Waveform Retracking for Improving Level Estimations From TOPEX/Poseidon, Jason-1, and Jason-2 Altimetry Observations Over African Lakes
Waveform Retracking for Improving Level Estimations From TOPEX/Poseidon, Jason-1, and Jason-2 Altimetry Observations Over African Lakes
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DOI：
10.1109/tgrs.2014.2357893
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发表时间：
2015-04
影响因子：
8.2
通讯作者：
B. Uebbing;J. Kusche;E. Forootan
中科院分区：
文献类型：
--
作者：
B. Uebbing;J. Kusche;E. Forootan
根据卫星高度计在内陆水体上空观测到的复杂雷达回波波形估计准确的水高，需要应用称为回溯器的后处理算法。本文介绍了一种新的重新跟踪算法--理论大地测量回溯算法(ITGR)，该算法应用于非洲湖泊上空的TOPEX/Poseidon(T/P)、Jason-1和Jason-2波形。ITGR算法首先分析返回波形的模式以识别可回溯波形。为了提供距离校正，它然后将最大似然估计器应用于灵活的波形模型，该模型是基于识别的峰值的数量及其在波形中的位置而构建的。ITGR还采用了一种可调的峰模型来处理对称和非对称的成形峰。因此，引入的方法在减轻波形模式中峰值的影响方面表现出一些技巧。我们通过将伏尔塔湖上空的回缩湖面高度(LLH)与每日验潮仪和各种重新跟踪算法得出的LLH进行比较，以及与全球水库和湖泊监测数据库中的LLH进行比较，验证了我们的回溯湖面高度(LLH)。我们在沃尔塔湖上空的观测结果表明，ITGR低位高度计与T/P的标准偏差为33 cm，与Jason-1高度计的标准偏差为10 cm，与Jason-2高度计的标准偏差为8 cm；与现有的追踪器相比，这意味着性能有所提高。对维多利亚湖陆地污染地区的调查证实了ITGR等次波形追踪器的优越性能。在奈瓦沙湖上，观察到了大部分镜面峰值波形模式，发现这些追踪器的性能与传统的阈值追踪器相似。
Estimating accurate water heights from complex radar return waveforms, as observed by satellite altimeters over inland water bodies, requires the application of postprocessing algorithms known as retrackers. This study introduces a new retracking algorithm, the Institute for Theoretical Geodesy Retracker (ITGR), which is applied to TOPEX/Poseidon (T/P), Jason-1, and Jason-2 waveforms over African lakes. The ITGR algorithm first analyzes the pattern of returned waveforms to identify retrackable waveforms. To provide range corrections, it then applies a maximum-likelihood estimator to a flexible waveform model, which is constructed based on the number of identified peaks and their position in the waveform. ITGR also adopts an adjustable peak model to deal with both symmetric and asymmetric shaped peaks. As a result, the introduced method exhibits some skill in mitigating the impact of peaks in the waveform pattern. We validated our retracked lake level heights (LLHs) over Lake Volta by comparing them to daily tide gauge and LLHs derived from various retracking algorithms, as well as to LLHs from the Global Reservoir and Lake Monitoring database. Our results over Lake Volta indicate that ITGR LLHs can be obtained with a standard deviation of 33 cm from T/P, 10 cm from Jason-1, and 8 cm from the Jason-2 altimeter; this represents an improved performance when compared to existing retrackers. Investigations over a land-contaminated region of Lake Victoria confirm the superior performance of subwaveform retrackers such as ITGR. Over Lake Naivasha, where mostly specular peak waveform patterns were observed, the performance of these retrackers was found similar to that of conventional threshold retrackers.