Patent GB-1230742-A (GB)
IPC: G09B9/30
Filed: 1969-02-07
Abstract: 1,230,742. Television; radar simulators. NORTH AMERICAN ROCKWELL CORP. 7 Feb., 1969 [1 April, 1968], No. 6842/69. Headings H4D and H4F. Apparatus for providing a real-time dynamic perspective display of the terrain on a contour map comprises means for scanning the map, from an initial position, along a pattern comprising a series of lines at increasing ranges from the initial position to produce signals representative of a continuous series of profile lines and means for displaying such profile lines. The contour map contains a series of equi-altitude lines defining a plurality of ribbons of terrain each characterized by a certain altitude range and adjacent ribbons are coded by giving then different optical properties, e.g. a repeating sequence of clear, gray, black, clear &c. which is "recognized" by a flying-spot scanner so that from the signals derived by scanning an unequivocal change in altitude can be assumed. The terrain represented on the map may be that in front of an aircraft or aircraft simulator. Fig. la, shows the contour map which, using the 1000 feet contour as a reference altitude, has the ribbon 5 of terrain on the "up-hill" side produced in "clear", the ribbon 4 between the 1100 and 1200 feet contours produced in gray and the ribbon 3 between the 1200 and 1300 feet contours produced in black. Thus all steps of increasing altitude are characterized by a step change in the darker direction of a change of from black to clear and all steps of decreasing altitude are characterized by a step change in the lighter direction or by a change of from clear to black. Fig. 1b shows the profile which would be obtained by scanning the map of Fig. 1a along a line AB. In the operation of the invention the map is scanned according to the pattern 6 shown in Fig. 3 where P 0  is the initial position (i.e. of the aircraft or simulator) the map being driven by drive mechanism 51 (Fig. 6) in accordance with the carying position of P 0 . The scanning is effected by a flying-spot scanner 50 and associated photo-cell 53 by means of a generator 52 supplying step deflecting waveforms #s, Fig. 7a, applied to the horizontal deflecting means and R s , Fig. 7b, applied to the vertical deflecting means such that considering the geometrical factors shown in Figs. 2, 3 and 4 and taking the map coding into account the output of the photo-cell 53 may be converted to incremental height quantities +#h and -#h which are combined in an algebraic adder 51 with the actual altitude h 0  of the aircraft (or simulator) derived from altimeter 56. The instantaneous value of R s , which is equal to R t  (see also Fig. 4), is then combined with the output h t  of adder 55 in a co-ordinate converter 57 to derive the angle αt and from this and the quantity # i , (= the instantaneous value of # s ) and from adjustable signals X 0  and Y 0 , which define the "boresight" direction, signals X and Y are derived in co-ordinate converter 58 and utilized to control the horizontal and vertical deflection of a display cathode-ray tube 59. The whole operation is controlled by a clock 61 which starts scan generator 52 the latter then being reset at the end of a complete scan by the output of a reset pulse generator 62 which also re-sets adder 55 and a Ghost Suppression stage 60. The latter operates to prevent the display of successive profile lines which are representative of altitudes lower than altitudes represented by previously traced profile line (i.e. profile lines which in a perspective display would be masked by the previously traced higher altitude profile lines) and comprises a plurality of storage units (one for each of the # s  scan steps shown in Fig. 7a) in which the derived αt signal for each  #s  step is stored under control signals from the clock 61. On the next scan the quantity at for each bearing angle # s  is compared with the stored value of <SP>α</SP>t for the previous scan and if the former is larger such value is stored and displayed on display tube 59 whereas if the current value of at is less than the stored value the incoming signal is prevented from diminishing the stored signal level and a blanking pulse is applied to the display tube over line 63. Fig. 8 shows the type of display produced when the deflection signals X and Y are utilized directly without "smoothing" and Fig. 9 shows the effect on the display of filtering the X and Y signals.