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14 pages, 5646 KiB

Open AccessCommunication

NSKY-CD: A System for Cloud Detection Based on Night Sky Brightness and Sky Temperature

by Luciano Massetti, Alessandro Materassi and Francesco Sabatini

Remote Sens. 2023, 15(12), 3063; https://doi.org/10.3390/rs15123063 - 12 Jun 2023

Viewed by 1505

Abstract

Cloud cover is important meteorological information that still requires expensive equipment to be monitored from the ground, especially at night. The use of artificial lights at night causes light pollution, and clouds amplify this by reflecting light downward. In addition, cloud thermal radiation [...] Read more.

Cloud cover is important meteorological information that still requires expensive equipment to be monitored from the ground, especially at night. The use of artificial lights at night causes light pollution, and clouds amplify this by reflecting light downward. In addition, cloud thermal radiation emissions affect sky temperature. In this study, we describe a system (NSKY-CD) that can be used to detect clouds at night since it integrates a sky quality meter that measures night sky brightness (NSB) and an air temperature and an infrared temperature sensor that measure sky temperature. We defined a cloud detection method based on fixed threshold values determined with two different procedures that we called ‘optimal’ and ‘antimode’. We then quantitatively assessed the performance of these methods in detecting the presence or absence of clouds in the urban area of Florence during two full moon cycles. Accuracy for the ‘optimal’ method varied between 87% and 91%, while for the ‘antimode’ method, it varied between 86% and 89%. Our results suggest that the two parameters are complementary since NSB has a better performance on moonless nights, and the difference between air temperature and sky temperature has a better performance on moonlit nights. Our method can also be used to analyze historical series of NSB to estimate cloud presence backwards, thus providing important information for meteorological, environmental and astronomical studies. Full article

(This article belongs to the Special Issue Light Pollution Monitoring Using Remote Sensing Data II)

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16 pages, 3433 KiB

Open AccessArticle

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

by Brian R. Espey, Xinhang Yan and Kevin Patrascu

Remote Sens. 2023, 15(12), 2973; https://doi.org/10.3390/rs15122973 - 07 Jun 2023

Viewed by 937

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Light Pollution Monitoring Using Remote Sensing Data II)

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22 pages, 3183 KiB

Open AccessArticle

Photometric Catalogue for Space and Ground Night-Time Remote-Sensing Calibration: RGB Synthetic Photometry from Gaia DR3 Spectrophotometry

by Josep Manel Carrasco, Nicolas Cardiel, Eduard Masana, Jaime Zamorano, Sergio Pascual, Alejandro Sánchez de Miguel, Rafael González and Jaime Izquierdo

Remote Sens. 2023, 15(7), 1767; https://doi.org/10.3390/rs15071767 - 25 Mar 2023

Cited by 2 | Viewed by 1961

Abstract

Recent works have made strong efforts to produce standardised photometry in RGB bands. For this purpose, we carefully defined the transmissivity curves of RGB bands and defined a set of standard sources using the photometric information present in Gaia EDR3. This work aims [...] Read more.

Recent works have made strong efforts to produce standardised photometry in RGB bands. For this purpose, we carefully defined the transmissivity curves of RGB bands and defined a set of standard sources using the photometric information present in Gaia EDR3. This work aims not only to significantly increase the number and accuracy of RGB standards but also to provide, for the first time, reliable uncertainty estimates using the BP and RP spectrophotometry published in Gaia DR3 instead of their integrated photometry to predict RGB photometry. Furthermore, this method allows including calibrated sources regardless of how they are affected by extinction, which was a major shortcoming of previous work. The RGB photometry is synthesised from the Gaia BP and RP low-resolution spectra by directly using their set of coefficients multiplied with some basis functions provided in the Gaia catalogue for all sources published in Gaia DR3. The output synthetic magnitudes are compared with the previous catalogue of RGB standards available. Full article

(This article belongs to the Special Issue Light Pollution Monitoring Using Remote Sensing Data II)

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16 pages, 4374 KiB

Open AccessArticle

Citizen Science to Assess Light Pollution with Mobile Phones

by Gorka Muñoz-Gil, Alexandre Dauphin, Federica A. Beduini and Alejandro Sánchez de Miguel

Remote Sens. 2022, 14(19), 4976; https://doi.org/10.3390/rs14194976 - 06 Oct 2022

