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Astronomers first recognised the deleterious effect of light pollution
on the night sky and its impact on their observations and moved observatories
to more distant sites. Currently sky brightness is estimated to be increasing at
approximately 6.5% per year in Europe, and nearly 10% globally. Some
observatory locations are being increasingly impacted by this growth and many
of today’s children will never see the Milky Way in a pristine night sky. While the
advent of LED technology should have heralded an improvement in night sky
conditions, there are additional problems with cheap blue-rich lighting
technology which, from an astronomer’s perspective, can lead to worsening sky
conditions.
Closer to our urban areas it is increasingly recognised that the bright night-time
environment is having important ecological and health consequences, as well as
an energy and carbon cost. For all these reasons we need to better understand
light pollution, its main sources, and how it can be mitigated. While a range of
empirical and analytic models have been developed to understand how light
leaves the urban environment, some involving the application of radiative
transfer codes, the assumptions and modelling can be either too simplistic or
overly computationally intensive to be applied to realistic urban environments.
In my talk I shall give an overview of light pollution and describe a
computationally efficient geographical information system (GIS) based approach
to the estimation of urban light pollution. I shall illustrate the approach with an
application to the question of how foliage affects light levels and also
quantitatively compare predictions with calibrated International Space Station
imagery.