GPS Synchronizing
I’ve recently been asked a little about GPS and Geotagging. Geotagging is the process of encoding the the location you took the photo (latitude and longitude) into each images’ EXIF data. Flickr, as well as a few others will use this information to place your image on a map.
So, you open one of the many tools out there to meld a GPS tracklog and JPEG image. The software takes location information the GPS (called a tracklog) and cross references each image against the time stamp in the track log and comes to a conclusion. But, have you thought that perhaps your Camera and GPS clocks are not exactly synchronized? Sure, you don’t need them perfect, but we would sure like to keep them as close as possible. Without GPS/Camera clock synchronization you could be encoding your images with location data that is minutes or even hours off! It all depends on how far the clocks in your devices are from each other.
There’s hope. If you don’t mind getting close you can make sure your clocks are set every time you start a photography session you intend to Geotag. Or, what I do is make sure I take a photograph of my GPS showing the time of day down to the second. At least all of the Geotagging programs I saw let me compensate for devices that are not perfectly synchronized. Open the image you took of the GPS clock, look at the image timestamp and do the math. Simple, done, and no fussing around complicated menus to set the clock on these devices each time you leave.
Some companies make a clip-on GPS unit with no display. They only record tracklogs (position and time, usually every so often) and can be retrieved via USB. While nice, they’re not much cheaper than a basic trail GPS with basic waypoint capabilities (no mapping). I say don’t worry about these unitaskers, get one with an LCD – who knows when you’ll want the GPS for hiking or other purposes?
-J
About a year ago when I first heard of geotagging I was also considering to buy a GPS data logger without a display, but I’m glad I didn’t. My iPhone 3G is now tracking my locations during my photoshoots. It’s a device I always carry with me and the app I use works as expected.
More info: http://www.galarina.eu/GeoLogTag/How_To.html
Thanks for this article, very interesting. I did a lot of research before I bought a system for my geocaching. It is such a fun hobby. What receiver do you use? Click here if you’d like to check out my site. Thanks again for a very educational site!