Comparison of altitude estimation using 2D and 3D radars over spherical earth

This paper presents a target altitude estimation approach based on multipath detections with range and range rate information from a 2D airborne radar. Using multipath detections has to deal with the following challenges: 1) Low probability of detection of the indirect path signal reflected by the sea surface; 2) Lack of an analytical expression for the relationship between the target state and the indirect path measurements over spherical Earth; 3) Unknown range measurement error standard deviation for the indirect path signal. Two estimators are developed: an adaptive multiple model iterated least squares (AMM-ILS) estimator for motion parameter estimation (noiseless target motion) and an AMM unscented Kalman filter (AMM-UKF) for dynamic state estimation (noisy target motion). The resulting altitude estimates from a 2D radar are compared to a 3D radar with range and elevation measurements. The simulation results show that the 2D radar provides better target altitude estimation accuracy than the 3D radar.