{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,10]],"date-time":"2025-12-10T08:48:52Z","timestamp":1765356532928,"version":"build-2065373602"},"reference-count":48,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2019,4,11]],"date-time":"2019-04-11T00:00:00Z","timestamp":1554940800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000104","name":"National Aeronautics and Space Administration","doi-asserted-by":"publisher","award":["NNX15AP36A"],"award-info":[{"award-number":["NNX15AP36A"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000203","name":"U.S. Geological Survey","doi-asserted-by":"publisher","award":["G14AC00370"],"award-info":[{"award-number":["G14AC00370"]}],"id":[{"id":"10.13039\/100000203","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Pseudo invariant calibration sites (PICS) have been extensively used for the radiometric calibration and temporal stability monitoring of optical satellite sensors. Due to limited knowledge about the radiometric stability of North Africa, only a limited number of sites in the region are used for this purpose. This work presents an automated approach to classify North Africa for its potential use as an extended PICS (EPICS) covering vast portions of the continent. An unsupervised classification algorithm identified 19 \u201cclusters\u201d representing distinct land surface types was used; three clusters were identified with spatial uncertainties within approximately 5% in the shorter wavelength bands and 3% in the longer wavelength bands. A key advantage of the cluster approach is that large numbers of pixels are aggregated into contiguous homogeneous regions sufficiently distributed across the continent to allow multiple imaging opportunities per day, as opposed to imaging a typical PICS once during the sensor\u2019s revisit period. This potential increase in temporal resolution could result in increased sensitivity for the quicker identification of changes in sensor response.<\/jats:p>","DOI":"10.3390\/rs11070875","type":"journal-article","created":{"date-parts":[[2019,4,12]],"date-time":"2019-04-12T03:46:37Z","timestamp":1555040797000},"page":"875","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":33,"title":["Classification of North Africa for Use as an Extended Pseudo Invariant Calibration Sites (EPICS) for Radiometric Calibration and Stability Monitoring of Optical Satellite Sensors"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8368-6399","authenticated-orcid":false,"given":"Mahesh","family":"Shrestha","sequence":"first","affiliation":[{"name":"Department of Electrical Engineering and Computer Science, South Dakota State University (SDSU), Brookings, SD 57007, USA"}]},{"given":"Larry","family":"Leigh","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering and Computer Science, South Dakota State University (SDSU), Brookings, SD 57007, USA"}]},{"given":"Dennis","family":"Helder","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering and Computer Science, South Dakota State University (SDSU), Brookings, SD 57007, USA"}]}],"member":"1968","published-online":{"date-parts":[[2019,4,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1016\/j.rse.2003.10.006","article-title":"Surface characterisation of the Dome Concordia area (Antarctica) as a potential satellite calibration site, using Spot 4\/Vegetation instrument","volume":"89","author":"Six","year":"2004","journal-title":"Remote Sens. 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