{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,14]],"date-time":"2025-10-14T11:34:29Z","timestamp":1760441669885,"version":"build-2065373602"},"reference-count":30,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2021,5,12]],"date-time":"2021-05-12T00:00:00Z","timestamp":1620777600000},"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>Due to geosynchronous synthetic aperture radar\u2019s (GEO SAR) high orbit and low relative speed, the integration time reaches up to hundreds of seconds for a fine resolution. The short revisit cycle is essential for remote sensing applications such as disaster monitoring and vegetation measurements. Three-dimensional (3D) scene imaging mode is crucial for long-term observation using GEO SAR. However, this mode will bring a new kind of space-variant error in elevation. In this paper, we focus on the analysis of the elevation space-variant error. First, the decorrelation problems caused by the spatial variation are presented. Second, by combining with the SAR imaging geometry, the elevation spatial variation is decomposed into two-dimensional (2D) space variation of range and azimuth. Third, an imaging algorithm is proposed to solve the 3D space variation and improve the focusing depth. Finally, simulations with dot-matrix targets and distributed targets are performed to validate the imaging method.<\/jats:p>","DOI":"10.3390\/rs13101888","type":"journal-article","created":{"date-parts":[[2021,5,12]],"date-time":"2021-05-12T22:46:14Z","timestamp":1620859574000},"page":"1888","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Elevation Spatial Variation Analysis and Compensation in GEO SAR Imaging"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9070-7186","authenticated-orcid":false,"given":"Faguang","family":"Chang","sequence":"first","affiliation":[{"name":"College of Electronic Science and Technology, National University of Defense Technology, No. 109 Deya Road, Changsha 410073, China"}]},{"given":"Dexin","family":"Li","sequence":"additional","affiliation":[{"name":"College of Electronic Science and Technology, National University of Defense Technology, No. 109 Deya Road, Changsha 410073, China"}]},{"given":"Zhen","family":"Dong","sequence":"additional","affiliation":[{"name":"College of Electronic Science and Technology, National University of Defense Technology, No. 109 Deya Road, Changsha 410073, China"}]},{"given":"Yang","family":"Huang","sequence":"additional","affiliation":[{"name":"College of Electronic Science and Technology, National University of Defense Technology, No. 109 Deya Road, Changsha 410073, China"}]},{"given":"Zhihua","family":"He","sequence":"additional","affiliation":[{"name":"College of Electronic Science and Technology, National University of Defense Technology, No. 109 Deya Road, Changsha 410073, China"}]},{"given":"Xing","family":"Chen","sequence":"additional","affiliation":[{"name":"College of Electronic Science and Technology, National University of Defense Technology, No. 109 Deya Road, Changsha 410073, China"}]}],"member":"1968","published-online":{"date-parts":[[2021,5,12]]},"reference":[{"key":"ref_1","unstructured":"DLR (2010). Terra SAR-X Ground Segment Basic Product Specification Document, German Aerospace Center. TX-GS-DD-3302."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"3179","DOI":"10.1109\/TGRS.2011.2178247","article-title":"TOPS interferometry with Terra SAR-X","volume":"50","author":"Prats","year":"2012","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_3","unstructured":"Tomiyasu, K. (1978, January 15\u201319). Synthetic aperture radar in geosynchronous orbit. Proceedings of the Digest International IEEE Antennas Propagation Symposium, College Park, MD, USA."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"324","DOI":"10.1109\/TGRS.1983.350561","article-title":"Synthetic Aperture Radar Imaging from an Inclined Geosynchronous Orbit","volume":"21","author":"Tomiyasu","year":"1983","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_5","unstructured":"Cutrona, L., and Skolnik, M. (1970). Radar Handbook, McGraw-Hill."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"2132","DOI":"10.1109\/36.868872","article-title":"A ground-based parasitic SAR experiment","volume":"38","author":"Cazzani","year":"2000","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_7","unstructured":"Erik, M. (1994). Handbook of Geostationary Orbits, Kluwer Academic Publishers. [1st ed.]."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"2924","DOI":"10.1109\/TGRS.2010.2042062","article-title":"Radar imaging from geosynchronous orbit: Temporal decorrelation aspects","volume":"48","author":"Bruno","year":"2010","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Kempf, T., Anglberger, H., and Suess, H. (2012, January 22\u201327). Depth-of-Focus Issues on Spaceborne very High Resolution SAR. Proceedings of the 2012 IEEE International Geoscience and Remote Sensing Symposium, Munich, Germany.","DOI":"10.1109\/IGARSS.2012.6351939"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Rodriguez-Cassola, M., Prats-Iraola, P., De Zan, F., Scheiber, R., and Reigber, A. (2013, January 21\u201326). Doppler-related focusing aspects in the TOPS imaging mode. Proceedings of the IEEE International Geoscience and Remote Sensing Symposium (IGARSS), Melbourne, Australia.","DOI":"10.1109\/IGARSS.2013.6723212"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"172","DOI":"10.1109\/LGRS.2004.842465","article-title":"Precise topography- and aperture-dependent motion compensation for airborne SAR","volume":"2","author":"Macedo","year":"2005","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"241","DOI":"10.1109\/7.18685","article-title":"Geometric accuracy in airborne SAR images","volume":"25","author":"Blacknell","year":"1989","journal-title":"IEEE Trans. Aerosp. Electron. Syst."