“Any sufficiently advanced memory card,” Arthur C. Clarke once didn’t write, “is indistinguishable from magic.”
But if he had written it, he could have been referring to the Eye-Fi Share card. It’s a 2-gigabyte memory card ($100), compatible with most digital cameras, with a twist: it has Wi-Fi networking built in. Each time you bring your camera home to your wireless network, it transmits your photos back to the computer, automatically and wirelessly. It can also upload them to Flickr, Picasa or another online photo-gallery site, automatically and wirelessly.

What’s the point? First, you’re saved the trouble of finding and attaching your U.S.B. transfer cable. Second, you skip the multi- step hassle of manually uploading the fresh pictures to a photo-sharing site.

Finally, there’s an enormous showoff factor, both for you and for the manufacturer. How on earth did they fit Wi-Fi circuitry into a regular-size SD card, which could hide behind a postage stamp?

In any case, this week, a new model arrives with an even more amazing trick up its sleeve.

You know how your digital camera gives every photo an invisible time and date stamp? Well, the Eye-Fi Explore ($130) card invisibly stamps every photo with where you took it.

That’s right: photo geotagging has finally come to a camera near you. Noting what photo was taken where used to require either tedious manual data entry or expensive add-on gear. Now it comes cheaply and automatically.

Once on your Mac or PC, each such photo shows the city and state where it was taken. You can also click to view either a street-map view or an aerial photo, clearly showing where you were standing when you pressed the shutter button. At long last, technology has reached a point where we don’t need to write “Eiffel Tower, 1988” on the back of the print as a reminder.

Photo Web sites like Flickr, Picasa and SmugMug can display these maps, too. Certain desktop photo programs, like Photoshop Elements 6, Picasa and (for the Mac) Ovolabs Geophoto.

Now, that’s a pretty interesting trick. But finding out how it’s done is even more interesting.

No, it’s not G.P.S. Even the Eye-Fi people can’t yet shrink a G.P.S. receiver to fit the sliver of an SD card.

Instead, this card incorporates a new technology, a rival to G.P.S., called W.P.S.—Wi-Fi Positioning System. A company called Skyhook came up with it. (Skyhook’s first well-known client was Apple. The original iPhone doesn’t have actual G.P.S., but it does have Skyhook’s “locate me” feature.)

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Understanding how Skyhook works requires slogging through some tech talk. But it’s fascinating, and it’s also the key to the Eye-Fi card’s strengths and limitations.

At this moment, more than 70 million Wi-Fi base stations are sitting in homes, offices and shops. Each broadcasts its own name and unique network address (called its MAC address — nothing to do with Mac computers) once a second. Although you’d need to be within 150 feet or so to actually get onto the Internet, according to Skyhook, a laptop can detect this powerful beacon signal from up to 1,500 feet away.

Metropolitan areas today are blanketed by overlapping Wi-Fi signals. At a typical Manhattan intersection, you might be in range of 20 base stations.

Skyhook’s big idea: If you could somehow correlate those beacon signals with their physical locations, you could pinpoint your own location, G.P.S.-style, but without G.P.S..

To that end, 500 full-time Skyhook employees have spent the last five years driving every road, lane and highway in every major American city —and, lately, European and Asian cities. Its equipment measures all those Wi-Fi signals leaking out of homes and stores and offices, and marries that information with the car’s G.P.S. location as it drives.

(Note: At no time does this equipment, or any iPhone or Eye-Fi card, actually connect to these base stations. They’re just reading the one-way beacon signal, which is broadcast even by password-protected base stations.)

So far, Skyhook’s database knows about 50 million hot spots—and the precise longitude and latitude of each.

And that’s it. Now any Wi-Fi gadget equipped with Skyhook’s software, like the iPhone and the new Eye-Fi card, can get a fix on its own position, accurate to around 100 feet.
As a bonus, the Skyhook system is self-healing. Suppose, for example, you’re standing on the street in Brooklyn. Your iPhone recognizes six Wi-Fi base stations around you — but one of them, according to the Skyhook database, is supposed to be in Connecticut.

Clearly, somebody moved (or moved the base station). Skyhook’s software says, “Well, the other five base stations are right where they’re supposed to be, but that sixth one looks suspicious. I’ll update my records to show that it has been moved to Brooklyn.”

Skyhook’s biggest weakness is coverage. The 50 million hot spots it knows, the company says, is enough to cover 70 percent of the populated areas in the United States and Canada, and 50 percent of Europe. But that means that the Eye-Fi card draws a blank in some of the situations when you’d most want a location fix for your photos: hiking, skiing, camping, boating or traveling abroad. These are places where you’re not likely to find any Wi-Fi signals at all.

(If that prospect bothers you, consider the $150 G.P.S. Photo Finder from ATP instead. After taking some photos, you slip your memory card into this tiny box, which stamps each picture with your current G.P.S. location. It’s more trouble than the Eye-Fi system, but at least it’s real G.P.S.)

On the other hand, Skyhook’s biggest strengths are how well it works indoors and how fast it works — one second for a fix. That makes it a perfect complement to G.P.S., which works terribly indoors, if at all, and can take up to a minute to find you.

(Indeed, the new iPhone, coming July 11, incorporates both G.P.S. and Skyhook. It even has a third location system, developed by Google, that pinpoints your location by studying your proximity to cellphone towers. That iPhone will really know where you are.)

Apart from the new geotagging feature, the new Eye-Fi card is the same as its geographically impaired predecessor, which is to say that it has the same downsides. For example, the card sends only JPEG files, not movies or RAW files. You can’t choose which photos to upload; the card always sends everything.

Two traditional Eye-Fi drawbacks, though, have been fixed. Formerly you never knew when the card was finished transmitting photos; now, Eye-Fi can send a text message to your phone when it’s safe to turn off the camera.

Nor are you limited to your own home hot spot anymore. For $15 a year, your card can use any of Wayport’s 10,000 commercial hot spots in the United States, or indeed any hot spot that’s completely open (no password, no welcome screen). The first year is free with the Explore card.

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There’s a lot of great technology at play here. The Skyhook network, incomplete though it may be, is just wickedly clever — you can’t believe that it works, let alone works so well, at least in the 8,000 cities it covers.

Skyhook technology is also available in AOL Instant Messenger, so you can see where your chat buddies are; in location-based games like Plunder and AreaCode; and in software like Trapster, which lets drivers report speed traps when they see one — and then Trapster-equipped drivers following behind are warned on their cellphones. There’s even a browser toolbar that lets you try finding yourself: loki.com.

And when the Eye-Fi card’s pictures do arrive on your computer, being able to see where they were taken is more than a novelty. It’s a huge leap forward in the art and the utility of digital photography.

source : http://www.nytimes.com