The performance of CryoSat-2 fully-focussed SAR for inland water-level estimation

Kleinherenbrink, M.; Naeije, M.C.; Slobbe, D.C.; Egido, Alejandro; Smith, Walter

doi:10.1016/j.rse.2019.111589

The performance of CryoSat-2 fully-focussed SAR for inland water-level estimation

Title

The performance of CryoSat-2 fully-focussed SAR for inland water-level estimation

Author

Kleinherenbrink, M. (TU Delft Mathematical Geodesy and Positioning)
Naeije, M.C. (TU Delft Astrodynamics & Space Missions)
Slobbe, D.C. (TU Delft Physical and Space Geodesy)
Egido, Alejandro (NOAA Laboratory for Satellite Altimetry; Global Science and Technology)
Smith, Walter (NOAA Laboratory for Satellite Altimetry)

Date

2020

Abstract

This paper applies the Fully-Focussed SAR (FF-SAR) algorithm to CryoSat-2 full-bit-rate data to measure water levels of lakes and canals in the Netherlands, and validates these measurements by comparing them to heights measured by gauges. Over Lake IJssel, a medium-sized lake, the FF-SAR height is biased about 6 cm below the gauge height, and a similar bias is found at six sites where CryoSat-2 crosses rivers and canals. The precision of the FF-SAR measurements depends on the extent of multi-looking (incoherent averaging along-track) applied. Over Lake IJssel the precision varies from 4 to 11 cm, decreasing as multi-looking increases. The precision of FF-SAR with 100 m of multi-looking is equivalent to that of the standard delay/Doppler processing, which has an along-track resolution of about 300 m. The width and orientation of rivers and canals limits the maximum available multi-looking. After removing the 6 cm bias, FF-SAR heights of rivers and canals have an accuracy between 2 cm and several decimeters, primarily depending on the presence of other water bodies lying within the cross-track measurement footprint, as these contaminate the waveform. We demonstrate that FF-SAR processing is able to resolve and measure small ditches only a few meters in width. The visibility of these signals depends on the angle at which CryoSat-2 crosses the ditch and on whether or not the ditch remains straight within CryoSat-2’s field of view. In the best-case scenario, straight ditches at nearly 90° to the CryoSat-2 ground track, the ditch signal has high enough signal-to-noise to allow sub-decimeter accuracy of FF-SAR height measurement.

Subject

Altimetry
CryoSat-2
FF-SAR
Inland water
Validation

To reference this document use:

http://resolver.tudelft.nl/uuid:691420d5-eab1-4590-bfec-0e95d080a973

DOI

https://doi.org/10.1016/j.rse.2019.111589

Embargo date

2020-12-11

ISSN

0034-4257

Source

Remote Sensing of Environment: an interdisciplinary journal, 237