When photography which is an art, intersects technology which is…not an art what do you get? You get some weird buzz words. Today’s star is Geotagging ! Think of it as Geographic Tags, or Geographic keywords. The thing that makes it weird is that GeoTags are actual coordinates, so they’re not related to tags or keywords at all. They’re not keywords…’cause they’re not even words.
What is Geotagging anyway?
Complicated buzzword, simple explanation. Geotagging means adding geographic location information as part of image metadata. So far there are two kinds of metadata (Read Image metadata definitions) that can be associated with an image: technical metadata and content metadata. For technical metadata we have the EXIF standard while for content metadata we have the IPTC/XMP standard. So, what about geotagging? It’s still metadata and as such it should fit in these formats.
Here is an easy way to remember the difference between EXIF and IPTC: EXIF metadata is intended for machines while IPTC metadata is intended for humans.
The interesting thing about both EXIF and IPTC is that they both contain geographic location data. However, the geographic data has different meaning in keeping with the kind of metadata each standard represents. EXIF is interested about technical information and it contains GPS information like Latitude, Longitude and Altitude. On the other hand the geographical information contained in IPTC has Country, City and State/Subregion which has to do with the content of the picture (more or less).
Place GPS location information into the EXIF metadata.
GPS information should be added in the GPS Information section of the EXIF metadata. Below you find the most commonly used GPS data fields in the EXIF metadata portion. You would probably really care about items 2 through 5, because that’s all you need for adding precise geotagging.
- GPSVersionID – 188.8.131.52 – this is the EXIF version supported by your camera or software.
- GPSLatitudeRef – N – This is the latitude reference, in this case North. It can be North or South.
- GPSLatitude – 51 12 33 – This is the latitude in degrees/minutes/seconds.
- GPSLongitudeRef – E – This is the longitude reference, in this case East. It can be East of West.
- GPSLongitude – 3 13 30 – This is the longitude in degrees/minutes/seconds.
- GPSAltitudeRef – Sea level – This is the altitude reference. In this case sea level.
- GPSAltitude – 30m – This is the actual altitude
- GPSTimeStamp – 10 10 18.00
Place literal geographic information into the IPTC metadata fields.
These is geographic information that is expressed in words :) instead of coordinates. GPS information matters only to computers and GPS devices and mean little to people. Geographic information that has words in it actually makes sense to humans…that’s what IPTC is for. The IPTC fields that are intended to hold geographic information are as follows:
- State/Subregion=Ile de France
It is true that you can use the
Keywords field in IPTC and include all the geographical information in there as well. However, these are the fields IPTC has intended for holding geographical data. I personally don’t use these fields and use only the
Wait…but how do I do this?
The short version is that if you don’t have any of automated GPS receivers that you can attach to your camera (see wired.com article link below), you have to obtain GPS information yourself and write it in the EXIF fields. And of course you need some software for that…both for getting the GPS information and for writing in the EXIF fields.
Here are some suggestions for applying geotags to your images:
- Buy a compact camera with a built in GPS like the Canon Powershot SX260. These cameras can write GPS location to EXIF portion of the pictures right when you shoot the picture.
- Get a regular GPS and see if you can sync the lat/long with your images once you transfer them to your computer. This is not easy however.
- Use some software like Picasa that allow you to point on a map and transfer all that information to the EXIF and IPTC fields. This is pretty cool I say !
Also take a look at this article from Wired.com. There is an SD card that can get GPS coordinates directly into your camera and write them into the EXIF…so you don’t have to do it manually.