Waveform contamination identification and accurate sea surface height extraction algorithm for high-frequency fully-focused SAR in severely interfered coastal regions

doi:10.11947/j.AGCS.2025.20240103

Abstract

Abstract:

In coastal regions, particularly within 3 km from the coast, the accurate estimation of sea surface height (SSH) has remained a significant challenge for satellite altimetry techniques. This study investigates the fully-focused SAR (FFSAR) altimetry technique and proposes a SSH estimation algorithm based on contamination rejection and range compensation. Tide gauge data are introduced as independent observations to validate the altimetry performance of FFSAR in severe interfered coastal areas under different along-track sampling rates (20, 80, 200, and 600 Hz). The experiment results show that: ① In the highly contaminated region within 3 km from the coast, increasing the FFSAR sampling rate from 20 Hz to 200 Hz significantly improves data availability and accuracy. ② The standard deviations of the altimetry results obtained using the proposed algorithm against the validation data are reduced from 0.36 (TGWD)、0.31 (EEMSHAVEN)、0.68 (DENHELDER) and 0.17 m (IJMON) to 0.22、0.22、0.48 and 0.14 m, respectively, corresponding to an improvement of over 20%. ③ At the 200 Hz sampling rate, the altimetry results from the proposed algorithm show better consistency with the validation data compared to the MWaPP and PP-OCOG algorithms.

Key words: SAR altimetry, FFSAR, coastal area, signal contamination, SSH extraction

CLC Number:

P229

Hongkai SHI, Xiufeng HE, Yihao WU, Xiangtian ZHENG, Minfeng SONG. Waveform contamination identification and accurate sea surface height extraction algorithm for high-frequency fully-focused SAR in severely interfered coastal regions[J]. Acta Geodaetica et Cartographica Sinica, 2025, 54(2): 272-285.

