) + βS(Vf )
s.t. W ≥ 0, H ≥ 0
Vf = W(αH + (1 − α)P)
 This is an optimization problem
Algorithm (Outline: Lin-PG for UCNMF).
Given 0 < ı < 1, 0 < < 1, 0 < ε < 1. Set γ0 = 1.
Initialize the matrices W ≥ 0, H ≥ 0.
Calculate the  J W 1, H 1
2. For k = 1, 2, . . .
(a) Assign γk ← γk-1 .
(b) If γk satisfies (1),
repeatedly increase it by γk←γk/δ until either γk does
not satisfy (1) or W, H keep the same before and after
the change of γk
Else repeatedly decrease γk by γk←γk· δ until γk satisfies (1).
(c) Update W by (2), H by (3).
(d) Calculate the  P J W k , H k 
3. Repeat step 2, until satisfying the stopping condition given
in (4).
4. Obtaining the fused image Vf = W(αH + (1 − α)P)
1.
F
F
1
2
3
4
Results
 proposed method UCNMF has the
advantage that it could advance the spatial
resolution of the hyperspectral image
without losing much its color information
Detection and classification
 Fusing data from hyperspectral imaging
(HSI) sensors with data from other sensors
can enhance overall detection and
classification performance.
 Fusing HSI data with foliage-penetration
synthetic aperture radar (FOPEN SAR) data
- feature level
 Fusing HSI data with high-resolution
imaging (HRI) data - data and feature level
HSI and FOPEN SAR Data Fusion
 FOPEN SAR and HSI sensors detection
capabilities complement each other.
 FOPEN SAR typically operates at 20 to 700
MHz. It penetrates foliage and detects targets
under tree canopy, but has significant clutter
returns from trees.
 HSI is capable of subpixel detection and
material identification
HSI and FOPEN SAR Data Fusion
 Both SAR and HSI systems may suffer
substantial false-alarm and missed
detection rates because of their respective
background clutter.
 Reduction in spectral dimensionality to the
HSI data cube in order to extract the
spectral features
HSI and FOPEN SAR Data Fusion
 PCA is used to decorrelate data and
maximize the information content in a
reduced number of features
 A matched-filtering algorithm with
thresholding was then applied to the HSI
data to detect all pixels of fabric nets.
HSI fabric-net detection with a matchedfiltering algorithm (left) and terrain
classification map (right).
 The map shows background classes for roads,
grass, trees, and shadow regions; these classes
result from an unsupervised data-clustering
operation that uses the first five principal
components
Combined FOPEN SAR-HSI Analysis and
Fusion
 The SAR data processed with pixel grouping and
threshold.
 Combined analyses, retained only SAR detections
from either open areas or around fabric nets
indicated in the HSI data.
 SAR detections that corresponded to
identifications of trees, far-from-open areas, or
nets on the HSI were considered false alarms.
SAR detection confirmed using HSI
material identified
 There are several strong SAR detections on the left
side of the open area.
 Three pixels match well with military gray-tan
paint, indicating the presence of a vehicle, possibly
military;
 This match confirms the SAR detection.
HSI and HRI Data Fusion
 Sharpening the HSI data
 conduct a combined spatial-spectral
analysis
 Background classification and anomaly
detection are first obtained from HSI data.
 Applying the results to the sharpened HSI
data provides enhanced background
classification and target detection.
HSI and HRI Data Fusion – cont’
 The HRI data provide target and
background boundaries with spatial edge
detection.
 These edges, combined with results from
the sharpened HSI data, spatially enhance
the definition of targets and backgrounds.
 Finally, spectral-matched filtering for target
detection is applied to the sharpened HSI
data.
References
 Shah, P.; Jayalakshmi, M.; Merchant, S.N.; Desai, U.B.; ,
"Hierarchical fusion using vector quantization for
visualization of hyperspectral images," Information Fusion
(FUSION), 2011 Proceedings of the 14th International
Conference on , vol., no., pp.1-8, 5-8 July 2011
 Z. Zhang, et al., Hyperspectral and panchromatic image
fusion using unmixing-based constrained nonnegative
matrix factorization, Optik - Int. J. Light Electron Opt.
(2012), http://dx.doi.org/10.1016/j.ijleo.2012.04.022
 Multisensor Fusion with Hyperspectral Imaging Data:
Detection and Classification
Su May Hsu , Hsiao-hua K. Burke

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