The X-Y calipers have four arm calipers which can record separate measurements from each of the two opposing sets of arms. One axis is transmitted up the line as positive pulses, while the other axis utilizes negative pulses when used on single conductor electric wireline. Additionally, X-Y calipers can offer a main idea of hole shape. What is more important is that they can be used to make somewhat more accurate estimations of hole volume than with a single axis caliper. The X-Y caliper would give an precise reading of both the minor and major axes of the ellipse if a hole were a true ellipse. However, the real world boreholes are never really round or really elliptical. Borehole volume computer modules have been manufactured for use with X-Y calipers.