{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,2]],"date-time":"2026-06-02T16:59:58Z","timestamp":1780419598424,"version":"3.54.1"},"reference-count":41,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2021,4,13]],"date-time":"2021-04-13T00:00:00Z","timestamp":1618272000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"his research was funded by the National Natural Science Foundation of China","award":["41871339"],"award-info":[{"award-number":["41871339"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Heterogeneity exists in the vertical distribution of the biochemical components of crops. A leaf chlorophyll deficiency occurs in the bottom- and middle-layers of crops due to nitrogen stress and leaf senescence. Some studies used multi-angular remote sensing data for estimating the vertical distribution of the leaf chlorophyll content (LCC). However, these studies performed LCC inversion of different vertical layers using a fixed view zenith angle (VZA), but rarely considered the contribution of the components of the non-target layers to the spectral response. The main goal of this work was to determine the LCC of different vertical layers of the canopy of winter wheat (Triticum aestivum L.), using multi-angular remote sensing and spectral vegetation indices. Different combinations of VZAs were used for obtaining the LCC of different layers. The results revealed that the responses of the transformed chlorophyll in reflectance absorption index (TCARI) and modified chlorophyll absorption in reflectance index (MCARI)\/optimized soil-adjusted vegetation index (OSAVI) to the upper-layer LCC were strongest at VZA 10\u00b0. For the middle-layer LCC, the response was strongest at 30\u00b0, but the response was significantly lower than that of the upper-layer. For the bottom-layer LCC, the responses were weak due to the obscuring effect of the upper- and middle-layer; thus, the LCC inversion of the bottom-layer data was not optimal for a single VZA. The optimal VZA or VZA combinations for LCC estimation were VZA 10\u00b0 for the upper-layer LCC (TCARI with coefficient of determination (R2) = 0.69, root mean square error (RMSE) = 4.80 ug\/cm2, MCARI\/OSAVI with R2 = 0.73, RMSE = 4.17 ug\/cm2), VZA 10\u00b0 and 30\u00b0 for the middle-layer LCC (TCARI with R2 = 0.17, RMSE = 4.81 ug\/cm2, MCARI\/OSAVI with R2 = 0.17, RMSE = 4.76 ug\/cm2), and VZA 10\u00b0, 30\u00b0, and 50\u00b0 for the bottom-layer LCC (TCARI with R2 = 0.40, RMSE = 6.29 ug\/cm2, MCARI\/OSAVI with R2 = 0.40, RMSE = 6.36 ug\/cm2). The proposed observation strategy provided a significantly higher estimation accuracy of the target layer LCC than the single VZA approach, and demonstrated the ability of canopy multi-angular spectral reflectance to accurately estimate the wheat canopy chlorophyll content vertical distribution.<\/jats:p>","DOI":"10.3390\/rs13081501","type":"journal-article","created":{"date-parts":[[2021,4,13]],"date-time":"2021-04-13T22:55:09Z","timestamp":1618354509000},"page":"1501","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":25,"title":["Using Multi-Angular Hyperspectral Data to Estimate the Vertical Distribution of Leaf Chlorophyll Content in Wheat"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7381-9293","authenticated-orcid":false,"given":"Bin","family":"Wu","sequence":"first","affiliation":[{"name":"Key Laboratory of Digital Earth Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China"},{"name":"University of Chinese Academy of Sciences, Beijing 100190, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wenjiang","family":"Huang","sequence":"additional","affiliation":[{"name":"Key Laboratory of Digital Earth Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China"},{"name":"Hainan Key Laboratory of Earth Observation, Hainan Institute of Aerospace Information Research Institute, Chinese Academy of Sciences, Sanya 572029, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Huichun","family":"Ye","sequence":"additional","affiliation":[{"name":"Key Laboratory of Digital Earth Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China"},{"name":"Hainan Key Laboratory of Earth Observation, Hainan Institute of Aerospace Information Research Institute, Chinese Academy of Sciences, Sanya 572029, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Peilei","family":"Luo","sequence":"additional","affiliation":[{"name":"Key Laboratory of Digital