A tool-geometry correction factor that is particular to calliper-based dipmeter and imaging tools. Caliper pairs (in four arm devices) and individual calipers (within six arm tools) expand to fill a wellbore. If the well bore is not circular, but say elliptical, the calipers will sit at different extensions, and pads will gather data at different depths. The swing arm correction is applied to bring data to a common depth point.
Each caliper of a fully independently six-arm tool can move without reference to each other during a logging run. This allows for the tool to be positioned within the well bore with a lower degree of symmetry than a typical four-arm tool. The loss of symmetry creates a more complex tool-positioning problem for a six-arm device.