Getting Lost With a Cellphone

WHEN it comes to navigation, so-called smartphones aren’t really so smart. If you want to find your way to your friends’ mountaintop country estate or to a remote bed and breakfast for some leaf peeping, standalone portable navigation devices, or PNDs, still rule.

To be sure, prices of PNDs have dropped, and their makers have turned their attention to providing turn-by-turn software to cellphone carriers and handset makers. Navigon, which makes cutting-edge PNDs, quietly left the American hardware market in May, deciding to focus instead on handsets as well as software for in-car systems. It already has mobile deals with Samsung in Europe and T-Mobile in Germany, and recently introduced a version of its Navigon MobileNavigator software for $89.99 for the Apple iPhone.

After the PND leaders, Garmin and TomTom, reported double-digit drops in revenue earlier this year, market watchers suggested that smartphones with navigation software might kill off PNDs just as they decimated PDAs. And then TomTom decided that if you can’t beat them, join them, introducing a $100 software version of its navigation application for the iPhone.

But using a cellphone to get directions on a long trip can be about as reliable as using a divining rod to dig a well. Wrong turns, dropped signals and incoming calls confuse most cellphone-based navigation applications.

The Navigon and TomTom iPhone programs are a case in point. Unlike a desktop or laptop computer, the iPhone cannot fully multitask, which means that if you’re using it for turn-by-turn directions and you then answer a call, the navigation function will go on hiatus.

Even phones that can juggle different tasks simultaneously can lead you astray, depending on the network. For example, the R.I.M. BlackBerry Bold on AT&T’s 3G network will continue directions in the background while you chat, but the BlackBerry Storm on Verizon Wireless will not. A R.I.M. spokesman, Erik Van Drunen, said this was because of the network’s limitations, not the phone.

Nevertheless, even with multitasking handsets, in many cases when the cellphone signal stops — say, on a rural road — so do the directions. The reason: because of the limited on-board memory of most cellphones, they must be regularly updated with directions via the cellular network, particularly on long trips. So even though you may still receive a GPS signal on your phone indicating your position, the directions will stop without the accompanying cellular signal. Not only can this be disturbing on a rainy night when there’s no gas station in sight, it can also be annoying when you make the inevitable off-route excursion.

“In some cases, it will download the entire route to the destination,” countered Sal Dhanani, a co-founder of TeleNav, which makes the mapping software for AT&T and T-Mobile’s $9.99-a-month service . “Unless you make a turn that’s not on the route. Then, if there’s no connection, it will lose you.”

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