{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,3]],"date-time":"2026-07-03T12:54:09Z","timestamp":1783083249780,"version":"3.54.6"},"reference-count":29,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2009,6,15]],"date-time":"2009-06-15T00:00:00Z","timestamp":1245024000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Data on the urban environment such as climate or air quality is usually collected at a few point monitoring stations distributed over a city. However, the synoptic viewpoint of satellites where a whole city is visible on a single image permits the collection of spatially comprehensive data at city-wide scale. In spite of rapid developments in remote sensing systems, deficiencies in image resolution and algorithm development still exist for applications such as air quality monitoring and urban heat island analysis. This paper describes state-of-the-art techniques for enhancing and maximising the spatial detail available from satellite images, and demonstrates their applications to the densely urbanised environment of Hong Kong. An Emissivity Modulation technique for spatial enhancement of thermal satellite images permits modelling of urban microclimate in combination with other urban structural parameters at local scale. For air quality monitoring, a Minimum Reflectance Technique (MRT) has been developed for MODIS 500 m images. The techniques described can promote the routine utilization of remotely sensed images for environmental monitoring in cities of the 21st century.<\/jats:p>","DOI":"10.3390\/s90604695","type":"journal-article","created":{"date-parts":[[2009,6,16]],"date-time":"2009-06-16T02:11:38Z","timestamp":1245118298000},"page":"4695-4708","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["High Resolution Remote Sensing of Densely Urbanised Regions: a Case Study of Hong Kong"],"prefix":"10.3390","volume":"9","author":[{"given":"Janet  E.","family":"Nichol","sequence":"first","affiliation":[{"name":"Department of Land Surveying and Geo-Informatics, Hong Kong Polytechnic University, Hong Kong, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Man Sing","family":"Wong","sequence":"additional","affiliation":[{"name":"Department of Land Surveying and Geo-Informatics, Hong Kong Polytechnic University, Hong Kong, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2009,6,15]]},"reference":[{"key":"ref_1","first-page":"973","article-title":"Policy document on earth observation for urban planning and management","volume":"73","author":"Nichol","year":"2007","journal-title":"Photo. Engin. Remote Sens."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"547","DOI":"10.14358\/PERS.75.5.547","article-title":"An emissivity modulation method for spatial enhancement of thermal satellite images in urban heat island analysis","volume":"75","author":"Nichol","year":"2009","journal-title":"Photo. Engin. Remote Sens."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1113","DOI":"10.1109\/36.700995","article-title":"A temperature and emissivity separation algorithm for advanced spaceborne thermal emission and reflection radiometer (ASTER) images","volume":"36","author":"Gillespie","year":"1998","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_4","unstructured":"ERSDAC - Earth Remote Sensing Data Analysis Center (available online at www.gds.aster.ersdac.or.jp\/gds_www2002\/service_e\/release_e\/set_release_e.html)."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"268","DOI":"10.1080\/00046973.1976.9648422","article-title":"The distinction between canopy and boundary-layer heat islands","volume":"14","author":"Oke","year":"1976","journal-title":"Atmosphere"},{"key":"ref_6","unstructured":"EPD (available online: http:\/\/www.epd-asg.gov.hk\/english\/pastapi\/pastapie.php)."},{"key":"ref_7","first-page":"15955","article-title":"Estimation of Saharan aerosol optical thickness from blurring effects in Thematic Mapper data","volume":"93","author":"Deschamps","year":"1998","journal-title":"J. Geophys. Res."},{"key":"ref_8","first-page":"1433","article-title":"Mapping of air pollution using satellite data","volume":"58","author":"Sifakis","year":"1992","journal-title":"Photo. Engin. Remote Sens."},{"key":"ref_9","unstructured":"Kaufman, Y., and Tanr\u00e9, D. (1998). NASA MOD04 Product Report."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"557","DOI":"10.1109\/TGRS.2004.824067","article-title":"Aerosol properties over bright reflecting source regions","volume":"42","author":"Hsu","year":"2004","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"D22S07","DOI":"10.1029\/2007JD008479","article-title":"Validation and understanding of MODIS aerosol products using ground-based measurements from the handheld sunphotometer network in China","volume":"112","author":"Li","year":"2007","journal-title":"J. Geophys. Res."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1029\/2001GL013205","article-title":"Validation of MODIS aerosol optical depth retrieval over land","volume":"29","author":"Chu","year":"2002","journal-title":"Geophys. Res. Lett."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/S0034-4257(98)00031-5","article-title":"AERONET-A federated instrument network and data archive for aerosol characterization","volume":"66","author":"Holben","year":"1998","journal-title":"Remote Sens. Environ."