Integrated satellite interferometry: Tropospheric noise, GPS estimates and implications for interferometric synthetic aperture radar products
Integrated satellite interferometry: Tropospheric noise, GPS estimates and implications for interferometric synthetic aperture radar products
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DOI：
10.1029/98jb02794
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发表时间：
1998-11-10
影响因子：
3.9
通讯作者：
Fang, P
中科院分区：
文献类型：
--
作者：
Williams, S;Bock, Y;Fang, P
干涉合成孔径雷达（干涉合成孔径雷达）与其他天文和空间大地测量技术一样，受到电磁波在中性大气中传播的时空可变延迟的限制。这些变化的统计分析，从各种各样的仪器，揭示了幂律依赖于频率的基本（柯尔莫哥洛夫）湍流的特征。Treuhaft和Lanyi [1987年]曾为甚长基线干涉测量法开发了延迟波动的一个主要组成部分-“湿”组成部分-的统计模型。目前在南加州已建立了一个连续的全球定位系统网络，该网络可沿着大地测量参数，以每小时为单位估算每个地点上空大气层造成的总延迟。这些测量结果符合Treuhaft和Lanyi（TL）统计模型的时间和空间。将TL统计模型应用于干涉合成孔径雷达问题，并用于产生在时间和/或空间上分离的两个点之间的协方差。通过误差的传播计算了由于大气变化引起的SAR产品（如地形和地表变形）的误差。通常有两种方法可以减少合成孔径雷达干涉测量产品中大气失真的影响，即叠加和校准。叠加涉及平均独立干涉图以减少噪声。校准涉及使用来自独立源的数据（例如来自连续GPS网络的总天顶延迟估计）来去除部分（或全部）延迟。尽管表面测量的空间密度相对较差，但如果测量足够准确，则可以使用校准来减少噪声。对流层噪声的减少随着测量点数量的增加和精度的增加而增加，直到最大根N，其中N是点的数量。堆叠和校准被证明是互补的，可以同时使用，以减少噪音，以达到以下的任一方法单独。
Interferometric synthetic aperture radar (INSAR), like other astronomic and space geodetic techniques, is limited by the spatially and temporally variable delay of electromagnetic waves propagating through the neutral atmosphere. Statistical analysis of these variations, from a wide variety of instruments, reveals a power law dependence on frequency that is characteristic of elementary (Kolmogorov) turbulence. A statistical model for a major component of the delay fluctuations, the "wet" component, has previously been developed by Treuhaft and Lanyi [1987] for very long baseline interferometry. A continuous Global Positioning System (GPS) network is now in place in southern California that allows estimation of, along with geodetic parameters, the total delay due to the atmosphere above each site on a subhourly basis. These measurements are shown to conform to the Treuhaft and Lanyi (TL) statistical model both temporally and spatially. The TL statistical model is applied to the problem of INSAR and used to produce the covariance between two points separated in time and/or space. The error, due to the atmospheric variations, for SAR products such as topography and surface deformation is calculated via propagation of errors. There are two methods commonly cited to reduce the effect of atmospheric distortion in products from SAR interferometry, stacking and calibration. Stacking involves averaging independent interferograms to reduce the noise. Calibration involves removing part (or all) of the delay using data from an independent source such as total zenith delay estimates from continuous GPS networks. Despite the relatively poor spatial density of surface measurements, calibration can be used to reduce noise if the measurements are sufficiently accurate. Reduction in tropospheric noise increases with increasing number of measurement points and increasing accuracy up to a maximum of root N, where N is the number of points. Stacking and calibration are shown to be complementary and can be used simultaneously to reduce the noise to below that achievable by either method alone.