# Integrating Textural and Spectral Features to Classify Silicate-Bearing Rocks Using Landsat 8 Data
## 4 Results and Discussions
### Spatial Textural Feature Analysis
#### 4.1.2 Feature Vector Selection  
In this study, our aim is to explore whether the incorporation of textural features can assist in distinguishing different silicate rocks. Hence, different combinations of texture images fused with all seven spectral features are examined. A total of 127 combinations of texture and spectral vectors are possible, as detailed in Table 2. Then, the J-M distance is calculated between pairwise rocks to select the optimal combinations of input feature vectors, as shown in Figure 5. Figure 5 shows the feasibility of different vector combinations for lithological identification in the form of matrix. Each element \((i,j)\) (here the \(i\) and \(j\) ranges from 1 to 7 and from 1 to 35, respectively) in the matrix indicates the vector combination in Series \(i\) and row \(j\) in Table 2. It needs to be noted that the element (0, 0) in the matrix (Figure 5) indicates the seven spectral vectors without textural features. The value of element \((i,j)\) indicates the J-M distance between two classes. For example, element (3, 4) indicates the vector combination in Series 3 and row 4 in Table 2, namely \(SF+TF126\); the value of element (3, 4) indicates the J-M distance between two classes calculated using the vector combination of \(SF+TF126\). The matrices in Figure 5 were quantified using shades of color, which will help to visually distinguish the different performances of vector combinations in identifying pairwise rocks. Figure 5 provides the following information:  
1. For all six groups of pairwise rocks, the J-M distance increases significantly with the number of textural vectors, indicating that the incorporation of texture is useful for improving the identification of rocks. Moreover, for the same number of textural vectors, different combinations of them generate different J-M distances. The statistically significant J-M distances for the same number of vectors are detailed in Table 3. The textural vectors of \(TF4\), \(TF7\), and \(TF6\) had better performance in identifying gabbro-serpentinite, while \(TF3\), \(TF5\), and \(TF1\) were more effective in identifying gabbro-granite. The textural vectors of \(TF2\) and \(TF3\) were more effective for gabbro-quartzose rock; \(TF4\), \(TF6\), and \(TF1\) for serpentinite-granite; \(TF4\), \(TF5\), and \(TF6\) for serpentinite-quartzose rock; and \(TF6\), \(TF2\), \(TF3\), and \(TF2\) were more effective for identifying granite-quartzose rock. For all six pairs of rocks, the J-M distance has the highest value when all seven vectors are incorporated. 2. It is clear that gabbro-serpentinite has the largest J-M distance, followed by serpentinite-granite, gabbro-granite, gabbro-quartzose rock, serpentinite-quartzose rocks and granite-quartzose rocks, which suggests that textural features are more useful for identifying granite and quartzose rocks. To further examine the performance of texture images in identifying different pairs of rocks, the increase in class separability for the seven series that have statistically significant J-M distances for the same numbers of feature vectors (Table 3) were calculated, as shown in Figure 6. The increase in class separability is, in fact, the difference in value of J-M distance between the seven series with the seven spectral vectors. It is evident that the incorporation of textural vectors has a remarkable effect on the following pairs of rocks: serpentinite-quartzose rock, granite-quartzose rock, gabbro-quartzose rock, and gabbro-granite. In particular, the textural vectors performed best on serpentinite-quartzose  
Figure 5: J–M distance of pairwise rocks in different combinations of texture and spectral vectors. Ga is gabbro, Se is serpentinite, Gr is granite, and Qu is quartzose rock. The labels in **(a)** also apply to (**b–f**). Different colors in this figure means the different J–M distance. A darker shades of color means a larger J–M distance. rock and granite-quartzose rock.