1. A two-dimensional sparse interferometric array for determining an angle of approach of an incoming signal incident to the array, comprising: a first plurality of elements in a first sub-array and a second plurality of elements in a second sub-array, the first sub-array having a size different from a size of the second sub-array and no three of the first and second pluralities of elements being co-linear, the first and second pluralities of elements forming a plurality of pairs of elements; wherein the first sub-array and the second sub-array of elements enables an unambiguous estimate of an angle of approach of the signal.