I have managed to obtain the displacement map from S1-A. However, the values appear to be too large for a 10 day period.

I've read that I should combine results from ascending and descending passes. How should I do this? averaging?

  • If you calculated a confidence measure together with your displacement maps you can have a look at this paper, where they combined ascending and descending displacement calculations on a glacier in the Alps.
    – Kersten
    Jan 19, 2016 at 12:54

1 Answer 1


Averaging is not the way to go. Because of the different viewing geometries, it is entirely possible to have positive displacement in the line of sight from one look direction, and no displacement from the other look direction, or any combination. Think of a point moving east and down by equal amounts. From the ascending

You can apply a 2-D decomposition of the individual line of sight phases or displacements (using geometry) to derive an east-west and an up-down component. The north-south component is difficult to retrieve precisely because of the satellite's polar orbit (cannot resolve along-track displacements unless they are very large). Not the most authoritative source, but see http://www.engr.mun.ca/~sircar/project1_files/grnd_mvt.pdf for an example.

The authoritative source is:

Hanssen, R.F. Radar Interferometry—Data Interpretation and Error Analysis, 2nd ed.; van der Meer, F., Ed.; Kluwer Academic Publishers: Dordrecht, The Netherlands, 2001.

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