A process for measuring the gradient or an n-th order derivative, in which n is greater than 1, in a direction z, of a component Hx of a magnetic field, the component being invariant, at least locally, in a direction y. The method includes: a) positioning of N (N>n+1) elementary field sensors, each sensor being offset, relative to the neighboring sensors, along y by a distance Ty and along the z axis by a distance Δz, b) measurement of the field by each of the N sensors, and c) calculation of the desired gradient, or the desired nth-order derivative, as a function of the measurements of the field obtained during b).