The vectorial image is not perfectly accurate. Graphic presents only basic content of street and city lights' heatmap. Some settlements could be missed or overexposed. The base data image (2012) was captured by NASA using the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite. 
Source image: https://eoimages.gsfc.nasa.gov/images/imagerecords/144000/144875/BlackMarble_2012_C1.jpg
Own work
ErenPasciaBulbul