I’m looking for a way to get approximate coordinates for one sub-swath of an Sentinel-1 SLC image (IW3 for example). I looked at manifest.safe in my data folder but there is only the global coordinates of the image.
For now, the only solution that I have is to get global coordinates of the image, divide the rectangle into 3 vertical rectangle and I got one rectangle for each sub-swath.
I wonder if there are more precise solution.
Does anyone have an hint for me? Thanks you
Open the S-1 SLC product in SNAP, go to Metadata => Original_Product_Metadata => annotation, you will see the metadata of all sub-swathes. Inside the sub-swath metadata, you will see Product => geolocationGrid which is probably what you are looking for
If I’m not mistaken the geolocation grid is based on ellipsoid geocoded coordinates so it is incorrect over areas that are not at sea-level. For some applications this does not matter but one should be aware of it.
Thanks! That was the information that I needed.
@mengdahl It shouldn’t be a problem for my range of accuracy but it’s good to know.
However, the geolocation grid points have a height attribute that is different from 0 and quasi constant over one line of the grid so it’s a bit curious.
For future reference for anyone else interested in using the GeolocationGrid:
This European Commission report: dx.doi.org/10.2788/132810 on pages 21 and 46 has information about the GeolocationGrid and why it isn’t good for direct use if you need high accuracy.