{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T12:42:55Z","timestamp":1760186575868,"version":"build-2065373602"},"reference-count":22,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2019,1,2]],"date-time":"2019-01-02T00:00:00Z","timestamp":1546387200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000006","name":"Office of Naval Research","doi-asserted-by":"publisher","award":["N00014-15-1-2044"],"award-info":[{"award-number":["N00014-15-1-2044"]}],"id":[{"id":"10.13039\/100000006","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The wavenumber-frequency spectra of many radar measurements of the sea surface contain a linear feature at frequencies lower than the first order dispersion relationship commonly referred to as the \u201cgroup line\u201d. Plant and Farquharson, showed numerically that the group line is at least partially caused by wave interference-induced breaking of steep short gravity waves. This paper uses two wave retrieval techniques, proper orthogonal decomposition (POD) and FFT-based dispersion curve filtering, to examine two X-band radar datasets, and compare wave orbital velocity reconstructions to ground truth wave buoy measurements within the field of view of the radar. POD allows group line energy to be retained in the reconstruction, while dispersion curve filtering removes all energy not associated with the first order dispersion relationship. Results show that when group line energy is higher or comparable to dispersion curve energy, the inclusion of this group line energy in phase-resolved orbital velocity reconstructions increases the accuracy of the reconstruction. This increased accuracy is demonstrated by higher correlations between POD reconstructed time series with buoy ground truth measurements than dispersion curve filtered reconstructions. When energy lying on the dispersion relationship is much higher than the group line energy, the FFT and POD reconstruction methods perform comparably.<\/jats:p>","DOI":"10.3390\/rs11010071","type":"journal-article","created":{"date-parts":[[2019,1,3]],"date-time":"2019-01-03T03:36:30Z","timestamp":1546486590000},"page":"71","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Group Line Energy in Phase-Resolved Ocean Surface Wave Orbital Velocity Reconstructions from X-band Doppler Radar Measurements of the Sea Surface"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5851-1186","authenticated-orcid":false,"given":"Andrew J.","family":"Kammerer","sequence":"first","affiliation":[{"name":"Marine Meteorology Division, Naval Research Laboratory, Monterey, CA 93943, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1294-6501","authenticated-orcid":false,"given":"Erin E.","family":"Hackett","sequence":"additional","affiliation":[{"name":"Department of Coastal and Marine Systems Science, Coastal Carolina University, Conway, SC 29528, USA"}]}],"member":"1968","published-online":{"date-parts":[[2019,1,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1049","DOI":"10.1029\/JC090iC01p01049","article-title":"A three-dimensional analysis of marine radar images for the determination of ocean wave directionality and surface currents","volume":"90","author":"Young","year":"1985","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1016\/S0378-3839(99)00032-0","article-title":"Use of nautical radar as a wave monitoring instrument","volume":"37","author":"Reichert","year":"1999","journal-title":"Coast. Eng."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1291","DOI":"10.1175\/1520-0426(2004)021<1291:IOMRIF>2.0.CO;2","article-title":"Inversion of marine radar images for surface wave analysis","volume":"21","author":"Rodriguez","year":"2004","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"95","DOI":"10.5194\/os-13-95-2017","article-title":"A simple method for retrieving significant wave height from Dopplerized X-band radar","volume":"13","author":"Carrasco","year":"2017","journal-title":"Ocean. Sci."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"16537","DOI":"10.3390\/rs71215851","article-title":"An adaptive method of wave spectrum estimation using X-band nautical radar","volume":"7","author":"Moloney","year":"2015","journal-title":"Remote Sens."