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dipmeter log A down-hole geophysical log designed to measure the dip and dip direction of dipping surfaces in a borehole. The logging tool consists of four resistivity logging devices set at 90° to one another, and held against the side of the borehole (see RESISTIVITY LOG; and RESISTIVITY METHODS). When wound back to the surface they respond instantly to layers of differing electrical resistivity (e.g. a clay horizon or porous sands) associated with the bedding, while dipping beds produce a response with a time delay related to the dip of the horizon. Computer processing of the data yields a tadpole plot of dips and dip directions in the well. It is claimed that dipmeter data can be used to identify tectonic as well as sedimentary structures. In practice, the data are often equivocal and must be interpreted with great caution.