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Full-diameter core is oriented by a variety of methods. Popular techniques include (i) direct core orientation down-hole, and (ii) core orientation by a combination of core measurement and external orientation data either recorded down-hole, such as dip-meter and borehole image data, or estimated from magnetic field vectors or seismic data. The latter of these core orientation techniques is described here. For the purpose of this discussion, the formation dip and azimuth, derived from seismic data, is combined with core measurement of reference markers to allow internal features comprising cross-stratification and faults to be oriented. However, the procedure is equally applicable to use of dip-meter, borehole image or magnetic field vector data. For instances where dip-meter or borehole image data are used, the formation dip is replaced with the orientation of the imaged feature. Where magnetic field vectors are used, the formation dip is replaced with the measured and known magnetic field vectors. Although the technique has been applied successfully in several major oilfields, it appears under-utilized. The technique is especially useful for old cores, where alternative orientation methods are no longer available.