1. n. [Formation Evaluation]

The response of a logging measurement as a function of the distance perpendicular to the tool. Radial responses are determined by computer simulation or laboratory measurement. For some measurements, mainly resistivity, the radial response can be shaped as desired through signal processing. In general, the radial response depends on the formation properties throughout the measurement volume. Most quoted radial responses have been determined in formations that are vertically homogeneous and have small radial changes. They can then be summarized by a geometrical factor or a pseudogeometrical factor. These factors are appropriate for volumetric measurements such as nuclear and resistivity measurements, but not for others such as acoustic propagation.

See: depth of investigation,  radial resolution,  vertical response