National Geophysical Data - Nighttime Lights Time Series

Overview

Version 2 DMSP-OLS Nighttime Lights Time Series

The files are cloud-free composites made using all the available
archived DMSP-OLS smooth resolution data for calendar years. In cases
where two satellites were collecting data – two composites were produced.
The products are 30 arc second grids, spanning -180 to 180 degrees
longitude and -65 to 65 degrees latitude. A number of constraints are
used to select the highest quality data for entry into the composites:

  • Data are from the center half of the 3000 km wide OLS swaths.
    Lights in the center half have better geolocation, are smaller,
    and have more consistent radiometry.
  • Sunlit data are excluded based on the solar elevation angle.
  • Glare is excluded based on solar elevation angle.
  • Moonlit data are excluded based on a calculation of lunar
    illuminance.
  • Observations with clouds are excluded based on clouds
    identified with the OLS thermal band data and NCEP surface
    temperature grids.
  • Lighting features from the aurora have been excluded in the
    northern hemisphere on an orbit-by-orbit manner using visual
    inspection.

Each composite set is named with the satellite and the year (F121995 is
from DMSP satellite number F12 for the year 1995). Three image types are
available as geotiffs for download from the version 2 composites:

F1?YYYY_v2_cf_cvg.tif: Cloud-free coverages tally the total number of observations that went into each 30 arc second grid cell. This image can be used to identify areas with low numbers of observations where the quality is reduced. In some years there are areas with zero cloud- free observations in certain locations. F1?YYYY_v2_avg_vis.tif: Raw avg_vis contains the average of the visible band digital number values with no further filtering. Data values range from 0-63. Areas with zero cloud-free observations are represented by the value 255. F1?YYYY_v2_stable_lights_avg_vis.tif: The cleaned up avg_vis contains the lights from cities, towns, and other sites with persistent lighting, including gas flares. Ephemeral events, such as fires have been discarded. Then the background noise was identified and replaced with values of zero. Data values range from 1-63. Areas with zero cloud-free observations are represented by the value 255.

Global composities are available for the satellite years below:

F101992 F101993 F101994 F121994 F121995 F121996 F121997 F121998 F121999 F141997 F141998 F141999 F142000 F142001 F142002 F152001 F152002 F152003 -————————————————————————————————- Each tar ball contains the raw average visible band, cleaned up average visible band, cloud free coverage data, and a readme file. The data files have been compressed with gzip. For information on tar and gzip see our link located at: http://www.ngdc.noaa.gov/dmsp/tar_zip.html -————————————————————————————————- Whenever using or distributing DMSP data or derived images, use the following credit: Image and data processing by NOAA’s National Geophysical Data Center. DMSP data collected by US Air Force Weather Agency. -————————————————————————————————- National Geophysical Data Center E/GC 325 Broadway Boulder, Colorado USA 80305-3328 Fax: 303-497-6513 -————————————————————————————————-