本文將介紹幾種常見的形變監測結果可視化方法，主要分爲監測結果和誤差可視化兩種，監測結果又分爲視線方向的監測結果和三維監測結果。
1 line-of-sight (LOS) direction 視線方向形變的可視化方式
1.1 Linear deformation rate 線性形變速度圖
如下：
Linear deformation rate
其中紅三角代表參考點，黑十字代表 continuous GPS (CGPS) station。該結果由19幅Envisat SAR影像通過PSInSAR處理得到，時間跨度爲： June 10, 2003 and July 8, 2008.
可以想象這裏的rate是通過形變總量除以總時間跨度得到的。
1.2 Deformation Time Series 形變時間序列圖
如下：
Deformation Time Series
其中紅三角代表參考點，這裏我有一個困惑：每一個形變圖都是相對於參考點的，那麼每一幅圖裏面的參考點有沒有變化呢？如果有，這個序列放在這兒有什麼可比性呢？可能的解釋是參考點相對火山口較遠，可以認爲不怎麼形變。
1.3 PSInSAR監測結果和CGPS測量結果對比圖
如下：
Comparison of timeseries PSInSAR measurements
with CGPS observations
其中，紅三角和藍色的點分別代表CGPS和PSInSAR的結果，注意橫軸表示的是時間，顯然並不是所有時間兩者都具有可比性。所以文中是這樣分析的：
The time series are complementary and they match reasonably well where they overlap in time (i.e., mostly within one standard deviation in the CGPS measurements), which demonstrates that MTInSAR can be useful either as a stand-alone tool or in conjunction with other deformation monitoring techniques.
雖然文獻裏沒有說，可以想象這裏的CGPS測量結果是要規劃到視線方向的。
2 三維形變的可視化方式
2.1 基於SAR影像進行三維形變監測的基本方法
Conventional InSAR techniques have demonstrated success in mapping surface displacements, but only in the radar line-of-sight (LOS) direction. Because SAR satellites occupy near-polar orbits (i.e., approximately N–S ground tracks and E–W look directions), it is impossible to measure small three-dimensional (3-D) surface displacements from LOS InSAR data alone, even when multiple independent interferograms with different viewing angles are used jointly.
However, when surface displacement magnitudes are on the order of meters, as is sometimes the case for large earthquakes, for example, it is possible to reconstruct the 3-D displacement field：
- using two interferograms (one ascending and one descending)
- one or two azimuth pixel offset tracking fields created by cross correlation of SAR images. This method depends on coherence of the image pairs and on the azimuth (along-track) pixel spacing of the SAR images. It can have low sensitivity to displacements in the along-track direction, depending on the pixel spacing.
- Multiple aperture interferometry (MAI) technique 是一種利用InSAR提高方位向位移測量精度的技術。 An MAI interferogram is created from forward- and backward-lookinginterferograms using sub-aperture InSAR processing. It hasbeen shown that the MAI technique has better sensitivity toalong-track displacements than the pixel offset tracking method（就是上面提到的基於SAR影像獲取水平方向位移的技術手段）.
2.2 三維形變可視化： 3-D displacement maps from MAI and LOS InSAR measurements
如下：
3-D displacement maps from MAI and LOS InSAR measurements
其中：
- a 降軌干涉圖
- b 一段時間後的升軌干涉圖
- c 對應a的降軌MAI干涉圖
- d 對應b的升軌MAI干涉圖
- e 三維位移場，其中箭頭和顏色分別表示位移的水平和垂直成分。這個圖是利用前四個結果得到的，至於怎麼得到的，無非是矢量分解，後面再細說。
說明：從北往南降軌，反之升軌，注意其中的LOS方向
3 參考文獻、圖片來源
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.