Geophysics uses methods of physics to investigate and define buried objects and materials without direct contact, allowing subsurface study without disturbing soil and cultural features as traditional excavation does. When combined with excavation, geophysical surveys reveal information about prehistoric architecture and how people used space within a village. Magnetometry measures changes in soil magnetism, readily detecting burned houses, hearths, and iron artifacts, and at Double Ditch Village it revealed the site's basic structure and many new aspects, especially two previously unknown fortification ditches, Ditches 3 and 4, with multiple bastions. This survey formed one of the largest magnetic data sets in the Americas and the world. Resistivity survey methods pass electrical current through the earth and record resistance caused by buried objects or soil variations; although less distinct, they complement magnetic survey results because wetter low areas such as ditches, house depressions, and basins show low resistivity, while drier high points such as mounds or middens show high resistivity.