- sneaky check opponents location and expansion
- in some circumstance know about destructible rocks fall
- you can use any unit (not only worker) to do any of this
- "closed areas" include walled-in Terran's base, so you can know when supply depot is down
- difference in worst case (when I find opponent on 3th possible location) on Delta Quadrant is about 15 seconds compared to "normal" way to scout.