Photos: Nearest Tube app makes iPhone reality better than real reality

Augmented reality promises to slap the knowledge of the Interwebs on to everything we see, and Nearest Tube is a new example. But is Apple going to hand AR to Android on a platter?

Normal reality is so lame, with boring, ugly old signs everywhere to point at stuff. We look forward to a future of naked streets where our handy smart phones tell us where we need to go using augmented reality (AR), which overlays information on to the real world.

Nearest Tube is an innovative AR app that takes advantage of the iPhone 3GS' built-in compass to show you -- surprise! -- where the nearest London Tube station is.

The app combines the compass info with GPS to overlay pointers showing the distance and direction to Tube stations far and wide. The higher icons show stations further away, and also kindly show the lines that run through each station and whether that station is the closest option for each line.

The distances were roughly accurate, although they're measured as the crow flies, and we haven't quite managed to get our crow-powered airship working yet, so they're a little bit short. For example, Waterloo was shown as being 1.04km away from Crave Towers, while Google maps estimates that the walking route will take 1.4km of shoe leather.

The video below is from its developers, Acrossair, who tells us Nearest Tube is awaiting approval from Apple and should be available for download from the App Store within two weeks, when it will set you back a meagre £1.19. Since it uses the compass, it'll only work for the iPhone 3GS and not the compass-less iPhone 3G.

Click 'continue' to see how the app worked for us when we hit the bricks in South London, and why the iPhone is going to lose its place in the new reality to Android if it doesn't pull its socks up.

When you lay the iPhone 3GS flat, Nearest Tube shows pointers to all the London Tube lines, colour-coded to match the line.

There are already several AR apps available for Android, such as the Crave fave Google Skymap. But our resident Android addict, Ian, was impressed by the smoothness of Nearest Tube as we panned around the scene, compared to the Android AR apps we've tried.

Nearest Tube uses images from the iPhone's camera, rather than a live video feed. That means we occasionally saw the square focus target that the camera uses, although we couldn't tap to focus on anything within the app. It also means it can't manipulate or analyse the image, so the pointers are positioned using only GPS and the compass, instead of recognising any visible landmarks or tags on billboards, for example.

While this works well for a Tube station app, Acrossair told us it's a major problem when trying to create AR apps that are linked more tightly with the real world. It pointed us to an open letter to Apple, signed by 14 software development companies and researchers, who are begging Apple to open its video camera API in the same way Android does, along with videos showing prototypes of the cool stuff that could be just around the corner for AR.

With access to the video stream, developers can do things such as recognise historic buildings and display tourist info, or clock a movie poster to overlay a streaming video trailer of the film. Developers are already working on prototypes using private APIs that Apple won't approve in the App Store, and they want Apple to release a public API that will make their applications App Store friendly.

We'll be taking some of the Android AR apps for a spin on the HTC Magic soon, so stay tuned for a test-drive on the current king of AR action.

The iPhone 3GS's compass can be messed up by nearby magnetic fields -- apparently London is built on a lump of lead, because we often find that the phone makes pleas for compass calibration, and Nearest Tube is no different.

The message usually disappears after a few seconds, however, even if we didn't do the figure-eight manoeuvre that it requested, and the app still worked when the error was visible.

One thing to note is that all this GPS and compass orienteering exhausted our iPhone, eating 20 per cent of the battery life during an hour of testing time. It's not an app that needs to run for hours though, since we only needed to check it once or twice to keep us on course to the Tube. For London types, we think it's a useful app that also offers a tantalising whiff of augmented realities to come.