Abstract: A method for use in seismic surveying includes determining the shape of a seismic cable during a seismic survey; determining the tension on the seismic cable at a plurality of points along the seismic cable; and predicting a current that will impact the seismic cable from the determined shape and the determined tension. The method may be practiced two-dimensionally in the context of a marine survey employing a towed streamer array or three-dimensionally in the context of laying an array of ocean bottom cables on the seabed. The predicted currents can, in some embodiments; be used to make steering corrections for the seismic cables.

Abstract: A method and apparatus for detecting areas of differential density in logs, cants, timbers, poles or trees comprises applying a signal to one or more pairs of electrodes and measuring the magnitude and phase shift of the voltage, current or impedance at an output electrode. Electrodes may be arranged in a circumferential or opposed configuration depending on scanned product shape, and may be stationary or move freely but are preferably in direct contact with wood surface. Wire brush electrodes are used in some embodiments. Measurements are taken in both directions between an electrode pair. Multiple frequencies may be employed. Different electrode sizes may be used for different measurements.

Abstract: A method and apparatus for detecting areas of differential density in logs, cants, timbers, poles or trees comprises applying a signal to one or more pairs of electrodes and measuring the magnitude and phase shift of the voltage, current or impedance at an output electrode. Electrodes may be arranged in a circumferential or opposed configuration depending on scanned product shape, and may be stationary or move freely but are preferably in direct contact with wood surface. Wire brush electrodes are used in some embodiments. Measurements are taken in both directions between an electrode pair. Multiple frequencies may be employed. Different electrode sizes may be used for different measurements.