Atmospheric delay analysis from GPS meteorology and InSAR APS
Atmospheric delay analysis from GPS meteorology and InSAR APS
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DOI：
10.1016/j.jastp.2012.06.005
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发表时间：
2012-09
影响因子：
1.9
通讯作者：
Shilai Cheng;D. Perissin;Hui Lin;Fulong Chen
中科院分区：
文献类型：
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作者：
Shilai Cheng;D. Perissin;Hui Lin;Fulong Chen
大气折射率不均匀引起的雷达大气去相关是卫星合成孔径雷达干涉测量(InSAR)高精度反演地球物理参数的一个重要限制因素。在毫米精度下，基于GPS气象学的水汽示踪技术被广泛应用于消除InSAR大气误差。然而，GPS和InSAR大气时延的可靠比较很少涉及，这主要是由于缺乏稳定和准确的InSAR大气相位。本文提出了一种GPS天顶对流层延迟(ZTD)和合成孔径雷达大气相位屏(APS)在差分和伪绝对模式下的比较方法。在实验中，收集了意大利科莫的ENVISAT ASAR APS地图和同步GPS运动测量数据进行一致性分析。此外，为了分离APSS内的不同分量，以延迟/仰角比的形式详细分析了大气延迟的层结效应。最后，在上述层结分析的基础上，对SARAPS和GPS的层结条件和假设湍流进行了差模比较。结果表明，从GPS延迟图和SARAPS图得到的分层比与标准差7.7 mm/km和偏差3.4 mm/km是一致的。在上升的情况下，分层比的相关系数在0.7以上。在差分模式下，大气总延迟符合小于4 mm的标准差(∼0.65 mm PWV)，相关系数大于0.6。对“伪绝对”模式下的总时延进行了比较，作为GPS和InSAR之间协议的另一种设想。此模式下的一致性略差于差分模式下的一致性。差值的标准偏差小于6 mm(∼1 mm PWV)，不同实现方式的相关系数约为0.5。上述工作中的比较结果提供了GPS和SARAPS大气测量具有可比性的定量范围。另一个重要的发现是，在大多数情况下，GPS和SARAPS之间的差异标准差在两种比较模式下都略小于SARAPS本身的标准差。这意味着利用高精度GPS气象产品校正SAR干涉测量中的大气误差的潜力，即对流层延迟或水汽。
Radar atmospheric decorrelation due to inhomogeneity of atmospheric refractivity is a critical limitation of satellite SAR interferometry (InSAR) in the high accuracy retrieving of geophysical parameters. With mm precision, a water vapor tracing technique based on GPS meteorology was widely employed to mitigate InSAR atmospheric errors. However, a reliable comparison of atmospheric delay between GPS and InSAR is rarely touched, mainly due to the scarcity of stable and accurate InSAR atmospheric phases. In the paper we propose a comparison methodology between GPS Zenith Tropospheric Delay (ZTD) and SAR Atmospheric Phase Screen (APS) in both differential and pseudo-absolute modes. In the experiment, ENVISAT ASAR APS maps and synchronous GPS campaign measurements in Como, Italy were collected for consistency analysis. Furthermore, the stratification effect of atmospheric delay, in a form of delay-to-elevation ratios, was particularly analyzed for the purpose of separating different components within APSs. Finally, with the above stratification analysis, terms of stratification and assumed turbulence from SAR APS and GPS were compared in differential mode. Presented results show that the stratified ratios from GPS delays and SAR APS maps are in agreement with a std of 7.7mm/km and a bias of 3.4mm/km. Correlation coefficients of stratified ratios are higher than 0.7 in ascending case. In differential mode, the atmospheric total delays coincide with STandard Deviations (STDs) smaller than 4mm (∼0.65mm PWV) and with correlation coefficients higher than 0.6. The comparison of total delays in ‘pseudo-absolute’ mode is provided as an alternative vision of the agreement between GPS and InSAR. The agreement in this mode was slightly worse than that in differential mode. STDs of the difference are smaller than 6mm (∼1mm PWV), and the correlation coefficients are about 0.5 for different implementation approaches. Above comparison results in the work provide a quantitative extent to which atmospheric measurements from GPS and SAR APS are comparable. Another significant finding is that in most cases the STD of difference (between GPS and SAR APS) is slightly smaller than STD of SAR APS itself in both comparison modes. It implies the potentiality to correct atmospheric errors in SAR interferometry with high-precision GPS meteorological products, i.e. tropospheric delay or water vapor.