ABSTRACTThe principle of optical pumping allows the design of magnetometers with high sensitivity. When mapping the field of the total magnetic force, it is no longer possible to make full use of the accuracy of the instruments because the accuracy of the reduction of the diurnal variation is limited. By simultaneously recording with two instruments in different altitudes, the vertical gradient can be measured which doe's not depend on the time variation of the magnetic field. Therefore, the gradiometer seems to be a more adequate tool for oil exploration than the magnetometer.It is investigated in this article whether the results of this gradiometer or the measurements of the total magnetic field by the high sensitive magnetometer are more useful in oil exploration. The article comes to the conclusion that for most problems of oil exploration the total magnetic field is a more valuable unit than the vertical gradient measured directly by the gradiometer. The total magnetic field allows a better investigation of the tectonics than the vertical gradient. The apparent advantages of the gradiometer claimed by its supporters are mainly based on inconsistent mathematical concepts.