8.1 Introduction

In order to find endmembers, two general approaches have been used in the past. One approach extracts all required endmembers simultaneously, referred to as simultaneous endmember extraction algorithm (SM-EEA) that has already been studied in Chapter 7. The other approach extracts endmembers one at a time sequentially, referred to as sequential EEA (SQ-EEA) which will be discussed in this chapter. In general, extraction of endmembers must be performed by finding all endmembers at once. Hence, an optimal EEA should be an SM-EEA. Unfortunately, this also requires an SM-EEA to conduct an exhaustive search for an optimal set of endmembers. Computationally speaking, this may not be a good option because the process will be extremely slow, especially when the number of endmembers grows. On the other hand, an SQ-EEA can become an acceptable alternative even if it may not be as optimal as an SM-EEA. As will be demonstrated by experiments, in most cases, an SQ-EEA is comparable to an SM-EEA with regard to performance of endmember extraction. Most importantly, two benefits gained by an SQ-EEA can really remedy two major drawbacks suffered from an SM-EEA. One benefit is significant reduction in computing time resulting from SQ-EEA that only needs to find one endmember at a time sequentially without finding all endmembers simultaneously as required by SM-EEA. The second benefit is that SQ-EEA retains previously generated endmembers while continuing to add new endmembers, an ...

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