The majority of geomorphological techniques seek either directly or indirectly to provide a rate of process operation in time or space. Thus, techniques of material properties (Part Three) allow us to predict failure on hillslopes, while drainage basin morphometry (Part Two) frequently facilitates a significant postdiction potential when combined with knowedge of contemporary processes. Thus, techniques capable of both postdiction (extrapolation from the present to the past of contemporary process-form interrelationships) and prediction are to be reviewed in the following sections. The advent in recent time of an ever-improving ability to be more precise over measurement of nearly every type has broadened the base from which process statements either forwards or backwards in time can be made. The geomorphologist now has data available from a spectrum of techniques, providing high resolution, from the micrometre scale to thousands of square kilometres of the Earth's surface.