## 4 Results
### Land Surface Temperature Statistic and Its Relationship with Impervious Surface Areas  
The results of LST retrieval (shown in Figure 4) correspond with the average temperature of each of the cities which was provided by the local statistics office. From 2009 to 2011, due to the influence of the construction of a new airport and the relocation and development of new industrial sites in the cities of HuaDu and CongHua, the urban heat center gradually expanded to a larger area. In addition, due to its geographic advantages, the ports in PanYu gradually fueled the economic development of the inland districts of Guangzhou and contributed to opening up its international trade. Along with such developments, the city of PanYu gradually became a new urban heat island. In the northern and northeastern parts of Guangzhou, surrounded by vegetated rolling hills, the UHI phenomenon was not quite as obvious. There was a positive correlation between the LST product of MODIS and that of HJ-1B (0.178, 0.253 and 0.215 in the year of 2009, 2010, and 2011 separately). In addition, this paper depicts the scatter diagram between the ISA and LST distribution. Figure 5 depicts a correlation between LST and ISA based on LSMA from 2009 and 2011; the correlation parameters were 0.107, 0.137 and 0.258, respectively. Although the distribution of LST and ISA based on LSMA show a positive correlation, a large percentage of high temperature areas are mainly located in areas with a low percentage of ISA in Guangzhou. As shown in the Figure 5, the high temperature areas (higher than 37 \({}^{\circ}\)C) of three years occupied the high percentage of ISA (more than 50%) less than 1%, of which were 0.0122% in 2009, 0.4317% in 2010, 0% in 2011. By contrast, even though there was a slightly negative correlation between the LST and ISA based on SVM-LSMA from 2009 and 2011 the correlation parameter of which were \(-0.1043\); \(-0.1395\); \(-0.3935\) respectively (shown in Figure 6). All the high temperature areas (higher than 37 \({}^{\circ}\)C) were located in areas with a high percentage, the amount of which were 43.15% in 2009, 51.73% in 2010, 65.71% in 2011. Therefore, the ISA results based on the object-based SVM-LSMA algorithm were more coincided with the urban heat phenomenon in Guangzhou. In order to study further the relationship between ISA and LST, we statistically analyzed the characteristics of LST distribution in the impervious surface areas. Before that, because the data was not recorded on the same date each year, a normalization method was used to reclassify the LST results into three types: High, Normal, and Low. The normalization equations are shown in Table 2. In Table 1, \(T_{a}\) represents the average LST and \(Sd\) represents the square deviation of LST. Figure 4: Land surface temperature distribution of Guangzhou from 2009 to 2010. Figure 5: Correlation analysis between pixel-wise impervious surface fraction results and land surface temperature: (**a**) 2009; (**b**) 2010; (**c**) 2011. Figure 6: Correlation analysis between object-based impervious surface fraction results and land surface temperature: (**a**) 2009; (**b**) 2010; (**c**) 2011. In Table 3, it shows that there were less than \(\pm\)0.3 \({}^{\circ}\)C fluctuations in the corresponding LST in impervious surface areas from 2009 to 2011. Within these three years, the percentage of the high temperature category in the impervious areas decreased slightly, from 16.24% to 15.02%. There were also some fluctuations in the percentage of normal- and low LST, these two types decreased to 66.48% and 18.47% in 2011. Nevertheless, it was obvious that the percentage of ISA increased steadily within these three years, with the annual growth rate of 2.03%. Its corresponding LST had reached an average LST of 37.24 \({}^{\circ}\)C, which was the highest within these three years. In summary, as a result of the rapid urbanization, the total percentage of impervious surface areas is still increasing. The expansion of ISA still plays a significant role in the urban heat island in Guangzhou.