Friday, May 16, 2008

A Faster, More Energy-Efficient GPS

New software could help make location-aware devices ubiquitous.

By Kate Greene

Tag, you’re it: This GPS device from Geotate, attached to the top of the camera, can capture just enough data from GPS satellites that the location of the device can be determined when the pictures are uploaded to a computer. By not processing the satellite data on a specialized GPS chip, Geotate’s approach saves time and battery power. Credit: Geotate

If you want to add location information to pictures today, it's a fairly tedious process. Many people manually annotate their pictures after they've uploaded them to a computer. And while some high-end cameras come equipped with a Global Positioning System (GPS) chip that captures the location information, this extra hardware is slow and can drain battery power. Now Geotate, a U.K.-based spinoff of Philips Research, thinks that it can make GPS faster and more energy efficient in any device.

As more people take pictures on digital cameras, there's a growing interest in making sure that those pictures are geotagged. When pictures contain location information, they could be easier to sort in personal photo software like iPhoto. And if geotagged pictures are uploaded to a photo-sharing site, such as Flickr, then others can benefit from the information when, say, planning a vacation. Right now, only a small fraction of photos contain any information about where they were taken.

To be sure, Geotate isn't the only company trying to make geotagging more common. Eye-Fi announced this week that it will sell a memory card for cameras that can automatically and wirelessly upload geotagged photos to a computer or photo-sharing site. Eye-Fi's technology differs from Geotate's in that it approximates a camera's location from the local Wi-Fi routers--information that's accessed via Skyhook Wireless's extensive database of Wi-Fi hot spots covering 70 percent of the United States.

Since Geotate's approach doesn't require a Wi-Fi signal, it's practical in more-remote locations. However, it falls short in major urban areas, where GPS signals tend to get blocked by tall buildings. Ultimately, the best geotagging results would come from a combination of services that use a variety of location-tracking technologies, suggests Alexandre Bayen, a professor of civil and environmental engineering at the University of California, Berkeley.

The basic idea behind Geotate's approach, called Capture and Process, is to collect only a small amount of information from the GPS satellites that help determine location, explains Chris Marshall, the company's CTO. And instead of processing this information on a GPS chip within a gadget, it's processed, with the help of software developed at the company, on a computer when the photos are uploaded. "If you can do the processing in software," says Marshall, "then you don't need a dedicated chip."

Traditional GPS systems require a lot of electronics, including amplifiers, filters, an antenna, and a processing chip. A GPS-enabled device listens to signals, which contain orbit information, from the GPS satellites. Using this information, the device can calculate the distance between itself and the satellite, and from that determine where it is. But it can take 30 seconds for a satellite to stream its position to a GPS receiver. And only after the GPS system decodes the orbit information from four satellites can it calculate the location--a process that requires the processor to churn through a relatively large amount of data.