S-1 Thermal Noise removal introduces Artefacts in the image


#1

Hello,

I am using SNAP 6.0 and S1TX 6.0.2

I have recently started getting artefacts in images after the S1-Thermal Noise Removal e.g. in S1A_IW_GRDH_1SDV_20180313T180532_20180313T180557_021000_0240E0_114C

Is this related to other posts that indicate processor change on 13th March?
How would I go about eliminating the thermal noise in this case?
Is there a way of automatically testing whether this artefact issue also affected other images?

Pre-Noise image:


Post-Noise image:

Thanks,
Sanjay.


GRD-Border-Noise and Thermal noise removal are not working anymore since March 13. 2018
GRD-Border-Noise and Thermal noise removal are not working anymore since March 13. 2018
#2

@lveci Hi Louis, Any thoughts at all? Thanks, Sanjay


#3

Hi, As described in Sentinel-1 quality disclaimer #30 and #31 (https://qc.sentinel1.eo.esa.int/disclaimer/30/ and https://qc.sentinel1.eo.esa.int/disclaimer/31/) there was a problem with noise removal of products processed just after the deployment of IPF v2.90 on 13th March 2018. The disclaimer #30 gives a list of affected S1-A products, including your product from 13th March. The problem was resolved on the 15th March with the distribution of a new AUX_PP1 auxiliary file (S1A_AUX_PP1_V20171017T080000_G20180315T153822.SAFE).


#4

Hello Peter,
Thanks for the much needed clarification!. Apologies for the noob query but how can I go about using the AUX_PP1 file?
Thanks,
Sanjay.


#5

Hello Sanjay,
The AUX_PP1 auxiliary file is used in the Sentinel1- Instrument Processing Facility (IPF) when the product is processed from raw data to the Level 1 product (such as GRDH). It is not possible to use the latest PP1 to correct your product.

However, as described in the Quality Disclaimers, it is possible to modify the noise vector annotation files to remove the corrupt noise vectors. In your example, the corrupt noise vectors are in the middle azimuth position and so the first and last noise vectors are both OK.

So if you replace the noise annotation files in your product (making backup copies first) in folder S1A_IW_GRDH_1SDV_20180313T180532_20180313T180557_021000_0240E0_114C.SAFE\annotation\calibration with those attached here, you should be able to perform denoising sucessfully.

noise-s1a-iw-grd-vh-20180313t180532-20180313t180557-021000-0240e0-002.xml (116.6 KB)
noise-s1a-iw-grd-vv-20180313t180532-20180313t180557-021000-0240e0-001.xml (116.6 KB)


#6

Many Thanks Peter for the explanation.


#7

Just wanted to confirm peter that your solution worked. I noticed that there many other of my files are listed in the disclaimer while I noticed the issue only on this particular image - is this a SNAP quirk?


#8

Hi, Good to hear that you have sucessfully denoised your image. For the other products in the disclaimer list, it is possible that many of the products are OK and do not need to have any noise vectors removed from the annotation. It is only by either performing denoising or checking the noise vectors themselves that it can be determined if there is a problem with a particular product.