Geotagging devices

Kattintson ide a magyar változatért

What is a geotag?

Tagging the photos with geographical coordinates is not a new thing, but it only starts to become easily available for most of us, regular users. Many of the currently available mobile phones provide this functionality out of the box. The ways to use these tagged photos is only limited by our imagination, and nearly all of the popular imaging services, including Facebook, Flickr, Google Earth and Panoramio support these tags. We can see that most of these applications fall into the social networking category, as geotagging makes the most sense when we share our photos with others. In private use geotagging can help us identify location of a street or a motif we photographed during a day long photo walk.

How do photos get the geo tags?

Generally the coordinates can be written into the files in two different ways:

• the device (in our case the camera) captures the coordinates and writes them into the EXIF header of the file
• the captured coordinates written into the files later by a software on a computer or a dedicated device.

In the first case the camera needs to know where it is at the moment of exposure. In most cases we need an external GPS receiver for that, but some cameras come with these built in (e.g. Nikon Coolpix P6000 or the recently announced Sony Cyber-shot DSC-HX5). If ease of use or comfort is a main issue, these cameras are hard to beat.

In the second case we have two options:

• the data is recorded at the time of exposure, and written into the image file later
• the position is logged continuously by the GPS logger, and the software looks up the position of the image in the log based on the time attribute.

In the second case time or time zone differences between the unit and the camera can cause serious positioning problems, therefore it is one of the most time consuming and most uncomfortable method. Despite of that, it holds some serious advantages. Since it records the position in every certain seconds or after so many meters of movement (depending on the settings) the logs can be used to trace the path of the photographer as well. In fact, the logs can be used to tag the photos of many tourists e.g. visiting a city together (assuming they move as a group and stay within a few meters of each other).

There seem to be a vast selection of Geo tagging softwares out there. We have decided to use TripPC and Locr GPS Photo for the GPS loggers, while some of our devices like the Jobo Photo GPS and the Eye-fi card came with their own software.

Tested devices

We have tried to select many different types of devices for the test. We had two GPS units attached directly to two DSLR cameras, a device that recorded GPS satellite signals at the time of exposure, and three GPS loggers. A Nikon GP-1 and a Foolography Unleashed were attached to a Nikon D300s and a D300 respectively. Jobo's Photo GPS was used to record signals of selected moments, while a Sony GPS-CS3, a MobilAction Technology I-GotU GT120 and a Qstarz Travel Recorder were used to constantly log our movements.

Although technically it is not a GPS device, the wi-fi enabled Eye-fi cards (when the necessary service is activated) can determine their position from the signals of available wi-fi access points. The technology is similar to the one used on GSM phone networks to determine location by triangulation. Obvious disadvantage of this technology is that it is only useful where hot-spots are available. It can work well in crowded cities, but hopeless in rural areas.