2025
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| 1. | Niklas Blum; Paul Matteschk; Yann Fabel; Bijan Nouri; Roberto Román; Luis F. Zarzalejo; Juan Carlos Antuña-Sánchez; Stefan Wilbert Geometric calibration of all-sky cameras using sun and moon positions: A comprehensive analysis Journal Article In: Solar Energy, vol. 295, pp. 113476, 2025, ISSN: 0038-092X. @article{BLUM2025113476,
title = {Geometric calibration of all-sky cameras using sun and moon positions: A comprehensive analysis},
author = {Niklas Blum and Paul Matteschk and Yann Fabel and Bijan Nouri and Roberto Román and Luis F. Zarzalejo and Juan Carlos Antuña-Sánchez and Stefan Wilbert},
url = {https://www.sciencedirect.com/science/article/pii/S0038092X25002397},
doi = {https://doi.org/10.1016/j.solener.2025.113476},
issn = {0038-092X},
year = {2025},
date = {2025-03-24},
urldate = {2025-01-01},
journal = {Solar Energy},
volume = {295},
pages = {113476},
abstract = {All-sky imagers (ASIs) have been applied to enable accurate very-short-term forecasts of the production of solar power plants and to derive measurements which facilitate the efficient and reliable operation of such plants. Overall, ASIs can support the grid integration and efficient operation of solar power plants. These tasks often require to reconstruct ‘world coordinates’ of observed scene points from their position in the ASI images. This requires a practically feasible geometric calibration of each ASI regarding camera-intrinsic lens distortion parameters and the ASI’s external orientation. We present ‘SuMo’ an open-source Python tool which determines all relevant parameters only using regular ASI images of Sun and Moon. The method avoids a manual interference on-site, can be applied retrospectively and can also be used to continuously monitor an ASI’s geometric calibration. We validate the calibration method on five cameras at three sites and over various datasets representing different seasons, atmospheric conditions, exposure times and sun/ moon elevation and azimuth angles. Already a single month of images from either summer or winter yields an accurate calibration (RMSE ?0.14?). A comparable calibration accuracy (RMSE 0.14 – 0.38?) could be achieved for all tested ASIs without modifying any of the method’s parameters. Image quality moderately influenced the calibration accuracy. An additional cross-validation with the star-based ORION calibration method further confirms the high accuracy of our method over the entire sky dome (MAE 0.14?). We provide a Python package and >2 years of ASI images and irradiance measurements with the publication.},
keywords = {All-sky imager, Celestial bodies, External orientation, Geometric calibration, Intrinsic calibration, sky camera},
pubstate = {published},
tppubtype = {article}
}
All-sky imagers (ASIs) have been applied to enable accurate very-short-term forecasts of the production of solar power plants and to derive measurements which facilitate the efficient and reliable operation of such plants. Overall, ASIs can support the grid integration and efficient operation of solar power plants. These tasks often require to reconstruct ‘world coordinates’ of observed scene points from their position in the ASI images. This requires a practically feasible geometric calibration of each ASI regarding camera-intrinsic lens distortion parameters and the ASI’s external orientation. We present ‘SuMo’ an open-source Python tool which determines all relevant parameters only using regular ASI images of Sun and Moon. The method avoids a manual