November 8, 2007
Geocoding Your Photos with Lightroom and HoudahGeo
Source: Lightroom Journal
Author: Eric Scouten
Earlier this year on Lightroom-news we brought you news of how to use GPS metadata in Lightroom to link to Google Maps and Google Earth. Ian Lyons of Computer-Darkroom mentioned how on a trip to Antarctica he used the LoadMyTracks and GPSPhotoLinker software to take the GPX data from his GPS device and synchronize this with the capture files he had imported to Lightroom. I was going to post a follow up story myself showing how this could be done using the above software programs. But meanwhile, Eric Scouten of the Lightroom team has posted a tutorial showing how to accomplish the same thing, but more simply by using the HoudahGeo software
Eric writes:
I’m kind of a metadata addict. And a map junkie. So it should be no surprise that I’ve been waiting for a long time for a program \to help me mark up my photos with the exact location of capture. I was very happy to learn this spring of a new application called HoudahGeo. Most of the geocoding apps I’ve seen before only write to JPEG files. HoudahGeo actually works directly on PSD and DNG files, among others, meaning I can actually mark up my master files instead of a derivative.
HoudahGeo is available only for Mac OS, and I’m not aware of any plans to make a Windows version available. I haven’t looked for a similar Windows application, but the tips below regarding how it would interact with Lightroom should apply if so. (Please add a comment if you’re aware of a good counterpart for Windows.)
In the Field
If you have a hand-held GPS unit that you can carry with you, the main thing you need to be concerned with is ensuring that your GPS and camera clocks are in sync with each other. Spend the time to get your camera within a minute or less of the GPS clock. If it’s not the same time zone, that’s OK; you can take care of that later.
And, of course, you need to have your GPS running while you’re shooting. I keep mine permanently tethered to the outside of my camera backpack. When I’m packing, I simply put the GPS in an outside pocket, leaving the tether cord in place. When I take the camera out of the pack to start shooting, I pull the GPS out, turn it on, and run its tether through the top handle on my camera bag so it’s not dangling. As long as the camera backpack stays on my back, I’m logging my location continuously.
Downloading Data
How you download data will, of course, be dependent on the make and model of your GPS unit and the software that comes with it. HoudahGeo claims to be able to read directly from the GPS unit. I like to keep the original GPS track log files, so I haven’t tried this feature myself. What is important is that you wind up with a GPX file. GPX is a standard interchange format for GPS marker data; you should be able to save to that format from whatever software comes with your GPS unit. The MapSource software that comes with my Garmin GPS can generate GPX files through its “Save As” menu item.
When you’re downloading data from your GPS, you should take a moment to look for bogus data in your track logs. Whenever you move with your GPS unit turned off (even a short distance), it will generate a lot of noise when you first turn it on again. (For example, see this rather improbable traversal of 105 miles in northern Minnesota that I supposedly accomplished in 30 seconds.) HoudahGeo isn’t able to sort out this errant data, so any photos taken shortly before or after turning on your GPS might get tagged with wildly incorrect locations. Take the time to use your GPS software to delete these incorrect data points.
Once you have a cleaned up GPX file, you’re ready to go!
A Caution
I generally convert all of my camera raw files to DNG as part of my import workflow. I’ve only occasionally used HG with original RAW files, and the results were not quite what I had hoped. If possible, I recommend using PSD, JPEG, and DNG files instead; I’ve done thousands of these files successfully.