SNAPHU Unwrapping


Yes, I have the images each 12 days, but my tesis duties is calculate the deformation month by month,
Can I add the interferograms later to obtain a monthly value?


you can calculate the displacement for intervals of 12 days and then summarize them for selected periods, e.g. months. If there are linear trends in displacement, these should add up.
Furthermore, you reduce the impact of atmospheric disturbances of single interferograms.

Although it is outdated regarding the used software, this tutorial provides the full workflow to work with several consecutive interferograms:


Sorry, but in the link I dont know what is the tutorial


You have to register to be able to see and download the slides.


ok gracias


Mr ABraun, excuse me but i have one ask very basic, but very important.
what is the funtion of calculate the coherence?
why I have do the calculate the coherence betwen the images?


coherence gives you an idea about where in your image the phase information is reliable. It is a measure for quality and decorrelation.

I recommend the ESA InSAR principle guidelines:


thank you Mr ABraun


how can I to add two phases unwraping in snap?


how Can i add two interferograms?


we discussed this here: Interferogram averaging for DEM generation


Hi Abraum
when I finish the interferogram generation and the layer of displacement I have a rating of colors and with values. I want to know what is the correct form of interpretation the values pisitive and negative. are the values positives elevation of terrain, and values negativ subsidence?


I recommend reading this topic: Some explanations about concepts of fringes of interferogram and coherence


Hi, what is the boundary of error of the InSAR?or the margen of error?


That is quite a general question. The smallest measurable displacement depends on the wavelength of the sensor (have a look at “height of ambiguity“ in the ESA documents above).
Further aspects include spatial resolution, perpendicular baseline (“critical baseline“) and the accuracy of the orbit information.

So it’s hard to give a number here, but these are some great sources: