Augmented reality, or AR, is a succinct name for a phenomenon that's beginning to make its mark on the world, and which some observers expect to be widespread in a decade.
AR does for the real world what VR, or virtual reality, did for the denizens of computer labs. Whereas VR created real-seeming realms that existed only in silicon, AR starts with the world around us, adding to it information specific to a particular location.
The devices that will bring AR to the masses are cellphones with built-in GPS receivers and digital compasses. So far there aren't many such handsets available; the best-known is Apple's newest iPhone, the 3GS and the HTC Hero, which uses Google's Android software.
The key thing each does is pinpoint where you are on the planet, which allows application developers and service providers to send useful - hopefully, anyway - information related to your location. The debate is yet to be had about what will be useful and how to best convey it: as plain lists or in potentially distracting graphical form.
What's clear, according to Luigi Cappel, a long-time watcher of smartphone developments, is that the devices will be in everyone's hands before long.
"In my opinion it's not going to be very long - maybe five to 10 years - before all phones are smartphones with GPSs and compasses. Then those location-based applications will be mainstream," says Cappel, of AA-owned GeoSmart, a digital mapping company.
But there's scepticism too. John Ballinger, one of a handful of New Zealanders who have made significant sums developing iPhone applications - his heart-rate monitor has earned about $60,000 - has trouble seeing how an AR program could be more useful than the bog-standard Maps app that comes with every iPhone.
Ballinger concedes, however, that he hasn't stood at an intersection in a foreign city lately, trying to figure out which of 10 streets he should head down to find the shop he's looking for.
Helping people out of such quandaries is precisely how AR buffs see the technology being used. One way of making such an application work is to use another standard phone feature: the camera.
Pointing the camera down Paris' Champs Elysees, with the precise location fixed by the GPS and compass, a service provider could overlay the names of landmarks visible in the camera image. Already, applications like Yelp and Wikitude do exactly that, to the excitement of the user community.
One of the potential AR pitfalls is clunkiness, says Emily Loughnan, whose Wellington company Click Suite has been developing interactive applications for 15 years.
"It annoys me when I see things done badly because then people say it's augmented reality that is hopeless. Well, it's not. It's quite an interesting technology. It's just that we haven't seen very many interesting applications of it yet."
She found an AR-like application was helpful in guiding her around San Francisco and can see uses in education, for things such as providing botanical information to students on field trips.
New Zealand-developed World Surfer, an application released this month for the iPhone and earlier for Android, might be described as AR-lite.
Arron Judson, who led World Surfer's development for US company GeoVector, says they shied away from the overlaying data approach of Yelp because of usability issues.
Instead, on the iPhone 3GS, World Surfer presents the user with a list of, for example, restaurants 30 degrees either side of the phone's compass heading, with the nearest at the top. A new list appears if the user changes direction, and the application will guide the user to their chosen point of interest.
"It's almost like having someone with me saying 'it's just over here - 50m to go, 20m to go, okay, you're there'," Judson says.
The wow factor of Yelp, however, means GeoVector is likely to bring out an interim World Surfer version with camera functionality, as the company works out the best way to let users interact with augmented information.
Commercial considerations will undoubtedly come into play. At $4.19, World Surfer is unlikely to be a goldmine. But GeoVector envisages also making money from information providers, whose products and services will be organised in channels that users can select from according to their tastes.
If you like Thai restaurants, withdraw money from ASB ATMs and buy groceries at Woolworths, for instance, a future version of World Surfer will find just those outlets for you.
Usability cautions aside, Click Suite's Loughnan has great expectations of AR's impact on the world. "It's just changing so amazingly fast," she says.
Augmented reality: A combination of a real scene, as viewed by a user, overlaid with computer-generated information, typically updated in real time.