Earth Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6042-396X","authenticated-orcid":false,"given":"Yu","family":"Ren","sequence":"additional","affiliation":[{"name":"Key Laboratory of Digital Earth Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China"},{"name":"University of Chinese Academy of Sciences, Beijing 100190, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Weiping","family":"Kong","sequence":"additional","affiliation":[{"name":"Key Laboratory of Quantitative Remote Sensing Information Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,4,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1230","DOI":"10.1016\/j.agrformet.2008.03.005","article-title":"Estimating chlorophyll content from hyperspectral vegetation indices: Modeling and validation","volume":"148","author":"Wu","year":"2008","journal-title":"Agric. Forest Meteorol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"574","DOI":"10.1109\/JSTARS.2011.2176468","article-title":"Using hyperspectral remote sensing data for retrieving canopy chlorophyll and nitrogen content","volume":"5","author":"Clevers","year":"2011","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"3030","DOI":"10.1016\/j.rse.2008.02.012","article-title":"PROSPECT-4 and 5: Advances in the leaf optical properties model separating photosynthetic pigments","volume":"112","author":"Feret","year":"2008","journal-title":"Remote Sens. Environ."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"876","DOI":"10.1017\/S0021859614000483","article-title":"Chlorophyll estimation in field crops: An assessment of handheld leaf meters and spectral reflectance measurements","volume":"153","author":"Casa","year":"2015","journal-title":"J. Agric. Sci."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"280","DOI":"10.1016\/S0034-4257(98)00038-8","article-title":"Estimating canopy water content of chaparral shrubs using optical methods","volume":"65","author":"Ustin","year":"1998","journal-title":"Remote Sens. Environ."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"416","DOI":"10.1016\/S0034-4257(02)00018-4","article-title":"Integrated narrow-band vegetation indices for prediction of crop chlorophyll content for application to precision agriculture","volume":"81","author":"Haboudane","year":"2002","journal-title":"Remote Sens. Environ."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1409","DOI":"10.2134\/agronj2007.0322","article-title":"Vertical profile and temporal variation of chlorophyll in maize canopy: Quantitative \u201ccrop vigor\u201d indicator by means of reflectance-based techniques","volume":"100","author":"Ciganda","year":"2008","journal-title":"Agron. J."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Lieth, H. (1975). Modeling the primary productivity of the world. Primary Productivity of the Biosphere, Springer.","DOI":"10.1007\/978-3-642-80913-2"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"451","DOI":"10.1007\/BF00325881","article-title":"Effects of leaf age, nitrogen nutrition and photon flux density on the distribution of nitrogen among leaves of a vine (Ipomoea tricolor Cav.) grown horizontally to avoid mutual shading of leaves","volume":"97","author":"Hikosaka","year":"1994","journal-title":"Oecologia"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"14","DOI":"10.1016\/j.fcr.2012.01.007","article-title":"Assessing the vertical footprint of reflectance measurements to characterize nitrogen uptake and biomass distribution in maize canopies","volume":"129","author":"Winterhalter","year":"2012","journal-title":"Field Crop. Res."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1081\/PLN-200042175","article-title":"Vertical distribution of nitrogen in different layers of leaf and stem and their relationship with grain quality of winter wheat","volume":"28","author":"Wang","year":"2005","journal-title":"J. Plant Nutr."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"165","DOI":"10.1007\/s11119-010-9166-5","article-title":"Estimation of vertical distribution of chlorophyll concentration by bi-directional canopy reflectance spectra in winter wheat","volume":"12","author":"Huang","year":"2011","journal-title":"Precis. Agric."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"322","DOI":"10.1016\/j.rse.2006.06.019","article-title":"View angle effects on relationships between MISR vegetation indices and leaf area index in a recently burned ponderosa pine forest","volume":"107","author":"Pocewicz","year":"2007","journal-title":"Remote Sens. Environ."