Modelling of light pollution in suburban areas using remotely sensed imagery and GIS

Abstract

This paper describes a methodology for modelling light pollution using geographical information systems (GIS) and remote sensing (RS) technology. The proposed approach attempts to address the issue of environmental assessment in sensitive suburban areas. The modern way of life in developing countries is conductive to environmental degradation in urban and suburban areas. One specific parameter for this degradation is light pollution due to intense artificial night lighting. This paper aims to assess this parameter for the Athens metropolitan area, using modern analytical and data capturing technologies. For this purpose, night-time satellite images and analogue maps have been used in order to create the spatial database of the GIS for the study area. Using GIS advanced analytical functionality, visibility analysis was implemented. The outputs for this analysis are a series of maps reflecting direct and indirect light pollution around the city of Athens. Direct light pollution corresponds to optical contact with artificial night light sources, while indirect light pollution corresponds to optical contact with the sky glow above the city. Additionally, the assessment of light pollution in different periods allows for dynamic evaluation of the phenomenon. The case study demonstrates high levels of light pollution in Athens suburban areas and its increase over the last decade.

Introduction

Night light emissions that originate mainly from large urban areas are among the main elements of environmental pollution. The rapid growth of night sky brightness due to light pollution is not only damaging the perception of the starry sky, but is also silently altering even the perception of moonlit nights by mankind (Cinzano et al., 2001a).

Astronomers are among the worst affected by urban sky glow (IDSA, 1996, Falchi and Cinzano, 2000), but environmentalists are also worried about the direct effects on wildlife, as well as the reduction in the overall ‘quality of life’ for the people of Europe. Among the negative effects of light pollution are: (i) disturbance of biological rhythms, (ii) psychological effects, and (iii) environmental degradation (Shaflik, 1997, Borg, 1996).

Over the last decades, many scientists have modelled light pollution in various ways, e.g. creating maps showing the sky glow variation at different altitudes and azimuths from different observation sites (Garstang, 1986), mapping artificial sky brightness in large territories (Cinzano et al., 2000, Cinzano et al., 2001b), spatial population definition using DMSP–OLS data (Elvidge et al., 1997), or urban area mapping (Imhoff et al., 1997). The interest in light pollution has been growing in many fields of science, extending from the traditional field of astronomy to atmospheric physics, environmental sciences, natural sciences and even human sciences (Cinzano et al., 2001a, Cinzano et al., 2001b; Doll et al., 2000), although the Greek literature on the issue is rather limited (Chalkias et al., 2002).

Artificial lighting disturbs the ‘tranquility’ (grade of naturality) of an area. This kind of pollution is directly correlated to the presence of human activities and for this reason is considered of high interest. Tranquility maps are a valuable tool for the classification of parts of the countryside, as well as for the classification of areas that are relatively undisturbed by noise and visual intrusion, areas representative of ‘unspoilt’ countryside.

Tranquility can be defined as ‘the sense of peace, quiet and natural pureness of the countryside’ (Bell, 1999). The main factors that disturb tranquility are:

• light pollution (buildings, human constructions, artificial lighting, etc.)

• noise pollution (road traffic, industry, railroads, etc.)

• absence of woodland.

While tranquility disturbance is profound in modern urban areas, suburban and rural areas also face the same problems due to urban growth, intense cultivation activities, transportation network expansion, etc.

This study was conducted within the framework of the European project MANTLE (mapping night-time light emissions). The main target of the MANTLE project was to assess the potential of using satellite resources to produce maps of light emissions and urban night-time light intensity levels in the EU.

The scope of this study is to develop and present a prototype methodology for modelling light pollution, as well as to estimate the grade of light pollution in Athens suburban areas by creating various corresponding maps.