Why geotag photographs? For me the benefit is identifying where I was when I took the picture. It is nice to name the places in the image. Particularly years after I took the picture. Below are the methods and software I use to geotag and later to geocode my photographs.
To start with, what is "Geotagging" and "Geocoding"? Geotagging is the process of embedding the geographical coordinates of where the picture was taken into the EXIF data of the image. Some cameras have GPS support built in adding coordinates immediately when the taking the picture. On camera GPS support is still rare but becoming increasingly popular. Other cameras can use the trip tracks captured by GPS Data loggers. Geocoding is the additional process of taking the geographical coordinates and adding place names to the EXIF data. Typically this is the country, city, state, and possibly a sublocation. For this discussion we are considering only DSLR support.
Geotagging images can use either built in camera GPS support or an external GPS data logger. Having built in GPS support is the most convenient. The GPS Digital Camera link has a good discussion with pros and cons.
On Camera GPS Receivers
The major issue is where the GPS receiver is power. Nikon was the first DLSR vendor to actively support geotagging. Proving that the leader can always be identified by the arrows in their back, Nikon caught a lot of flack because they used the camera battery for GPS power. Under normal circumstances this is not an issue. In an urban environment we are actively shooting fot the duration of an event. GPS probably isn't necessary for the event anyway.
The problem is our expectations. We expect that a fresh battery will support hundreds if not thousands of shots. When on safari we expect a fresh battery to last all day. While hiking through the wilderness we finally, after many hours, came across a terrific critter picture. We raise the camera . . . and shoot blanks. With no notification the GPS sucked the camera battery dry. Canon and likely all other vendors, including Nikon, will use separate battery supplies for GPS receivers. In a choice between camera or GPS, most would prefer the camera work as expected. GPS coordinates are not critical.
Unquestionably, with a separate battery supply, on camera GPS support is the way to go. The image will be tagged with GPS coordinates within 50', typically less than 20',of the actual location. There is no fussing with the actual camera clock time or time zone offsets required to geotag photos from GPS tracks.
Geotagging using GPS tracks
Devices with a screen to display a map are commonly called mapping loggers. The dominant vendors are Garmin, TomTom, Magellan, and DeLorme. Any of the handhelds with a 12 to 18 hour battery life are acceptable. A variety of models are available to suit any budget. They all support downloading GPX tracks to a computer.
Alternatively, there are a huge number of GPS data loggers on the market. Data loggers have the advantage over handheld GPS devices of being lighter, smaller, and longer battery life. Many of them have Blue Tooth support for smart phones and tablets giving improved accuracy and battery life. After trying several different vendors I settled on the qstarz bt-q1000xt. It is rock solid and reliable. They are easily attached to a camera strap using a key ring.
Geotagging software identifies the image location by comparing the time recorded in the image EXIF field with the GPX track time from the data logger. The first challenge is data logger time is always Greenwich Mean Time (GMT). Camera time is generally set to somewhere else in the world. Or not, depending on whether your camera's time was ever set. Here are the steps to geotag images:
- Here is the first opportunity to minimize the time required to accurately geotag images. At the start of the trip synchronize the camera clock to the nearest second. If there isn't a mapping GPS device available then use a phone before leaving civilization. Try to get the camera clock to the nearest second. Geotagging software will ask for a time zone offset from where the images were taken from Greenwich Mean Time (GMT. One solution is to set the camera time to GMT and forget about the offset. That solution has disadvantages. For instance, in the Marshall Islands lunch time would appear to be midnight. But if the camera is set to an arbitrary time, then much time is spent determining the odd offset to GMT trying to place the image where you know the image was captured. In Dallas the GMT offset is -6 hours (-5 hours DST) and Yangoon it is +6.5 hours. Set the camera to the nearest second before taking pictures!
- Export the data logged track files to GPX tracks. In some cases the data logger vendor will provide the software. In other cases a hard drive mode can be acitvated when attached to a USB port. This allow copying files directly to the computer.
- The next step is to insert the coordinates from the GPS tracks into the EXIF data in the images. Geotagging Software is very popular. Geosetter seems to be the best free tool that has raw file support. Photomechanic writes coordinate data directly into RAW files which I find helpful. Then there is Adobe Lightroom, the elephant in the room. Release 4 will now geotag and reverse geocode the coordinates to populate the sublocation, city, state and country fields.
- Reverse geo coding is still a work in progress. It is harder because a call must be made to an external database such as Google to extract the place names. Photo Mechanic is thinking about developing support. It looks like Geosetter now provides support up to the City level. They have made progress in the last few years that I need to look into. Lightroom now provides the best support.
But Lightroom writes the data into a "shadow database" and not directly into the EXIF data. The information can be committed but only one sublocation at a time. Or Jeffrey’s “Geoencoding Support” Plugin for Lightroom can be used. Jeffrey makes a living augmenting Adobe software shortcomings. I have several of his plug-ins. They have all worked flawlessly. I typically donate $20 for plug-ins I use. After reverse gecoding Burma pictures a couple days I succumbed to Jeffrey's offer. It saved a lot of time.