Large-diameter boreholes drilled at the Nevada Test Site for the Department of Energy frequently exhibit an elongation in response to the regional stress field. Single-axis, decentralized logging tools invariably migrate to the long axis of the hole while logging. The long axis is the roughest and is more frequently washed out. The design of these tools therefore ensures that the worst possible side of the borehole is being logged. A new line of geophysical logging tools has been developed at the suggestion of EG and G, Energy Measurements, Inc., to overcome the effect of borehole elongation. A pair of orienting arms set at 90/sup 0/ to the measurement axis effectively turn the tool so that measurements are always recorded on the smoother, short side of the borehole. 3 refs., 5 figs.