{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,20]],"date-time":"2026-02-20T18:39:15Z","timestamp":1771612755884,"version":"3.50.1"},"reference-count":36,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2018,1,19]],"date-time":"2018-01-19T00:00:00Z","timestamp":1516320000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>In conventional synthetic aperture radar (SAR), sensors with a fixed look angle are assumed, and the scattering properties are considered as invariant in the azimuth. In some new SAR modes such as wide-angle SAR and circular SAR (CSAR), the azimuthal angle of view is much larger. Anisotropic targets which have different physical shapes from different angles of view are difficult to interpret in the traditional observation model if variations remain unconsidered. Meanwhile, SAR polarimetry is a powerful tool to analyze and interpret targets\u2019 scattering properties. Anisotropic targets can be precisely described with polarimetric signatures from different angles of view. In this paper, polarimetric data is separated into sub-apertures to provide polarimetric properties from different angles of view. A multi-aperture observation model which contains full polarimetric information from all angles of view is then established. Based on the multi-aperture observation model, multi-aperture polarimetric entropy (MAPE) is defined and is suggested as an extension of polarimetric entropy in multi-aperture situations. MAPE describes both targets\u2019 polarimetric properties and variations across sub-apertures. Variations across the azimuth are analyzed and anisotropic and isotropic targets are identified by MAPE. MAPE can be used in many polarimetric wide angle and CSAR applications. Potential applications in target discrimination and classification are discussed. The effectiveness and advantages of MAPE are demonstrated with polarimetric CSAR data acquired from the Institute of Electronics, Chinese Academy of Sciences airborne CSAR system at P-band.<\/jats:p>","DOI":"10.3390\/rs10010123","type":"journal-article","created":{"date-parts":[[2018,1,22]],"date-time":"2018-01-22T04:51:13Z","timestamp":1516596673000},"page":"123","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Analysis of Azimuthal Variations Using Multi-Aperture Polarimetric Entropy with Circular SAR Images"],"prefix":"10.3390","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3002-5474","authenticated-orcid":false,"given":"Feiteng","family":"Xue","sequence":"first","affiliation":[{"name":"Department of Information and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China"},{"name":"Institute of Electronics, Chinese Academy of Sciences, 19 North 4th Ring Road West, Haidian District, Beijing 100190, China"},{"name":"Key Laboratory of Technology in Geospatial Information Processing and Application System, the Institute of Electronics of the Chinese Academy of Sciences (IECAS), Beijing 100190, China"}]},{"given":"Yun","family":"Lin","sequence":"additional","affiliation":[{"name":"Department of Information and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China"},{"name":"Institute of Electronics, Chinese Academy of Sciences, 19 North 4th Ring Road West, Haidian District, Beijing 100190, China"},{"name":"Key Laboratory of Technology in Geospatial Information Processing and Application System, the Institute of Electronics of the Chinese Academy of Sciences (IECAS), Beijing 100190, China"}]},{"given":"Wen","family":"Hong","sequence":"additional","affiliation":[{"name":"Department of Information and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China"},{"name":"Institute of Electronics, Chinese Academy of Sciences, 19 North 4th Ring Road West, Haidian District, Beijing 100190, China"},{"name":"Key Laboratory of Technology in Geospatial Information Processing and Application System, the Institute of Electronics of the Chinese Academy of Sciences (IECAS), Beijing 100190, China"}]},{"given":"Qiang","family":"Yin","sequence":"additional","affiliation":[{"name":"College of Information Science and Technology, Beijing University of Chemical Technology, Beijing 100190, China"}]},{"given":"Bingchen","family":"Zhang","sequence":"additional","affiliation":[{"name":"Department of Information and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China"},{"name":"Institute of Electronics, Chinese Academy of Sciences, 19 North 4th Ring Road West, Haidian District, Beijing 100190, China"},{"name":"Key Laboratory of Technology in Geospatial Information Processing and Application System, the Institute of Electronics of the Chinese Academy of Sciences (IECAS), Beijing 100190, China"}]},{"given":"Wenjie","family":"Shen","sequence":"additional","affiliation":[{"name":"Department of Information and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China"},{"name":"Institute of Electronics, Chinese Academy of Sciences, 19 North 4th Ring Road West, Haidian District, Beijing 100190, China"},{"name":"Key Laboratory of Technology in Geospatial Information Processing and Application System, the Institute of Electronics of the Chinese Academy of