Many a traveler can't get much farther than the end of the driveway without his GPS navigation system up and running. But ask that wayward traveler to venture indoors and things are likely to break down entirely.

Because of the intricacies and delicacy of satellite communications, traditional GPS simply doesn't work indoors -- nor, as you're likely to know already, does it work in tunnels, and it often fails if you're standing next to a tall building or, God help you, under the limb of a shady tree.

The industry has come up with workarounds to help drivers keep some semblance of signal when they experience intermittent interruptions outdoors, but no one so far has come up with a way to let GPS keep working when, say, you're wandering around the mall.

But that's essentially what Finnish developers at the Kamppi shopping center in Helsinki have done, pioneering a system that lets you use a GPS-like technology to orient yourself within the building, where typical GPS can't reach at all.

The system is a lot like Assisted GPS in design, which uses cell phone towers to fill in for satellites when they're out of range and unavailable. In the Kamppi test project, however, the mall uses Wi-Fi transmitters to triangulate the location of the shopper. The shopper uses his cell phone to figure out his location, which is cross-referenced with a map loaded on the phone. (How this data gets to the phone isn't disclosed in the linked story; presumably shoppers will need to download a special application including the map and the triangulation software for their phone -- a Nokia, naturally -- to make it work.)

This isn't the first time such a technology has been attempted. The original iPhone had a faux GPS system driven by triangulating Wi-Fi signals that worked much the same way, though it was designed for use outdoors and often had questionable accuracy.

Now in public testing, the system could eventually become an invaluable tool for navigating airports, museums, or even your local Wal-Mart.