In advance of Facebook's expected announcement on location, Foursquare on Tuesday unveiled updated privacy settings, as well as pages dedicated to explaining what information the service shares publicly.

Foursquare lets you "check in" to locations via your mobile device and share that information on Foursquare and other social-networking sites. Tuesday's update now lets users choose whether to share their e-mail and phone number with friends. User can also opt out of "mayorships," a reward given to those who check in most at a certain location.

Foursquare also promised more control over e-mail settings.

For those who are unsure about what information is shared on Foursquare, the company set up a dedicated page explaining its privacy policy.

"It seems that a lot of concerns over information sharing on location-based services arise from confusion over what is shared and where it's shared, so we've put together an explanation of the different ways foursquare uses and shares location information," the company wrote in a blog post.

Location data is only shared by those who opt to "check in" somewhere, whether it be a restaurant, a friend's house, or the office coffee pot. If you'd rather not remember a particular check-in, Foursquare provides the option to delete places from your check-in history.

There is also the option to go "off the grid" and check into places without sharing your exact location. This way, you can continue to earn badges and points while maintaining privacy. It would show up as "Chloe [off the grid]" rather than "Chloe [PCMag offices]."

Foursquare also said it uses your phone's location to "tailor the Foursquare experience," but only has access to recent data.

"We save this information until the next time you launch the foursquare app, at which time we delete your old location information and replace it with your most recent location information," according to the privacy page.

Foursquare also put together a privacy grid that shows exactly what is shared on the service.

Facebook, meanwhile, is hosting a news event at its Silicon Valley headquarters Wednesday night, where it is expected to unveil its own location-based service. PCMag will be at the event, and bring you all the news later this evening.