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"347","DOI":"10.1175\/JTECH-D-16-0158.1","article-title":"Polar Fourier transform processing of marine radar signals","volume":"34","author":"Lyzenga","year":"2017","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Lyzenga, D., Nwogu, O., Beck, R., O\u2019Brien, A., Johnson, J., de Paolo, A., and Terrill, E. (2015, January 31). Real-time estimation of ocean wave fields from marine radar data. Proceedings of the IEEE International Geoscience and Remote Sensing Symposium, Milan, Italy.","DOI":"10.1109\/IGARSS.2015.7326606"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Lyzenga, D., Nwogu, O., Trizna, D., and Hathaway, K. (2010, January 25\u201330). Ocean wave field measurements using X-band Doppler radars at low grazing angles. Proceedings of the IEEE International Geoscience and Remote Sensing Symposium, Honolulu, HI, USA.","DOI":"10.1109\/IGARSS.2010.5650065"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"631","DOI":"10.1109\/LGRS.2010.2043712","article-title":"Surface-wavefield estimation from coherent marine radars","volume":"7","author":"Nwogu","year":"2010","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"C6","DOI":"10.1029\/2012JC007986","article-title":"Origins of features in wave number-frequency spectra of space-time images of the ocean","volume":"117","author":"Plant","year":"2012","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1267","DOI":"10.1175\/1520-0426(2001)018<1267:AOSFRS>2.0.CO;2","article-title":"Airborn optical system for remote sensing of ocean waves","volume":"18","author":"Dugan","year":"2001","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"309","DOI":"10.1016\/S0034-4257(02)00116-5","article-title":"Surface current measurements using airborne visible image time series","volume":"83","author":"Dugan","year":"2003","journal-title":"Remote Sens. Environ."},{"key":"ref_13","first-page":"1","article-title":"Measuring currents in a coastal inlet by advection of turbulent eddies in airborn optical imagery","volume":"117","author":"Dugan","year":"2012","journal-title":"J. Geophys. Res."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"18391","DOI":"10.1029\/96JC01685","article-title":"Observed wavenumber-frequency properties of microwave backscatter from the ocean surface at near-grazing angles","volume":"101","author":"Frasier","year":"1996","journal-title":"J. Geophys. Res."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"470","DOI":"10.1109\/48.809268","article-title":"Nonlinear features in wave-resolving microwave radar observations of ocean waves","volume":"24","author":"Stevens","year":"1999","journal-title":"IEEE J. Ocean. Eng."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1109\/48.557536","article-title":"X-band low-grazing-angle ocean backscatter obtained during LOGAN 1993","volume":"22","author":"Rino","year":"1997","journal-title":"IEEE J. Ocean. Eng."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Kammerer, A.J., and Hackett, E. (2017). Use of proper orthogonal decomposition for extraction of ocean surface wave fields from X-band radar measurements of the sea surface. Remote Sens., 9.","DOI":"10.3390\/rs9090881"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Smith, G.E., O\u2019Brien, A., Pozderac, J., Baker, C.J., Johnson, J.T., Lyzenga, D.R., Nwogu, O., Trizna, D.B., Rudolf, D., and Schueller, G. (2013, January 16). High power coherent-on-receive radar for marine surveillance. Proceedings of the 2013 International Conference on Radar, Adelaide, Australia.","DOI":"10.1109\/RADAR.2013.6652028"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"588","DOI":"10.1109\/TIT.1972.1054886","article-title":"A covariance approach to spectral moment estimation","volume":"18","author":"Miller","year":"1972","journal-title":"IEEE Trans. Inf. Theory."},{"key":"ref_20","unstructured":"Drazen, D., Merrill, C., Gregory, S., and Fullerton, A. (2016, January 11\u201316). Interpretation of in-situ ocean environmental measurements. Proceedings of the 31st Symposium on Naval Hydrodynamics, Monterey, CA, USA."},{"key":"ref_21","unstructured":"Kammerer, A.J. (2017). The Application of Proper Orthogonal Decomposition to Numerically Modeled and Measured Ocean Surface Wave Fields Remotely Sensed by Radar. [Master\u2019s Thesis, Coastal Carolina University]."},{"key":"ref_22","unstructured":"Hackett, E.E., Merrill, C.F., and Geiser, J. (2014, January 2\u20137). The application of proper orthogonal decomposition to complex wave fields. Proceedings of the 30th Symposium on Naval Hydrodynamics, Hobart, Australia."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/1\/71\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T12:23:13Z","timestamp":1760185393000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/1\/71"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,1,2]]},"references-count":22,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2019,1]]}},"alternative-id":["rs11010071"],"URL":"https:\/\/doi.org\/10.3390\/rs11010071","relation":{},"ISSN":["2072-4292"],"issn-type":[{"type":"electronic","value":"2072-4292"}],"subject":[],"published":{"date-parts":[[2019,1,2]]}}}