11 Multiple Methods Surveys: Case Studies Kenneth L. Kvamme, Jay K. Johnson, and Bryan S. Haley he foregoing chapters have demonstrated that a geophysical survey with a single instrument can provide much insight. Yet, most instruments respond primarily to a single physical property of the earth: magnetometry to soil magnetism, resistivity and electromagnetic induction to soil conductivity, and ground-penetrating radar (GPR) primarily to soil dielectric properties (Weymouth 1986:371). It is easy to conclude that surveys with multiple methods must offer greater insights because different dimensions of the subsurface are being quantified. Buried cultural features not revealed by one method might be made visible by another (Clay 2001; Piro et al. 2000). Addition- ally, subsurface features indicated by one method may be very different from and add complementary information to patterns revealed by another, as when a hearth and burned elements of a house are shown by magnetometry while soil changes that make up the house floor are portrayed by resistivity, conductivity, or radar methods. Recent advances in computer graphics and geographic information system (GIS) technology allow various data sets to be overlain or combined, making possible simultaneous vi- sualization of features in each. Moreover, new GIS-based “data fusion” methods seek ways to combine the multidimensional imagery into composite data sets that enhance interpretability through the use of principal components analysis, statistical, or con- text-based methods (Johnson and Haley 2004; Kvamme 2001; Piro et al. 2000).