Automated image endmember extraction from hyperspectral imagery is a challenge and a critical step in spectral mixture
analysis (SMA). Over the past years, great efforts were made and a large number of algorithms have been proposed to
address this issue. Iterative error analysis (IEA) is one of the well-known existing endmember extraction methods. IEA
identifies pixel spectra as a number of image endmembers by an iterative process. In each of the iterations, a fully
constrained (abundance nonnegativity and abundance sum-to-one constraints) spectral unmixing based on previously
identified endmembers is performed to model all image pixels. The pixel spectrum with the largest residual error is then
selected as a new image endmember. This paper proposes an updated version of IEA by making improvements on three
aspects of the method. First, fully constrained spectral unmixing is replaced by a weakly constrained (abundance
nonnegativity and abundance sum-less-or-equal-to-one constraints) alternative. This is necessary due to the fact that only
a subset of endmembers exhibit in a hyperspectral image have been extracted up to an intermediate iteration and the
abundance sum-to-one constraint is invalid at the moment. Second, the search strategy for achieving an optimal set of
image endmembers is changed from sequential forward selection (SFS) to sequential forward floating selection (SFFS)
to reduce the so-called "nesting effect" in resultant set of endmembers. Third, a pixel spectrum is identified as a new
image endmember depending on both its spectral extremity in the feature hyperspace of a dataset and its capacity to
characterize other mixed pixels. This is achieved by evaluating a set of extracted endmembers using a criterion function,
which is consisted of the mean and standard deviation of residual error image. Preliminary comparison between the
image endmembers extracted using improved and original IEA are conducted based on an airborne visible infrared
imaging spectrometer (AVIRIS) dataset acquired over Cuprite mining district, Nevada, USA.
A procedure has been developed to measure the spatial mis-registration of the bands of imaging spectrometers using data acquired by the sensor in flight. This is done for each across-track pixel and for all bands, thus allowing the measurement of the instrument's 'keystone' and related inter-band spatial shifts. The procedure uses spatial features present in the scene. The inter-band spatial relationship determinations are made by correlating these features as detected by the various bands. Measurements have been made for a number of instruments including the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), Hyperion, Compact Airborne Spectrographic Imager (casi), SWIR (Short Wave Infra-Red) Full Spectrum Imager (SFSI), and Aurora. The measurements on AVIRIS data were performed as a test of the procedure; since AVIRIS is a whisk-broom scanner it is expected to be free of keystone. The airborne Aurora, casi, and SFSI and the satellite sensor Hyperion are all pushbroom instruments, exhibiting varying degrees of keystone. The potential impact of keystone upon spectral similarity measures is examined.
A procedure has been developed to measure the band-centers and bandwidths for imaging spectrometers using data acquired by the sensor in flight. This is done for each across-track pixel, thus allowing the measurement of the instrument's slit curvature or spectral 'smile'. The procedure uses spectral features present in the at-sensor radiance which are common to all pixels in the scene. These are principally atmospheric absorption lines. The band-center and bandwidth determinations are made by correlating the sensor measured radiance with a modelled radiance, the latter calculated using MODTRAN 4.2. Measurements have been made for a number of instruments including Airborne Visible and Infra-Red Imaging Spectrometer (AVIRIS), SWIR Full Spectrum Imager (SFSI), and Hyperion. The measurements on AVIRIS data were performed as a test of the procedure; since AVIRIS is a whisk-broom scanner it is expected to be free of spectral smile. SFSI is an airborne pushbroom instrument with considerable spectral smile. Hyperion is a satellite pushbroom sensor with a relatively small degree of smile. Measurements of Hyperion were made using three different data sets to check for temporal variations.
Selecting the best classification bands from hyperspectral images for particular remote sensing application is one of the most important problems in utilizing hyperspectral images. In this paper, the best classification bands selection problem is regarded as optimal feature subset selection problem and the bands in original bands set are divided into redundant and irrelevant. In order to eliminate these two type bands, a multi-level optimal classification bands selection model from hyperspectral images based on genetic algorithm and rough set theory is proposed. Through the initial two steps of the multi-level model, the dimension reduction step and the genetic algorithm based filter step, most of redundant and irrelevant bands are deleted from the original images bands set. From the machine learning perspective, the multi-level model can take both advantages of the filter and wrapper models.
In this paper, an extension matrix based rule inductive learning algorithms have been presented. Exception the introduction of this rule inductive learning algorithm, we proposed a novel algorithm for discreting continuous valued attributes which is essential preprocessing step for applying symbol rule inductive algorithms to remotely sensed data analysis. Some initial results are finally given which can demonstrate the advantages of rule-based classification.
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