Localization refers to the process of estimating ones location (and often orientation) within an environment. Ground vehicle automation, which offers the potential for substantial safe-ty and logistical benefits, requires accurate, robust localization. Current localization solutions, including GPS/INS, LIDAR, and image registration, are all inherently limited in adverse condi-tions. This paper presents a method of localization that is robust to most conditions that hinder ex-isting techniques. MIT Lincoln Laboratory has developed a new class of ground penetrating radar (GPR) with a novel antenna array design that allows mapping of the subsurface domain for the purpose of localization. A vehicle driving through the mapped area uses a novel real-time correla-tion-based registration algorithm to estimate the location and orientation of the vehicle with re-spect to the subsurface map. A demonstration system has achieved localization accuracy of 2 cm. We also discuss tracking results for the first autonomous vehicle to use this technology and the po-tential for miniaturized general use systems.