Sciences (IECAS), Beijing 100190, China"}]},{"given":"Yue","family":"Zhao","sequence":"additional","affiliation":[{"name":"Department of Information and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China"},{"name":"Institute of Electronics, Chinese Academy of Sciences, 19 North 4th Ring Road West, Haidian District, Beijing 100190, China"},{"name":"Key Laboratory of Technology in Geospatial Information Processing and Application System, the Institute of Electronics of the Chinese Academy of Sciences (IECAS), Beijing 100190, China"}]}],"member":"1968","published-online":{"date-parts":[[2018,1,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"384","DOI":"10.1049\/iet-rsn.2008.0086","article-title":"Scatterers characterisation in radar imaging using joint time-frequency analysis and polarimetric coherent decompositions","volume":"4","author":"Duquenoy","year":"2010","journal-title":"IET Radar Sonar Navig."},{"key":"ref_2","first-page":"164","article-title":"Wide-angle SAR imaging","volume":"5427","author":"Moses","year":"2004","journal-title":"Int. Soc. Opt. Eng."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1109\/TGRS.2013.2269194","article-title":"Fully-Polarimetric High-Resolution 3-D Imaging with Circular SAR at L-Band","volume":"52","author":"Ponce","year":"2014","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Lin, Y., Hong, W., Tan, W., and Wang, Y. (2012, January 22\u201327). Airborne circular SAR imaging: Results at P-band. Proceedings of the IEEE International Geoscience and Remote Sensing Symposium, Munich, Germany.","DOI":"10.1109\/IGARSS.2012.6352051"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1664","DOI":"10.1109\/8.650078","article-title":"Scattering center parameterization of wide-angle backscattered data using adaptive Gaussian representation","volume":"45","author":"Trintinalia","year":"1997","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"79","DOI":"10.1109\/MSP.2014.2312099","article-title":"Modeling and Interpretation of Scattering Mechanisms in Polarimetric Synthetic Aperture Radar: Advances and perspectives","volume":"31","author":"Sato","year":"2014","journal-title":"IEEE Signal Process. Mag."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"593","DOI":"10.1109\/TGRS.2011.2160647","article-title":"Filtering and Segmentation of Polarimetric SAR Data Based on Binary Partition Trees","volume":"50","author":"Salembier","year":"2012","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"519","DOI":"10.1109\/TGRS.2004.842108","article-title":"Unsupervised Classification of Polarimetric Synthetic Aperture Radar Images Using Fuzzy Clustering and EM Clustering","volume":"43","author":"Kersten","year":"2005","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"36","DOI":"10.1109\/36.20273","article-title":"Unsupervised classification of scattering behavior using radar polarimetry data","volume":"27","year":"1989","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"21","DOI":"10.5589\/m04-062","article-title":"Nonstationary natural media analysis from polarimetric SAR data using a two-dimensional time-frequency decomposition approach","volume":"31","author":"Ferrofamil","year":"2005","journal-title":"Can. J. Remote Sens."},{"key":"ref_11","unstructured":"Ainsworth, T.L., Jansen, R.W., Lee, J.S., and Fiedler, R. (July, January 28). Sub-aperture analysis of high-resolution polarimetric SAR data. Proceedings of the IEEE 1999 International Geoscience and Remote Sensing Symposium (IGARSS \u201999), Hamburg, Germany."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"81","DOI":"10.1049\/ip-rsn:19971048","article-title":"Detecting anisotropic scattering with hidden Markov models","volume":"144","author":"Flake","year":"2002","journal-title":"IEE Proc. Radar Sonar Navig."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"46","DOI":"10.1109\/36.898664","article-title":"Multi-aspect target detection for SAR imagery using hidden Markov models","volume":"39","author":"Runkle","year":"2001","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2264","DOI":"10.1109\/TGRS.2003.817188","article-title":"Scene characterization using subaperture polarimetric SAR data","volume":"41","author":"Reigber","year":"2003","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"5176","DOI":"10.1080\/01431161.2016.1230283","article-title":"Anisotropic analysis of polarimetric scattering and case studies with UAVSAR images","volume":"37","author":"Li","year":"2016","journal-title":"Int. J. Remote Sens."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1406","DOI":"10.1049\/el.2016.1764","article-title":"Adaptive imaging of anisotropic target based on circular-SAR","volume":"52","author":"Zhao","year":"2016","journal-title":"Electron. Lett."