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Wavelet Spectral Analysis for Automatic Reduction of Hyperspectral Imagery



Table1. Similarity Measures Between The Original Versus the Reconstructed Spectral Signature for one Class in our image.
Level Correlation
1 .9974
2 .9936
3 .9804
4 .9558
5 .9224

Table2. Number of training data for classification
Class Name Training data (NO.of pixels)
Wood 1290
Grass\paster 467
Soybeans-notill 1108
Corn 700
Corn-notill 1527
Hay_windrowed 630
Grass\trees 868
Alfalfa 92
Oatas 303
Grass\pastuer-moved 2645
Soybeans-clean 710
Corn-min 921

4. Wavelet-Based Reduction and Classification Accuracy
We have experimentally validated our Wavelet Based dimension reduction by using remotely sensed image tests from a hyperspectral scene. Using the ENvironment for Visualizing Images (ENVI) as a tool for classification accuracy to assess the accuracy of our Wavelet Based method and PCA we calculated the error (confusion) matrix of several classification methods for the same level of compression between the Wavelet and PCA.

Supervised classification methods are trained on labeled data. As the number of bands increases the number of training data for classification is increased too. In usual the minimum number of training data for each class is 10N, where N is the number of bands. The details about the number of training pixels are shown in Table2.

Now it is the turn of introducing four statistical supervised classification methods that we used in this work.

Maximum Likelihood (ML)
This method assumes that the statistical for each class in each band are normally distributed and computes all of the probability of classes for each pixel and assign that pixel to the class with the highest probability value.

MahalaniBis distance (MB)
This algorithm is similar to ML algorithm but in MB algorithm it is assumed that the covariance matrix of all classes is equivalent and of course this algorithm is faster than ML algorithm.

Minimum Distance (MD)
In this algorithm for each training sample region the mean is calculated and also the Euclidean distance between each pixel and the means of each training sample region is calculated. The pixel is labeled to that class that has minimum distance.

ParallelePiped (PP)
The parallelepiped classifier is a very simple classifier, in this algorithm the range in all bands describes a multidimensional box or parallelepiped, if, on classification, pixel are found to lie in such a parallelepiped they are labeled as belong to that class.

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