ABraun, thanks for you reply. I am using intensity data, so it is already detected data and not SLC/L0. I am using Envisat ASAR Precision Mode .N1 format intensity data (.IMG/IMP format with coordinates), and ALOS-1 PALSAR Level 1.5 CEOS data. I understood your point as valid, but it took me some time to figure out how to actually re-project the data, as some tools did not apply. Finally, I’ve figured this out:
For Envisat ASAR IMG/IMP .N1 data, apply the Radar > Ellipsoid Correction > Gelocation-Grid function. I exported the output in ENVI format, and opened in ENVI, this time the coordinates are attached.
However, for ALOS-1 PALSAR Level 1.5 CEOS data, the Geolocation-Grid function does not work, as it says “Source product should not be map projected.” I tried to use the Radar > Geometric > Update Geo Reference function instead, which requires DEM to be provided or will auto-download. This function works and generates output, however this output again does not contain the coordinates when exported to ENVI or GeoTIFF formats. I also tried the Raster > Geometric Operations > Reproduction tool, but that says “SAR products should be terrain corrected or ellipsoid corrected.” So I am stuck with the ALOS data.
So the question now is: How to export coordinates for ALOS-1 PALSAR Level 1.5 CEOS data? If SNAP says "Source product is already map projected, why dose it not export the coordinates in any format?