Radarsat-1: problem in coordinate conversion with state vectors.

Dear all,

I have got a series of Radarsat-1 SLC data (complex).
I implemented a coordinate converter which is able to perform the conversion from (rox, col) to (lat, lon, h) coordinate (from image to geodetic coordinate system).
The converter takes as input:
- azimuth and range first times
- position and velocity state vectors
- wavelength
- line and pixel time interval.

To be more precise I have to add that:
- azimuth first time is taken from the 'acquisition time of zero doppler image line' metadata, supposing that this value is the mid line azimuth time;
- range first time has been computed from the 'slant range first' metadata;
- the state vectors have been extracted from the CEOS file and have been converted from ECI to ECEF coordinate system;

However, I extract the geodetic and image coodinate and the center of the image, which are included in the metadata, and I try to do the convertion by myself; without getting the right result.

Has anyone got any suggestions for me? I'm going mad!

Marco