Fig. 1. Spatial distribution of 200 cities around the world (a) and 80 cities along the Belt and Road (b)

Fig. 2. Spatial distribution of intercalibrated nighttime lights along the Belt and Road (a), and the distribution of intercalibrated nighttime lightsin Zhengzhou, China (b)

Fig. 3. Division of 1 km concentric ring layer and spatial distribution of urban land in Zhengzhou, China

Fig. 4. Net increase in urban land along the Belt and Road from 1992 to 2015

Fig. 5. Inter-annual changes of urban land area in the ten major sub-regions from 1992 to 2015

Fig. 6. Fitting curves of urban land density functions in 1992, 2003 and 2015

Fig. 7. Box-plots of fitting parameters α, c, and D of urban land density functions of different urban sizes in 1992, 2003 and 2015

Fig. 8. Fitting curves of urban land density functions of three different urban sizes along the Belt and Road

Fig. 9. Fitting curves of urban land density functions in the six sub-regions along the Belt and Road

Fig. 10. Statistics of k_p for different urban sizes in 1992, 2003 and 2015

Fig. 11. Changes of main urban areas of different urban sizes from 1992 to 2003 and 2003 to 2015

Fig. 12. Comparison of the growth rates r₂ and r₁ for different urban sizes from 1992 to 2003 and 2003 to 2015

Fig. 13. Statistical relationship between the weighted lighting area and urban land area of 9 cities along the Belt and Road

Fig. 14. Statistical relationship between urban land area and urban population of 9 cities along the Belt and Road

Fig. 15. Comparative analysis of urban land area of ESA-CCI and GAIA in 1992, 2003 and 2015