Resolution of Azimuthal and Vertical Arrival Angles at a Rotatable Horizontal Line Array

A Horizontal Line Array (HLA) receiver is subject to left-right bearing ambiguity. It is also susceptible to bearing bias caused by non-zero vertical arrival angles. The true bearing angle and the vertical arrival angle may both be estimated if a second observation is made, with the HLA rotated to a new heading. A closed-form solution is presented for the case of stationary source and receiver. For small observation errors, the resulting errors in the estimated angles can also be expressed in closed form.