Detection functions for archaeological survey

This paper presents the results of several experiments to investigate how the detection functions of surveyors vary for different artifact types on surfaces with differing visibility when visual surface inspection ("fieldwalking") is the survey method. As prospecting theory predicts, successful detection declines exponentially with distance away from transects and detection as a function of search time displays diminishing returns. However, these functions vary by visibility, artifact type, and other factors. The incidence of false targets-incorrect identifications of artifacts-has somewhat more impact at greater range but has little or no relationship with search time. Our results provide a rationale for selection of transect intervals and distribution of survey effort, and also facilitate evaluation of survey results, allowing more realistic estimates of how much a survey missed.