Setting GPSAltitude as a fraction?

[mij]

I have a tool which generate shell scripts to add EXIF information to new files.  This has been working perfectly for a long time, but I am having a problem updating it to support GPS.

As the altitude value is stored in XMP as a fraction, this is the figure I have to pass to ExifTool. From what I have read by searching to see if anyone else have this issue, it seems that it should be converted automatically.  Unfortunately instead ExifTool is just taking the numerator as a decimal value and discarding the rest.

Here is a sample script (with just the GPS tags shown):

#!/bin/sh
exiftool -EXIF:GPSLatitude="51,25.5191" -EXIF:GPSLatitudeRef="N" -EXIF:GPSLongitude="0,5.5239" -EXIF:GPSLongitudeRef="W" -EXIF:GPSAltitude="73336/1067" -EXIF:GPSAltitudeRef#="0" -EXIF:GPSTimeStamp=" 17:18:56Z" -overwrite_original_in_place img_1119048b.jpg

And this is the output:

Code Select Expand

GPS Altitude                    : 73336 m Above Sea Level
GPS Latitude                    : 51 deg 25' 31.15" N
GPS Longitude                   : 0 deg 5' 31.43" W
GPS Position                    : 51 deg 25' 31.15" N, 0 deg 5' 31.43" W

I have even tried adding a '#' as a suffix to the field, and tested with and without quotes and group name but it has made no difference.

Is there a way of getting ExifTool to understand the altitude in this format, or do I need to convert it manually?  Although I will not lose any meaningful precision that way, it just seems a little messy converting it back and forwards.

Thanks,

Michael.

[Phil Harvey]

While a recently added new feature allows you to enter simple rational values as fractions, the GPS values do not support this feature because they aren't simple.  I could presumably get this to work for Altitude because currently the additional logic just strips off the "above/below sea level" from this value when writing, but the GPSLatitude/Longitude are more complex than this due to the flexibility of allowed input formats.

If doing the division is possible for you, I would suggest that as a good alternative.  There shouldn't be any significant loss in precision:

Code Select Expand

> exiftool a.xmp -xmp:gpsaltitude=68.7310215558
    1 image files created

> cat a.xmp
<?xpacket begin='' id='W5M0MpCehiHzreSzNTczkc9d'?>
<x:xmpmeta xmlns:x='adobe:ns:meta/' x:xmptk='Image::ExifTool 8.35'>
<rdf:RDF xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>

<rdf:Description rdf:about=''
  xmlns:exif='http://ns.adobe.com/exif/1.0/'>
  <exif:GPSAltitude>73336/1067</exif:GPSAltitude>
</rdf:Description>
</rdf:RDF>
</x:xmpmeta>
<?xpacket end='w'?>


So in this case you would get 73336/1067, exactly what you want.  In general, the only difference you should see is that ExifTool will reduce the fraction to remove common factors from the numerator and denominator.

- Phil

[mij]

Sorry for not replying sooner, but if doing the conversion myself is best then I that it is pretty easy to do so.

It is certainly a lot easier than having to convert the longitude and latitude myself, so a small price to pay for that flexibility!

Thanks,

Michael.