If you're like me, you're well used to navigating the world with a GPS mapping app on your smartphone. But have you ever given a thought to the work that goes into getting all that information into the map? It's a lot more than just photographing street scenes, as I found out recently when I took a ride in a Nokia mapping car.
The most noticeable feature of the car, beyond its bright blue color and the distinctive "Here" logo on the door, is the apparatus on the roof.
"On top we have really high-precision cameras and panoramic cameras," said Cliff Fox, senior vice president of location content at Nokia.
Fox pointed to two sets of cameras. A lower set that gathers images of road signs, shop names, address plates and other information that can be used to identify and supplement map data, and an upper set that captures panoramic images of the car's surroundings.
"The truly unique sensor is the one that's rotating up here," he said, pointing to a silver cylindrical object in between the upper and lower cameras that was spinning at a fast pace. "This is a laser sensor. There are 64 lasers in this. It's actually collecting 1.3 million points of data every second and this is what allows us to capture the world in 3D."
The laser bounces off every reflective object around the car, including buildings, pedestrians, signs, trees and even road markings. It helps to produce an incredibly detailed three-dimensional map of the surroundings.
There's a screen inside the car that provides a better look at what that laser scanner is capturing. A mass of lines, each representing the beam path the laser is taking, flash and pulse make it difficult to immediately see exactly what the laser is capturing. But after a couple of seconds of staring at it, me eyes sorted out the jumble of lines, and the buildings, cars and people passing by were easy to make out.
To keep its maps up-to-date and expand the service, these cars are on the road almost every day. The one I'm riding in spends most of its time in California, racking up tens of thousands of miles each year. The driver is guided by a custom smartphone app that shows roads traveled and those not.
"Maintaining the map is much harder than building it the first time," said Fox. "We have to maintain these maps forever and we need to understand what's changed. So we have over 80,000 sources of information that we use to help us identify change in the real world. And then once we understand where change is occurring, we'll send cars out to collect the real data."
Some of that information comes as anonymous data from users.
"We actually get 13 billion points of data every month from people who are driving the roads, and because we can see where people are driving, we can see where there are changes in the road network."
The result is the rich mixture of information that makes up the mapping services available from your cellphone.
Nokia has just opened up its mapping platform to non-Nokia smartphones. Its mapping data is shared throughout Windows Phone 8 handsets and the company hopes to attract Apple users with a soon-to-be-launched app for its Here.com service. Nokia is also making the platform available to other phone makers under a license.
Martyn Williams covers mobile telecoms, Silicon Valley and general technology breaking news for The IDG News Service. Follow Martyn on Twitter at @martyn_williams. Martyn's e-mail address is firstname.lastname@example.org