Abstract: Radar display apparatus employs digital techniques to convert range/azimuth scan to T.V. scan. A digital store contains data defining the brightness of levels for the picture cells of a T.V. display. The store is continuously updated in accordance with received video from a digitiser. The correct cell in the store for updating is identified by converting polar coordinates to Cartesian coordinates in a Sin .theta., Cos .theta. generator and integrators. The contents of the store for the addressed picture cell is modified by a control unit in accordance with the digitised video return so as to represent the degree of positive correlation of returns in that cell on successive azimuth scans of the radar. Thus the brightness or color of the cell on the T.V. display represents this degree of correlation.