As you may have seen on the Twitter blog , geotagging is now
available for all users and developers throughout Twitter's APIs.
Specific geotagging methods have been added and existing formats
expanded to accommodate this rich new information.
To get started developing with this API and sending geotweets, check out
Geotweets now carry the geotag whenever available and whenever they
appear in our REST, Search, and Streaming APIs.
Remember, geotagging is disabled by default on users' accounts.
Encourage your users to enable it by sending them to their settings
page . From that page, a user can turn this feature on by checking
the "Enable geotagging" checkbox. Alternatively, we're also providing
a mobile optimized geotagging settings page  that you can send them
too as well. As a developer, you can determine whether a user has
enabled geotagging by calling the users/show method  or in any
other <user> element returned by the REST API where a user object
shows up -- just look for the geo_enabled flag.
For more hints on how to use geotagging, check out our Geotagging Best
Practices page  where we have UX mock-ups, hints on how to best
support user privacy, and more.
We're really excited about this feature! And more is coming.
Go get lost. We'll send help.
Twitter Platform Team