unexplored; unsurveyed
Used for areas, fields, or topics that have not yet been investigated or surveyed. Often appears in academic, scientific, or geographical contexts.
That area remains unexplored.
More researchers are tackling unexplored fields.
未調査 is a more general term for 'not yet investigated', used in everyday contexts, whereas 未踏査 is more formal and often implies physical exploration.
Compound of 未 (mi, 'not yet') + 踏査 (tōsa, 'survey, exploration'). 踏査 itself is a Sino-Japanese word meaning 'to explore on foot'.