What Makes Google’s Maps So Good

Wow. Nothing makes you appreciate something like losing it.

Nobody ever raved about Google’s mapping app for phones until they saw how hard it was for Apple to come up with a rival. In my Times column today, I wrote about the challenges Apple has faced in replacing its iPhone GPS/mapping app, substituting its own data sources for Google’s. I noted that the new app is beautiful and will be really terrific someday — once it does a better job of incorporating all of its various data sources.

In researching the story, I interviewed representatives from Apple and Google. At Google, I spoke with Manik Gupta, senior product manager for Google Maps, and Daniel Graf, director of Google Maps for Mobile.

What I realized is that mapping the world is a staggering, gigantic, vast, inconceivably huge and ambitious project. It represents years and years of hand-tuning and manual effort.

I was surprised to learn that, like Apple, Google began its efforts by licensing petabytes of data from outside geodata companies.

They include TomTom, the same company that Apple’s using. (The other big map vendor is NavTeq, which Nokia bought a few years ago; I guess that explains why Apple and Google aren’t using NavTeq’s data. Too bad — by all accounts, the map app on Nokia’s Windows Phone is pretty great; I’ll be trying it out shortly.)

But that’s just the basic data. “We start with licensed stuff, then expand and enhance it,” Mr. Gupta said. Google has supplemented it with years of additional data gathering, involving its Street View cars, satellite data and human labor.

And it shows. As of 2008, for example, onto those digital maps of the world Google had overlaid 13 million miles of turn-by-turn directions in 22 countries; today, it has 26 million miles of guidance in 187 countries.

“It’s fair to say that in the mapping world, you can’t just throw money at it and then you have it the next day. This takes time,” Mr. Gupta said. “It took a lot of time to get where we’re at.” He said that even now, Google is far from done; error reports still flow in by the thousands.

Many of them come from Google Map Maker, a Web site that is live in 200 countries (and just started in the United States) that lets average citizens make corrections to Google’s maps as they find them. You can, for example, draw a line to represent a new road.

Like Apple, Google also collects location and movement data (anonymously) from millions of smartphones as they’re driven around; from this information, Apple and Google can determine when, for example, a one-way street has been mislabeled in its data.

You may be familiar with Street View, a Google exclusive that lets you stand at a certain spot on the map and “look around.” You can see a photo of the address you seek, and use your mouse to turn right or left and actually move through the still photos. It’s an amazing way to see what it’s like to be at that spot.

Street View isn’t available for the entire world, but you’d be surprised at how many inhabited areas are covered: Google’s GPS- and camera-equipped Street View cars have, so far, driven five million miles through 3,000 cities in 40 countries.

What you may not realize, however, is that those photos are far more than just helpful references for you, the viewer. Google’s software analyzes what’s in those photos. Its image-recognition software can read the text on street signs, storefront signs, hotel names and so on. It can tell a major road from a minor one, a single-lane road from multilane and one-way streets from two-way streets. Street View, in other words, generates still more useful data for Google’s maps.

I asked Google why its satellite photos don’t seem to display the same jarring seams that are showing up on Apple’s — obvious borders between side-by-side tiles that were taken at different times of the year or in different weather.

“When you look at Google Earth,” I was told, “you can see that the globe is made from a mosaic of aerial and satellite photos, often taken in different lighting and weather. We license these photos from multiple providers, possibly the same ones that Apple uses; but we’ve had the time to come up with a smoothing algorithm. In January, we introduced a new way to render them, smooth them out, make them seamless. But by no means have we perfected this.”

On this call, Google pointed out a new feature that I hadn’t seen before: compass mode. On an Android phone, you can call up a location like Trafalgar Square in London. You hold the phone in front of you to see a Street View-like photo of the scene — and as you look left, right, up, down, or behind you, the view changes, as though you’re looking through a magic window at another place in the world. You can even use Compass mode to look around inside places — I tried Delfina, the San Francisco restaurant — to get a feel of the décor before you go there.

Can you imagine how powerful Compass mode will be once it covers most of the earth’s developed areas? It will give you a sort of instant teleportation, a way to travel without travel, a sense of a place without having to go there.

What I’ve learned from this deep dive into the making of map apps is that you can’t just license a bunch of data, bake at 350 degrees and come up with a useful tool. Gathering the data is only the starting point; from there, it takes years to reconcile it, correct it and make it useful. (This Atlantic article offers a good look at the kind of hand-tuning that Google’s minions do constantly.)

By the way, let me be clear: I have no doubt that Apple’s Maps app will get there. We’ve seen this movie before — remember MobileMe? It, too, was very rough when it made its debut. Today, its successor, iCloud, is smooth and sensationally useful. Maps will be, too.

But I suspect that Apple has just realized the same thing I have: that we may live on a small blue planet, but digitally representing every road, building and point of interest is a task of almost unimaginable difficulty. Let’s be grateful that another major player has just joined the attempt.