{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,15]],"date-time":"2026-06-15T23:33:19Z","timestamp":1781566399539,"version":"3.54.5"},"reference-count":81,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2021,1,23]],"date-time":"2021-01-23T00:00:00Z","timestamp":1611360000000},"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":["41804004, 41820104005, 41531068"],"award-info":[{"award-number":["41804004, 41820104005, 41531068"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Canadian Space Agency SOAR-E program","award":["SOAR-E-5489"],"award-info":[{"award-number":["SOAR-E-5489"]}]},{"name":"Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan)","award":["CUG190633"],"award-info":[{"award-number":["CUG190633"]}]},{"name":"Spanish Ministry of Science, Innovation and Universities, State Research Agency (AEI) and the European Regional Development Fund","award":["TEC2017-85244-C2-1-P"],"award-info":[{"award-number":["TEC2017-85244-C2-1-P"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>This study presents a demonstration of the applicability of machine learning techniques for the retrieval of crop height in corn fields using space-borne PolSAR (Polarimetric Synthetic Aperture Radar) data. Multi-year RADARSAT-2 C-band data acquired over agricultural areas in Canada, covering the whole corn growing period, are exploited. Two popular machine learning regression methods, i.e., Random Forest Regression (RFR) and Support Vector Regression (SVR) are adopted and evaluated. A set of 27 representative polarimetric parameters are extracted from the PolSAR data and used as input features in the regression models for height estimation. Furthermore, based on the unique capability of the RFR method to determine variable importance contributing to the regression, a smaller number of polarimetric features (6 out of 27 in our study) are selected in the final regression models. Results of our study demonstrate that PolSAR observables can produce corn height estimates with root mean square error (RMSE) around 40\u201350 cm throughout the growth cycle. The RFR approach shows better overall accuracy in corn height estimation than the SVR method in all tests. The six selected polarimetric features by variable importance ranking can generate better results. This study provides a new perspective on the use of PolSAR data in retrieving agricultural crop height from space.<\/jats:p>","DOI":"10.3390\/rs13030392","type":"journal-article","created":{"date-parts":[[2021,1,25]],"date-time":"2021-01-25T09:59:40Z","timestamp":1611568780000},"page":"392","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":29,"title":["Crop Height Estimation of Corn from Multi-Year RADARSAT-2 Polarimetric Observables Using Machine Learning"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4293-3354","authenticated-orcid":false,"given":"Qinghua","family":"Xie","sequence":"first","affiliation":[{"name":"School of Geography and Information Engineering, China University of Geosciences (Wuhan), Wuhan 430074, China"},{"name":"Institute for Computer Research (IUII), University of Alicante, E-03080 Alicante, Spain"},{"name":"Department of Geography and Environment, The University of Western Ontario, London, ON N6A 5C2, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8404-0530","authenticated-orcid":false,"given":"Jinfei","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Geography and Environment, The University of Western Ontario, London, ON N6A 5C2, Canada"},{"name":"Institute for Earth and Space Exploration, The University of Western Ontario, London, ON N6A 3K7, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4216-5175","authenticated-orcid":false,"given":"Juan","family":"Lopez-Sanchez","sequence":"additional","affiliation":[{"name":"Institute for Computer Research (IUII), University of Alicante, E-03080 Alicante, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xing","family":"Peng","sequence":"additional","affiliation":[{"name":"School of Geography and Information Engineering, China University of Geosciences (Wuhan), Wuhan 430074, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5504-206X","authenticated-orcid":false,"given":"Chunhua","family":"Liao","sequence":"additional","affiliation":[{"name":"Department of Geography and Environment, The University of Western Ontario, London, ON N6A 5C2, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jiali","family":"Shang","sequence":"additional","affiliation":[{"name":"Ottawa Research and Development Centre, Agriculture and Agri-Food Canada, Ottawa, ON K1A 0C6, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jianjun","family":"Zhu","sequence":"additional","affiliation":[{"name":"School of Geosciences and Info-Physics, Central South University, Changsha 410083, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Haiqiang","family":"Fu","sequence":"additional","affiliation":[{"name":"School of Geosciences and Info-Physics, Central South University, Changsha 410083, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"J.","family":"Ballester-Berman","sequence":"additional","affiliation":[{"name":"Institute for Computer Research (IUII), University of Alicante, E-03080 Alicante, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,1,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"130","DOI":"10.1016\/j.rse.2016.10.007","article-title":"Retrieval of agricultural crop height from space: A comparison of SAR techniques","volume":"187","author":"Erten","year":"2016","journal-title":"Remote Sens. 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