I need a list of XMP metadata fields that are mapped somewhere else. I want to repurpose one to contain an error estimate when I guess at a geolocation for a scanned transparency. I have tried EXIF\User Comment but am informed that it is mapped to an (unknown) XMP field.
NOTE: Trivial issue, this can wait.
Would Attributes be suitable for this? It sounds like information that doesn't necessarily need to be carried within the image.
This would also avoid any issues with mapping.
The purpose is for images I send to other people. The GPS hanging off my pack strap is good to 5 m in most cases but when I pick a place off Google Earth to match a transparency shot from a Cessna 182 in 1985, I want to express an error to go with it.
The Metadata Working Group publishes the specification which explains which EXIF/IPTC/GPS fields are to be mapped to XMP and vice-versa.
You can download it here:
http://www.metadataworkinggroup.com/specs/
I have no easier list for you because it's not just a tag<->tag mapping. There is much more involved.
You can also look at the iptc2....args and xmp2...args files shipped with ExifTool (you'll find these in the IMatch program files folder) to see which tags are mapped between the different standards. I's a bit complicated, I'm afraid.
Why not use one of the text fields, e.g. description, to record the error?
If your images don't already have too many keywords, perhaps you could use a set of hierarchical keywords, e. g., GPSAccuracy|Excellent, GPSAccuracy|Moderate, etc.?
Thanks, all, I'll figure this one out somehow.