A comparative study of NPP-VIIRS and DMSP-OLS nighttime light imagery for derivation of urban demographic metrics

Nighttime light imageries from two generations of sensors - Defense Meteorological Satellite Program´s Operational Linescan System (DMSP-OLS) and Visible Infrared Imaging Radiometer Suite carried by the Suomi National Polar-Orbiting Partnership (NPP-VIIRS), were utilized to characterize urban areas from the perspective of three aspects (i.e., urban extent, population, and socio-economic activities). The results reveal that remotely sensed nighttime light signal was highly correlated to urban extent, population, and socio-economic activities. The number of urban areas and the total area through thresholding indicates that a 0.06 threshold significantly reduced the blooming effect around large urban areas without attenuating the number of individual small urban clusters for the DMSP-OLS imagery, while this value was smaller than 0.01 for the NPP-VIIRS image. This smaller threshold suggests the superiority of NPP-VIIRS over DMSP-OLS for the delineation of small urban clusters. Furthermore, a comparison between equivalent diameter (ED) and the ratio of area to perimeter suggests that the extracted urban areas (ED <; 50KM) from the NPP-VIIRS imagery was more effective to reveal the spatial complexity than those from DMSP-OLS data. The intra and extra structures of urban areas tended to be hidden in the DMSP-OLS imagery, while this information was much clearer in the NPP-VIIRS imagery. However, NPP-VIIRS imagery did not show apparent advantages over DMSP-OLS on the modeling of overall urban population at the county level in the U.S.A. although NPP-VIIRS had stronger intensity to reflect urban population density. The correlations between socio-economic indicators and nighttime variables demonstrate that NPP-VIIRS can depict urban socio-economic activities better than DMSP-OLS. It is also apparent that education and income index were negatively correlated with light intensity per person, but Gini Coefficient was positively correlated with average light intensity (per - M), implying that larger inequality of income or wealth existed in the urbanized areas with stronger night-lights intensity.