Characterisation of night-time outdoor lighting in urban centres using cluster analysis of remotely sensed light emissions

TL;DR

This study uses satellite imagery and cluster analysis to characterize and compare night-time outdoor lighting in urban centers over time, revealing increased emissions and a shift towards blue light, with implications for monitoring light pollution.

Contribution

It demonstrates the feasibility of using ISS satellite images combined with cluster analysis to characterize urban night-time lighting emissions over time.

Findings

Overall increase in light emissions from 2012 to 2021

Shift in light emissions towards blue spectrum

ISS imagery can effectively characterize artificial light emissions

Abstract

Evidence of the negative impact of light pollution on ecosystems is increasing every year. Its monitoring and study requires the identification, characterisation and control of the emitting sources. This is the case of urban centres with outdoor lighting that spills light outside the place it is intended to illuminate. The quantity and nature of the pollutant (artificial light at night) depends on the lamps used and how they are positioned. This is important because a greater proportion of blue light means a greater scattering effect. In this study, we analysed the emissions of 100 urban centres in the north of Granada province (Spain), using International Space Station (ISS) images from 2012 and 2021, in order to compare the results with public lighting inventories and verify the validity of these data for characterising night-time lighting emissions. Using inference and cluster analysis techniques, we confirmed an overall increase in emissions and a shift in their colour towards blue, consistent with the results of the lighting inventory analysis. We concluded that it is possible to use ISS imagery to characterise artificial light emissions and the lighting that causes them, none the less there are a number of inherent problems with the data and the way it was collected that require the results to be interpreted with caution.