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Author |
Bará, S.; Nievas, M.; Sanchez de Miguel, A.; Zamorano, J. |
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Title |
Zernike analysis of all-sky night brightness maps |
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Year |
2014 |
Publication |
Applied Optics |
Abbreviated Journal |
Appl Opt |
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Volume |
53 |
Issue  |
12 |
Pages |
2677-2686 |
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Keywords |
modeling; light at night; light pollution; all-sky; Zernike polynomials; image decomposition; sky brightness |
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Abstract |
All-sky night brightness maps (calibrated images of the night sky with hemispherical field-of-view (FOV) taken at standard photometric bands) provide useful data to assess the light pollution levels at any ground site. We show that these maps can be efficiently described and analyzed using Zernike circle polynomials. The relevant image information can be compressed into a low-dimensional coefficients vector, giving an analytical expression for the sky brightness and alleviating the effects of noise. Moreover, the Zernike expansions allow us to quantify in a straightforward way the average and zenithal sky brightness and its variation across the FOV, providing a convenient framework to study the time course of these magnitudes. We apply this framework to analyze the results of a one-year campaign of night sky brightness measurements made at the UCM observatory in Madrid. |
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Address |
Ãrea de Óptica, Dept. de FÃsica Aplicada, Fac. de FÃsica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain |
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Optical Society of America |
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English |
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0003-6935 |
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PMID:24787595 |
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IDA @ john @ |
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318 |
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Author |
Estrada-García, R.; García-Gil, M.; Acosta, L.; Bará, S.; Sanchez de Miguel, A.; Zamorano, J. |
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Title |
Statistical modelling and satellite monitoring of upward light from public lighting |
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Journal Article |
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Year |
2015 |
Publication |
Lighting Research and Technology |
Abbreviated Journal |
Lighting Res. & Tech. |
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Issue |
1477153515583181 |
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1-30 |
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Keywords |
Remote sensing; radiative transfer; modeling; skyglow; light pollution; urban |
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Abstract |
In this work, we propose an approach to estimating the amount of light wasted by being sent towards the upper hemisphere from urban areas. This is a source of light pollution. The approach is based on a predictive model that provides the fraction of light directed skywards in terms of a small set of identified explanatory variables that characterise the urban landscape and its light sources. The model, built via the statistical analysis of a wide sample of basic urban scenarios to compute accurately the amount of light wasted at each of them, establishes an optimal linear regression function that relates the fraction of wasted flux to relevant variables like the kind of luminaires, the street fill factor, the street width, the building and luminaire heights and the walls and pavement reflectances. We applied this model to evaluate the changes in emissions produced at two urban nuclei in the Deltebre municipality of Catalonia. The results agree reasonably well with those deduced from the radiance measurements made with the VIIRS instrument onboard the Suomi-NPP Earth orbiting satellite. |
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Escola Tècnica Superior d’Enginyeria Industrial de Barcelona (ETSEIB), Universitat Politècnica de Catalunya, Spain; manuel.garcia.gil(at)upc.edu |
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Sage |
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English |
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English |
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IDA @ john @ |
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1155 |
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Author |
Kocifaj, M. |
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Title |
Light-pollution model for cloudy and cloudless night skies with ground-based light sources |
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Journal Article |
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Year |
2007 |
Publication |
Applied Optics |
Abbreviated Journal |
Appl. Opt. |
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Volume |
46 |
Issue |
15 |
Pages |
3013 |
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Keywords |
light pollution; modeling |
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Abstract |
The scalable theoretical model of light pollution for ground sources is presented. The model is successfully employed for simulation of angular behavior of the spectral and integral sky radiance and∕or luminance during nighttime. There is no restriction on the number of ground-based light sources or on the spatial distribution of these sources in the vicinity of the measuring point (i.e., both distances and azimuth angles of the light sources are configurable). The model is applicable for real finite-dimensional surface sources with defined spectral and angular radiating properties contrary to frequently used point-source approximations. The influence of the atmosphere on the transmitted radiation is formulated in terms of aerosol and molecular optical properties. Altitude and spectral reflectance of a cloud layer are the main factors introduced for simulation of cloudy and∕or overcast conditions. The derived equations are translated into numerically fast code, and it is possible to repeat the entire set of calculations in real time. The parametric character of the model enables its efficient usage by illuminating engineers and∕or astronomers in the study of various light-pollution situations. Some examples of numerical runs in the form of graphical results are presented. |
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0003-6935 |
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Call Number |
IDA @ john @ |
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277 |
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Author |
Kocifaj, M. |
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Title |
Two-stream approximation for rapid modeling the light pollution levels in local atmosphere |
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Journal Article |
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Year |
2012 |
Publication |
Astrophysics and Space Science |
Abbreviated Journal |
Astrophys Space Sci |
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Volume |
341 |
Issue |
2 |
Pages |
301-307 |
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Keywords |
Light pollution; Atmospheric effects; Methods: numerical; Radiative transfer; Scattering; modeling; two-stream approximation |
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Abstract |
The two-stream concept is used for modeling the radiative transfer in Earth's atmosphere illuminated by ground-based light sources. The light pollution levels (illuminance and irradiance) are computed for various aerosol microphysical parameters, specifically the asymmetry parameter g A , single scattering albedo ω A , and optical thickness τ A . Two distinct size distributions of Junge's and gamma-type are employed. Rather then being a monotonic function of τ A , the diffuse illuminance/irradiance shows a local minimum at specific τ A, lim independent of size distribution taken into consideration. The existence of local minima has relation to the scattering and attenuation efficiencies both of which have opposite effects. The computational scheme introduced in this paper is advantageous especially if the entire set of calculations needs to be repeated with an aim to simulate diffuse light in various situations and when altering optical states of the atmospheric environment. |
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0004-640X |
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IDA @ john @ |
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273 |
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Author |
Zeng, C.; Zhou, Y.; Wang, S.; Yan, F.; Zhao, Q. |
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Title |
Population spatialization in China based on night-time imagery and land use data |
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Journal Article |
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Year |
2011 |
Publication |
International Journal of Remote Sensing |
Abbreviated Journal |
International Journal of Remote Sensing |
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Volume |
32 |
Issue |
24 |
Pages |
9599-9620 |
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Keywords |
DMSP-OLS; remote sensing; light at night; population; modeling |
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Abstract |
Population is a key indicator of socioeconomic development, urban planning and environmental protection, particularly for developing countries like China. But, census data for any given area are neither always available nor adequately reflect the internal differences of population. The authors tried to overcome this problem by spatializing the population across China through utilizing integer night-time imagery (Defense Meteorological Satellite Program/Operational Linescan System, DMSP/OLS) and land-use data. In creating the population linear regression model, night-time light intensity and lit areas, under different types of land use, were employed as predictor variables, and census data as dependent variables. To improve model performance, eight zones were created using night-time imagery clustering and shortest path algorithm. The population model is observed to have a coefficient of determination (R 2) ranging from 0.80 to 0.95 in the research area, which remained the same in different years. A comparison of the results of this study with those of other researchers shows that the spatialized population density map, prepared on the basis of night-time imagery, reflects the population distribution character more explicitly and in greater detail. |
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State Key Laboratory of Remote Sensing Science , Jointly Sponsored by the Institute of Remote Sensing Applications of the Chinese Academy of Sciences and Beijing Normal University , Beijing, 100101, PR China |
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0143-1161 |
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IDA @ john @ |
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228 |
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