1. An electrical survey in which current electrodes on the ground surface at specific azimuths from a drill hole are used with one or both potential electrodes in the hole. The electrodes in the borehole may be raised successively to develop a log with the objective of determining the direction toward better mineralization. 2. A survey method in which the potential electrodes are moved along radii about a drill hole that contains a fixed current electrode. The second current electrode (‘‘infinite electrode’’) is a great distance away. Also called radial survey. 3. Azimuthal and radial ‘‘arrays’’ usually refer to dipole-dipole surveys where all electrodes are on the surface, in contrast to an azimuthal ‘‘survey’’ involving a drill hole.