GPS tag edits Not Working

[sebm]

Hi. I have a bunch of files where the tags are all messed up: I believe thanks to faulty GPS on the camera and likely my bad efforts to fix the tags.

Am trying to use this command to use the file modify date to overwrite the GPSTimeStamp and GPSDateStamp. It seems to work - no syntax errors and it processes the files but all the XMP files remain unchanged even though it sees all of them. Any idea what the problem might be?

exiftool -ext xmp "-GPSTimeStamp<FileModifyDate" -globaltimeshift -7 "D:\Seb Documents\My Videos\Need Sorting\MTS Files not rejected\Change Dates-SIN

[Phil Harvey]

The problem is that GPSTimeStamp only exists in EXIF.  For XMP you need to write GPSDateTime.

- Phil

[StarGeek]

Also, if it matters, copying directly from the FileModifyDate will end up with a time zone in XMP:GPSDateTime.  If the addition of the  GlobalTimeShift option is to adjust the time to UTC, then you're going to want to remove the time zone from the copy.  Adding something like this to the command
-d "%Y:%m:%d %H:%M:%SZ"

[sebm]

Thanks so much. SOLVED.