| 摘要 |
<p>A streamer 21 has groups of at least two piezo-ceramic hydrophones 201,202 arranged as a vertical array. The vertical pressure gradient measured at two hydrophones 201,202 having a vertical distance between them, calculated by subtraction of the two pressure measurements, is used to identify upward and downward propagating waves and hence remove ghosts from seismic data. The vertical distance between two hydrophones will vary as the cable twists, so the rotation of the cable is measured by inclinometers distributed along the cable. Alternatively the rotation of the cable is determined by analysing the arrival times of signals reaching the hydrophones from existing acoustic positioning system sources, or from the seismic source itself.</p> |
