The nondestructive techniques used in geophysical prospecting and to generate archaeological data without excavation. It is a general term for reconnaissance and surface survey techniques that leave subsurface archaeological deposits undisturbed. Reconnaissance and site survey methods use such devices as aerial photography and pedestrian survey to detect subsurface features and sites. It includes the detection of hidden archaeological features such as walls, pits, or roads by means of sound or radar impulses passed through the ground.