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Eyes in The Sky

Editor's Note: Editor's Note: The following article is reprinted with permission from E-Access Bulletin, the free email newsletter on access to technology by blind and vision-impaired people, Issue 47, November, 2003:

The ability to know exactly where you are at any particular time by using signals sent from satellites is of clear use to people sailing boats or driving cars. But it is also of enormous value to people who are blind, potentially allowing far greater independence of movement.

Currently, the main working technology in this field is the Global Positioning System (GPS), which uses a network of 24 satellites in geostationary orbits 11,000 miles high positioned so that at least three are visible from any point on the Earth.

GPS receivers use triangulation of radio signals sent by these satellites to work out the position of a person or object to within 10 metres or so. The system is owned, operated and licensed for civilian use by the US military, which itself uses an enhanced service with an accuracy of one centimetre or less.

The main player in the application of GPS technology to location finders for blind people is Canadian firm VisuAide, with its Victor Trekker device (, which came on to the UK market in June this year with assistance from the RNIB.

"People are exploring their locale like they've never been able to do in the past," says Mervyn Robertson, technical director of Sight and Sound Technology

( which distributes the Trekker. It currently costs 1,125 UK pounds, although the price will come down, he says.

A Personal Digital Assistant (PDA) with a GPS receiver attached to a harness, the device is hooked up to an electronic voice-box that provides location data to the user using electronic maps developed by Navigation Technologies (

The Trekker allows users to add to existing information by recording "points of interest" such as "I'm home now" or "I'm at the bank" which can be recorded and played back on familiar routes. Where the information is available, Robertson says, pub and restaurant names are programmed into maps.

"You can say "where am I?" and it'll say "

23 South Street", but it doesn't allow you to pre-plan a route," says Robertson. However, this looks set to change this February, when the Trekker will provide a free upgrade to all users, making route-planning available for the first time.

One potential pitfall of GPS is loss of signal. If a satellite is out of range or if users are situated in built-up areas for example, navigation temporarily disappears. "In a narrow street or alley, if you don't have the satellite to view, you could potentially be in a bit of trouble," Robertson says.

Dr. John Gill, chief scientist at the RNIB, says that for GPS technology to work well, navigational data needs to include temporary as well as permanent outdoor features and information such as which side of the Town Hall the front entrance is located, or whether there are roadworks.

Dr. Gill says the most promising development in this field is being developed by a team at Brunel University headed by Professor Bala Balachandran. The team is developing a system which uses existing mobile phone technology linked to a control centre staffed by human operators.

"A blind person will never totally rely on technology," Balachandran says. "They like a friendly voice at the other end. If the blind person wants to go from A to B, they press a button and an operator knows exactly the location of the blind person." The operator sees a digital map with the whereabouts of the user and verbally guides them.

The beauty of the Brunel system is that users don't have to have guidance all the time and the navigated area doesn't have to be familiar territory, he says. The opportunity for two-way conversation also makes it a potentially useful tool for people with intellectual as well as visual impairments.

To avoid signal loss inside buildings or underground, the Brunel team have also devised a wearable TV camera to allow the operator to continue guiding.

The system also has the potential to allow relatives or friends to navigate the vision-impaired user.

The Brunel project already has the support of mobile phone company 02 and the mapping agency Ordnance Survey, but is currently seeking further funding to develop the product for market. When ready the device should cost no more than a high specification mobile phone, Balachandran says.

One final concern remains. Because GPS is US military-owned, in times of war or crisis the system could theoretically be cut off or restricted. "You're at the beck and call of the American military," Robertson says. This could soon change with the launch of GALILEO, a complementary European navigation system due to launch its first satellite next year ( The future for Europe could be pinpoint accurate.

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