Location in tweets: coordinates vs. place



I’m trying to figure out, how reliable location information in tweets are.

Regarding “coordinates”, documentations states: “The longitude and latitude of the Tweet’s location, as an collection in the form of [longitude, latitude].” But what how exactly are these coordinates assigned to a tweet. I assume (a) from the mobile phone when the users allows it, (b) from third-party apps like Instagram. What else? (I observed, for example, that a large number of tweets in my database that stem from Instagram have the exact same geolocation. That kind of makes question the usefulness.)

The “place” fields seems even more vague: “When present, indicates that the tweet is associated (but not necessarily originating from) a Place” and “Tweets associated with places are not necessarily issued from that location but could also potentially be about that location.”

What are common caveats when considering location information?