Abstract
Satellite radar altimetry is an important technique for monitoring the water levels of oceans and inland water bodies, especially in areas where in-situ data are sparse or nonexistent. This study presented an automatic multiscale-based peak detection retracker (AMPDR). The retracker can extract a robust threshold level for each track, then the stable lake level can be obtained from the multipeak waveforms using a shortest-path algorithm. Additionally, the retracker can be used for mountain lakes and for flat lakes, and is also suitable for many kinds of altimetry data, such as those of Cryosat-2, Sentinel-3, and Jason-2/3. To validate the lake levels derived by the AMPDR retracker, the in-situ gauge data of seven lakes in the Tibetan Plateau and two lakes in a flat area are used. Moreover, seven existing retrackers are compared to evaluate the performance of the proposed AMPDR retracker. The results suggest that AMPDR can efficiently process many complex multipeak waveforms, and the AMPDR has the lowest mean of all track standard deviations over all lakes. The root-mean-squared error (RMSE) of the lake level time series obtained using AMPDR is the lowest over several lakes: The mean RMSEs of all the lakes overpassed by Cryosat-2, Sentinel-3, and Jason-2/3 are 0.149, 0.139, and 0.181 m, respectively. The AMPDR retracker is easy to implement, computationally efficient, and can give a height estimate for even the most contaminated waveforms.
Highlights
Satellite altimetry technology has been widely used since the 1990s to monitor water levels over inland waters [1]–[5]
A novel retracker (AMPDR) was proposed that can be applied to various altimeter data
automatic multiscale-based peak detection retracker (AMPDR) is not a pure, single-waveform retracker, and its key is to identify the water-surface signal of the waveform by using a peak detection and a robust statistical method, which can process the complex waveforms contaminated by land signals
Summary
Satellite altimetry technology has been widely used since the 1990s to monitor water levels over inland waters [1]–[5] This is because hydrological stations cannot be set up or Manuscript received July 06, 2020; revised October 21, 2020. Compared with a traditional altimeter, a radar altimeter such as Sentinel-3 or Jason-2/3 displays a great improvement in the observation of nadir points. It operates with an open-loop tracking mode, which can control the return echo acquisition phase by properly setting its range window in time, based on prior on-board surface elevation information [18], [19]. The data produced using these techniques improve the quality of observation points to some extent, there is still a problem of complex waveform pollution [4], [8], [21]
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