Crab Angle Estimation with Two Dimensional Cross Correlations and Centroids.

This study is concerned with a high range resolution radar system for measuring the crab angle of landing aircraft. Previous attempts to measure the crab angle by means of one dimensional cross correlation techniques had proved to be unsuccessful, and the data from flight tests was examined to determine whether accurate estimates could be obtained by using two dimensional cross correlation techniques and centroids. Hundreds of different types of estimators were examined, each one corresponding to different possibilities for data smoothing, data weighting, thresholding, and outlier removal however, none of these methods produced satisfactory results. The probable cause for the poor performance was determined to be a lack of similarity in the returns from the two radars used in the system. The dissimilarity between the two returns was apparently caused by range differentials, aircraft roll, as well as the crab angle itself.