They Know Where You Are

Once in New York, the Explore found its footing again. It put photos from a Midtown stretch of Park Avenue and the Brooklyn Heights abode of two friends within a few dozen yards of their actual locations and was almost as accurate with pictures taken outside the Harlem apartment of another couple.

But Eye-Fi placed shots from inside the Harlem apartment three miles south. The spot it pinpointed looked suspiciously familiar -- as it should have: Those friends lived in that location (on the Upper East Side) until late last year.

Explaining that coincidence, as well as the Explore's flubs on the train, requires some detail about how this card and its software cooperate to put your photos on the map.

The card first records the unique signatures of any nearby wireless networks -- the anonymous media access control (MAC) address encoded in every networking device. Once it uploads your photos, Eye-Fi runs those MAC addresses through a database of WiFi networks compiled by a Boston firm, Skyhook Wireless, that sends cars with WiFi and GPS sensors down one street after another through parts of North America, Europe and Asia.

The limits of Skyhook's database -- also employed by Apple's iPhone and iPod Touch -- restrict the reach of the Eye-Fi's geotagging. When it contains limited, out-of-date information -- say, if Skyhook's record of my friends' wireless network dated to their old apartment -- the system can give an incorrect identification.

And if the Explore can't sniff any wireless networks at all, its software has to give up. That alone rules out Eye-Fi's card for many trips, inasmuch as a basic reason to go on vacation is to escape the clutches of the Web.

For those travels, a camera with a Global Positioning System receiver might make a lot more sense but would cost too much and consume even more electricity.

And yet, the electronics industry can do an amazing job of cutting costs and extending battery life when it must. Someday, all digital photography will work like the best parts of my Eye-Fi experience -- and our cameras may remember more about our trips than we will.

Living with technology, or trying to? E-mail Rob Pegoraro atrobp@washpost.com. Read more athttp://blog.washingtonpost.com/fasterforward.