@bbarris I have seen that you have resolved this issue. This post is just to clarify the way the imagery is made
The SLC and GRD images are goereferenced in the sense that it is provided with them a set of tie points (in the tiff tags and in the XML annotations) giving the correspondance between SAR timing and lat, lon.
The geo-referencing is done using a simplified earth model which is a flat earth inflated with the average scene height.
In addition, GRD are ground range projected with this earth model.
What are the consequences of that?
For an IW images having for ex. IW1 over the sea and having gradually IW2, IW3 going to the mountains, the average height won’t be 0.
Therefore if you geocode your image with the built-in earth model (i.e the tie-points) the SAR (IW1) data won’t match with the coast lines. The error made in range is related to the error made in the height.
Being this a problem, there are several options:
- orto-rectification using a better height mode like a
DEM. That way the geolocation will be perfect (to the accuracy of your DEM) - if the orto-rectification is not an option and if you want a “GRD-like” image:
- starting from SLC using a different height in the SRGR step(I don’t know how far this is configurable in the S1TBX
- starting from GRD you could simply estimate the range error induced by the height error made
Nuno Miranda
S-1 Data Quality Manager