},{"key":"ref_17","first-page":"254","article-title":"Estimation and removing of anisotropic scattering for multiaspect polarimetric SAR image","volume":"4","author":"Li","year":"2015","journal-title":"J. Radars"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Xu, F., Li, Y., and Jin, Y.Q. (2016). Polarimetric\u2013Anisotropic Decomposition and Anisotropic Entropies of High-Resolution SAR Images. IEEE Trans. Geosci. Remote Sens., 1\u201316.","DOI":"10.1109\/TGRS.2016.2565693"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"68","DOI":"10.1109\/36.551935","article-title":"An entropy based classification scheme for land applications of polarimetric SAR","volume":"35","author":"Cloude","year":"1997","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_20","unstructured":"Lee, J.S., and Pottier, E. (2009). Polarimetric Radar Imaging: From Basics to Applications, CRC Press."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"2249","DOI":"10.1109\/36.789621","article-title":"Unsupervised classification using polarimetric decomposition and the complex Wishart classifier","volume":"37","author":"Lee","year":"1999","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"786","DOI":"10.1109\/36.298008","article-title":"Precision SAR processing using chirp scaling","volume":"32","author":"Raney","year":"1994","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_23","first-page":"78","article-title":"Scattering property based contextual PolSAR speckle filter","volume":"63","author":"Mullissa","year":"2017","journal-title":"Int. J. Appl. Earth Obs. Geoinf."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"3039","DOI":"10.1109\/TGRS.2008.922033","article-title":"Evaluation and Bias Removal of Multilook Effect on Entropy\/Alpha\/Anisotropy in Polarimetric SAR Decomposition","volume":"46","author":"Lee","year":"2008","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_25","unstructured":"Lee, J.S., Ainsworth, T.L., Kelly, J., and Lopez-Martinez, C. (2008, January 2\u20135). Statistical evaluation and bias removal of multi-look effect on Entropy\/ alpha\/Anisotropy in polarimetric target decomposition. Proceedings of the 7th European Conference on Synthetic Aperture Radar, Friedrichshafen, Germany."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"855","DOI":"10.1109\/36.298013","article-title":"The Wavenumber Shift in SAR Interferometry","volume":"29","author":"Gatelli","year":"1994","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1699","DOI":"10.1109\/TGRS.2005.852084","article-title":"Four-component scattering model for polarimetric SAR image decomposition","volume":"43","author":"Yamaguchi","year":"2005","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"963","DOI":"10.1109\/36.673687","article-title":"A three-component scattering model for polarimetric SAR data","volume":"36","author":"Freeman","year":"1998","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_29","unstructured":"Pottier, E. (1994, January 8\u201312). Radar target decomposition theorems and unsupervized classification of full polarimetric SAR data. Proceedings of the Geoscience and Remote Sensing Symposium, 1994. IGARSS \u201994. Surface and Atmospheric Remote Sensing: Technologies, Data Analysis and Interpretation., International, Pasadena, CA, USA."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"498","DOI":"10.1109\/36.485127","article-title":"A review of target decomposition theorems in radar polarimetry","volume":"34","author":"Cloude","year":"1996","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"2332","DOI":"10.1109\/36.964969","article-title":"Unsupervised classification of multifrequency and fully polarimetric SAR images based on the H\/A\/Alpha-Wishart classifier","volume":"39","author":"Pottier","year":"2001","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"2058","DOI":"10.1109\/TGRS.2005.853934","article-title":"Statistical Assessment of Eigenvector-Based Target Decomposition Theorems in Radar Polarimetry","volume":"43","author":"Pottier","year":"2005","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Cloude, S.R. (2010). Polarisation: Applications in Remote Sensing, Oxford University Press.","DOI":"10.1093\/acprof:oso\/9780199569731.001.0001"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2363","DOI":"10.1109\/36.789635","article-title":"Polarimetric SAR speckle filtering and its implication for classification","volume":"37","author":"Lee","year":"1999","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"176","DOI":"10.1109\/TGRS.2005.859338","article-title":"Scattering-model-based speckle filtering of polarimetric SAR data","volume":"44","author":"Lee","year":"2006","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"2299","DOI":"10.1080\/01431169408954244","article-title":"Classification of multi-look polarimetric SAR imagery based on complex Wishart distribution","volume":"15","author":"LEE","year":"1994","journal-title":"Int. J. Remote Sens."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/1\/123\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T14:51:52Z","timestamp":1760194312000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/1\/123"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,1,19]]},"references-count":36,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2018,1]]}},"alternative-id":["rs10010123"],"URL":"https:\/\/doi.org\/10.3390\/rs10010123","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,1,19]]}}}