The Quest for Reliable Directions

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A Dead-End Turn

A Dead End i

Visitors to Jacob Sisk's house hit a snag when Web services recommend a non-existent right turn on Loma Vista Place. Sophia Choi hide caption

toggle caption Sophia Choi
A Dead End

Visitors to Jacob Sisk's house hit a snag when Web services recommend a non-existent right turn on Loma Vista Place.

Sophia Choi

As the world grows more complicated, so do methods for navigating through it. Often, the Internet is more reliable than a human when it comes to giving directions. But in some areas, that's not the case.

When friends want to visit Jacob Sisk, for instance, MapQuest sends them on a route through Los Angeles that includes a right-hand turn on Loma Vista Place. But driving the route is impossible: far from a "street," Loma Vista Place is actually a sidewalk that goes up a set of stairs.

A test of two other main map services besides MapQuest, Yahoo and Google, shows that all of them try to send drivers up the stairs. Since they all rely on the same road database company, NAVTEQ, for their road databases, the problem is duplicated on all the map sites.

To give directions, the Web sites consult a digital atlas of the country, built on road databases provided by companies like NAVTEQ.

Computers at each service then create an optimum route between the start and end points, taking into account things like favoring major thoroughfares and avoiding left turns. The proprietary programs that solve these problems have continued to evolve since 1959, when Dutch computer programmer Edsger Dijkstra developed an algorithm in to find the quickest route between two places.

Officials at each company say inaccuracies are rare. MapQuest, for instance, which doles out about 7 million sets of directions every day, says that less then a tenth of 1 percent of its users contact the company — and only a fraction of those are complaints.

Meanwhile, NAVTEQ, the road database company, has hundreds of people driving around the country, trying to find snags in their data. NAVTEQ says the Loma Vista Place problem is being fixed. And some day soon, Jacob Sisk won't have to give out directions himself.

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