},{"key":"ref_14","first-page":"D13211","article-title":"Second-generation operational algorithm: Retrieval of aerosol properties over land from inversion of Moderate Resolution Imaging Spectroradiometer spectral reflectance","volume":"112","author":"Levy","year":"2007","journal-title":"J. Geophys. Res."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"D22S08","DOI":"10.1029\/2007JD008474","article-title":"Evaluation of the MODIS aerosol products at two AERONET stations in China","volume":"112","author":"Mi","year":"2007","journal-title":"J. Geophys. Res."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2650","DOI":"10.1109\/TGRS.2005.856627","article-title":"Retrieval, validation, and application of the 1-km aerosol optical depth from MODIS measurements over Hong Kong","volume":"43","author":"Li","year":"2005","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"28003","DOI":"10.1029\/97JD02074","article-title":"Earth surface reflectivity climatology at 340\u2013380 nm from TOMS data","volume":"102","author":"Herman","year":"1997","journal-title":"J. Geophys. Res."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"4070","DOI":"10.1029\/2002JD002429","article-title":"A database of spectral surface reflectivity in the range 335\u2013772 nm derived from 5.5 years of GOME observations","volume":"108","author":"Koelemeijer","year":"2003","journal-title":"J. Geophys. Res."},{"key":"ref_19","first-page":"123","article-title":"Operational atmospheric correction of MODIS visible to middle infrared land surface data in the case of an infinite Lambertian target","volume":"1","author":"Qu","year":"2006","journal-title":"Earth Science Satellite Remote Sensing, Science and Instruments"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"2101","DOI":"10.1175\/1520-0477(1998)079<2101:SARATS>2.0.CO;2","article-title":"SBDART: A research and teaching software tool for plane-parallel radiative transfer in the Earth's atmosphere","volume":"79","author":"Ricchiazzi","year":"1998","journal-title":"Bull. Amer. Meteor. Soc."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"831","DOI":"10.1175\/1520-0477(1998)079<0831:OPOAAC>2.0.CO;2","article-title":"Optical properties of aerosols and clouds: the software package OPAC","volume":"79","author":"Hess","year":"1998","journal-title":"Bull. Amer. Meteor. Soc."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"12085","DOI":"10.1029\/1999JD900040","article-title":"Retrieval of aerosol properties over the ocean using global ozone monitoring experiment measurements: method and applications to test case","volume":"104","author":"Torricella","year":"1999","journal-title":"J. Geophys. Res."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"3959","DOI":"10.1016\/j.atmosenv.2007.01.048","article-title":"Spatio-temporal variability of atmospheric aerosol from MODIS data over northeast asia in 2004","volume":"41","author":"Lee","year":"2007","journal-title":"Atmos. Environ."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1127","DOI":"10.1001\/jama.295.10.1127","article-title":"Fine particulate air pollution and hospital admission for cardiovascular and respiratory diseases","volume":"295","author":"Dominici","year":"2006","journal-title":"J. Am. Med. Asso."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"4492","DOI":"10.1016\/j.atmosenv.2007.01.046","article-title":"An empirical relationship between PM2.5 and aerosol optical depth in Delhi Metropolitan","volume":"41","author":"Kumar","year":"2007","journal-title":"Atmos Environ."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"2095","DOI":"10.1029\/2003GL018174","article-title":"Intercomparison between satellite-derived aerosol optical thickness and PM2.5 mass: Implications for air quality studies","volume":"30","author":"Wang","year":"2003","journal-title":"Geophys. Res. Lett."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"2495","DOI":"10.1016\/j.atmosenv.2004.01.039","article-title":"Qualitative and quantitative evaluation of MODIS satellite sensor data for regional and urban scale air quality","volume":"38","author":"Holloman","year":"2004","journal-title":"Atmos. Environ."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"3269","DOI":"10.1021\/es049352m","article-title":"Estimating Ground-Level PM2.5 in the eastern United States using satellite remote sensing","volume":"39","author":"Liu","year":"2005","journal-title":"Environ. Sci. Tech."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"7190","DOI":"10.1016\/j.atmosenv.2005.08.036","article-title":"Correlating MODIS aerosol optical thickness data with ground-based PM2.5 observations across Texas for use in a real-time air quality prediction system","volume":"39","author":"Hutchison","year":"2005","journal-title":"Atmos. Environ."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/9\/6\/4695\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T22:10:35Z","timestamp":1760220635000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/9\/6\/4695"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2009,6,15]]},"references-count":29,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2009,6]]}},"alternative-id":["s90604695"],"URL":"https:\/\/doi.org\/10.3390\/s90604695","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2009,6,15]]}}}