3.4.3. Block Sequence

proposed PSP-OMPBS.

Since the step method only considers image sampling in the horizontal direction, we further consider another method, which can consider both vertical and horizontal directions simultaneously, called the block method. The block method first splits the image into several *b* × *b* square blocks, as shown in Figure 3c. Then the new pixel is picked from each block in turn. In such a design, the sampling process is performed on the full spatial domain. Theoretically, it would shorten convergence time of PSP-BS, too.

**Figure 3.** Illustration of the pixel transmission sequence of a 9 × 9 hyperspectral image formed by different methods. (**a**) A band-interleaved-by-sample/pixel (BIS/BIP) sequence. (**b**) Step method with *k* = 5. (**c**) The block method with *b* = 3.

In the later sections, we call the PSP-OMPBS implemented with original BIS/BIP sequence, step sequence, and block sequence PSP-OMPBS, S-PSP-OMPBS, and B-PSP-OMPBS, respectively. Finally,wesummarizethedistinctfeaturesofOMPBSandtheproposedPSP-OMPBSinTable1.

 **Table 1.** The basic properties of orthogonal matching pursuit-based BS (OMPBS) and the

