Stephen Shankland of CNET.com has been writing a number of stories about "geotagging"--that is, organizing photos by location. This can be done manually on a site like Flickr; you drag your photos onto a map and thereafter they stay associated with that location. This can be handy if you're looking for pictures of, say, the U.S.S. Constitution, it makes as much sense to look for photos by location as by keyword. And, if the keywords aren't obvious or unique, it may make a lot more sense.
That said, manually tagging things is a pain and, if one doesn't have obvious geographical features in the photo, it may be hard to locate them exactly on a map. So--how about marrying GPS data to the photos? It's a sound idea, it's doable, but it requires a slightly convoluted workflow as the technology stands today.
Here are my experiences from last weekend during which I took a little hike around Leominster State Forest in Massachusetts as an opportunity to conduct my first geotagging experiment. I used a Garmin 76CS GPS unit in combination with my Canon Powershot G5 camera. Flickr is my photosharing site of choice, so I'll be describing procedures specific to there.
1. Make sure that the time on the camera and GPS are synced up. I've been trying out using GMT on my camera rather than local time. That has its pros and cons but, for this purpose, it's simpler to have your camera set to the same local time as the GPS unit (i.e., if your GPS is observing Daylight Savings Time, make sure that's consistent with how your camera is set). Having the two gadgets on the same page is important because the time represents the common thread between the GPS data and the photos.
2. Turn on your GPS and set the track log on. For this to work, the GPS unit has to stay on and be attached somewhere that it has a good view of the sky. You can't stick it in your backpack or turn it off to save batteries.
3. Enjoy your walk or bike.
4. When you get home, it's a good idea to make sure Flickr is configured properly before doing anything else. What's next isn't obvious (Thanks Stephen!). Select the "You" drop-down menu under the Flickr logo. Go to "Your Account," then the "Privacy and Permissions" tab. "Import EXIF location data" must be set to "Yes." You may also need to change some of the other privacy settings if you want others to see your geotagging. Note that this step must be done before importing.
5. Now you need to get your track data off the GPS. In the case of Garmin, the track data is in GPX format; these are XML files that associate a time stamp with a location stamp. When you connect your GPS to your computer, the computer may see your GPS as a drive--in which case just copy the GPX files to a directory on your computer. In my case, the Garmin 76CS didn't show up as a drive so I used a handy little free (donations accepted) utility called GPSBabel to pull down the track data. (GPSBabel also does all manner of format conversions but I didn't need to do anything that complicated.)
6. Next, I used a program called Downloader Pro to download the photos from my camera and merge them with the GPS data. I've used Downloader Pro for a while; it lets you very flexibly rename and organize your pictures as you load them onto your computer. For our current purposes, it also lets you point to a directory containing track files. If a photo was taken within a user-defined time threshold of a GPS track data point, it will write the GPS coordinates to the photo's EXIF data. (I haven't experimented to figure out the details of how the program interpolates between data points or otherwise figures out the exact value to write.)
7. Now, do whatever image cleanup, editing, etc. you like with your photos and upload to Flickr. If you managed to avoid some of the pilot error mistakes I made along the way, your results should look like this.