Cited by 2 | Viewed by 3105

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Light Pollution Monitoring Using Remote Sensing Data II)

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16 pages, 3223 KiB

Open AccessArticle

Night-Time Skyglow Dynamics during the COVID-19 Epidemic in Guangbutun Region of Wuhan City

by Chengen Li, Xi Li and Changjun Zhu

Remote Sens. 2022, 14(18), 4451; https://doi.org/10.3390/rs14184451 - 06 Sep 2022

Cited by 3 | Viewed by 1449

Abstract

The COVID-19 epidemic lockdown has a direct influence on urban socioeconomic activity, including night-time light (NTL) changes. Night-time skyglow, a form of light pollution caused by NTL, is also affected by public emergencies. Here we investigated the impact of the lockdown on the [...] Read more.

The COVID-19 epidemic lockdown has a direct influence on urban socioeconomic activity, including night-time light (NTL) changes. Night-time skyglow, a form of light pollution caused by NTL, is also affected by public emergencies. Here we investigated the impact of the lockdown on the night-time skyglow in the Guangbutun region of Wuhan, China. We monitored the night-time sky from 1 November 2019 to 12 April 2020 and compared the intraday skyglow pattern and day-to-day variation of skyglow before and during the lockdown. We found that the detected earliest shutdown timing of lights (STL) was moved from 22:00 (before the lockdown) to 21:30 (after entering the lockdown), and the fluctuation of skyglow decreased significantly during the lockdown. Furthermore, we found the night-time skyglow at various time intervals generally decreased and then recovered during the lockdown. The most severe decrease in zenith sky brightness (ZSB) was observed at the 21:30–22:00 time interval, with a decrease ratio (DR) of 72.1% and a recovery ratio (RR) of only 22.6%. On the other hand, the skyglow near midnight was the least affected by the lockdown, and the RR (32.6% and 24.3%) was comparable to the DR (30.4% and 38.2%), which means the skyglow at this time basically recovered to the pre-epidemic level. We conclude that long-term monitoring of sky brightness using single-channel photometers, such as SQMs, can provide a multi-temporal microscopic perspective for studying the dynamics of skyglow caused by human activities. Full article

(This article belongs to the Special Issue Light Pollution Monitoring Using Remote Sensing Data II)

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18 pages, 112839 KiB

Open AccessArticle

Georeferencing Urban Nighttime Lights Imagery Using Street Network Maps

by Peter Schwind and Tobias Storch

Remote Sens. 2022, 14(11), 2671; https://doi.org/10.3390/rs14112671 - 02 Jun 2022

Cited by 4 | Viewed by 2462

Abstract

Astronaut photography acquired from the International Space Station presently is the only available option for free global high-resolution nighttime light (NTL) imagery. Unfortunately, these data are not georeferenced, meaning they cannot easily be used for many remote sensing applications such as change detection [...] Read more.

Astronaut photography acquired from the International Space Station presently is the only available option for free global high-resolution nighttime light (NTL) imagery. Unfortunately, these data are not georeferenced, meaning they cannot easily be used for many remote sensing applications such as change detection or fusion. Georeferencing such NTL data manually, for example, by finding tie points, is difficult due to the strongly differing appearance of any potential references. Therefore, realizing an automatic method for georeferencing NTL imagery is preferable. In this article, such an automatic processing chain for the georeferencing of NTL imagery is presented. The novel approach works by simulating reference NTL images from vector-based street network maps and finding tie points between these references and the NTL imagery. To test this approach, here, publicly available open street maps are used. The tie points identified in the reference and NTL imagery are then used for rectification and thereby for georeferencing. The presented processing chain is tested using nine different astronaut photographs of urban areas, illustrating the strengths and weaknesses of the algorithm. To evaluate the geometric accuracy, the photography is finally matched manually against an independent reference. The results of this evaluation depict that all nine astronaut photographs are georeferenced with accuracies between 2.03 px and 6.70 px. This analysis demonstrates that an automatic georeferencing of high-resolution urban NTL imagery is feasible even with limited attitude and orbit determination (AOD). Furthermore, especially for future spaceborne NTL missions with precise AOD, the algorithm’s performance will increase and could also be used for quality-control purposes. Full article

(This article belongs to the Special Issue Light Pollution Monitoring Using Remote Sensing Data II)

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35 pages, 9591 KiB

Open AccessArticle

Remote Sensing of Aerosols at Night with the CoSQM Sky Brightness Data

by Charles Marseille, Martin Aubé, Africa Barreto and Alexandre Simoneau

Remote Sens. 2021, 13(22), 4623; https://doi.org/10.3390/rs13224623 - 17 Nov 2021

Cited by 5 | Viewed by 1816

Abstract

Aerosol optical depth is an important indicator of aerosol particle properties and their associated radiative impacts. AOD determination is very important to achieve relevant climate modelling. Most remote sensing techniques to retrieve aerosol optical depth are applicable to daytime given the high level [...] Read more.

