The Collaborative International Dictionary of English v.0.48:

Locator \Lo"ca*tor\, n.
   One who locates, or is entitled to locate, land or a mining
   claim. [U.S.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

locator
    n 1: a person who fixes the boundaries of land claims [syn:
         locator, locater]