The hidden information in your photos that you probably aren't aware of
In last month's issue ("Dangerous Information Hidden in Your Digital Photos, Part 1" http://kadansky.com/files/newsletters/2011/2011_12_29.html) I wrote about how your GPS-equipped smartphone camera (or digital camera) may be storing your physical location in the "metadata" of every photo you take. I described:

• How location metadata (also called "geotags") stored in your photo files reveals where you were when you took each photo, along with the date and time and other information.
• How this information is stored as latitude and longitude, and how easy it is for anyone to translate those numbers into a street address.
• How dangerous it may be for you to post such photos online, or email them to anyone, or if your computer (or its backup) is compromised or stolen, because identity thieves, burglars, stalkers, pedophiles, and others may then exploit this location information to learn where and when you and (your family) spend your time.
• How you can probably turn off the GPS unit in your phone or camera to prevent it from putting this information into future photos you take.

So, now that you've learned how to avoid geotagging photos you take in the future, the next step is to deal with the photos you've already taken that may contain location metadata.

How can you find out if your existing photos contain location metadata?
When you open a picture file on your computer, you normally only see the image. In order to see the metadata, you have to dig a little deeper. Some picture display or editing programs may not be designed to show metadata at all, and others may not show the geotags.

The technical term for the way metadata is stored in JPG image files is Exif - Exchangeable image file format. This is a standard dating back to 1995 that defines a broad array of "tags" that may be present in the metadata, including date, time, resolution, model of phone or camera, flash mode, f-stop, etc. For our purposes, there are many GPS-related Exif tags, but the most important ones store the GPS location information in latitude and longitude.

I have not yet found an easy-to-use program that scans all of your photos and tells you which ones have geotags. What I have found are some labor-intensive ways that you can look at the metadata in a small sample of photos to see if they contain geotags:

• Windows Vista and Windows 7: Right-click the file, click Properties, click the "Details" tab. Scroll down and look for a "GPS" section. If it's there, you'll see the photo's Latitude and Longitude.
• Windows XP: I could not find a built-in function to do this in XP. See "Jeffrey's Exif viewer" web site, below.
• Macintosh: Open the file in the Preview program, then click the Tools menu and choose "Show Inspector." If you see a "GPS" tab, select it to see the Latitude and Longitude. You can then click "Locate" and you'll see the exact street location on Google Maps (http://maps.google.com). You can also drag and drop a folder onto Preview to inspect multiple files in a single window.
• Windows or Macintosh: If you upload a JPG file to "Jeffrey's Exif viewer" web site at http://regex.info/exif.cgi it will show you the file's metadata, including any geotags.
• Windows or Macintosh: If you're already using Google's Picasa software (http://picasa.google.com), it can display a picture's geotags, but I wouldn't install Picasa just for this purpose since it's a large, complicated, and intrusive program.

How do you remove location metadata from your existing photos?
Similarly, I have not yet found an easy-to-use program that removes geotags with all the features I would like. I've tested many programs, each with a different combination of good and confusing features. Here is my bottom-line advice:

• The most efficient (and least-confusing) approach is to use a program that removes geotags (and other metadata) from your picture files by directly modifying them in-place, as opposed to making copies of your files with slightly different names and then modifying the copies.
• Therefore, before running any program that (depending on how you use it) may modify every photo stored on your computer, be sure you have a good backup system in place. It's not likely, but if something goes wrong, every one of your photos may be at risk.
• Decide whether you want to remove geotags from every possible picture, or only from pictures in a particular set of folders, or only from a handful of pictures.

With that in mind, here are the programs that I've found that seem to do the job, given the limited amount of time I've had in which to test them:

• Windows (all versions from 98 to 7): BatchPurifier LITE (http://www.digitalconfidence.com/downloads.html) - This free program only cleans JPG files (the $19 full version cleans metadata from 20 file types, including Microsoft Office files and more). Drag and drop your picture files or folders into the main window, then click "Next" and choose the "Including subfolders" and "Overwrite original files" options. It will change the modification date and time of all files it processes.
• Macintosh: SmallImage (http://www.iconus.ch/fabien/products/sieng/sieng.html) - This free program only cleans JPG files. Turn off the "Recompress" and "Scaling" options; leave the "Add Suffix" option ON but remove the suffix text ("-small") so it will overwrite your files (not create copies). Drag and drop your picture files or folders into the main window, then click "Process."
• Windows or Macintosh: If you're already using Google's Picasa software (http://picasa.google.com), it can remove a picture's geotags, but I wouldn't install Picasa just for this purpose since it's a large, complicated, and intrusive program.
• Windows or Macintosh: ExifTool (http://en.wikipedia.org/wiki/ExifTool) - This free but complicated command-line tool can do almost anything - scan an unlimited number of picture files and report which ones contain geotags, remove them, and even preserve each file's modification date and time - but the price of its power is its complexity.
• iPhone: ExifRemover (http://itunes.apple.com/us/app/exifremover/id438392458?mt=8) - Available from the iTunes App Store for $1.99, the description says it makes "cleaned" copies of your photos inside your iPhone, but I have not tested it.

What about the photos still in my smartphone or camera that have geotags?
My advice is to transfer those photos to your computer, examine and clean them as I've described above, and then delete them from your phone or camera.

What about photos I've already posted online?
It's complicated. Some online systems like Facebook apparently strip all metadata from the photos you upload to them. While this helps protect your privacy by removing any geotags, it also has many people complaining that their Copyright metadata are being removed for no good reason. Other photo-sharing systems like Flickr encourage geotags to provide interesting photos of specific places in the world, but they also give you the option to remove geotags when uploading photos.

My advice is:

• Ask before uploading: What metadata do they remove, if any?
• If you're concerned about this issue, don't rely on someone else to remove your metadata, remove it yourself before you upload.

Conclusions

• While this is a somewhat complicated issue, there are steps you can take, not only to find out whether your privacy is at risk but also to do something about it.
• There are software tools to help you check your photos for hidden location metadata ("geotags") and to remove them.
• Some photo-sharing sites already remove metadata, but don't assume they all do. Be a careful consumer and ask!

Where to go from here

• Whether they contain location metadata (geotags) or not, the photos that you post online (or email to other people) reveal information about you, your family, your hobbies, your possessions, your work, where you spend your time, and more. I recommend that you review everything you put on the internet (photos, text you've written, audio and video clips you've recorded, etc.) and ask yourself: Beyond geotags in your photos, what information are you posting online? What does it reveal about you, your family, your habits, and your life that may put your privacy and your safety at risk?
• See last month's issue for more about this problem: "Dangerous Information Hidden in Your Digital Photos, Part 1" (http://kadansky.com/files/newsletters/2011/2011_12_29.html)  
• "The Top 12 Myths about Embedded Photo Metadata": http://www.controlledvocabulary.com/blog/top-metadata-myths.html 
• http://en.wikipedia.org/wiki/Exif 
• http://en.wikipedia.org/wiki/Geotagging 

If you're confused or frustrated by something on your computer, I like to say, "You can do it!" You might just need a little encouragement, or information, or change of perspective, and that's where I come in.

How to contact me:
email: martin@kadansky.com
phone: (617) 484-6657
web: http://www.kadansky.com

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I love helping people learn how to use their computers better! Like a "computer driving instructor," I work 1-on-1 with small business owners and individuals to help them find a more productive and successful relationship with their computers and other high-tech gadgets.