The largest section of the screen is the navigation map. When traveling, the software zooms in or pulls out the map depending on how fast you're driving. So, if you're booking up a highway, you can see quite a bit of distance. But if you're driving more slowly on local roads, your visible distance is quite a bit less, but the detail is more measurable.

We found this auto-scaling feature to work sporadically. In fact, on one exit, trying to get onto the Major Deegan in New York City, it jumped from long view to local view to long view again, all in about 10 feet of travel.

Also on the map is your computed route. When you set up your trip, you specify where your destination is going to be (more on that later), and the program will calculate your best route. The light blue line on the map is that route. That light blue line will prove critical when you're driving.

Moving down the screen is an information bar. On the left is an indicator that generally tells you what direction you're going to need to head next, and about how far away that is. In the figure above, it's showing a left turn in 0.19 miles, onto Elysian Park Avenue.

Complementing all this is a pleasant woman's voice telling you important details about your travel, like "Left turn ahead" or "Highway intersection ahead," or our favorite: "You are off-route." She can be pretty stern when you're off route, but if you happen to make a turn correctly, you're rewarded with a very nice pavlovian bell.

You are off route
One thing I really like about this product is that if you do get off route (let's assume you took a wrong turn or simply decided to go a different way), after about a quarter mile, the software will decide to recompute your route to the destination from your new location.

The recompute process can take a minute or so, and sometimes you'll need to just keep going in a random, but consistent direction before the software catches up with where you're going, but it does, eventually, get you back on route.

As technologically impressive as this is, in practice, this recompute delay can be a serious problem. As you might imagine, driving an extra minute or an extra mile or so in New York City before the system picks up on it can change everything. In fact, you can be in a totally different part of Manhattan, driving on a road hard to extract yourself from, when Ostia finally catches up.

We found ourselves, a number of times, yelling at each other with this script:

"Where do I go?"

"I don't know!"

"Well, what does the GPS say?"

"It's not saying anything..." and getting more and more frustrated as we got deeper and deeper into unfamiliar territory.

It does catch up, though. On our trip to Yankee Stadium, we took a wrong turn and wound up going up the Major Deegan in the wrong direction. The software started complaining about being off route, the little green arrow wound up pointing in completely the wrong direction, but the little blue route path on the map had it right. The GPS did find us a safe U-turn and got us going back down the Major Deegan in the correct direction.