nostr:npub120zh308gs69j3vwgvvrzgglv58vsk3q0vef43uajyu0lc3mtldsq2p33r2
>We're also working on an Activity extension spec for geotagging, so other projects can use this too\!
You don't need to. The location property and Place type are part of ActivityStreams:
https://www.w3.org/TR/activitystreams-vocabulary/#dfn-location