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"Latitude is a new feature for Google Maps on your mobile device," said Vic Gundotra, VP of engineering on Google's mobile team, in a blog post. "It's also an iGoogle gadget on your computer. Once you've opted in to Latitude, you can see the approximate location of your friends and loved ones who have decided to share their location with you. So now you can do things like see if your spouse is stuck in traffic on the way home from work, notice that a buddy is in town for the weekend, or take comfort in knowing that a loved one's flight landed safely, despite bad weather."
Anticipating criticism from privacy groups, Gundotra explains that Google has designed the service with privacy controls. "Everything about Latitude is opt-in," he said. "You not only control exactly who gets to see your location, but you also decide the location that they see."
Latitude is distinct from Google's My Location service, which locates mobile users on Google Maps, either by GPS or cell-tower proximity for mobile phones without GPS. Unlike Latitude, My Location does not link one's location to a Google Account or mobile phone number.
Latitude requires a Google Account. For people who want to use the Latitude iGoogle gadget to share location data while using a computer, Google Gears must be installed.
Users who opt in to Latitude can select friends from among their Google contacts with whom they want to share location information. They can also invite people to participate by entering any e-mail address, a viral marketing feature likely to lead to more Google Accounts.
The location-sharing request can offer the following terms: accept and share back, accept but hide my location, don't accept, and block.
Latitude users sharing their location, whether sender or recipient, can configure friend-specific privacy preferences to share best available location, share city level location only, or hide from this friend. There's also a global privacy setting that allows automatic location detection, manual location declaration, and location hiding.
Google says that it stores only the most recent automatic or manually entered location data for Latitude users, and that it doesn't store location data for users who have chosen to hide their location.
Google's manual location declaration appears to function in the same way that Yahoo's FireEagle location service does in that it allows people to lie about their location. This is by design.
Latitude plays nicely with other Google communication tools like Google Talk, the company's IM client. "Google Talk is integrated with Latitude, so you and your friends can update your status messages and profile photos on the go and see what everyone is up to," said Google engineer Charles Mendis in a blog post. "You can also call, SMS, IM, or e-mail each other within the app."
Latitude is available for BlackBerry, S60, and Windows Mobile devices, with Android support coming in the next few days. Google expects to bring Latitude to the iPhone, through Google Mobile App, soon.
One reason for the delay in bringing Latitude to the iPhone may be that Latitude's location-update process runs in the background, something that isn't allowed on iPhone apps, at least not yet. Apple disallowed background processes in part because they drain battery power. That restriction may be lifted as future software and hardware developments mitigate the power-consumption issue.
Google, in a Latitude help document, warns, "Continuous location sharing uses a lot of data. An unlimited data plan is strongly recommended before using this feature."