interference on-site, can be applied retrospectively and can also be used to continuously monitor an ASI’s geometric calibration. We validate the calibration method on five cameras at three sites and over various datasets representing different seasons, atmospheric conditions, exposure times and sun/ moon elevation and azimuth angles. Already a single month of images from either summer or winter yields an accurate calibration (RMSE ?0.14?). A comparable calibration accuracy (RMSE 0.14 – 0.38?) could be achieved for all tested ASIs without modifying any of the method’s parameters. Image quality moderately influenced the calibration accuracy. An additional cross-validation with the star-based ORION calibration method further confirms the high accuracy of our method over the entire sky dome (MAE 0.14?). We provide a Python package and >2 years of ASI images and irradiance measurements with the publication. |
2021
|
| 2. | J C Antuña-Sánchez; R Román; V E Cachorro; C Toledano; C López; R González; D Mateos; A Calle; Á M de Frutos Relative sky radiance from multi-exposure all-sky camera images Journal Article In: Atmospheric Measurement Techniques, vol. 14, no. 3, pp. 2201–2217, 2021. @article{amt-14-2201-2021,
title = {Relative sky radiance from multi-exposure all-sky camera images},
author = {J C Antuña-Sánchez and R Román and V E Cachorro and C Toledano and C López and R González and D Mateos and A Calle and Á M de Frutos},
url = {https://amt.copernicus.org/articles/14/2201/2021/},
doi = {10.5194/amt-14-2201-2021},
year = {2021},
date = {2021-03-22},
journal = {Atmospheric Measurement Techniques},
volume = {14},
number = {3},
pages = {2201--2217},
abstract = {All-sky cameras are frequently used to detect cloud cover; however, this work explores the use of these instruments for the more complex purpose of extracting relative sky radiances. An all-sky camera (SONA202-NF model) with three colour filters narrower than usual for this kind of cameras is configured to capture raw images at seven exposure times. A detailed camera characterization of the black level, readout noise, hot pixels and linear response is carried out. A methodology is proposed to obtain a linear high dynamic range (HDR) image and its uncertainty, which represents the relative sky radiance (in arbitrary units) maps at three effective wavelengths. The relative sky radiances are extracted from these maps and normalized by dividing every radiance of one channel by the sum of all radiances at this channel. Then, the normalized radiances are compared with the sky radiance measured at different sky points by a sun and sky photometer belonging to the Aerosol Robotic Network (AERONET). The camera radiances correlate with photometer ones except for scattering angles below 10?, which is probably due to some light reflections on the fisheye lens and camera dome. Camera and photometer wavelengths are not coincident; hence, camera radiances are also compared with sky radiances simulated by a radiative transfer model at the same camera effective wavelengths. This comparison reveals an uncertainty on the normalized camera radiances of about 3.3?%, 4.3?% and 5.3?% for 467, 536 and 605?nm, respectively, if specific quality criteria are applied.},
keywords = {Radiative transfer, sky camera, sky radiance},
pubstate = {published},
tppubtype = {article}
}
