978-1-4673-0174-9/12/$31.00 ©2012 IEEE 610 ICALIP2012
Unsupervised Hyperspectral Image Classification Algorithm
By Integrating Spatial-Spectral Information
Belkacem Baassou, Mingyi He,Shaohui Mei, Yifan Zhang
Shaanxi Provincial Key Laboratory of Information Acquisition and Processing (IAP)
School of Electronics and Information, Northwestern Polytechnical University, Xi'an, 710129, China
myhe@nwpu.edu.cn,gaga05@hotmail.fr
Abstract
An integrated spatial-spectral information algorithm
for hyper spectral image classification is proposed,
which uses spatial pixel association (SPA)by exploiting
spectral information divergence (SID),and spectral
clustering to reduce regions number and improve
classification accuracy .Moreover, a class boundary
correction method is also developed to minimize the
misclassified pixels at the edge of each class and to
solve the problem of merged classes. Experiments with
hyper spectral data demonstrate the effectiveness and
advantages of the proposed frame work over some
traditional methods in term of classification accuracy.
1. Introduction
The development of image sensor technology has
made it possible to capture image data in hundreds of
contiguous and very narrow spectral channels covering
a broad spectrum of wavelength, providing a large
amount of detailed information about the spatial and
spectral characteristics of the materials that are present
in the scene. Recently, interest in hyper spectral
imagery has increased; it is viewed as an emerging
valuable remote sensing technology in both military and
civilian applications
[1]
such as wide-area
reconnaissance, vegetation classification, scientific
sensing, environ-mentalmonitoring, lunar soil
identification, targets search, rescue operations, and
also in biomedical applications such as skin cancer
diagnosis.
Hyperspectral image classification is the process of
assigning all pixels in a digital image to particular
classes according to their characteristics
[2]
. As a result
we obtain a thematic map in which each pixel belongs
to a particular class. There are two main classification
schemes, the Supervised and
theUnsupervisedClassification.Supervised classification
can be defined as the process of using samples of
known identity to classify pixels of unknown identity,
while unsupervised classification can be defined as the
identification of natural groups or structures within the
data. It clusters pixels in a data set based only on their
statistics without using previous knowledge about the
spectral classes presented in the image
[3]
. The K-means
algorithm is one of the most commonly used
unsupervised classification schemes
[4]
.
Recent studies show that besides the spectral
information, the spatial information may also provide a
useful knowledge and can greatly improve the
performance of the classification of hyperspectral
images
[5]
.Unfortunately, the spatial information has not
got much attention in the previous research.
In this paper, both spatial and spectral information
are exploited to achieve a better clustering performance.
A spatial pixel association(SPA) process
[6]
isused to
fully exploit the spatial similarity between pixels and
their neighbors by using the Spectral Information
Divergence criterion in order to characterize the
spectral properties provided in a single pixel vectorand
to measure spectral similarity between adjacent
pixels.Moreover, a neighborhood correction algorithm
is carried out as a post processing step to further
improve the performance of classification and to orient
misclassified pixels to take their suitable classes. After
correction a spectral clustering process has been applied
to exploit the information provided by the spectral
dimension in the aim of increasing the classification
performance. Finally, experiments on AVIRIS
hyerspectral data are conducted to verify the
performance of the proposed approachand for
comparison with some traditional methods.
2. Methodology
In a hyperspectral image, pixels from a
homogeneous ground object often present in adjacent
areas, which enable us to use the information provided
by the spatial adjacent pixels location for better