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Lookup NU author(s): Emeritus Professor Philip Moore, Dr Christopher PearsonORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2025 by the authors.Highlights: What are the main findings? SARin data can be used to derive the roll-angle from oceanic passes and the off-pointing angle of cross-track water reflectors. Estimation of offset-angle enables correction for GDR altimetric height and location of inland water reflectors. What are the implications of the main findings? Correction for cross track reflectors yields additional height data for inland water studies. Even for inland water identifiable at nadir, off-pointing considerations can improve the water height estimation. Cryosat-2 SARin altimetric FBR data facilitates an opportunity to investigate phase differences between inland water radar reflections at the two antennae. With the antennae positioned cross-track, SARin was designed for the recovery of slope over ice margins, but here, it was used to recover off-pointing over inland waters. The ability to measure non-nadir off-pointing is verified using ocean data near the Amazon estuary to determine the satellite roll angle. Over inland waters, off-pointing requires correction to the nadir range and the geographic location of the reflectance. By using an SRTM-based water mask, the number of inland water reflectance increases significantly when off-pointing is considered. Comparisons between altimetric and river heights utilise gauge data at Tabatinga on the Solimões–Amazon. A least-squares adjustment yielded a river slope of −0.03506 ± 0.00003 m/km and a mean velocity of 1.803 ± 0.014 m/s over a river stretch of nearly 290 km. RMSE differences between the gauge and altimetry improve from 0.423 m to 0.404 m when off-pointing is taken into account for nadir inland water returns, showing the asymmetric effect of off-pointing. If all potential off-pointings are considered, the number of measurements increases by 66%, but the RMSE of 0.524 m is higher due to additional errors in the off-pointing corrections.
Author(s): Moore P, Pearson C
Publication type: Article
Publication status: Published
Journal: Remote Sensing
Year: 2025
Volume: 17
Issue: 21
Online publication date: 02/11/2025
Acceptance date: 28/10/2025
Date deposited: 24/11/2025
ISSN (electronic): 2072-4292
Publisher: MDPI
URL: https://doi.org/10.3390/rs17213627
DOI: 10.3390/rs17213627
Data Access Statement: No new data were created or analyzed in this study
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