Patent GB-1076574-A (GB)
Title: Improvements relating to apparatus for displaying information, especially for air traffic control
Inventor: HERSCH WOLFGANG
IPC: G01S7/20
Filed: 1963-02-27
Abstract: 1,076,574. Radar; cathode-ray oscilloscopes. ELECTRIC & MUSICAL INDUSTRIES Ltd. Feb. 27, 1964 [Feb. 27, 1963], No. 7821/63. Headings H4D and H4T. A representation of an echo signal from an aircraft in a predetermined space is entered into an address of a store, a two-dimensional display produces an image representing a perspective view from an adjustable position of an outline of the boundaries of the space, three co-ordinate signals are obtained from the stored representation to define the position of the aircraft in the space, and the three coordinate signals are transformed into two control signals for the display to indicate the presence of the aircraft at the position corresponding to its actual position in the space. The display described is on the flat screen of a cathode-ray tube (C.R.T.), the aircraft positions are found by radar and the space is a cube. Alternative space figures are a vertical sectoral prism and a cylinder. Reticules (9, Fig. 1), may be arranged to move slowly up the cube (8) to indicate increasing height and each aircraft mark is arranged to be increased or reduced in intensity as the recticule passes through its height. Views of geographical features (10, 11) and outlines of airways may be added. Different features may be in different colours, e.g. different types of aircraft may be shown in different colours, and spot size may be made proportional to aircraft size. x and y deflection waveforms are produced in known manner from signals representing the position of each element in three-dimensional co-ordinates X, Y, Z by an analogue computer. Aspect control means afford rotation of the picture about a vertical axis and tilting about a horizontal axis for visual assessment of target range and height; the control may be operated by a "joy-stick" " or be operated in response to movement of the observer s body. The air space is divided into cells; in the computer memory each cell is defined by a unique address by digital coding and a computer continually translates the instantaneous position of each aircraft into the appropriate memory address. The C.R.T. beam traces a parallelogram of faint lines representing an XY plane; before the raster begins the X and Y co-ordinates of all aircraft in that plane are transferred into a register (Fig. 2) having X- addresses (13) and Y-addresses (14). Generators (15, 16) produce in succession the co-ordinate of every address in that plane and these are passed to comparators (17, 18) and if an aircraft is present in the cell a coincidence gate (19) either produces an intensity-modulation pulse for the C.R.T. or changes spot colour. The C.R.T. deflection means are preceded by digital-analogue converters and the analogue computer which generates the necessary and y waveforms. After exploration of an XY plane the register is cleared and the next higher plane is explored. The screen after-glow time is of the order of the time taken to scan the cube, e.g. one second. In another embodiment the C.R.T. beam first traces the outlines of the cube, reticules and obstacles; in a subsequent trace the deflection of the beam jumps in succession from one aircraft to another under the control of a circuit which interrogates sequentially the computer memory containing the aircraft positions. The display is produced at 25 pictures per second. Different features may be produced on corresponding C.R.T. screens, with optical projection on to a common screen via colour filters. Expansion or contraction of any of the three co-ordinate scales may be provided for. If the screen (1, Fig. 1) has sufficient afterglow, each aircraft mark has a " tail " indicating direction and speed of movement; if the screen afterglow is short the "tail" " is effected in response to stored information relating to previous aircraft positions. Alpha-numeric characters contained in panels outside the main display may be linked to relevant aircraft by electronically generated leading lines.