Investigating SAR Altimetry over the Great Salt Lake – Comparing SAMOSA+/++ and ALES+ SAR

Martina Wenzl (ESA-ESRIN, Italy)


Marcello Passaro (Deutsches Geodätisches Forschungsinstitut der Technischen Universität München (DGFI-TUM) , Germnay); Marco Restano (SERCO, c/o ESA-ESRIN, Italy); Jérôme Benveniste (ESA-ESRIN, Italy)

Event: 2020 Ocean Surface Topography Science Team Meeting (virtual)

Session: Instrument Processing: Measurement and Retracking

Presentation type: Type Forum

The advent of SAR altimetry allowed the production of data with a high spatial resolution (300 m along-track). Investigations in the inland water domain clearly benefited from SAR altimetry and future processing strategies (e.g. the fully-focused SAR, FF-SAR) are expected to improve further the quantity and quality of water level estimates over small water bodies.
The proposed work aims at investigating the quality of Sentinel-3 water level retrievals over the Great Salt Lake. Data are processed through the ESA G-POD/SARvatore online and on-demand processing service for the exploitation of CryoSat-2 and Sentinel-3 data ( and obtained by using the SAMOSA+ and SAMOSA++ retrackers. In addition, the newly adopted ALES+ SAR processer for Sentinel-3A/B, developed within the current ESA Baltic+ SEAL project (, is used to estimate water levels. ALES+ SAR was tailored to coastal regions and not specifically designed for the inland water domain. However with the Great Salt Lake being the 8th largest terminal lake worldwide, this study area marks the transition between the inland water domain and the coastal region.
The GPOD/SARvatore data is processed using a dedicated inland water processing option (HPR, ‘high posting rate’: zero-padding, 80 Hz posting rate, hamming window) and the official S3 processing profile (official S3: 20 Hz posting rate) for comparison. The ALES+ SAR retracker is applied to the official S3 processed data as well. Empirical retrackers outputs, available in the official 20-Hz Sentinel-3 LAN products, are also considered and the water flag in GPOD/SARvatore is used to identify the water areas.
The GPOD/SARvatore and ALES+ SAR data are validated based on their distance to the gauge stations. Key parameters like Pulse Peakiness, Misfit and the ALES+ SAR quality flag are used to filter the data and provide a robust error characterization method.
The study is expected to offer possible synergies with SWOT and support the comparison of SAR estimates with FF-SAR estimates obtained at a comparable along-track resolution.
Martina Wenzl