Although the clinometer-based Hewett method and Jacob staff method of stratigraphic-section measurement appear similar, they are fundamentally different. In the general case of strike-oblique traverses (where traverse obliquity may range from 0° to 90°) the Hewett method gives rigorous results with a single formula. Except in the special case of a strike-normal traverse, the Jacob staff method does not give direct measurement of stratigraphic thickness; the error increases substantially with increasing dip and with increasing departure from a strike-normal traverse. A simple mathematical explanation for the paradox is given, along with a graph which shows the magnitude of the error resulting from assumption of direct measurement of thickness by the Jacob staff method.

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