How MapQuest Gets You From Here to There

It's not all algorithms. Think geographers driving around in a Ford Taurus.

In the tradition of Lewis and Clark, the team of Lynch and Clark is traveling west to explore uncharted territory—in this case, a recently expanded subdivision called Avalon Way, outside Baltimore.

Patrick Lynch, a field analyst, and Maureen Clark, an area manager, work for Navigation Technologies, an 18-year-old outfit in Chicago. Every month, they travel 1,000 miles in Maryland, Virginia, and West Virginia, observing and recording data. When you request directions from MapQuest, the Internet mapping service, you're ultimately relying on Lynch, Clark, and about 400 other geographers on the road.

MapQuest uses state-of-the-art satellite images and computer algorithms, but it also relies on actual observations in the field. So it is that an army of modern-day explorers is continually remapping the nation. As Clark steers a Ford Taurus through Avalon Way's newest streets, she recites what she sees, starting with street names and building numbers at the beginning and end of a block. "Hemison— H-e-m-i-s-o-n —Court. There's a gate . . . number four is on the right."

Lynch scribbles on a digital notepad attached to a laptop wedged between them. His writing appears instantly on the map, in bright yellow scrawl. Navigation Technologies' field analysts record up to 150 attributes for any given road—speed limit, turn restrictions, exit numbers, paved or unpaved—along with gas stations, restaurants, and hotels. "Most people hear what I do, and they think I'm just cruising around for hours," says Lynch. "But you're concentrating the whole time. You don't want to miss anything."

Back at the office, Lynch and Clark submit the data they've collected to Navigation Technologies' digital-mapping facility, in Fargo, North Dakota. There, cartographers and editors compare the data to satellite images and existing maps before adding it to the database, which already reflects 4.6 million miles of North American roads and more than 8 million miles in 39 countries. Once a quarter, the company sends an update to MapQuest and other clients.

From there, it's MapQuest's show. When someone requests directions, MapQuest's software "geocodes" the starting and ending points, translating the addresses into longitudes and latitudes. Then algorithms identify possible routes, taking into account requests for local roads instead of highways and other factors such as "turn costing." "Lefts are harder to make than rights," explains MapQuest.com general manager David Schafer. "If we can get you there by turning right three times and avoiding two left turns, we will."

In July, MapQuest produced about 750 million maps and 100 million routes for 32 million unique visitors to the site. And when it steers people wrong? Two customer-support employees in Denver follow up on feedback to ascertain if the problem is the result of a customer's error, unclear directions, or a flaw or gap in the database.

Until recently, MapQuest was inadvertently routing westbound drivers onto the Pennsylvania Turnpike north of Philadelphia using a ramp for E-ZPass drivers only. Now it sends them to the next exit. The first ramp was faster, but the MapQuest database didn't show that it was an E-ZPass lane. Most likely, modern-day mappers hadn't visited the ramp. Which means Lynch and Clark have miles and miles to drive.

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