{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,5]],"date-time":"2026-02-05T10:53:47Z","timestamp":1770288827976,"version":"3.49.0"},"reference-count":71,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2023,12,2]],"date-time":"2023-12-02T00:00:00Z","timestamp":1701475200000},"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":["41971306"],"award-info":[{"award-number":["41971306"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The Leaf Area Index (LAI) is a crucial vegetation parameter for climate and ecological models. Reflectance anisotropy contains valuable supplementary information for the retrieval of properties of an observed target surface. Previous studies have utilized multi-angular reflectance data and physically based Bidirectional Reflectance Distribution Function (BRDF) models with detailed vegetation structure descriptions for LAI estimation. However, the optimal selection of viewing angles for improved inversion results has received limited attention. By optimizing directional observations and integrating the PROSAIL and Ross\u2013Li models, this study aims to enhance LAI estimation from MODIS BRDF data. A dataset of 20,000 vegetation parameter combinations was utilized to identify the directions in which the PROSAIL model exhibits higher sensitivity to LAI changes and better consistency with the Ross\u2013Li BRDF models. The results reveal significant variations in the sensitivity of the PROSAIL model to LAI changes and its consistency with the Ross\u2013Li model over the viewing hemisphere. In the red band, directions with high sensitivity to LAI changes and strong model consistency are mainly found at smaller solar and viewing zenith angles. In the near-infrared band, these directions are distributed at positions with larger solar and viewing zenith angles. Validation using field measurements and LAI maps demonstrates that the proposed method achieves comparable accuracy to an algorithm utilizing 397 viewing angles by utilizing reflectance data from only 30 directions. Moreover, there is a significant improvement in computational efficiency. The accuracy of LAI estimation obtained from simulated multi-angle data is relatively high for LAI values below 3.5 when compared with the MODIS LAI product from two tiles. Additionally, there is also a slight improvement in the results when the LAI exceeds 4.5. Overall, our results highlight the potential of utilizing multi-angular reflectance in specific directions for vegetation parameter inversion, showcasing the promise of this method for large-scale LAI estimation.<\/jats:p>","DOI":"10.3390\/rs15235609","type":"journal-article","created":{"date-parts":[[2023,12,2]],"date-time":"2023-12-02T13:45:41Z","timestamp":1701524741000},"page":"5609","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Enhancing Leaf Area Index Estimation with MODIS BRDF Data by Optimizing Directional Observations and Integrating PROSAIL and Ross\u2013Li Models"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2768-7960","authenticated-orcid":false,"given":"Hu","family":"Zhang","sequence":"first","affiliation":[{"name":"School of Geographic and Environmental Sciences, Tianjin Normal University, Tianjin 300387, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1352-5143","authenticated-orcid":false,"given":"Xiaoning","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Mechatronical Engineering, Beijing Institute of Technology, Beijing 100081, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9477-9155","authenticated-orcid":false,"given":"Lei","family":"Cui","sequence":"additional","affiliation":[{"name":"School of Geographic and Environmental Sciences, Tianjin Normal University, Tianjin 300387, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1257-9449","authenticated-orcid":false,"given":"Yadong","family":"Dong","sequence":"additional","affiliation":[{"name":"Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1963-4145","authenticated-orcid":false,"given":"Yan","family":"Liu","sequence":"additional","affiliation":[{"name":"Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China"}]},{"given":"Qianrui","family":"Xi","sequence":"additional","affiliation":[{"name":"School of Geographic and Environmental Sciences, Tianjin Normal University, Tianjin 300387, China"}]},{"given":"Hongtao","family":"Cao","sequence":"additional","affiliation":[{"name":"School of Geographic and Environmental Sciences, Tianjin Normal University, Tianjin 300387, China"}]},{"given":"Lei","family":"Chen","sequence":"additional","affiliation":[{"name":"School of Geographic and Environmental Sciences, Tianjin Normal University, Tianjin 300387, China"}]},{"given":"Yi","family":"Lian","sequence":"additional","affiliation":[{"name":"School of Geographic and Environmental Sciences, Tianjin Normal University, Tianjin 300387, China"}]}],"member":"1968","published-online":{"date-parts":[[2023,12,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"390","DOI":"10.1016\/j.agrformet.2018.11.033","article-title":"Review of indirect optical measurements of leaf area index: Recent advances, challenges, and perspectives","volume":"265","author":"Yan","year":"2019","journal-title":"Agric. 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