An optimal trade-off between the width of the subarray aperture and the width of the interferometer base line is performed that achieves a specified elevation angle estimation error while minimizing the overall height of the interferometer configuration. Statistical decision theory is used to analyze and design a separate sensor for resolving the interferometer ambiguities. For coverage over 2.5 to 40 in elevation and +/-60 in azimuth, two 7-wavelength subarrays separated by 8 wavelengths are sufficient for 1-mrad elevation-angle errors. A 4-element nonuniformly spaced array of dipole antennas mounted on tri-plane reflectors renders the probability of an ambiguity error less than 0.004.