B011 MODELLING THE MEAGNETIC FIELD GRADIENT FOR ARCHAEOLOGICAL STRUCTURES IN SAQQARA (EGYPT) SUMMARY 1 The magnetic prospection for archaeological structures in the northern cemetery of Saqqara (Egypt) was carried out with a fluxgate gradiometer. The magnetic image showed an outline of a large tomb complex. An algorithm was developed to model the vertical gradient of the vertical component of the magnetic field for spherical units located at arbitrary locations and depths. We tried to simulate the archaeological structures with spheres of different sizes depths and lateral offsets using the potential equation of a sphere with a volume of an enclosing