基本原理
一切都要從基本原理說起
上面的基本原理給出了干涉相位和高程與形變的關係，與此同時也給出干涉相位和基線（或者是軌道數據）的關係。這裏的基本原理是下面的分析以及其他分析的基礎。
軌道誤差的處理辦法
上面的基本思想就是“自洽”，這個裏面有一個原理，即上面公式描述的基線、地形以及相位等的關係，那麼在這個公式的前提下，整個系統內部要自洽，不能相互矛盾。當然了這裏的處理只能提高相對精度，而不能提高絕對精度，不過對於某些應用好像是已經夠了。
上面的步驟只能得到某些點上的軌道糾正信息，要得到每一個點上的軌道糾正信息需要進行一個擬合：
To eliminate the residual orbital contribution in an interferogram, we count the residual fringes on the interferogram and attribute them to an error in the slave orbit (Plate 1). This approximation is acceptable because the phenomenon depends mainly on the relative, rather than absolute, positions of the orbits. We seek two corrections to the slave orbit, a vertical and a lateral deviation, both of which change linearly with time along track as a * bt and c * dt. To determine the four coefficients a, b, c, and d, we choose four points as far apart as possible in the final image, typically at the corners. We then count the residual fringes between them. The four coefficients
are the solution of a linear system of four equations involving the positions of the four points and the number of cycles at each of them. The orbit can then be corrected for any epoch in time, and the interferogram can be adequately corrected everywhere. Usually, we apply the correction to the final product, because the error committed on the slave orbit is too small to alter the previous processing steps. If necessary, we could completely reiterate the processing with the corrected slave orbit, but a single correction is sufficient in practice.
這是一種方法 這種方法必須要估計DEM輔助數據的精度吧。
其他的方法：
In a slightly different approach, Murakami et al. [1996] use GPS measurements of surface displacement at seven bench marks within about 15 km of the Northridge earthquake epicenter to adjust the orbital parameters. They obtain residual differences (GPS minus JERS-1 radar) of less than 3 cm in range, smaller than the 3.5-cm uncertainty of the GPS measurements.
More widely separated control points (e.g., the four corners of the 100 by 100 km image) provide a better estimate of the orbital separation, which varies mostly over long wavelengths [Massonnet et al., 1996a].
精確的軌道數據對干涉處理的意義
Note that, when co-registering parameters derived from orbits are sufficiently accurate, it is possible to include the co-registration in the focusing operator.
計算基線
圖像匹配
圖像定位（相位模擬）
參考文獻
Hooper, A., Bekaert, D., Spaans, K., & Arıkan, M. (2012). Recent advances in SAR interferometry time series analysis for measuring crustal deformation. Tectonophysics, 514, 1-13.
Zhong, L., & Dzurisin, D. (2014). Insar imaging of aleutian volcanoes. Springer Praxis Books, 2014(8), 1778–1786.
Ketelaar, V. (2009). Satellite radar interferometry : subsidence monitoring techniques.
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