A Stepwise Calibration of Global DMSP/OLS Stable Nighttime Light Data (1992–2013)

Xuecao Li,Yuyu Zhou

doi:10.3390/rs9060637

Abstract

The Defense Meteorological Satellite Program (DMSP)/Operational Linescan System (OLS) stable nighttime light (NTL) data provide a wide range of potentials for studying global and regional dynamics, such as urban sprawl and electricity consumption. However, due to the lack of on-board calibration, it requires inter-annual calibration for these practical applications. In this study, we proposed a stepwise calibration approach to generate a temporally consistent NTL time series from 1992 to 2013. First, the temporal inconsistencies in the original NTL time series were identified. Then, a stepwise calibration scheme was developed to systematically improve the over- and under- estimation of NTL images derived from particular satellites and years, by making full use of the temporally neighbored image as a reference for calibration. After the stepwise calibration, the raw NTL series were improved with a temporally more consistent trend. Meanwhile, the magnitude of the global sum of NTL is maximally maintained in our results, as compared to the raw data, which outperforms previous conventional calibration approaches. The normalized difference index indicates that our approach can achieve a good agreement between two satellites in the same year. In addition, the analysis between the calibrated NTL time series and other socioeconomic indicators (e.g., gross domestic product and electricity consumption) confirms the good performance of the proposed stepwise calibration. The calibrated NTL time series can serve as useful inputs for NTL related dynamic studies, such as global urban extent change and energy consumption.

Highlights

The Defense Meteorological Satellite Program (DMSP)/Operational Linescan System (OLS)stable nighttime light (NTL) data have been extensively used in a range of study fields, including socioeconomic research, electricity generation activity, population distribution, urban extent mapping, and environmental assessment [1,2,3,4,5,6,7,8,9]
This study aims to provide a calibrated DMSP/OLS NTL time series (1992–2013) with the following criteria: (1) to improve the systematic consistency of NTL time series derived from different satellites instead of the whole NTL dataset; (2) to make full use of the temporally neighbored image as a reference for calibration at the global level; and (3) to generate a temporally consistent long-term NTL time series with less modifications of the original digital number (DN) values
We evaluated the agreement of NTL images derived from different satellites in the same year after calibration using an indicator of normalized difference index (NDI) [25]

Summary

Introduction

Stable nighttime light (NTL) data have been extensively used in a range of study fields, including socioeconomic research, electricity generation activity, population distribution, urban extent mapping, and environmental assessment (e.g., light pollution) [1,2,3,4,5,6,7,8,9]. Due to the lack of on-board calibration, varied atmospheric conditions, satellite shift or sensor degradation, the obtained digital number (DN) of NTL time series cannot be directly used across years to detect these dynamics [15,16]. A variety of studies have been carried out to calibrate the NTL dataset for achieving a temporally consistent and comparable time series. Elvidge et al [16] proposed a general framework for calibrating

Objectives

Methods

Results

Conclusion