Gao et al. (2019) Analysis of Retrackers’ Performances and Water Level Retrieval over the Ebro River Basin Using Sentinel-3

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Identification

• Journal: Remote Sensing
• Year: 2019
• Authors: Qi Gao, Eduardo Makhoul, Maria‐José Escorihuela, Mehrez Zribi, Pere Quintana Seguí, Pablo Nilo García, M. Roca
• DOI: 10.3390/rs11060718

Research Groups

Researchers focused on continental hydrology and remote sensing applications within the Ebro River basin, Spain.

Short Summary

This study developed and evaluated a new Digital Elevation Model (DEM)-informed waveform portion selection method combined with SAR altimetry retrackers to minimize land contamination and accurately retrieve water levels over small- to middle-sized inland water bodies (130 m to 4.5 km). The method achieved high accuracy, with unbiased root-mean-square errors (RMSEs) down to 0.16 m over a 400 m wide reservoir.

Objective

• To retrieve accurate water levels from Level-1B Sentinel-3 SAR altimetry data over small- to middle-sized inland water bodies (130 m to 4.5 km) by developing and evaluating a specialized waveform portion selection method that minimizes land contamination and selects the nadir return associated with the water body.

Study Configuration

• Spatial Scale: Small- to middle-sized inland water bodies (ranging from 130 m to 4.5 km wide) located in the Ebro River basin, Spain (specifically Ebro Reservoir and Ribarroja Reservoir).
• Temporal Scale: Retrieval of time series of water levels.

Methodology and Data

• Models used: Threshold retracker, Offset Center of Gravity (OCOG) retracker, Two-step SAR physical-based retracker. A new subwaveform-based waveform portion selection method utilizing Digital Elevation Model (DEM) information was implemented to fit multipeak waveforms.
• Data sources: Level-1B Sentinel-3 satellite altimetry data; Digital Elevation Model (DEM); In situ measurements (used for validation).

Main Results

• The proposed waveform portion selection method, which incorporates DEM information, significantly improved the retrieval accuracy by effectively isolating the water body's nadir return from land contamination in multipeak waveforms.
• No significant difference in performance was found among the three evaluated retrackers (Threshold, OCOG, Two-step SAR physical-based) when coupled with the new selection method.
• Validation against in situ measurements showed strong agreement: unbiased root-mean-square errors (RMSEs) were achieved down to 0.28 m for the Ebro Reservoir (approximately 1.8 km wide) and down to 0.16 m for the Ribarroja Reservoir (approximately 400 m wide).

Contributions

• Successful demonstration of high-accuracy water level retrieval (RMSEs down to 0.16 m) using SAR altimetry over challenging small inland water bodies (down to 400 m wide).
• Introduction and validation of a novel waveform portion selection method that leverages DEM data to effectively mitigate land contamination, a critical issue for altimetry over continental waters.
• Validation of Level-1B Sentinel-3 data utility for continental water resource management in complex river basin environments.

Funding

Not specified in the paper text.

Citation

@article{Gao2019Analysis,
  author = {Gao, Qi and Makhoul, Eduardo and Escorihuela, Maria‐José and Zribi, Mehrez and Quintana‐Seguí, Pere and García, Pablo Nilo and Roca, M.},
  title = {Analysis of Retrackers’ Performances and Water Level Retrieval over the Ebro River Basin Using Sentinel-3},
  journal = {Remote Sensing},
  year = {2019},
  doi = {10.3390/rs11060718},
  url = {https://doi.org/10.3390/rs11060718}
}

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