Gravimagnetic Anomaly Formulae for Extended Homogeneous Prisms

Anomaly formulae are known in closed form for homogeneous prismatic targets, as well as their limiting forms for prisms of infinitesimal or infinite extent, but the transition from finite to limiting form is numerically ill-conditioned. In the case of elongated prisms and thin sheets, we show how dominant terms in the polyhedral anomaly formulae can cancel analytically before numerical evaluation, allowing the limiting forms to be approached in a numerically stable way. We demonstrate the superiority of the new formulae over standard anomaly formulae by computing the relative anomaly deviation from the limiting form. Numerical breakdown is avoided in the new formulation.