One-Man Scouting Party is an achievement/trophy in Fallout 3.
It is granted for discovering 100 locations.
Requirements[]
Mark 100 locations on the map. The Explorer perk puts all locations in the Capital Wasteland on the map, but it does not discover them. The player must travel to a location, whereupon the symbol on the Pip-Boy will change from 
, and it will be considered discovered, also permitting fast travel to that location.