Two new ERT array optimisation strategies are presented that attempt to maximise the spatial resolution of the image for a given number of measurements. Synthetic modelling studies and inversions are used to assess the performance of the optimised arrays against arrays of standard Wenner-Schlumberger and Dipole-Dipole configurations. For the same number of configurations, the optimised arrays are found to perform at least as well as, and mostly better than, the standard arrays.