Empirical Modelling of Public Lighting Emission Functions

Espey, B. R.

doi:10.3390/rs13193827

“…For the residential areas, we chose locations where various types of LPS lighting dominated. This is because these older units have the widest distribution of light, and so the largest proportion of direct to diffuse emission, with up to 10% of the lamp output being directly emitted above the horizontal for LPS 55 W prismatic lens units [9]. Our aim was also to model locations which can be readily compared with spacecraft data, and the relatively monochromatic light provided by LPS units facilitates calculations to convert from lumens to watts, which are the more standard units for earth observation (see also Section 3.7).…”

Section: Dublin Residential Areasmentioning

confidence: 99%

“…Remote Sens. 2023, 15, 2973 2 of 16 As discussed in our first paper [9]-hereafter Paper One-our method to obtain the emission function involves an innovative, semi-empirical, GIS-based approach. In this approach, we model the emission data from the ground upwards using information about public lighting, including the angular photometry of the individual lanterns, as well as elevation data at 1-2 m spatial resolution to provide detailed information on obstructions, and we refer the reader to Paper One for background details.…”

Section: Introductionmentioning

confidence: 99%

Real-World Urban Light Emission Functions and Quantitative Comparison with Spacecraft Measurements

Espey

¹

,

Yan

²

,

Patrascu

³

2023

Remote Sensing

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We provide quantitative results from GIS-based modelling of urban emission functions for a range of representative low- and mid-rise locations, ranging from individual streets to residential communities within cities, as well as entire towns and city regions. Our general aim is to determine whether lantern photometry or built environment has the dominant effect on light pollution and whether it is possible to derive a common emission function applicable to regions of similar type. We demonstrate the scalability of our work by providing results for the largest urban area modelled to date, comprising the central 117 km2 area of Dublin City and containing nearly 42,000 public lights. Our results show a general similarity in the shape of the azimuthally averaged emission function for all areas examined, with differences in the angular distribution of total light output depending primarily on the nature of the lighting and, to a smaller extent, on the obscuring environment, including seasonal foliage effects. Our results are also consistent with the emission function derived from the inversion of worldwide skyglow data, supporting our general results by an independent method. Additionally, a comparison with global satellite observations shows that our results are consistent with the deduced angular emission function for other low-rise areas worldwide. Finally, we validate our approach by demonstrating very good agreement between our results and calibrated imagery taken from the International Space Station of a range of residential locations. To our knowledge, this is the first such detailed quantitative verification of light loss calculations and supports the underlying assumptions of the emission function model. Based on our findings, we conclude that it should be possible to apply our approach more generally to produce estimates of the energy and environmental impact of urban areas, which can be applied in a statistical sense. However, more accurate values will depend on the details of the particular locations and require treatment of atmospheric scattering, as well as differences in the spectral nature of the sources.

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“…Existing skyglow models have used estimated factors for blocking (Aubé & Simoneau, 2018), or inferred it indirectly from observations (Falchi et al., 2016; Kocifaj et al., 2019). However, these methods do not yet correctly account for the geographic variability in obstacle properties (see e.g., Espey, 2021). Direct measurement of the upward light emission using multi‐angle views is therefore critically important for the progress of this field, and cannot wait for future satellites.…”

Section: Evaluating Impact and Properties Of Artificial Lightsmentioning

confidence: 99%

Multiple Angle Observations Would Benefit Visible Band Remote Sensing Using Night Lights

Kyba

¹

,

Aubé

²

,

Bará

³

et al. 2022

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The spatial and angular emission patterns of artificial and natural light emitted, scattered, and reflected from the Earth at night are far more complex than those for scattered and reflected solar radiation during daytime. In this commentary, we use examples to show that there is additional information contained in the angular distribution of emitted light. We argue that this information could be used to improve existing remote sensing retrievals based on night lights, and in some cases could make entirely new remote sensing analyses possible. This work will be challenging, so we hope this article will encourage researchers and funding agencies to pursue further study of how multi-angle views can be analyzed or acquired.Plain Language Summary When satellites take images of Earth, they usually do so from directly above (or as close to it as is reasonably possible). In this comment, we show that for studies that use imagery of Earth at night, it may be beneficial to take several images of the same area at different angles within a short period of time. For example, different types of lights shine in different directions (street lights usually shine down, while video advertisements shine sideways), and tall buildings can block the view of a street from some viewing angles. Additionally, since views from different directions pass through different amounts of air, imagery at multiple angles could be used to obtain information about Earth's atmosphere, and measure artificial and natural night sky brightness. The main point of the paper is to encourage researchers, funding agencies, and KYBA ET AL.

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“…2 of 15 knowledge there have been no integration of lighting and obstruction information to produce a comprehensive picture -see, e.g. [10].…”

Section: Introductionmentioning

confidence: 99%

Real-World Urban Light Emission Functions and Quantitative Comparison With Spacecraft Measurements

Espey¹,

Yan²,

Patrascu³

2023

Preprint

0

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We provide quantitative results from GIS-based modelling of urban emission functions for a range of representative low- and mid-rise locations, ranging from individual streets to residential communities within cities as well as entire towns and city regions with the aim of whether lantern photometry or built environment has the dominant effect on light pollution. We demonstrate the scalability of our work by providing results for the largest urban area modelled to date, comprising the central 117 km2 area of Dublin City and containing nearly 42,000 public lights. Our results show a general similarity in the shape of the azimuthally-averaged emission function for all areas examined, with differences in total light output distribution depending primarily on the nature of the lighting and, to a smaller extent, on the obscuring environment including seasonal foliage effects. A comparison with global satellite observations shows that they are consistent with the deduced angular emission function for other low-rise areas worldwide. We further validate our approach by comparing results for a range of urban locations by the close agreement observed in a detailed comparison of with calibrated imagery from the International Space Station. To our knowledge, this is the first such detailed quantitative verification of light loss calculations.

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Empirical Modelling of Public Lighting Emission Functions

Cited by 11 publications

References 17 publications

Real-World Urban Light Emission Functions and Quantitative Comparison with Spacecraft Measurements

Real-World Urban Light Emission Functions and Quantitative Comparison with Spacecraft Measurements

Multiple Angle Observations Would Benefit Visible Band Remote Sensing Using Night Lights

Real-World Urban Light Emission Functions and Quantitative Comparison With Spacecraft Measurements

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