1531548 Seismic exploration ENTREPRISE DE RECHERCHES ET D'ACTIVITES PETROLIERES 9 June 1976 [16 June 1975] 23886/76 Heading G1G [Also in Division H3] In seismic exploration, signals from a particular shot are picked up at each of a number of detecting positions and each signal is sampled and digitized, one bit per sample, by comparing it with a reference voltage selected at random from a plurality of equally spaced reference voltages, and the digitized samples are recorded at respective image points on a two-dimensional time position plot so that the value of the detected signal at any one time/position point is represented by the average density of colour around that point.
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