Jie,

The current version of Micromine has an option on the image option in Visex to select a saved coordinate conversion.  It works a treat.  In older versions I used ot copy the georeference points to a Micromine file and then run that file through the coordinate conversion and then feel the converted points into the georeference.  The new system is much better in that it allow images with embedded georeferences to be converted on the fly.

Thanks Keith. I converted some plans and cross sections using the latest version. The image conversion option works well for the plans, but some cross section images disappeared/partially disappeared after applying coordinate conversion. Is there a way to fix it? or do I have to copy and convert the georeference points manually?

Jie,

It sounds to me as though there is a rotation involved so that when you look at the sections a portion of them is now outside the clipping window.  Turn of the clipping or make the section window larger.  You may need ot go to a different set of section definitions (assuming you are using a section control file) for the new coordinate system.