Refers to a location previously mentioned or understood from context. Common in news reports and formal writing.
事件は同地で発生した。
The incident occurred at the same place.
A large-scale flood occurred there last month.
同地には多くの観光客が訪れる。
Many tourists visit that place.
The press corps visited that place last week to report on the story.
He has been living there since ten years ago.
同地 refers back to a place already mentioned in the text, while 当地 means 'this place' — the location of the speaker or writer.
同地 is a formal anaphoric term pointing back to a previously named place, whereas 現地 means 'the actual site' or 'on the ground', often used for fieldwork or local conditions.
Compound of 同 (same) and 地 (place). A straightforward Sino-Japanese word.