Geotagging adds geographic location data, specifically latitude and longitude coordinates, as well as city and state details to photos you take with your camera and Eyefi card via the Eyefi Geotagging service. The location metadata (or geotag) can then be used by applications to show and share where a photo was taken. The Eyefi Geotagging service adds geotags to a photo in one of two ways, depending on the type of file used: geotags in JPEG photos are stored in photos' existing EXIF data, while RAW files include an XMP sidecar file.
Using WPS to determine location
Eyefi cards use Wi-Fi Positioning System (WPS) for geotagging purposes. While similar, WPS is not the same as Global Positioning System (GPS), which is used in most location devices. WPS uses surrounding wireless networks to triangulate the location where the photo was taken, unlike GPS, which uses satellites.
Many things must happen for the latitude and longitude to end up in the EXIF data of a photo. First, a camera captures the photo. An Eyefi card detects any Wi-Fi networks in the area and records the MAC addresses of each one while not actually connecting to them. The MAC addresses are stored in the Eyefi card with the picture until it uploads the photo. Once the Eyefi card comes into contact with a configured wireless network and the photos begin transferring, the WPS data is sent to the Skyhook WPS service. At that time, the Skyhook WPS service translates and triangulates the WPS data to determine latitude and longitude. Skyhook then sends this information back to Eyefi's servers, which write the latitude and longitude to the photographs EXIF. At this point, the photo is delivered in its entirety to your computer or online photo sharing web site.
Geotags in JPEG photos
Desktop applications such as Apple iPhoto, Adobe's Photoshop Elements, Google's Picasa, Ovolabs Geophoto, and Microsoft's Pro Photo Tools can take advantage of geotagged photos and even allow you to edit or change the location data associated with an individual or group of photos.
Many online photo sharing services offer varying degrees of support for geotaged photos. Some simply display the city and state information from the EXIF metadata. Others such as SmugMug, Picasa and Flickr provide users ways to view and organize photos by location, letting you view maps of where you took your pictures.
Geotags in RAW files
When Eyefi geotags a RAW photo it creates an XMP sidecar file. The geodata is stored in a separate file with the same base name as the photo. For example, if the RAW file name is DSC_6543.NEF, the XMP sidecar with the associated geotags will be stored in a file named DSC_6543.XMP.
You will need a third-party application to use the geotags in the XMP file. Adobe Lightroom and Apple Aperture both support XMP sidecar files and are capable of displaying the geotag data included in an XMP file created by Eyefi. In order to view the geodata for a RAW file, you will need to import or open the associated XMP file along with the original RAW file.
Note: You can only geotag RAW images on a computer. Eyefi will not create XMP files when uploading RAW images to an FTP server, Eyefii View, or Evernote.
Geotagging on mobile devices:
The iOS app from Eyefi currently does not geotag photos in any capacity, whether through Wi-Fi positioning or the phone's GPS.
The Eyefi Android app can geotag photos using the phone's GPS. This feature is only available for Eyefi cards that support geotagging.
When you take a photo on your phone or tablet, your device geotags that photo; later, when you use the Eyefi app to transfer that photo to your computer, Eyefi will also send that geotag data. However, images that are transferred to an iPhone or iPad from a camera through the Eyefi app will not be geotagged on the device.
If a phone or tablet is set to automatically upload images it receives from an Eyefi card to the computer, the Eyefi servers or Eyefi Helper software will attempt to geotag a photo before delivering it to the computer (just as it would if the image was transferred directly to the computer). Please note that iPhones and iPads do not geotag photos, so if you manually share the image later there will not be any geodata.