You will get the best coverage by using the Enterprise version of PowerTrack, as it is full fidelity.
It would be worthwhile to note that a rather small percentage of users geotag their Tweets, but a larger number of users do have locations added to their bio on which you can filter. You can learn more about the available operators with the Enterprise tier of product here:
https://developer.twitter.com/en/docs/tweets/rules-and-filtering/overview/premium-operators
If you are looking to use a free option, do know that you can use statuses/filter, but you will run into rate limits and other restrictions.
I also suggest that you keep an eye on our roadmap, specifically this item.
