Sorry, I thought you wanted to export your images with metadata attached.
I only know of two built-in ways to export metadata:
- File -> Export -> Metadata; you already tried it and found the results insufficient
- File -> Export -> Master; and set the Metadata option to "Include IPTC4XMP Sidecar File"
This second methode will export the Master image file (delete it, if you do not want it) and an additional file with IPTC and EXIF tags, like this
<rdf:Description rdf:about='' xmlns:exif='http://ns.adobe.com/exif/1.0/'>
<exif:GPSLatitude>21,59.08662000N</exif:GPSLatitude>
<exif:GPSLongitude>159,32.12172000W</exif:GPSLongitude>
<exif:GPSAltitude>670400/1000</exif:GPSAltitude>
<exif:GPSAltitudeRef>0</exif:GPSAltitudeRef>
</rdf:Description>
Perhaps you can use this as a starting point.
For more EXIF tags you will have to write an AppleScript or an Automator workflow. I posted an Automator Workflow here: http://dreschler-fischer.de/FAQ/Scripts_Services/Entries/2012/2/8_Write_EXIF_Inf o_to_a_File.html
This is a service to be called from Aperture; it writes EXIF tags to a textfile. You can use it as a template and add more EXIF- and IPTC fields in a similar fashion.
Regards
Léonie
P.S: If you export the master, make sure to write your IPTC data to the master file: Use Batch Change for this.