The data was recorded by the Defense Meteorological Satellite Program (DMSP) in the National Geophysical Data Center (NGDC), now part of NOAA National Centers for Environmental Information (NCEI). The data was collected using polar orbiting satellites that provide full cover of the globe twice a day. The satellites have an Operation Linescan system which allows them to detect low levels of visible-near infrared radiance at night. With this data, it is possible to detect clouds illuminated by moonlight, lights from cities and towns, industrial sites, gas flares, fires, lightning, and aurora. The Nighttime Lights of the World data set was complied from Defense Meteorological Satellite Program (DMSP) data spanning October 1994 - March 1995.
In this particular visualization, which is similar to the original Earth at Night dataset, the lights have been colorized based on the light source. The white represents lights generated from electricity, the red shading shows fires, the pink shading indicates light from squid fishing boats, and the blue spots are gas flares from oil rigs. Each is one year's worth of data. The differentiation of fires, boats, electric lights and gas flares was all done by temporal analysis (do the lights stay constant and do they move). The instrument itself is not able to distinguish between them.