XMP:XMP-exif:GPS* - duplicate or not (-a)

[user2014]

Hello,

(command line and stay_open behaviour is identical)

calling "exiftool picture.cr2" shows all tags except duplicates (e.g. XMP:XMP-exif:GPS*). They are omitted.
calling "exiftool -a picture.cr2" shows all tags including duplicates.
If the XMP-region contains none of these duplicate tags the values from EXIF:GPS:GPS* are used for the XMP:XMP-exif:GPS* tags (?).
If one of  the duplicate tags in the XMP-region was found, the value of this tag is used (in my opinion - correct).

But how can one distinguish if the value is from the XMP-region (if the XMP-tag exists) or from the EXIF-region (if the XMP-tag does not exist) ? How can one determine if the XMP-tag exists at all, or which XMP-tags are already in use in the file ?

In my opinion these are two different sets of tags (in this special case with the same values) and not references to the EXIF:GPS-region.
Also the data-types differ between the two sets (string vs. numeric, signed values vs. unsigned and ref - GPSLatitude, GPSLatitudeRef, ...)

I think there should be a switch/option where I get only the plain existing tags, no duplicates, no references, no calculated values.
Only tags which are "physically" stored inside the file - in all regions.

Then it's up to the user / application which tags to use,read,write,copy,...

Similar to the -e option (existing option - which is only for composite-tags).

Thank you

PS:
Is there a list of all duplicate tags with a similar behaviour ?

[Phil Harvey]

If the XMP-region contains none of these duplicate tags the values from EXIF:GPS:GPS* are used for the XMP:XMP-exif:GPS* tags (?).

I don't understand.  Are you copying tags?  If so, what command are you using?

Is there a list of all duplicate tags with a similar behaviour ?

No.  it is not possible to make a complete list since some tags are generated dynamically when reading.  Or are you talking about writing?

- Phil