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An Approach Based on Reference for Improving the Accuracy of the Time Series of Water Levels in Coastal Areas and Lakes
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Zahra Esmaeili   , Behzad Voosoghi * , Arash Amini , Mahmoud Pirooznia |
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Abstract: (579 Views) |
| The efficiency of satellite altimetry in coastal and inland water areas is facing limitations due to increased noise in base observations (waveforms). Although these limitations have somewhat decreased with the emergence of new generations of satellite altimetry missions and the development of various retracking algorithms, they still remain a challenge. In previous approaches, the use of all altimetry data from different cycles (all), their medians, and means has been the method for representing the cycle and forming a time series of water levels in a pass. In this study, an innovative approach called the reference-based approach has been proposed to select this representative. In the reference-based approach, the representative with the characteristic of water level closer to the reference water level time series is selected to improve the accuracy of the water level time series in coastal areas (0–1 kilometers) as well as the time series resulting from conventional altimetry missions in inland water. The reference water level time series for coastal areas at a distance from the shore (1–5 kilometers) and for lakes has been obtained from the new generation altimetry mission. In addition to the proposed approach, all, mean and median approaches have also been evaluated. To improve the accuracy of the water level time series within one kilometer of the northern and southwestern shores of the Alcudia Gulf, data from passes 244 of Sentinel-3A and 57 of Sentinel-3B, as well as data from passes 141 of Sentinel-3A and 220 of Jason-3 satellites passing over Lake Vattern in Sweden, have been used from 2016 to 2023. The evaluation results of the water level time series obtained from the proposed approach compared to the optimal previous approach in comparison to in situ gauge data show an improvement in RMSE ranging from 43% to 72% in the studied lake and from 7% to 87% in coastal areas. Also, this comparison shows an increase of 33% and 6% to 40% of the correlation coefficient parameter for Lake Vattern and coastal areas of Alcudia, respectively. After the proposed approach, the median, mean, and all approaches, respectively, showed optimal performance. In addition to increasing the accuracy of water level time series near the shore, the proposed approach has also increased the efficiency of conventional altimetry missions in inland waters by increasing the number of observations and their appropriate distribution in these areas. |
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| Keywords: Satellite altimetry, Sentinel-3, Mean, Median, Reference |
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Type of Study: Research |
Subject:
Geodesy
Received: 2024/03/18 | Accepted: 2024/06/26 | ePublished ahead of print: 2025/03/17
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