Using a 12-channel GPS receiver of its own design, Sony has entered the portable navigation market with a new system that promises rapid and reliable location calculations even in urban canyons and other difficult environments.

The first product in Sony's new Nav-U line, the NV-U70 features a full-color 3.5-in. touch screen and 1 GB of imbedded flash memory preloaded with street-level maps for the entire continental U.S.

In addition to imbedded maps, a DVD-ROM offers full maps for Canada, Alaska and Puerto Rico. Sony's initial maps do not include truck restrictions, although the unit's map database can be updated through a USB connection to a PC.

Drawing on the company's audio experience, the NV-U70 also provides clear, audible voice prompts even under noisy conditions with a built-in two-way speaker, according to Andrew Sivori, general manager of the company's mobile electronics group.

Operational features include simple on-the-fly rerouting around traffic congestion and one-touch routing to a home location.

Other features include a vehicle cradle with a light-weight bracket that can be mounted on a windshield or dashboard and a rechargeable lithium-ion battery said to operate the portable unit up to four hours when it's removed from the cradle.

Options include additional mounting bracket/charger units for moving the NV-U70 between vehicles and an external GPS antenna.

With a retail price of just under $700, the NV-U70 will be available online at www.sonystyle.com in February or from selected retailers.