GPS documentation out of date?

[eponymous]

The GPS tag info in FAQ 14 and the tag names GPS section seems out of date with the 2.3.1 exif spec here (which also agrees with the 2012 2.3 version in this respect).

In particular the lat and long tags are supposed to contain NSEW info and the Ref tags for each are to have been "merged" with them (whatever that means exactly).

In practice I find that the lat and long exif tags as reported by exiftool do in fact contain the correct information, which in the binary form of exiftool output means that west and south coordinates are negative (since the binary versions are in essence northings and eastings) and in the text versions end with N, S, E, or W. In other words, the exiftool behavior seems correct (though I haven't done extensive testing), but the documentation isn't.


Do I have this right?


TIA.

[StarGeek]

The GPS tag info in FAQ 14 and the tag names GPS section seems out of date with the 2.3.1 exif spec here

That is not the EXIF spec.  That is the Exif 2.32 metadata for XMP.  See XMP exif Tags.

You'll find the Exchangeable image file format for digital still cameras: Exif Version 2.32 here.

[eponymous]

That is not the EXIF spec.  That is the Exif 2.32 metadata for XMP.  See XMP exif Tags.

You'll find the Exchangeable image file format for digital still cameras: Exif Version 2.32 here.

Thanks. That's helpful.

Do I understand this correctly then:

It looks from the man page that exiftool with append the hemisphere info to lat and long where it's present, so I get that info even though lat and long don't explicitly include it.

Code Select Expand

> exiftool -GPSLatitude -GPSLongitude file.jpg

GPS Latitude                    : 37 deg 48' 31.89" N
GPS Longitude                   : 122 deg 12' 23.64" W

> exiftool -b -GPSLatitude -GPSLongitude file.jpg

37.80885833
-122.20656667

[StarGeek]

You need to include the -a (-duplicates) option and -G (-groupNames) option to see both duplicates and the location.  The resulting output would be something like this

Code Select Expand

C:\>exiftool -g1 -a -s -GPSLatitude* -GPSLongitude* y:\!temp\Test4.jpg
---- GPS ----
GPSLatitudeRef                  : North
GPSLatitude                     : 37 deg 48' 31.89"
GPSLongitudeRef                 : West
GPSLongitude                    : 122 deg 12' 23.64"
---- Composite ----
GPSLatitude                     : 37 deg 48' 31.89" N
GPSLongitude                    : 122 deg 12' 23.64" W

or this

Code Select Expand

C:\>exiftool -g1 -a -s -GPSLatitude* -GPSLongitude* y:\!temp\Test4.jpg
---- GPS ----
GPSLatitudeRef                  : North
GPSLatitude                     : 37 deg 48' 31.89"
GPSLongitudeRef                 : West
GPSLongitude                    : 122 deg 12' 23.64"
---- XMP-exif ----
GPSLatitude                     : 37 deg 48' 31.89" N
GPSLongitude                    : 122 deg 12' 23.64" W
---- Composite ----
GPSLatitude                     : 37 deg 48' 31.89" N
GPSLongitude                    : 122 deg 12' 23.64" W
GPSLatitudeRef                  : North
GPSLongitudeRef                 : West

The first has GPS coordinates in the EXIF group.  The second also includes the XMP-exif GPS coordinates, which are set as described in your first post.

The final group is the Composite group, which are derived from other tags in the file.  In this case, exiftool creates a complete Latitude and Longitude coordinate set so they can be accurately copied to other tags/files.

[eponymous]

Thanks! Very helpful. I clearly have image files with a mix of GPS tags.