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1735","DOI":"10.1109\/LGRS.2015.2422893","article-title":"Absolute height estimation using a single Terra SAR-X staring spotlight acquisition","volume":"12","author":"Duque","year":"2015","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"6003","DOI":"10.1109\/TGRS.2013.2294353","article-title":"On the Processing of Very High Resolution Spaceborne SAR Data","volume":"52","author":"Prats","year":"2014","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"349","DOI":"10.1109\/LGRS.2007.895712","article-title":"Comparison of topography- and aperture-dependent motion compensation algorithms for airborne SAR","volume":"4","author":"Prats","year":"2007","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Hu, B., Jiang, Y., Zhang, Y., and Yeo, T. (2015, January 26\u201331). Accurate slant range model and focusing method in geosynchronous SAR. Proceedings of the 2015 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), Milan, Italy.","DOI":"10.1109\/IGARSS.2015.7326818"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1732","DOI":"10.1109\/LGRS.2014.2307167","article-title":"An Optimal Resolution Steering Method for Geosynchronous Orbit SAR","volume":"11","author":"Zhang","year":"2014","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Wu, X., Zhang, S., and Xiao, B. (2012, January 19\u201320). An advanced equivalent slant range model and image formation in geosynchronous SAR. Proceedings of the 2012 International Workshop on Microwave and Millimeter Wave Circuits and System Technology, Chengdu, China.","DOI":"10.1109\/MMWCST.2012.6238179"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2286","DOI":"10.1109\/LGRS.2015.2470516","article-title":"Generalized omega-K algorithm for geosynchronous SAR image formation","volume":"12","author":"Hu","year":"2015","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Geng, J., Yu, Z., Li, C., and Wei, L. (2019). Squint Mode GEO SAR Imaging Using Bulk Range Walk Correction on Received Signals. Remote. Sens., 11.","DOI":"10.3390\/rs11010017"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Li, Z., Li, C., Yu, Z., Zhou, J., and Chen, J. (2011, January 24\u201329). Back projection algorithm for high resolution GEO-SAR image formation. Proceedings of the 2011 IEEE International Geoscience and Remote Sensing Symposium, Vancouver, BC, Canada.","DOI":"10.1109\/IGARSS.2011.6048967"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1109\/LGRS.2006.885862","article-title":"A Two-Dimensional Spectrum for Bistatic SAR Processing Using Series Reversion","volume":"4","author":"Neo","year":"2007","journal-title":"IEEE. Geosci. Remote Sens. Lett."},{"key":"ref_23","unstructured":"Zhu, Y., Ke, M., Zhang, T., Li, G., and Ding, Z. (2018, January 4\u20137). Image Representation of GEO SAR Time-Variant Scene. Proceedings of the 12th European Conference on Synthetic Aperture Radar, Aachen, Germany."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Li, D., Zhu, X., Dong, Z., Yu, A., and Zhang, Y. (2020). Background Tropospheric Delay in Geosynchronous Synthetic Aperture Radar. Remote. Sens., 12.","DOI":"10.3390\/rs12183081"},{"key":"ref_25","unstructured":"Curlander, J., and McDonough, R. (1991). Synthetic Aperture Radr: Systems and Signal Processing, John Wiley Sons."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/s11432-013-5009-0","article-title":"Modeling and high-precision processing of the azimuth shift variation for spaceborne HRWS SAR","volume":"56","author":"Feng","year":"2012","journal-title":"Sci. China Inf. Sci."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"3999","DOI":"10.1109\/JSTARS.2015.2418814","article-title":"Modeling and Processing of Two-Dimensional Spatial-Variant Geosynchronous SAR Data","volume":"8","author":"Li","year":"2015","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_28","unstructured":"Hu, C., and Tao, Z. (2010, January 7\u201310). The accurate resolution analysis in Geosynchronous SAR. Proceedings of the 8th European Conference on Synthetic Aperture Radar, Aachen, Germany."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"2493","DOI":"10.1109\/TGRS.2008.917599","article-title":"Focusing Bistatic SAR Data Using the Nonlinear Chirp Scaling Algorithm","volume":"46","author":"Wong","year":"2008","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"16","DOI":"10.1109\/TGRS.2018.2886817","article-title":"A two-step nonlinear chirp scaling method for multichannel GEO spaceborne-airborne bistatic SAR spectrum reconstructing and focusing","volume":"57","author":"An","year":"2019","journal-title":"IEEE Trans. Geosci. Remote Sens."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/10\/1888\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:59:37Z","timestamp":1760162377000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/10\/1888"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,5,12]]},"references-count":30,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2021,5]]}},"alternative-id":["rs13101888"],"URL":"https:\/\/doi.org\/10.3390\/rs13101888","relation":{},"ISSN":["2072-4292"],"issn-type":[{"type":"electronic","value":"2072-4292"}],"subject":[],"published":{"date-parts":[[2021,5,12]]}}}