Throughout the 17th century, Santa Catalina de Guale served as the northern outpost of Spanish colonization along the Atlantic seaboard. Abandoned in 1680 and lost in the forests of St. Catherine's Island, the mission site was relocated 300 years later by a systematic proton magnetometer survey. Analysis of magnetic data was greatly enhanced by the use of several computer graphic formats. The results of the survey, analysis, computer graphic production, and test excavations are presented.