base in
1. To root something in a particular thing, idea, or finding. In this usage, a noun or pronoun can be used between "base" and "in." There's no way this data is based in reality!
2. To operate or function from a particular place. Our corporate headquarters is based in Spokane.
3. To locate something in a particular place. In this usage, a noun or pronoun can be used between "base" and "in." If we base our club in the English department office, then we can meet in there on Wednesday afternoons.