By Dermot McGrath In Paris

A new navigation tool to help blind and partially sighted people find their way around city streets is about to be tested under a new European project.

The handheld device uses advanced European Space Agency (Esa) satellite technology to locate and guide pedestrians in real-time over a wireless internet connection.

It will be tested in coming weeks by volunteers from Once, Spain's national organization for the blind.

Current satellite navigation based on the global positioning system (GPS) works fine for many location-based services, but lacks the precision needed for detailed navigation along city streets.

This is principally because tall buildings in urban areas, as well as other obstacles like trees, impede the ability of receivers on the ground to track GPS satellites, resulting in a positioning accuracy that is often little better than 30 to 40 metres.

Improved accuracy

It should allow the blind user to navigate using a map, just as a sighted person can Alfredo Catalina, GMV Sistemas

To improve the accuracy of GPS positioning to a few meters, Europe is developing the Egnos system, which broadcasts augmentation signals through geo-stationary satellites, enabling receivers on the ground to correct errors in GPS signals.

To get around the problem of buildings obscuring the Egnos signal, the European Space Agency created a complementary technology, known as SisNet, to relay the signal in real-time over the internet using wireless networks.

The new handheld system, developed by Spanish company GMV Sistemas, makes use of this technology to improve the accuracy of GPS positions to a few meters, making it sensitive enough to locate obstacles in the street.

GMV Sistemas' personal navigator for the blind, called Tormes, includes a Braille keyboard, a voice synthesizer and a GPS receiver.

The latest version comes packed with an "always-on" GPRS wireless internet connection, providing access to the SisNet services.

Personal navigators

By connecting the world of navigation with the Internet, we are opening up many new possibilities Javier Ventura-Traveset, Esa

All this hi-tech gadgetry gives users constant updates about their location and tells them which road they are walking down, which buildings are near them and when they are approaching a junction.

"We think that the addition of SisNet to Tormes is very interesting," says Alfredo Catalina who is overseeing the project at GMV. "It should allow the blind user to navigate using a map, just as a sighted person can."

The addition of an internet connection also has the potential to enhance the function of personal navigators in other ways.

"When you are connected to the internet you can also send messages back," explains Javier Ventura-Traveset from Esa.

"You can ask for directions to a particular place or say that you are lost or have had an accident. By connecting the world of navigation with the internet, we are opening up many new possibilities."

Tormes is expected to be ready to begin tests in early February.

"We will do two tests, one with and one without the Egnos/SisNet technology so that we can compare them," says Felix Toran-Marti from ESA.

"Members of Once will be helping to define the tests and assess the performance of the technology."

Egnos is the first element of the European satellite navigation strategy and a major stepping-stone towards Galileo, Europe's own global satellite navigation system for the future.

Consisting of 30 satellites in medium-Earth orbit plus an associated network of ground stations, Galileo is expected to deliver an independent, civilian-controlled positioning service worldwide with metre-scale accuracy.