  The analysis of the colour of artificial lights at night has an impact on
diverse fields, but current data sources have either limited resolution or
scarce availability of images for a specific region. In this work, we propose
crowdsourced photos of streetlights as an alternative data source: for this, we
designed NightUp Castelldefels, a pilot for a citizen science experiment aimed
at collecting data about the colour of streetlights. In particular, we extract
the colour from the collected images and compare it to an official database,
showing that it is possible to classify streetlights according to their colour
from photos taken by untrained citizens with their own smartphones. We also
compare our findings to the results obtained from one of the current sources
for this kind of study. The comparison highlights how the two approaches give
complementary information about artificial lights at night in the area. This
work opens a new avenue in the study of the colour of artificial lights at
night with the possibility of accurate, massive and cheap data collection.
