IV. ANOMALY DETECTION
Detecting anomalies in the radar imagery involves
locating pixels with spectral signatures that are significantly
different from the background. RX Anomaly detector, a
training–free unsupervised classification scheme, detects
signatures that are distinct from the surroundings with no prior
knowledge. These unsupervised techniques are very fast and
do not depend on ground truth information. The algorithm
uses the covariance matrix to calculate the Mahalanobis
distance between the test pixels and the mean of the
background pixels. Suppose D is the number of spectral bands
and r is a Dx1 column pixel vector of the image. Then the RX
detector (RXD) implements a filter specified by