Data Background & Collation Methodology

Satellites from the United States Air Force Defense Meteorological Satellite Program (DMSP) circle the earth 14 times per day. They record the intensity of Earth-based lights with their Operational Linescan System (OLS) sensors since the 1970s, with a digital archive beginning in 1992. These sensors were designed to collect low-light imaging data for the purpose of detecting moonlit clouds, but a byproduct is that lights from human settlements are recorded. Each satellite observes every location on the planet every night at some instant between 8:30 and 10:00 pm local time. National Oceanic and Atmospheric Administration’s (NOAA) National Geophysical Data Center (NGDC) processes this data by removing observations for places experiencing the bright half of the lunar cycle, the summer months when the sun sets late, auroral activity (the northern and southern lights),and forest fires. Observations where cloud cover obscures the earth’s surface are also excluded.These restrictions remove intense sources of natural light, leaving mostly man-made light. Finally, data from all orbits of a given satellite in a given year are averaged over all valid nights to produce a satellite-year dataset.

Raw Data Variants: DMSP|OLS {1992 - 2013}

There are two sets of zipped files for each satellite-year: “Average Visible, Stable Lights, & Cloud Free Coverages” and “Average Lights x Pct”. The latter multiplies each pixel by the percent frequency of light detection. Though without any specific clarification the former, composite is what is used in ecocnomic analyis by Henderson and Shenoy. The latter is generally to infer gas flaring volumes.We have distributed the numbers for 2001 and 2011 to verify this.

  • There are two broad bands Average and Composite, Composite has following sub-categories
  • Average Visible
  • Cloud Free
  • Stable

A distribution of the same is shown below.

From the distribution (comparing it with H&W tables) there are two options, one is to use

Scatter Plot 2001: Night Lights {Composite Stable} & GSDP

Appendix Charts

Single Year Composite Stable Distribution

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