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Evaluation of the First Sub-waveform Re-tracking method to improve the accuracy of satellite altimetry observations in coastal areas (Case Study: Coastal Area of the Persian Gulf)
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Parisa Agar *   , Behzad Voosoghi , Shirzad Roohi , Arash Amini |
| K. N. Toosi University of Technology |
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Abstract: (1270 Views) |
Radar satellite is a kind of remote sensing techniques for monitoring water bodies. In coastal areas due to the presence of non-water objects inside the footprint, the radar waveforms are deviated from the so-called ocean model, i.e. Brown shape. This makes the ranges and consequently water level measurements erroneous. Therefore, re-tracking the waveforms in this area is necessary to provide reliable products. In this study, water level variations at 2 and 10 km distance from the coast from 2018/01/17 to 2019/09/27 have been investigated. To this end, L2 and L1b data of SRAL altimeter sensor of Sentinel-3 along the tracks of 25,139 and 468 have been used. We estimated the water level variation from re-tracking the first meaningful sub-waveform, from re-tracking the whole waveform with the threshold re-tracker and from L2 products. These water levels have been validated against in-situ gauge data from Boshahr and Kangan tide gauge stations. We found that at 2 km distance from the coast, the re-tracking of the first meaningful sub-waveform with an improvement of RMSE of 27%, 29% and 27% with respect to the re-tracking the whole waveform shows a better performance for the three mentioned tracks (with 71%, 27% and 27% multi-peak waveforms) respectively. The RMSEs improvement of this scenario are about 51%, 32% and 31% with respect to the L2 products for the three tracks. At 10 km from the coast, over tracks of 25 and 139 with 64% and 15% multi-peak waveforms, the first sub-waveform scenario has an improvement of 31% and 8% with respect to the whole waveform scenario. It outperforms the L2 products with an improvement of 44% and 8% for these two tracks respectively at this distance from the cost. In the case of track 468 due to the lower number of multi-peak waveforms (about 12%) we came up with the same result for L1b and L2 products. While the results express the necessity of re-tracking coastal waveforms, they introduce the optimal performance of the first meaningful sub-waveform re-tracking. |
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| Keywords: Radar Altimeter, Sentinel-3, Coastal area, SAR, First meaningful Sub-waveform Re-tracking |
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Full-Text [PDF 1398 kb]
(240 Downloads)
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Type of Study: Research |
Subject:
Geodesy
Received: 2021/07/7 | Accepted: 2021/09/28 | ePublished ahead of print: 2023/03/12 | Published: 2023/05/21
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