},{"key":"ref_14","first-page":"827","article-title":"Vertical profile of leaf senescence during the grain-filling period in older and newer maize hybrids","volume":"44","author":"Valentinuz","year":"2004","journal-title":"Crop Sci."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2634","DOI":"10.1080\/01431161.2015.1041176","article-title":"Estimating winter wheat (Triticum aestivum) LAI and leaf chlorophyll content from canopy reflectance data by integrating agronomic prior knowledge with the PROSAIL model","volume":"36","author":"Li","year":"2015","journal-title":"Int. J. Remote Sens."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"240","DOI":"10.1007\/s10812-016-0276-3","article-title":"Comparison of four chemometric techniques for estimating leaf nitrogen concentrations in winter wheat (Triticum aestivum) based on hyperspectral features","volume":"83","author":"Li","year":"2016","journal-title":"J. Appl. Spectrosc."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.rse.2018.04.024","article-title":"Estimating leaf chlorophyll status using hyperspectral lidar measurements by PROSPECT model inversion","volume":"212","author":"Sun","year":"2018","journal-title":"Remote Sens. Environ."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"111","DOI":"10.1016\/j.agrformet.2012.10.004","article-title":"Canopy vertical heterogeneity plays a critical role in reflectance simulation","volume":"169","author":"Wang","year":"2013","journal-title":"Agric. Forest Meteorol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"273","DOI":"10.1016\/S0034-4257(98)00059-5","article-title":"Quantifying chlorophylls and caroteniods at leaf and canopy scales: An evaluation of some hyperspectral approaches","volume":"66","author":"Blackburn","year":"1998","journal-title":"Remote Sens. Environ."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1491","DOI":"10.1109\/36.934080","article-title":"Scaling-up and model inversion methods with narrowband optical indices for chlorophyll content estimation in closed forest canopies with hyperspectral data","volume":"39","author":"Miller","year":"2001","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"492","DOI":"10.1007\/s004420050337","article-title":"The photochemical reflectance index: An optical indicator of photosynthetic radiation use efficiency across species, functional types, and nutrient levels","volume":"112","author":"Gamon","year":"1997","journal-title":"Oecologia"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/0034-4257(85)90034-3","article-title":"Directional reflectance factor distributions for cover types of Northern Africa","volume":"18","author":"Kimes","year":"1985","journal-title":"Remote Sens. Environ."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"445","DOI":"10.1006\/jema.1996.0106","article-title":"Modeling the effects of land use change on the water temperature in unregulated urban streams","volume":"49","author":"LeBlanc","year":"1997","journal-title":"J. Environ. Manag."},{"key":"ref_24","first-page":"1319","article-title":"Inversion of winter wheat foliage vertical distribution based on canopy reflected spectrum by partial least squares regression method","volume":"27","author":"Wang","year":"2007","journal-title":"Guang Pu Xue Yu Guang Pu Fen Xi"},{"key":"ref_25","first-page":"1599","article-title":"Assessment of chlorophyll content using a new vegetation index based on multi-angular hyperspectral image data","volume":"34","author":"Liao","year":"2014","journal-title":"Spectrosc. Spectr. Anal."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Kong, W., Huang, W., Zhou, X., Ye, H., Dong, Y., and Casa, R. (2017). Off-nadir hyperspectral sensing for estimation of vertical profile of leaf chlorophyll content within wheat canopies. Sensors, 17.","DOI":"10.3390\/s17122711"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"236","DOI":"10.1109\/TGRS.2016.2604492","article-title":"Effect of vertical distribution of crop structure and biochemical parameters of winter wheat on canopy reflectance characteristics and spectral indices","volume":"55","author":"Zhao","year":"2016","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1802","DOI":"10.3389\/fpls.2019.01802","article-title":"Estimation of vertical leaf nitrogen distribution within a rice canopy based on hyperspectral data","volume":"10","author":"He","year":"2019","journal-title":"Front. Plant Sci."