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References 36

[1]	许厚泽, 王海瑛, 陆洋, 等. 利用卫星测高数据推求中国近海及邻域大地水准面起伏和重力异常研究[J]. 地球物理学报, 1999(4): 465-471.
	XU Houze, WANG Haiying, LU Yang, et al. Geoid undulations and gravity anomalies from T/P and ERS-1 altimeter data in the China sea and vicinity[J]. Chinese Journal of Geophysics (in Chinese), 1999, 42(4): 465-471.
[2]	李建成, 金涛勇. 卫星测高技术及应用若干进展[J]. 测绘地理信息, 2013, 38(4): 1-8.
	LI Jiancheng, JIN Taoyong. On the main progress of satellite altimetry and its applications[J]. Journal of Geomatics, 2013, 38(4): 1-8.
[3]	SHI Hongkai, HE Xiufeng, WU Yihao, et al. Spectrally consistent mean dynamic topography by combining mean sea surface and global geopotential model through a least squares-based approach[J]. Frontiers in Earth Science, 2022, 10: 795935.
[4]	VIGNUDELLI S, AKHIR M F, ZAINOL Z, et al. Coastal altimetry[M]. San Diego: Elsevier, 2023: 1-19.
[5]	WU Yihao, ABULAITIJIANG A, FEATHERSTONE W E, et al. Coastal gravity field refinement by combining airborne and ground-based data[J]. Journal of Geodesy, 2019, 93(12): 2569-2584.
[6]	VIGNUDELLI S, BIROL F, BENVENISTE J, et al. Satellite altimetry measurements of sea level in the coastal zone[J]. Surveys in Geophysics, 2019, 40(6): 1319-1349.
[7]	IDRIS N H, VIGNUDELLI S, DENG Xiaoli. Assessment of retracked sea levels from Sentinel-3A synthetic aperture radar (SAR) mode altimetry over the marginal seas at Southeast Asia[J]. International Journal of Remote Sensing, 2021, 42(4): 1535-1555.
[8]	DENG X, FEATHERSTONE W E. A coastal retracking system for satellite radar altimeter waveforms: application to ERS-2 around Australia[J]. Journal of Geophysical Research: Oceans, 2006, 111(C6): 2005JC003039.
[9]	RANEY R K. The delay/Doppler radar altimeter[J]. IEEE Transactions on Geoscience and Remote Sensing, 36(5): 1578-1588.
[10]	LABROUE S, BOY F, PICOT N, et al. First quality assessment of the Cryosat-2 altimetric system over ocean[J]. Advances in Space Research, 2012, 50(8): 1030-1045.
[11]	JIANG Liguang, NIELSEN K, DINARDO S, et al. Evaluation of Sentinel-3 SRAL SAR altimetry over Chinese rivers[J]. Remote Sensing of Environment, 2020, 237: 111546.
[12]	PENG Fukai, DENG Xiaoli. Validation of Sentinel-3A SAR mode sea level anomalies around the Australian coastal region[J]. Remote Sensing of Environment, 2020, 237: 111548.
[13]	DINARDO S, MARALDI C, CADIER E, et al. Sentinel-6 MF Poseidon-4 radar altimeter: main scientific results from S6PP LRM and UF-SAR chains in the first year of the mission[J]. Advances in Space Research, 2024, 73(1): 337-375.
[14]	BOY F, DESJONQUERES J D, PICOT N, et al. CryoSat-2 SAR-mode over oceans: processing methods, global assessment, and benefits[J]. IEEE Transactions on Geoscience and Remote Sensing, 2017, 55(1): 148-158.
[15]	DINARDO S. Techniques and applications for satellite SAR altimetry over water, land and ice[DB/OL]. Darmstadt: Technische Universität. [2024-04-03]. https://tuprints.ulb.tu-darmstadt.de/id/eprint/11343.
[16]	KLEINHERENBRINK M, NAEIJE M, SLOBBE C, et al. The performance of CryoSat-2 fully-focussed SAR for inland water-level estimation[J]. Remote Sensing of Environment, 2020, 237: 111589.
[17]	EGIDO A, SMITH W H F. Fully focused SAR altimetry: theory and applications[J]. IEEE Transactions on Geoscience and Remote Sensing, 2017, 55(1): 392-406.
[18]	HERNÁNDEZ-BURGOS S, GIBERT F, BROQUETAS A, et al. A fully focused SAR Omega-K closed-form algorithm for the Sentinel-6 radar altimeter: methodology and applications[J]. IEEE Transactions on Geoscience and Remote Sensing, 2024, 62: 3367544.
[19]	施宏凯. 融合SAR高度计及多源测高数据的海岸带稳态海面地形重建方法研究[D]. 南京: 河海大学, 2022.
	SHI Hongkai. Coastal mean dynamic topography modeling method from SAR and multi-source altimetric data[D]. Nanjing: Hohai University, 2022.
[20]	RIEU P, MOREAU T, AMAROUCHE L, et al. From unfocused to fully-focused SAR processing: benefits for different surfaces[C]//Proceedings of 2018 Progress in Radar Altimetry Symposium. Ponta Delgada: [s.n.], 2018: 20.