All-sky cameras are frequently used to detect cloud cover; however, this work explores the use of these instruments for the more complex purpose of extracting relative sky radiances. An all-sky camera (SONA202-NF model) with three colour filters narrower than usual for this kind of cameras is configured to capture raw images at seven exposure times. A detailed camera characterization of the black level, readout noise, hot pixels and linear response is carried out. A methodology is proposed to obtain a linear high dynamic range (HDR) image and its uncertainty, which represents the relative sky radiance (in arbitrary units) maps at three effective wavelengths. The relative sky radiances are extracted from these maps and normalized by dividing every radiance of one channel by the sum of all radiances at this channel. Then, the normalized radiances are compared with the sky radiance measured at different sky points by a sun and sky photometer belonging to the Aerosol Robotic Network (AERONET). The camera radiances correlate with photometer ones except for scattering angles below 10?, which is probably due to some light reflections on the fisheye lens and camera dome. Camera and photometer wavelengths are not coincident; hence, camera radiances are also compared with sky radiances simulated by a radiative transfer model at the same camera effective wavelengths. This comparison reveals an uncertainty on the normalized camera radiances of about 3.3?%, 4.3?% and 5.3?% for 467, 536 and 605?nm, respectively, if specific quality criteria are applied. |
2019
|
| 3. | J.A. Benavent-Oltra; R. Román; J.A. Casquero-Vera; D. Pérez-Ramirez; H. Lyamani; P. Ortiz-Amezcua; A.E. Bedoya-Velasquez; G. Moreira; A. Lopatin; A. Barreto; J.L Guerrero-Rascado; D. Fuertes; C. Toledano; B. Torres; O. Dubovik; P. Goloub; F.J. Olmo; L. Alados-Arboledas Using GRASP with lidar, lunar photometer and sky-images to retrieve atmospheric aerosol microphysics night-time profiles Conference Final ACTRIS-2 General Meeting 2019, ACTRIS Darmstadt, Germany, 2019. @conference{Benavent-Oltra2019b,
title = {Using GRASP with lidar, lunar photometer and sky-images to retrieve atmospheric aerosol microphysics night-time profiles},
author = {J.A. Benavent-Oltra and R. Román and J.A. Casquero-Vera and D. Pérez-Ramirez and H. Lyamani and P. Ortiz-Amezcua and A.E. Bedoya-Velasquez and G. Moreira and A. Lopatin and A. Barreto and J.L Guerrero-Rascado and D. Fuertes and C. Toledano and B. Torres and O. Dubovik and P. Goloub and F.J. Olmo and L. Alados-Arboledas},
year = {2019},
date = {2019-04-01},
booktitle = {Final ACTRIS-2 General Meeting 2019},
address = {Darmstadt, Germany},
organization = {ACTRIS},
keywords = {atmospheric aerosols, GRASP, lunar photometry, sky camera},
pubstate = {published},
tppubtype = {conference}
}
|
2018
|
| 4. | R. Román; A. Barreto; A. Berjón; F.J. Olmo; V.E. Cachorro; A.M. de Frutos; L. Alados-Arboledas Effect of city light in the recorded Moon signal Conference 6th Iberian Meeting on Aerosol Science and Technology (RICTA'18), University of the Basque Country (UPV/EHU) Bilbao, Spain, 2018. @conference{Román2018b,
title = {Effect of city light in the recorded Moon signal},
author = {R. Román and A. Barreto and A. Berjón and F.J. Olmo and V.E. Cachorro and A.M. de Frutos and L. Alados-Arboledas},
year = {2018},
date = {2018-06-20},
booktitle = {6th Iberian Meeting on Aerosol Science and Technology (RICTA'18)},
address = {Bilbao, Spain},
organization = {University of the Basque Country (UPV/EHU)},
keywords = {HDR, moon, sky camera},
pubstate = {published},
tppubtype = {conference}
}
|
