The light pollution map has two base layers (road and hybrid Bing maps), VIIRS/World Atlas overlays and point feature overlay (SQM, SQC and Observatories).
Direct annual comparisons are to be avoided as there are too many factors involved. If you want an analysis of radiance (VIIRS/DMSP) changes over a period of time, then please use the Lighttrends application.
For more information view the help.
Send comments about the map to Jurij Stare