Error with coregistration of complex products

Dear all,

I’m using SNAP 5.0 with Sentinel1 TOPSAR products.
Here are the steps I’ve done so far:
Step1: TOPSAR Pre-Processing:
TOPSAR Split --> TOPSAR Deburst --> TOPSAR Merge . Works fine

Then I wanted to calibrate my products, use terrain correction and coregister the TC products.
Step2: Radiometric Calibration
Step3: Geometric Terrain Correction (Range-Doppler)
Step 4: Coregistration (Coregistration)

For this process, I’d like to keep the complex information, so I used everywhere the option “Output complex data”. The Calibration step works fine with it, as does the TC. It occured to me though that the coregistration does not work with Complex output TC data. I always get the error [Error: [NodeId:Warp] The product ‘S1A_…deb_mrg_CalIQ_TCIQ_Stack’ already contains a band with the name ‘Intensity_VH_slv2_…’] I’ve checked. I’ve no product named ‘S1A_…deb_mrg_CalIQ_TCIQ_Stack’ and the TC complex products have no other bands than I,Q, and Intensity. The funny thing is, if I perform the TC without checking the option “Output Complex Data”, the coregistration works fine. But then, I only have the Intensity images, and my IQ products are lost. That’s not what I want.

I’ve looked in the forum but found no corresponding error message so far. Can you please help me with this matter?

Thanks a lot,

What were you planning to do with the phases afterwards? After step 3 you have interpolated noise that is not really useful for anything…

Hi again,

So I kind of found out a work around for that problem, even if I’m not totally happy with it. What I really wanted to do was:

  1. to estimate the coherence in a 6 days intervall for 25 S1 IW data (for this, I need the complex data)
  2. at the same time keep the backscatter intensity information (calibrated) in order to build a mean over all my acquisitions

For this, I wanted to use the GraphBuilder with Batch Processing, in order to accelerate the whole process. I think (please tell me if I’m wrong!) that both steps are not feasible at the same time (due to the error described before).

So this is what I do:

  1. use the Graph TopSAR Coreg Interferogram IW All Swaths, replacing “Interferogram” through “Coherence” calculation . I have to perform that for all data pairs separately, which takes quite a long time
  2. Use Batch Processing for coregistering all the intensities (steps described in the previous post, this time without “output complex data”

After that, I perform TC separately for both 1) and 2) results and stack them. Coregistration here of 1) and 2) doesn’t work. If I try coregistration before TC, I get an empty coregistered Coherence image, and if I try it after TC, I get the same error as described in my first post.

@mengdahl yes, you’re right. I didn’t want to use the phases, but anyway, it’s the same nonsense if I want to calculate the coherence. Anyway, I tried also without Step 3 (TC) but got there weird results after coregistration (horizontal fringes probably corresponding to a misregistration). But as you see from this post, the error still subsists by trying to coregister two TC images.

You need to calculate coherence (and do all InSAR-processing) before step 3. If you want an InSAR-stack you should co-register before TC.