By Mark Ward
Technology correspondent, BBC News website, San Diego
Scottish researchers are turning to camera phones to help bridge the virtual and real worlds.
Invisible art works adorn buildings around Edinburgh
Using image-matching algorithms the researchers have found a way to adorn the real world with digital content.
The technology has already been used to create a guide of Edinburgh that allows people to find virtual artworks placed around the city using their mobile.
Another related project uses the technology to automatically update a person's blog with their location.
"It's about using a camera phone as a magic wand," said Dr Mark Wright of the Division of Informatics at the University of Edinburgh who came up with the idea.
At the heart of Spellbinder, as the project is known, is a database of all the places that participants have added data to. People query it by taking a snap of a location with their phone then using multimedia text messages to send it to Spellbinder.
Dr Wright said powerful image-matching algorithms are used to analyse the image that can deal with snaps of the same place being taken under different lighting conditions or orientations.
Once Spellbinder has worked out the location of an image it consults the database and sends back an image with the extras added to it.
Previous projects to augment the real world with digital content used barcodes on objects or a software download that participants installed on their phones.
Gamers shoot snaps of the images on rival players' clothes
But barcodes required someone to go out labelling everything, Dr Wright said, and software can be hard to maintain and tweak for every possible handset that could use it.
The first use of the system has been in an Invisible Art project set in Edinburgh. This, said Dr Wright, encouraged people to explore the city and take snaps of landmarks to see whether others had added anything to them.
A game has also been developed using the system in which players wear a large individual image on their body and are given a "base" or location to protect.
Points are given for shooting snaps of the images on rival players' clothes or of their base.
Another project called Comera could be a boon to keen bloggers or users of social networking sites such as Facebook or MySpace as it consults the Spellbinder database to automatically update webpages with location data.
Although Spellbinder has been used to spot locations it could, said Dr Wright, be used to match almost anything.
"With Spellbinder, the real world becomes a computational resource," he said.
The project was unveiled at the Siggraph show held in San Diego, US from 5-9 August.