Elastic Recoil Detection Analysis (ERDA) with primary ion beams having energies in the MeV/nucleon range allows the measurement of absolute concentrations and depth profiles especially of low Z elements in the surface layers of a solid. In the present work, we use simple mathematical relations for defining the optimal measurement geometry with respect to measuring large depths with high intensities. Results obtained by the straightforward surface approximation are shown and compared to calculations with a more complete model. A parameter discussion is given examining optimal geometries for different experimental set-ups. When using detectors sensitive to very low energies in order to be able to analyse large depths, the intensity loss due to the typically smaller solid angles of these detectors can be compensated by the higher intensity of the recoils in the corresponding geometry.