Abstract
Remotely sensed artificial lighting radiances at night can provide spatially explicit proxy measures of the magnitude of human activity. Satellite-derived nighttime light images, mainly provided by the Defense Meteorological Satellite Program (DMSP) and the Visible Infrared Imaging Radiometer Suite (VIIRS) day/night band (DNB), have been increasingly used to study demographic and socioeconomic activities for a wide range of issues—for instance, human population dynamics, economic growth, and urbanization process—at multiple scales. In practice, the lack of texture information regarding man-made surfaces would usually lead to substantial difficulty in delineating the spatial dynamics in human settlements due to the diverse distributions of artificial nocturnal lighting sources, which are closely related to the predominant land-use/land-cover (LULC) types and their evolutions. An understanding of how nighttime lighting signals respond to synchronous anthropogenic LULC changes, therefore, is crucially important for the spatiotemporal investigations of human settlement dynamics. In this study, we used DMSP-derived nighttime light (NTL) data and Landsat-derived LULC maps to quantitatively estimate the pixel-level responses of NTL signals to different types of human-induced LULC conversions between 1995 and 2010 across China. Our results suggest that the majority (>70%) of pixel-level LULC conversions into artificial lands (including urban, rural, and built-up lands) might show a statistically significant increase in nighttime brightness with an average >20 (in digital number, DN) step change in nighttime lights (dNTL), both of which are distinctly higher than that in the LULC conversions into non-man-made surfaces on the whole. A receiver operating characteristic (ROC) curve-based analysis implies that we might have an average chance of ~90% to identify the nationwide LULC conversions into man-made surfaces from all types of conversions through the observed changes in artificial nocturnal luminosity signals. Moreover, ROC curve-based analyses also yield two nation-level optimal dNTL thresholds of 4.8 and 7.8 DN for recognizing newly emerged three types of artificial lands and urban lands between 1995 and 2010 across the entire country, respectively. In short, our findings reveal fundamental insights into the quantitative connections between the anthropogenic LULC changes and the corresponding responses of synchronous nightlight signals at the pixel-level, which are generally essential for further applications of satellite-derived nocturnal luminosity data in the spatiotemporal investigations of human settlement dynamics.
Highlights
Satellite-based observations of artificial nocturnal brightness have been extensively used for a range of issues related to human activity because of the well-documented significant relationships between nighttime lighting (NTL) signals and several urbanization, demographic, and socioeconomic variables over time and space [1,2,3,4,5,6,7,8,9,10]
The saturation and over-glow effects of nightlight signals can markedly affect the spatial identifications of artificial land features [25,31,34]
In the absence of explicit target pixels and included non-target pixels likely occur in the periphery of local hot spots of urbanizing texture information regarding artificial surfaces, it is often very hard to spatially identify diverse areas, where the capability of nighttime lighting signals is probably limited by both the complexity human activities and their dynamics at a fine scale merely using the observed magnitude of nighttime of human activity and the over-glow effect of Defense Meteorological Satellite Program (DMSP) NTL images
Summary
Satellite-based observations of artificial nocturnal brightness have been extensively used for a range of issues related to human activity because of the well-documented significant relationships between nighttime lighting (NTL) signals and several urbanization, demographic, and socioeconomic variables over time and space [1,2,3,4,5,6,7,8,9,10]. An understanding of the connection between nighttime lights and corresponding land features and how nightlight signals respond to anthropogenic land-use and land-cover (LULC) changes at the pixel level is crucial for further applications of remotely sensed nocturnal luminosity data. Despite their fundamental importance, these two issues are less well understood. This study, together in association with our previous investigation [16], represents an attempt to provide a basic understanding of the connections between two satellite-based observations of nocturnal light radiances and the LULC types and their synchronous alterations for further applications of nighttime light data in studies of human settlement dynamics
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