| 5. | J.A. Benavent-Oltra; R. Román; P. Ortiz-Amezcua; D. Pérez-Ramirez; A. Cazorla; A. Barreto; J.L. Guerrero-Rascado; C. Toledano; A. Lopatin; B. Torres; O. Dubovik; P. Goloub; F.J. Olmo; L. Alados-Arboledas Aerosol microphysical profiling combining multiwavelength lidar, lunar-photometry and sky camera images Conference 4th ACTRIS-2 General Meeting, ACTRIS Nafplio, Greece, 2018. @conference{Benavent-Oltra2018g,
title = {Aerosol microphysical profiling combining multiwavelength lidar, lunar-photometry and sky camera images},
author = {J.A. Benavent-Oltra and R. Román and P. Ortiz-Amezcua and D. Pérez-Ramirez and A. Cazorla and A. Barreto and J.L. Guerrero-Rascado and C. Toledano and A. Lopatin and B. Torres and O. Dubovik and P. Goloub and F.J. Olmo and L. Alados-Arboledas},
year = {2018},
date = {2018-04-17},
booktitle = {4th ACTRIS-2 General Meeting},
address = {Nafplio, Greece},
organization = {ACTRIS},
keywords = {aerosol, LIDAR, lunar photometry, sky camera},
pubstate = {published},
tppubtype = {conference}
}
|
2017
|
| 6. | R. Román, A. Barreto, A. Berjón, F.J. Olmo; L. Alados-Arboledas. City light against Moon signal Conference Lunar Photometry Workshop 2017, Grupo de Óptica Atmosférica de la Unviersidad de Valladolid (GOA/UVA) y Agencia Estatal de Meteorología (AEMet) Izaña (Tenerife), España, 2017, (Lunar Photometry Workshop 2017). @conference{ROMAN2017IZOcitylight,
title = {City light against Moon signal},
author = {R. Román, A. Barreto, A. Berjón, F.J. Olmo and L. Alados-Arboledas.},
year = {2017},
date = {2017-06-08},
booktitle = {Lunar Photometry Workshop 2017},
address = {Izaña (Tenerife), España},
organization = {Grupo de Óptica Atmosférica de la Unviersidad de Valladolid (GOA/UVA) y Agencia Estatal de Meteorología (AEMet)},
note = {Lunar Photometry Workshop 2017},
keywords = {High dynamic range, moon, sky camera},
pubstate = {published},
tppubtype = {conference}
}
|
| 7. | R. Román, J.A. Benavent-Oltra, P. Ortiz-Amezcua, D. Pérez-Ramírez, A. Cazorla, A. Barreto, J.L. Guerrero-Rascado, C. Toledano, A. Lopatin, B. Torres, O. Dubovik, P. Goloub, F.J. Olmo; L. Alados-Arboledas Retrieval of aerosol properties profiles at night combining lunar photometer, lidar and sky camera measurements. Conference Grupo de Óptica Atmosférica de la Unviersidad de Valladolid (GOA/UVA) y Agencia Estatal de Meteorología (AEMet) Izaña (Tenerife), España, 2017, (Lunar Photometry Workshop 2017). @conference{ROMAN2017IZOlidarGRASP,
title = {Retrieval of aerosol properties profiles at night combining lunar photometer, lidar and sky camera measurements.},
author = {R. Román, J.A. Benavent-Oltra, P. Ortiz-Amezcua, D. Pérez-Ramírez, A. Cazorla, A. Barreto, J.L. Guerrero-Rascado, C. Toledano, A. Lopatin, B. Torres, O. Dubovik, P. Goloub, F.J. Olmo and L. Alados-Arboledas},
year = {2017},
date = {2017-06-08},
address = {Izaña (Tenerife), España},
organization = {Grupo de Óptica Atmosférica de la Unviersidad de Valladolid (GOA/UVA) y Agencia Estatal de Meteorología (AEMet)},
note = {Lunar Photometry Workshop 2017},
keywords = {GRASP, High dynamic range, LIDAR, lunar photometry, moon, sky camera},
pubstate = {published},
tppubtype = {conference}
}
|
| 8. | J.A. Benavent-Oltra, R. Román, D. Pérez-Ramírez, P. Ortiz-Amezcua, A. Cazorla, A. Barreto, J.L. Guerrero-Rascado, C. Toledano, A. Lopatin, B. Torres, O. Dubovik, P. Goloub, F.J. Olmo; L. Alados-Arboledas. Preliminary results of aerosol profile retrievals at night combining multi-wavelength lidar, lunar-photometry and sky camera images Conference International Coordination-group for Laser Atmospheric Studies (ICLAS) Bucharest, Rumanía, 2017, (28th International Laser Radar Conference (ILRC28)). @conference{Benavent2017_ILRC,
