The Image | Image Registration and Warping command in Didger is used to georeference an image (and one image only). It will show you any previously entered calibration points and is only available if there are no other digitized or imported objects in the project (just a single image).

The Map | Coordinate Conversion command is used to georeference or "calibrate" the entire project (vector files, image and vector data, more than one image, etc). It will not show you the previously entered calibration points, but it does allow you to recalibrate a project that contains both an image and other digitized objects.

For example:

1. If you import a georeferenced image (or calibrate it during import) and want to go back and recalibrate it, use the Image | Image Registration and Warping command.
2. If you import a georefenced image (or calibrate it during import), digitize some objects or import other data into the project, and then want to recalibrate the project, use the Map | Coordinate Conversion command.