{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,4]],"date-time":"2026-04-04T05:19:55Z","timestamp":1775279995395,"version":"3.50.1"},"reference-count":45,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2021,4,27]],"date-time":"2021-04-27T00:00:00Z","timestamp":1619481600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["42071351"],"award-info":[{"award-number":["42071351"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100012166","name":"National Key Research and Development Program of China","doi-asserted-by":"publisher","award":["2020YFA0608501"],"award-info":[{"award-number":["2020YFA0608501"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100012166","name":"National Key Research and Development Program of China","doi-asserted-by":"publisher","award":["2017YFB0504204"],"award-info":[{"award-number":["2017YFB0504204"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100018617","name":"Liaoning Revitalization Talents Program","doi-asserted-by":"publisher","award":["XLYC1802027"],"award-info":[{"award-number":["XLYC1802027"]}],"id":[{"id":"10.13039\/501100018617","id-type":"DOI","asserted-by":"publisher"}]},{"name":"One Hundred Talents Program of the Chinese Academy of Science","award":["Y938091"],"award-info":[{"award-number":["Y938091"]}]},{"name":"One Hundred Talents Program of the Chinese Academy of Science","award":["Y674141001"],"award-info":[{"award-number":["Y674141001"]}]},{"name":"Project supported discipline innovation team of Liaoning Technical University","award":["LNTU20TD-23"],"award-info":[{"award-number":["LNTU20TD-23"]}]},{"name":"Liao-ning Key Program Serving for the Social-Economy Development of Towns at North-West Liaoning","award":["10147-0816-1"],"award-info":[{"award-number":["10147-0816-1"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Optical remote sensing indices play an important role in vegetation information extraction and have been widely serving ecology, agriculture and forestry, urban monitoring, and other communities. Remote sensing indices are constructed from individual bands depending on special characteristics to enhance the typical spectral features for the identification or distinction of surface land covers. With the development of quantitative remote sensing, there is a rapid increasing requirement for accurate data processing and modeling. It is well known that the geometry-induced variation observed in surface reflectance is not ignorable, but the situation of uncertainty thereby introduced into these indices still needs further detailed understanding. We adopted the ground multi-angle hyperspectrum, spectral response function (SRF) of Thematic Mapper (TM), Enhanced Thematic Mapper (ETM+), Operational Land Imager (OLI), Moderate-Resolution Imaging Spectroradiometer (MODIS), and Multi-Spectral Instrument (MSI) optical sensors and simulated their sensor-like spectral reflectance; then, we investigated the potential angle effect uncertainty on optical indices that have been frequently involved in vegetation monitoring and examined the forward\/backward effect over both the ground-based level and the actual Landsat TM\/ETM+ overlapped region. Our results on the discussed indices and sensors show as following: (1) Identifiable angle effects exist with a more elevated influence than that introduced by band difference among sensors; (2) The absolute difference between forward and backward direction can reach up to \u22120.03 to 0.1 within bands of the TM\/ETM+ overlapped region; (3) The investigation at ground level indicates that there are different variations of angle effect transmitted to each remote sensing index. Regarding cases of crop canopy at various growth phases, most of the discussed indices have more than a 20% relative difference to nadir value except Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) with the magnitude lower than 10%, and less than 16% of Normalized Burn Ratio (NBR). For the case of wax maturity stage, the relative difference to nadir value of Enhanced Vegetation Index (EVI), Soil-Adjusted Vegetation Index (SAVI), Ratio Vegetation Index (RVI), Char Soil Index (CSI), NBR, Normalized Difference Moisture Index (NDMI), and SWIR2\/NIR exceeded 50%, while the values for NBR and NDMI can reach up to 115.8% and 206.7%, respectively; (4) Various schemes of index construction imply different propagation of angle effect uncertainty. The \u201cdifference\u201d indices can partially suppress the directional influence, while the \u201cratio\u201d indices show high potential to amplify the angle effect. This study reveals that the angle-induced uncertainty of these indices is greater than that induced by the spectrum mismatch among sensors, especially under the case of senescence. In addition, based on this work, indices with a suppressed potential of angle effect are recommended for vegetation monitoring or information retrieval to avoid unexpected effects.<\/jats:p>","DOI":"10.3390\/rs13091699","type":"journal-article","created":{"date-parts":[[2021,4,27]],"date-time":"2021-04-27T21:18:20Z","timestamp":1619558300000},"page":"1699","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":27,"title":["Angle Effect on Typical Optical Remote Sensing Indices in Vegetation Monitoring"],"prefix":"10.3390","volume":"13","author":[{"given":"Lingxiao","family":"Gu","sequence":"first","affiliation":[{"name":"College of Surveying and Mapping and Geographic Science, Liaoning Technical University, Fuxin 123000, China"}]},{"given":"Yanmin","family":"Shuai","sequence":"additional","affiliation":[{"name":"Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China"},{"name":"Research Center for Ecology and Environment of Central Asia, Chinese Academy of Sciences, Urumqi 830011, China"},{"name":"University of Chinese Academy of Sciences, Beijing 100049, China"}]},{"given":"Congying","family":"Shao","sequence":"additional","affiliation":[{"name":"College of Surveying and Mapping and Geographic Science, Liaoning Technical University, Fuxin 123000, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3923-6056","authenticated-orcid":false,"given":"Donghui","family":"Xie","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Remote Sensing Science, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China"}]},{"given":"Qingling","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Aeronautics and Astronautics, Sun Yat-sen University, Guangzhou 510006, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2948-4590","authenticated-orcid":false,"given":"Yaoming","family":"Li","sequence":"additional","affiliation":[{"name":"Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China"},{"name":"Research Center for Ecology and Environment of Central Asia, Chinese Academy of Sciences, Urumqi 830011, China"},{"name":"University of Chinese Academy of Sciences, Beijing 100049, China"}]},{"given":"Jian","family":"Yang","sequence":"additional","affiliation":[{"name":"College of Surveying and Mapping and Geographic Science, Liaoning Technical University, Fuxin 123000, China"}]}],"member":"1968","published-online":{"date-parts":[[2021,4,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"4149","DOI":"10.3390\/rs6054149","article-title":"Determination of carbonate rock chemistry using laboratory-based hyperspectral imagery","volume":"6","author":"Zaini","year":"2014","journal-title":"Remote Sens."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"3209","DOI":"10.1080\/01431160701469024","article-title":"Extracting impervious surfaces from medium spatial resolution multispectral and hyperspectral imagery: A comparison","volume":"29","author":"Weng","year":"2008","journal-title":"Int. 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