title = {Preliminary results of aerosol profile retrievals at night combining multi-wavelength lidar, lunar-photometry and sky camera images},
author = {J.A. Benavent-Oltra, R. Román, D. Pérez-Ramírez, P. Ortiz-Amezcua, A. Cazorla, A. Barreto, J.L. Guerrero-Rascado, C. Toledano, A. Lopatin, B. Torres, O. Dubovik, P. Goloub, F.J. Olmo and L. Alados-Arboledas.},
year = {2017},
date = {2017-05-28},
address = {Bucharest, Rumanía},
organization = {International Coordination-group for Laser Atmospheric Studies (ICLAS)},
note = {28th International Laser Radar Conference (ILRC28)},
keywords = {GRASP, High dynamic range, LIDAR, lunar photometry, moon, sky camera},
pubstate = {published},
tppubtype = {conference}
}
|
| 9. | J.A. Benavent-Oltra, R. Román, D. Pérez, P. Ortiz-Amezcua, A. Cazorla, A. Barreto, J.L. Guerrero-Rascado, C. Toledano, A. Lopatin, B. Torres, O. Dubovik, P. Goloub, F.J. Olmo; L. Alados-Arboledas. Preliminary results of aerosol profile retrievals at night combining multi-wavelength lidar, lunar photometry and sky camera images Conference European Research Infrastructure for the observation of Aerosol, Clouds, and Trace gases (ACTRIS) Granada, España, 2017, (3rd ACTRIS-2 General Meeting). @conference{BENAVENT2017ACTRISGRANADA,
title = {Preliminary results of aerosol profile retrievals at night combining multi-wavelength lidar, lunar photometry and sky camera images},
author = {J.A. Benavent-Oltra, R. Román, D. Pérez, P. Ortiz-Amezcua, A. Cazorla, A. Barreto, J.L. Guerrero-Rascado, C. Toledano, A. Lopatin, B. Torres, O. Dubovik, P. Goloub, F.J. Olmo and L. Alados-Arboledas.},
year = {2017},
date = {2017-02-03},
address = {Granada, España},
organization = {European Research Infrastructure for the observation of Aerosol, Clouds, and Trace gases (ACTRIS)},
note = {3rd ACTRIS-2 General Meeting},
keywords = {GRASP, High dynamic range, LIDAR, lunar photometry, moon, sky camera},
pubstate = {published},
tppubtype = {conference}
}
|
| 10. | R. Román; A. Cazorla; C. Toledano; F.J. Olmo; V.E. Cachorro; A. de Frutos; L. Alados-Arboledas Cloud cover detection combining high dynamic range sky images and ceilometer measurements Journal Article In: Atmospheric Research, vol. 196, pp. 224 - 236, 2017, ISSN: 0169-8095. @article{ROMAN2017224,
title = {Cloud cover detection combining high dynamic range sky images and ceilometer measurements},
author = {R. Román and A. Cazorla and C. Toledano and F.J. Olmo and V.E. Cachorro and A. de Frutos and L. Alados-Arboledas},
url = {http://www.sciencedirect.com/science/article/pii/S0169809516307475},
doi = {10.1016/j.atmosres.2017.06.006},
issn = {0169-8095},
year = {2017},
date = {2017-01-01},
journal = {Atmospheric Research},
volume = {196},
pages = {224 - 236},
keywords = {Aerosols, clouds, High dynamic range, sky camera},
pubstate = {published},
tppubtype = {article}
}
|
2016
|
| 11. | R. Román, B. Torres, D. Fuertes, V.E. Cachorro, O. Dubovik, C. Toledano, A. Cazorla, A. Barreto, J.L. Bosch, T. Lapyonok, R. González, P. Goloub, M.R. Perrone, F.J. Olmo, A. de Frutos; L. Alados-Arboledas. Using the lunar aureole derived from All-Sky cameras for the retrievals of aerosol microphisycal properties Conference European Research Infrastructure for the observation of Aerosol, Clouds, and Trace gases (ACTRIS) Barcelona, España, 2016, (2nd ACTRIS-2 WP2 Workshop). @conference{ROMAN2016actrisBCN,
title = {Using the lunar aureole derived from All-Sky cameras for the retrievals of aerosol microphisycal properties},