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Luo, J., Ma, R., Feng, H., and Li, X. (2016). Estimating the total nitrogen concentration of reed canopy with hyperspectral measurements considering a non-uniform vertical nitrogen distribution. Remote Sens., 8.","DOI":"10.3390\/rs8100789"},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Ye, H., Huang, W., Huang, S., Wu, B., Dong, Y., and Cui, B. (2018). Remote estimation of nitrogen vertical distribution by consideration of maize geometry characteristics. Remote Sens., 10.","DOI":"10.3390\/rs10121995"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1562","DOI":"10.1016\/S2095-3119(19)62686-9","article-title":"Estimating total leaf nitrogen concentration in winter wheat by canopy hyperspectral data and nitrogen vertical distribution","volume":"18","author":"Duan","year":"2019","journal-title":"J. Integr. Agric."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.indcrop.2018.02.051","article-title":"Assessing leaf nitrogen concentration of winter oilseed rape with canopy hyperspectral technique considering a non-uniform vertical nitrogen distribution","volume":"116","author":"Li","year":"2018","journal-title":"Ind. Crop. Prod."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"6387","DOI":"10.1038\/s41598-018-24369-0","article-title":"Parameterization of the vertical distribution of leaf area index (LAI) in rice (Oryza sativa L.) using a plant canopy analyzer","volume":"8","author":"Hirooka","year":"2018","journal-title":"Sci. Rep."},{"key":"ref_34","unstructured":"Kim, M.S., Daughtry, C., Chappelle, E., McMurtrey, J., and Walthall, C. (1994). The Use of High Spectral Resolution Bands for Estimating Absorbed Photosynthetically Active Radiation (A Par), CNES, Proceedings of the 6th International Symposium on Physical Measurements and Signatures in Remote Sensing, Val d\u2019Isere, France, 17\u201324 January 1994."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"229","DOI":"10.1016\/S0034-4257(00)00113-9","article-title":"Estimating corn leaf chlorophyll concentration from leaf and canopy reflectance","volume":"74","author":"Daughtry","year":"2000","journal-title":"Remote Sens. Environ."},{"key":"ref_36","first-page":"42","article-title":"The application of double factor variance analysis of repeated trials with unequal frequency","volume":"3","author":"Yu","year":"1996","journal-title":"Stat. Thinktank"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"72","DOI":"10.1016\/S1002-0160(14)60077-1","article-title":"Site-specific nitrogen management in dry direct-seeded rice using chlorophyll meter and leaf colour chart","volume":"25","author":"Ali","year":"2015","journal-title":"Pedosphere"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"96","DOI":"10.1016\/j.fcr.2006.09.014","article-title":"Comparison of petiole nitrate concentrations, SPAD chlorophyll readings, and QuickBird satellite imagery in detecting nitrogen status of potato canopies","volume":"101","author":"Wu","year":"2007","journal-title":"Field Crop. Res."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"391","DOI":"10.1080\/01904167.2016.1240200","article-title":"Chlorophyll meter readings, N leaf concentration and their relationship with N use efficiency in oregano","volume":"40","author":"Dordas","year":"2017","journal-title":"J. Plant Nutr."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"12","DOI":"10.1016\/j.fcr.2015.10.003","article-title":"Indicators for diagnosing nitrogen status of rice based on chlorophyll meter readings","volume":"185","author":"Yuan","year":"2016","journal-title":"Field Crop. Res."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"751","DOI":"10.1016\/j.isprsjprs.2011.08.001","article-title":"An investigation into robust spectral indices for leaf chlorophyll estimation","volume":"66","author":"Main","year":"2011","journal-title":"ISPRS J. Photogramm. Remote Sens."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/8\/1501\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:47:42Z","timestamp":1760161662000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/8\/1501"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,4,13]]},"references-count":41,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2021,4]]}},"alternative-id":["rs13081501"],"URL":"https:\/\/doi.org\/10.3390\/rs13081501","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,4,13]]}}}