[21]	SCHLEMBACH F, EHLERS F, KLEINHERENBRINK M, et al. Benefits of fully focused SAR altimetry to coastal wave height estimates: a case study in the North Sea[J]. Remote Sensing of Environment, 2023, 289: 113517.
[22]	EGIDO A, DINARDO S, RAY C. The case for increasing the posting rate in delay/Doppler altimeters[J]. Advances in Space Research, 2021, 68(2): 930-936.
[23]	FENG Hui, EGIDO A, VANDEMARK D, et al. Exploring the potential of Sentinel-3 delay Doppler altimetry for enhanced detection of coastal currents along the Northwest Atlantic shelf[J]. Advances in Space Research, 2023, 71(1): 997-1016.
[24]	CHOI J H, JANG J H, ROH J E. Design of an FMCW radar altimeter for wide-range and low measurement error[J]. IEEE Transactions on Instrumentation and Measurement, 2015, 64(12): 3517-3525.
[25]	杨双宝. 基于合成孔径技术的高精度雷达高度计技术研究[D]. 北京: 中国科学院研究生院(空间科学与应用研究中心), 2007.
	YANG Shuangbao. High-precision radar altimeter technology based on synthetic aperture techniques[D]. Beijing: Chinese Academy of Sciences (The National Space Science Center), 2007.
[26]	KLEINHERENBRINK M, SMITH W H F, NAEIJE M C, et al. The second-order effect of Earth's rotation on Cryosat-2 fully focused SAR processing[J]. Journal of Geodesy, 2020, 94(1): 7-16.
[27]	ROUFFI F. Product data format specification - SRAL and MWR Level 1 products[EB/OL]. [2023-11-15]. https://sentinels.copernicus.eu/documents/247904/2753172/Sentinel-3-Product-Data-Format-Specification-Level-1-products.pdf/2b7c773b-44ca-447e-9b86-f7ebd231261c?t=1611592438951.
[28]	EHLERS F, SCHLEMBACH F, KLEINHERENBRINK M, et al. Validity assessment of SAMOSA retracking for fully-focused SAR altimeter waveforms[J]. Advances in Space Research, 2023, 71(3): 1377-1396.
[29]	BOY F, CRETAUX J F, BOUSSAROQUE M, et al. Improving Sentinel-3 SAR mode processing over lake using numerical simulations[J]. IEEE Transactions on Geoscience and Remote Sensing, 2022, 60: 1-18.
[30]	JAIN M, ANDERSEN O B, DALL J, et al. Sea surface height determination in the Arctic using Cryosat-2 SAR data from primary peak empirical retrackers[J]. Advances in Space Research, 2015, 55(1): 40-50.
[31]	YUAN Jiajia, GUO Jinyun, ZHU Chengcheng, et al. SDUST2020 MSS: a global 1′×1′ mean sea surface model determined from multi-satellite altimetry data[J]. Earth System Science Data, 2023, 15(1): 155-169.
[32]	LARSON K M, RAY R D, WILLIAMS S D P. A 10-year comparison of water levels measured with a geodetic GPS receiver versus a conventional tide gauge[J]. Journal of Atmospheric and Oceanic Technology, 2017, 34(2): 295-307.
[33]	HOFSTEDE J L A. Process-response analysis for Hörnum tidal inlet in the German sector of the Wadden sea[J]. Quaternary International, 1999, 60(1): 107-117.
[34]	TOMIĆ M, BREILI K, GERLACH C, et al. Validation of retracked Sentinel-3 altimetry observations along the Norwegian coast[J]. Advances in Space Research, 2024, 73(8): 4067-4090.
[35]	KE B, ZHANG L, XU J, et al. Determination of the mean dynamic ocean topography model through combining multi-source gravity data and DTU15 MSS around China's coast[J]. Advances in Space Research, 2019, 63(1): 203-212.
[36]	SCHLEMBACH F, PASSARO M, DETTMERING D, et al. Interference-sensitive coastal SAR altimetry retracking strategy for measuring significant wave height[J]. Remote Sensing of Environment, 2022, 274: 112968.

采样率/Hz	TGW2/m	AWG/m
20	0.136	0.115
80	0.141	0.117
200	0.139	0.118
600	0.160	0.145

采样率/Hz	TGWD/m	EEMSHAEN/m	DENHELDER/m	IJMON/m
20	0.36	0.31	0.68	0.17
80	0.35	0.27	0.56	0.18
200	0.22	0.22	0.48	0.14
600	0.27	0.26	0.51	0.15

测高结果/Hz	Max/m	Min/m	Mean/m	SD/m
20	0.74	-0.82	0.05	0.36
80	0.85	-0.70	0.10	0.35
200	0.43	-0.36	0.04	0.22
600	0.51	-0.41	0.05	0.27

测高结果	TGWD	EEMSHAVEN	DENHELDER	IJMON
200 Hz PP-OCOG	0.57	0.76	1.33	0.20
200 Hz MWaPP	0.56	0.73	1.28	0.13
200 Hz FFSAR_RNG	0.22	0.22	0.48	0.14