Sentinel 1 GRD preprocessing using GCP for Geocoding

Microwave Toolbox
#1

Hi,
We all know that In order to have a good comparison between two things, they should be comparable.

I started looking at two S1A-IW-GRD products which are taken from the same location in the temporal distance of 12 days (They are both in ascending mode).

Observations:

  1. the two tiles (lets call them Master and Slave) do not have the same number of rows and/or columns:
    Master (X,Y) = (25979, 16694)
    Slave (X,Y) = (25978, 16695)

  2. I used GDAL to see the information regarding the GCPs of the same GCPs belonging to each tile:

(north-west) pixels
Master 1 (0.00P,0.00L) -> (5.8071029E,45.4207633N,1353.21)
SLave 1 (0.00P,0.00L) -> (5.8073678E,45.4208335N,1353.21)

(north-east) pixels
Master 21 (25978.00P,0.00L) -> (9.0883795E,45.8208640N,1353.29)
Slave 21 (25977.00P,0.00L) -> (9.0885275E,45.8208917N,1353.29)

(south-west) pixels
Master 190 (0.00P,16693.00L) -> (5.3597872E,46.9157973N,497.42)
Slave 190 (0.00P,16694.00L) -> (5.3602404E,46.9159847N,506.19)

(south-east) pixels
Master 210 (25978.00P,16693.00L) -> (8.7320729E,47.3168078N,497.41)
Slave 210 (25977.00P,16694.00L) -> (8.7324286E,47.3169477N,506.18)

One can see differences of coordinate values between the counterpart GCP couples of each tile.

Question
For this inconsistency can I do Geocoding on Master and Slave images individually in order to ameliorate this differences between the two data before applying co-registration?

Thanks for any comments on this
Sina

#2

yes, SNAP allows to use geocoded products in the coregistration, but you have to make sure that you select “geolocation” instead of “orbit” in the ‘initial offset method’

Two similar questions were discussed here: Radiometric & Geometric Correction Workflow and Sentinel-1 Geocode Export