Lake Level Estimation Based on CryoSat-2 SAR Altimetry and Multi-Looked Waveform Classification
Lake Level Estimation Based on CryoSat-2 SAR Altimetry and Multi-Looked Waveform Classification
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DOI：
10.3390/rs8110885
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发表时间：
2016-10
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影响因子：
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通讯作者：
F. Göttl;D. Dettmering;F. Müller;C. Schwatke
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文献类型：
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作者：
F. Göttl;D. Dettmering;F. Müller;C. Schwatke
在这项研究中，可靠的水位为四湖估计的基础上创新的处理策略，使用半自动CryoSat-2合成孔径雷达（SAR）多看波形分类。在内陆测高应用中，有效水回波的选择是一个重要的步骤。为了识别可靠的观测值，允许一个准确的重跟踪，CryoSat-2 SAR多视波形的无监督分类方法已开发的基础上的k-均值算法。通过这种方法，可以考虑水面范围或周围淹没区的变化。此外，改进的阈值Retracker的修改版本的开发，以获得最佳的结果湖的高度。所使用的方法是基于通过采用高度阈值的最佳子波形的识别。验证派生的CryoSat-2合成孔径雷达时间序列与现场测量数据产生的均方根（RMS）之间的差异3和90厘米的不同湖泊。与模拟的CryoSat-2水高度相比，根据AltWater数据库中使用的方法，我们的水位时间序列在RMS精度方面略有改善，但由于缺乏可靠的观测，它们包含更多的差距。与传统的雷达高度计任务，如环境卫星或杰森-2相比，基于SAR的时间序列显示较小的RMS差异的小湖泊，但较大的RMS差异的大湖泊覆盖的多个重复任务。所提出的新的处理策略可以很容易地采用到其他卫星测高SAR数据，如从新的哨兵-3使命。
In this study, reliable water levels for four lakes are estimated based on an innovative processing strategy using a semi-automatic CryoSat-2 Synthetic Aperture Radar (SAR) multi-looked waveform classification. The selection of valid water returns is an essential step in inland altimetry applications. In order to identify reliable observations allowing for an accurate retracking, an unsupervised classification method for CryoSat-2 SAR multi-looked waveforms has been developed based on the k-mean algorithm. With this approach, changes in the water surface extent or surrounding inundation areas can be taken into account. In addition, a modified version of the Improved Threshold Retracker is developed in order to obtain optimal results for the lake heights. The used method is based on the identification of the optimal sub-waveform by employing height thresholds. The validation of the derived CryoSat-2 SAR time series with in-situ gauging data yields root mean square (RMS) differences between 3 and 90 cm for the different lakes. Compared to modeled CryoSat-2 water heights derived according to the approach used in the AltWater database our water level time series are slightly improved in terms of RMS accuracy but they contain more gaps due to the lack of reliable observations. In comparison with classical radar altimeter missions such as Envisat or Jason-2, the SAR-based time series show smaller RMS differences for the small lakes but larger RMS differences for the large lakes covered by multiple repeat missions. The presented innovative processing strategy can be easily adopted to other satellite altimetry SAR data such as from the new Sentinel-3 mission.