There are two ways we can determine whether a Tweet is within the designated radius for a Twitter Lead search.
The first would be if the Twitter user has enabled their location to be automatically determined when Tweeting. If this is the case, we would be able to find the coordinates of where the Tweet was sent from and include it. Tweeting with your location is disabled by default for everyone, so a user must actively turn this on.
The second way is when a Twitter user manually sets their coordinates in their Twitter settings, at which point we would then find all of their Tweets to be within the designated search radius, providing those manually set coordinates are somewhere within that area.