author = {R. Román, B. Torres, D. Fuertes, V.E. Cachorro, O. Dubovik, C. Toledano, A. Cazorla, A. Barreto, J.L. Bosch, T. Lapyonok, R. González, P. Goloub, M.R. Perrone, F.J. Olmo, A. de Frutos and L. Alados-Arboledas.},
year = {2016},
date = {2016-11-03},
address = {Barcelona, España},
organization = {European Research Infrastructure for the observation of Aerosol, Clouds, and Trace gases (ACTRIS)},
note = {2nd ACTRIS-2 WP2 Workshop},
keywords = {GRASP, High dynamic range, LIDAR, lunar photometry, moon, sky camera},
pubstate = {published},
tppubtype = {conference}
}
|
| 12. | R. Román, B. Torres, D. Fuertes, C. Toledano, O. Dubovik, V.E. Cachorro, T. Lapyonok, R. González, A. Barreto, C. Velasco-Merino, A. Cazorla, J.L. Bosch, P. Goloub, L. Blarel, F.J. Olmo, A. de Frutos, L. Alados-Arboledas The use of a sky camera to observe the relative radiances of the lunar aureole and the effect of aerosol over them Conference Universidade de Aveiro Aveiro, Portugal, 2016, (IV Iberian Meeting on Aerosol Science and Technology (RICTA2016)). @conference{ROMAN2016ricta,
title = {The use of a sky camera to observe the relative radiances of the lunar aureole and the effect of aerosol over them},
author = {R. Román, B. Torres, D. Fuertes, C. Toledano, O. Dubovik, V.E. Cachorro, T. Lapyonok, R. González, A. Barreto, C. Velasco-Merino, A. Cazorla, J.L. Bosch, P. Goloub, L. Blarel, F.J. Olmo, A. de Frutos, L. Alados-Arboledas},
year = {2016},
date = {2016-06-28},
address = {Aveiro, Portugal},
organization = {Universidade de Aveiro},
note = {IV Iberian Meeting on Aerosol Science and Technology (RICTA2016)},
keywords = {GRASP, High dynamic range, LIDAR, lunar photometry, moon, sky camera},
pubstate = {published},
tppubtype = {conference}
}
|
| 13. | J. C. Antuña-Sánchez; V. Cachorro; J. C. Antuña-Marrero; A. M. de Frutos
The highest Saharan dust event ever measured at Valladolid, Spain, seen by the RaspCloud camera Conference Santas, Brasil, 2016, (IX Taller de Mediciones con Lidar en Latinoamérica (WLMLA)
). @conference{Antuña-Sánchez2016b,
title = {The highest Saharan dust event ever measured at Valladolid, Spain, seen by the RaspCloud camera},
author = {J. C. Antuña-Sánchez and V. Cachorro and J. C. Antuña-Marrero and A. M. de Frutos
},
year = {2016},
date = {2016-04-17},
address = {Santas, Brasil},
note = {IX Taller de Mediciones con Lidar en Latinoamérica (WLMLA)
},
keywords = {sky camera},
pubstate = {published},
tppubtype = {conference}
}
|
2015
|
| 14. | J. C. Antuña-Sánchez; N. Díaz; R. Estevan; A. M. de Frutos Cloud camera design from a Raspberry Pi Conference Cayo Coco, Cuba, 2015, (VIII Taller de Mediciones con Lidar en Latinoamérica (WLMLA)
). @conference{Antuña-Sánchez2015,
title = {Cloud camera design from a Raspberry Pi},
author = {J. C. Antuña-Sánchez and N. Díaz and R. Estevan and A. M. de Frutos},
year = {2015},
date = {2015-04-14},
address = {Cayo Coco, Cuba},
note = {VIII Taller de Mediciones con Lidar en Latinoamérica (WLMLA)
},
keywords = {sky camera},
pubstate = {published},
tppubtype = {conference}
}
|
| 15. | J.C. Antuña-Sánchez, N. Díaz, R. Estevan, A.M. de Frutos,; J.C. Antuña-Marrero Cloud camera design using a Raspberry Pi Journal Article In: Optica Pura y Aplicada, vol. 48, no. 3, pp. 199-205, 2015. @article{ANTUNA2015OPA,
title = {Cloud camera design using a Raspberry Pi },
author = {J.C. Antuña-Sánchez, N. Díaz, R. Estevan, A.M. de Frutos, and J.C. Antuña-Marrero},
year = {2015},
date = {2015-01-01},
journal = {Optica Pura y Aplicada},
volume = {48},
number = {3},
pages = {199-205},
keywords = {sky camera},
pubstate = {published},
tppubtype = {article}
}
|
