The transverse gradiometer is merely two magnetometers spaced horizontal and transverse to the direction of flight. The difference in intensity divided by the distance is approximately equal to the gradient (within 1% if sensor spacing is less than one tenth of the distance to anomalies). The objective of this configuration is to obtain total intensity data of extremely high accuracy throughout the survey area, especially in the large unmapped region between adjacent profile lines. The data are normally unknown in such a region and is perhaps the principal reason for a) inaccuracies in slopes as applied to depth-to-basement estimates for petroleum exploration; b) unmapped anomalies which occur between flight lines for mineral exploration; c) anomalies which close around flight lines and other such errors in maps in the location and shape of the anomaly sources, and d) the requirement to fly closely spaced lines to adequately portray the data.