{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T02:08:03Z","timestamp":1760148483140,"version":"build-2065373602"},"reference-count":34,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2023,5,10]],"date-time":"2023-05-10T00:00:00Z","timestamp":1683676800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Natural Science Foundation of China","award":["42272346","2021YFG0319","scsxdz2020yb08","SYZXW2017101"],"award-info":[{"award-number":["42272346","2021YFG0319","scsxdz2020yb08","SYZXW2017101"]}]},{"name":"Sichuan Science and Technology Program","award":["42272346","2021YFG0319","scsxdz2020yb08","SYZXW2017101"],"award-info":[{"award-number":["42272346","2021YFG0319","scsxdz2020yb08","SYZXW2017101"]}]},{"name":"Opening Fund of Geomathematics Key Laboratory of Sichuan Province","award":["42272346","2021YFG0319","scsxdz2020yb08","SYZXW2017101"],"award-info":[{"award-number":["42272346","2021YFG0319","scsxdz2020yb08","SYZXW2017101"]}]},{"DOI":"10.13039\/501100004613","name":"China Geological Survey (CGS)","doi-asserted-by":"publisher","award":["42272346","2021YFG0319","scsxdz2020yb08","SYZXW2017101"],"award-info":[{"award-number":["42272346","2021YFG0319","scsxdz2020yb08","SYZXW2017101"]}],"id":[{"id":"10.13039\/501100004613","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>How to extract the indicative signatures from the spectral data is an important issue for further retrieval based on remote sensing technique. This study provides new insight into extracting indicative signatures by identifying oblique extremum points, rather than local extremum points traditionally known as absorption points. A case study on retrieving soil organic matter (SOM) contents from the black soil region in Northeast China using spectral data revealed that the oblique extremum method can effectively identify weak absorption signatures hidden in the spectral data. Moreover, the comparison of retrieval outcomes using various indicative signature extraction methods reveals that the oblique extremum method outperforms the correlation analysis and traditional extremum methods. The experimental findings demonstrate that the radial basis function (RBF) neural network retrieval model exposes the nonlinear relationship between reflectance (or reflectance transformation results) and the SOM contents. Additionally, an improved oblique extremum method based on the second-order derivative is provided. Overall, this research presents a novel perspective on indicative signature extraction, which could potentially offer better retrieval performance than traditional methods.<\/jats:p>","DOI":"10.3390\/rs15102508","type":"journal-article","created":{"date-parts":[[2023,5,11]],"date-time":"2023-05-11T01:37:24Z","timestamp":1683769044000},"page":"2508","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Organic Matter Retrieval in Black Soil Based on Oblique Extremum Signatures"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1444-744X","authenticated-orcid":false,"given":"Mingyue","family":"Zhang","sequence":"first","affiliation":[{"name":"Geomathematics Key Laboratory of Sichuan, Chengdu University of Technology, Chengdu 610059, China"},{"name":"College of Mathematics and Physics, Chengdu University of Technology, Chengdu 610059, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Maozhi","family":"Wang","sequence":"additional","affiliation":[{"name":"Geomathematics Key Laboratory of Sichuan, Chengdu University of Technology, Chengdu 610059, China"},{"name":"College of Mathematics and Physics, Chengdu University of Technology, Chengdu 610059, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Daming","family":"Wang","sequence":"additional","affiliation":[{"name":"Tianjin Center of China Geological Survey, Tianjin 300170, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shangkun","family":"Wang","sequence":"additional","affiliation":[{"name":"Geomathematics Key Laboratory of Sichuan, Chengdu University of Technology, Chengdu 610059, China"},{"name":"College of Mathematics and Physics, Chengdu University of Technology, Chengdu 610059, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wenxi","family":"Xu","sequence":"additional","affiliation":[{"name":"Geomathematics Key Laboratory of Sichuan, Chengdu University of Technology, Chengdu 610059, China"},{"name":"College of Mathematics and Physics, Chengdu University of Technology, Chengdu 610059, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,5,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"562","DOI":"10.1007\/s11769-013-0626-5","article-title":"Soil Degradation and Food Security Coupled with Global Climate Change in Northeastern China","volume":"23","author":"Gong","year":"2013","journal-title":"Chin. 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