Objectives It is important to know the pattern of Pakistan's regional development for the construction of China-Pakistan Economic Corridor.
Methods We used visible infrared imager radiometer suite(VIIRS) nighttime light remote sensing image as the main data source, and implemented Savitzky-Golay(SG) filtering algorithm to repair the missing values of the images. Night time light change ratio (NLCR), Mann-Kendall(MK) trend test method and rank-size rule were carried out to study the nighttime light change patterns of province level, city level, geographic grid level, and east-west zone in Pakistan.
Results The analysis result of NLCR shows that from 2012 to 2019, NLCR of the entire Pakistan is 47.96% and all provincal regions has developed to a certain degree with NLCR larger than 15%. NLCR of Gwadar Port is 126.94%, which is the highest in 15 node cities on east and west lines of China-Pakistan Economic Corridor. Additionally, the development of 15 node cities on east and west lines of China-Pakistan Economic Corridor was unbalanced. The results of MK trend test show that at the geographic grid scale of 5 km, there are 1 905 grids with the total nighttime light upward trend in Punjab and 338 grids with the total nighttime light downward trend in Sindh. It is found that most grids with the total nighttime light downward trend are located in rural areas of Sindh, which is consistent to the fact that there is a serious power shortage problem in rural areas of Sindh. The analysis results of rank-size rule show that the Pareto indexes of both eastern and western zones are gradually decreased, indicating that the distribution of urban size in Pakistan becomes more balanced. And the lack of stable power supply may be the reasons for the low brightness of nighttime light in some areas.
Conclusions The regional development patterns of Pakistan under long-term time series and multiple spatial scales can provide a certain scientific basis for the planning of China-Pakistan Economic Corridor.
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