Abstract
Spaceborne global navigation satellite system reflectometry (GNSS-R) data collected by the UK TechDemoSat-1 (TDS-1) satellite is applied to retrieve global lake levels for the first time. Lake levels of 351 global lakes (area greater than 500 km2 and elevation lower than 3000 m each) are estimated using TDS-1 Level 1b data over 2015–2017. Strong correlations (overall R2 greater than 0.95) are observed among lake levels derived from TDS-1 and other altimetry satellites such as CryoSat-2, Jason, and Envisat (the latter two are collected by Hydroweb), although with large root-mean-square error (RMSE) (tens of meters) mainly due to the fact that TDS-1 is not dedicated for altimetry measuring purpose. Examples of the Caspian Sea and the Poyang Lake show consistent spatial and temporal variations between TDS-1 and other data sources. The results in this paper provide supportive information for further application of GNSS-R constellations to measure altimetry of inland water bodies.
Highlights
Global navigation satellite system reflectometry (GNSS-R) is a bistatic radar approach to infer surface properties through analyzing the reflected GNSS signals from the Earth’s surface
Previous GNSS-R altimetry mainly focused on sea surface height [12], whilst only a few studies concentrated on the water level of inland lakes [13,14,15]
The capability of using spaceborne TDS-1 GNSS reflections to estimate global lake level has been demonstrated for the first time, and the results have been compared with the results from traditional satellite altimeters
Summary
Global navigation satellite system reflectometry (GNSS-R) is a bistatic radar approach to infer surface properties through analyzing the reflected GNSS signals from the Earth’s surface. Common methods to monitor lake level include in situ measurements from hydrologic stations and observations from satellite altimeters [9]. Satellite altimeters provide an alternative way to monitor lake level with fine temporal and spatial resolutions (e.g., 183 d/70 m for ICESat, 30 d/1.6 km for CryoSat-2, and 35 d/1.7 km for Envisat) [10]. Previous GNSS-R altimetry mainly focused on sea surface height [12], whilst only a few studies concentrated on the water level of inland lakes [13,14,15]. This paper first demonstrates the advantages and limitations of using TDS-1 GNSS reflections to estimate global lake level. Data used are collected by the space GNSS receiver remote sensing instrument (SGR-ReSI) on board of TDS-1.
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