Yes, you are right. Twitter doesn't provide location-based filtering. Though twitterCounter has done it. How? I don't think they are dependent on Twitter to fetch the user's location. There might be many approaches but below is the one I could think of.
- a)Have different account based on location/country and follow users who have maximum followers.
b)Now use twitter API to fetch friend with maximum followers. Store in DB and run above cron job on the specific time period.
2)Fetch Ids of possible users having maximum followers and maintain their location manually.
I don't know why twitter doesn't provide such a basic feature but we may expect to see in future API release.
Additionally, I would like to listen if anybody has precise knowledge of how they have location-based stats.