{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T00:30:44Z","timestamp":1760229044780,"version":"build-2065373602"},"reference-count":47,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2022,5,27]],"date-time":"2022-05-27T00:00:00Z","timestamp":1653609600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Hong Kong Research Grants Council","award":["CRF C4139-20G","AoE\/E-603\/18","XDA19090108","2019YFC1510400","2017YFB0503605"],"award-info":[{"award-number":["CRF C4139-20G","AoE\/E-603\/18","XDA19090108","2019YFC1510400","2017YFB0503605"]}]},{"name":"Strategic Priority Research Program of the Chinese Academy of Sciences","award":["CRF C4139-20G","AoE\/E-603\/18","XDA19090108","2019YFC1510400","2017YFB0503605"],"award-info":[{"award-number":["CRF C4139-20G","AoE\/E-603\/18","XDA19090108","2019YFC1510400","2017YFB0503605"]}]},{"name":"National Key R&amp;D Program of China","award":["CRF C4139-20G","AoE\/E-603\/18","XDA19090108","2019YFC1510400","2017YFB0503605"],"award-info":[{"award-number":["CRF C4139-20G","AoE\/E-603\/18","XDA19090108","2019YFC1510400","2017YFB0503605"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>PM2.5 participates in light scattering, leading to degraded outdoor views, which forms the basis for estimating PM2.5 from photographs. This paper devises an algorithm to estimate PM2.5 concentrations by extracting visual cues and atmospheric indices from a single photograph. While air quality measurements in the context of complex urban scenes are particularly challenging, when only a single atmospheric index or cue is given, each one can reinforce others to yield a more robust estimator. Therefore, we selected an appropriate atmospheric index in various outdoor scenes to identify reasonable cue combinations for measuring PM2.5. A PM2.5 dataset (PhotoPM-daytime) was built and used to evaluate performance and validate efficacy of cue combinations. Furthermore, a city-wide experiment was conducted using photographs crawled from the Internet to demonstrate the applicability of the algorithm in large-area PM2.5 monitoring. Results show that smartphones equipped with the developed method could potentially be used as PM2.5 sensors.<\/jats:p>","DOI":"10.3390\/rs14112572","type":"journal-article","created":{"date-parts":[[2022,5,31]],"date-time":"2022-05-31T02:30:06Z","timestamp":1653964206000},"page":"2572","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Measuring PM2.5 Concentrations from a Single Smartphone Photograph"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0844-2973","authenticated-orcid":false,"given":"Shiqi","family":"Yao","sequence":"first","affiliation":[{"name":"Department of Geography and Resources Management, The Chinese University of Hong Kong, Hong Kong, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4155-2330","authenticated-orcid":false,"given":"Fei","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Geography and Resources Management, The Chinese University of Hong Kong, Hong Kong, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5063-3522","authenticated-orcid":false,"given":"Bo","family":"Huang","sequence":"additional","affiliation":[{"name":"Department of Geography and Resources Management, The Chinese University of Hong Kong, Hong Kong, China"},{"name":"Institute of Space and Earth Information Science, The Chinese University of Hong Kong, Hong Kong, China"},{"name":"Shenzhen Research Institute, Chinese University of Hong Kong, Hong Kong, China"}]}],"member":"1968","published-online":{"date-parts":[[2022,5,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"World Health Organization (2016). 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