A technique to refine the elevation estimates in low-angle tracking data measured with an array antenna

A technique to refine target elevation estimates by modifying the antenna calibration table is described. The data were measured with an array antenna and low-level aircraft flying over water. An optical tracker mounted close to the antenna provided an independent measure of the target elevation. In data measurement, there was an unknown error source which produced a date-dependent offset in the antenna boresight direction. A previous analysis of the data, using the singular value decomposition method, found that there were false tracks branching out from the target and image tracks. The modified calibration table significantly reduces both the number of these false tracks and the scattering of the estimates close to the output target tracks. It also reveals that the gradient of the output target track was less negative than that of the optical track. A possible link between this property and the data-dependence of the offset in antenna boresight direction is discussed