Aerosol optical depth is an important indicator of aerosol particle properties and their associated radiative impacts. AOD determination is very important to achieve relevant climate modelling. Most remote sensing techniques to retrieve aerosol optical depth are applicable to daytime given the high level of light available. The night represents half of the time but in such conditions only a few remote sensing methods are available. Among these approaches, the most reliable are moon photometers and star photometers. In this paper, we attempt to fill gaps in the aerosol detection performed with the aforementioned techniques using night sky brightness measurements during moonless nights with the novel CoSQM, a portable, low-cost and open-source multispectral photometer. In this paper, we present an innovative method for estimating the aerosol optical depth using an empirical relationship between the zenith night sky brightness measured at night with the CoSQM and the aerosol optical depth retrieved during daytime from the AErosol Robotic NETwork. Although the proposed method does not measure the AOD directly, an empirical relationship with the CE318-T is shown to give good results at the location of Santa Cruz de Tenerife. Such a method is especially suited to light-polluted regions with light pollution sources located within a few kilometres of the observation site. A coherent day-to-night aerosol optical depth and Ångström Exponent evolution in a set of 354 days and nights from August 2019 to February 2021 was verified at the location of Santa Cruz de Tenerife on the island of Tenerife, Spain. The preliminary uncertainty of this technique was evaluated using the variance under stable day-to-night conditions, set at 0.02 for aerosol optical depth and 0.75 for the Ångström Exponent. These results indicate the set of CoSQM and the proposed methodology appear to be a promising tool, adding new information on the optical properties of aerosols at night, which could be of key importance in improving climate predictions. Full article

(This article belongs to the Special Issue Light Pollution Monitoring Using Remote Sensing Data II)

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Review

Jump to: Research

34 pages, 6624 KiB

Open AccessReview

Research Progress, Hotspots, and Evolution of Nighttime Light Pollution: Analysis Based on WOS Database and Remote Sensing Data

by Chenhao Huang, Yang Ye, Yanhua Jin and Bangli Liang

Remote Sens. 2023, 15(9), 2305; https://doi.org/10.3390/rs15092305 - 27 Apr 2023

Cited by 3 | Viewed by 2348

Abstract

With the rapid development of the global economy, the over-expansion of outdoor artificial light at night (ALAN) in cities has led to increasingly severe light pollution worldwide. More and more studies have paid attention to the problem of light pollution, but there is [...] Read more.

With the rapid development of the global economy, the over-expansion of outdoor artificial light at night (ALAN) in cities has led to increasingly severe light pollution worldwide. More and more studies have paid attention to the problem of light pollution, but there is still a lack of systematic literature review on nighttime light pollution in terms of research progress, hotspots, and its evolutions. For this purpose, this study firstly analyzed current research actuality and trends about nighttime light pollution via a comprehensive retrospect of pertinent literature and summarized the adverse effects and monitoring technologies of light pollution by VOSviewer-based keyword co-occurrence technique. Additionally, the study explored the variation tendency of nighttime light pollution in typical countries from 2013 to 2021 based on remote-sensing data and further proposed management suggestions to protect the nighttime environment. The results indicate that the research popularity of nighttime light pollution has been increasing recently, especially after the opening of diversified remote-sensing data in 2012; the main research topics are dominated by adverse effects and monitoring technologies, where the latter is represented by ground survey and remote-sensing observation; the total levels of ALAN intensity are relatively high in most developed countries, but the mean and per capita values are decreasing, and the above phenomenon in developing countries show the opposite trend. This study expects to integrate the literature analysis method and remote-sensing data to demonstrate the research status and variation trends of nighttime light pollution systematically so as to provide scientific references for the assessment and management of the nighttime light environment. Full article

(This article belongs to the Special Issue Light Pollution Monitoring Using Remote Sensing Data II)

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