Automatic coregistration S1 GRD data

I’m trying to coregistrate two geoTIFF GRD data from two different orbits with Automatic Coregistration tool.
Before this operation I have applied range-doppler terrain correction.
When I launch the operation the following error message appairs:
GCP_Selection: GCP_Selection computeSlaveGCPs: GCP-Selection getCoarseSlaveGCPPosition: java.lang.NullPointerException”.
What is the meaning of this message?
Thank you.

Could you please be more specific on the processing steps involved.
You should read the products through the manifest file (within the GRD product folder) or directly the *zip file, not opening the GeoTIFF file. In the latter case you are omitting of the product metadata.
Please also note that the accuracy of the terrain correction depends on the orbit state vectors. So, you might not need to apply additional coregistration if precise orbits are used.

GeoTIFF file comes from range-doppler terrain correction operation.
When I use the mainfest file other error messages appear:
CreateStack: CreateStack: subSamplingX> 0.0” and “Error finding optimal master: Ellipsoid.ell2xyz: input values for phi/lambda have to be in radians

I would try co-registration by Create Stack. After terrain correction the data should be almost in the same geometry, a simple small shift should be enough to align the images.

BTW did you use restituted or precise orbits?

You should usually only export to another file format such as GeoTIFF at the end of your processing when you want to make your data interoperable with other software. If you will continue to process in the toolbox, keep the data in DIMAP format or somethings like vector data may get lost.
Also, in create stack, if using the orbits to calculate the initial offset fails due to missing information then use the products geolocation.

Thank you very much. I have another problem. I have to coregistrate Cosmo-SkyMed data. They have GeoTIFF format and are GTC.
Whatever operation I try to execute, SNAP can’t recognise them as SAR data: if I try to apply a range-doppler terrain correction message error say:“input should be a SAR product”.
If I try to automatic coregistrate:“input values fot phi/lambda have to be in radians”.
What should I do to work with this data?
Thank you.

These are GeoTIFF GTC from some other software? If so, they won’t have the required metadata to continue processing with in the toolbox.

I have downloaded them from ASI as GeoTIFF.

Then I would say they are unsupported. Even if they had the proper
metadata in some format, the toolbox would need a reader to be able to
abstract that information into something useable.