Metadata Description - JOBO PHOTOGPS User Manual

17. Metadata Description

Every digital photo contains extra information, known as metadata. Some metadata is always written
to the file which contains the image data. Further information may be stored in an associated file,
known as a "sidecar". For JPEG files, the metadata is usually stored in the file itself. (Note that
image data and metadata are kept apart in JPEG files, so that each can be updated without
interfering with the other. On the other hand, camera "RAW" images are not intended to be
updated, so the metadata is held in a sidecars.
When the camera takes a photo, it writes some metadata into the file which contains the image.
This will include the date and time when the photo was taken and, typically, other information
about the image such as camera settings and exposure time. When the photos are geotagged, the
photoGPS software writes geographical metadata to the image or its sidecar file.
The photoGPS software works with four different metadata types:
IPTC (International Press Telecommunications Council). This is an older meta information format and the
information is gradually migrating to XMP. IPTC tags hold information relating to the photographer (e.g.
copyright, contact details) and information on the subject of the image (e.g. location, keywords etc.).
XMP (Extensible Metadata Platform). This is an open XML-based metadata format created by Adobe. Typically,
it duplicates (and extends) the IPTC information. photoGPS also use XMP to store the Points of Interest (POI)
data.
Windows (Microsoft Windows file properties). photoGPS sets a number of Windows XP/Vista file properties
such as Title, Subject and Keywords.
There are 3 categories of photoGPS metadata
GPS - the date, time and position (latitude,longitude and altitude) of the photoGPS when the photo was
taken.
Reverse Geocoding - the address corresponding to the GPS position. This comprises 4 lines: 3 address lines
and the Country, e.g. "Redcoat Lane, Weybridge, Surrey, England". Note that in the descriptions below, the 4
lines are represented as:
<Address Line 1>, <Address Line 2>, <Address Line 3> and <Country>
POIs - a list of points of interest, written as a string containing delimiters to separate each POI and the fields
within it.
The full list of metadata tags written by photoGPS is as follows:
The values for these 2 tags are fixed:
EXIF:GPSVersionID
EXIF:GPSMapDatum
The values shown here are examples.
EXIF:GPSLatitudeRef
EXIF:GPSLatitude
2 2 0 0
WGS-84
N
51.5120877998972
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