Default pixel spacing

As I know, in gpt Ellipsoid-Correction-RD, the default pixel spacing is 0.0 (meter and deg).
Does it mean that the pixel spacing is set automatically as source GR pixel spacing like that of GUI?
or should I determine the value same as the input data?

Thank you.

Are you trying to run “Range Doppler Terrain Correction” operator with a S-1 SLC product? If yes, I’d suggest you to download the corresponding GRD product and the operator with the GRD product.