So, there is literally no difference in how you would handle this with GraphQL vs a traditional RESTful API. All you have to do is pass query variables in your query... and then pass those variables to whatever model method / service RPC you call to grab location data.

If you are using React, you can learn more about request variables here:

http://dev.apollodata.com/react/queries.html

Variables are also how you submit data in mutations.

I highly recommend Apollo for a client side GraphQL implementation. They are the best