GB2030685A - Artillery Fire Control Training Equipment - Google Patents

Abstract

Simulation equipment for training observers in the direction of artillery fire has an optical projector for projecting a picture of a target area terrain on to a screen (3). A television projector (5, 6) is arranged to superimpose moving targets, shell bursts and other transient visual effects on to the projected picture under the control of a computer which stores information as to the topography of the terrain. Loudspeakers (7, 8, 9, 10) provide audible effects under the control of the computer. The equipment also includes an instructor's control unit by means of which the instructor can select any one of several different firing exercises and initiate a simulated firing sequence. This control unit has a visual display unit (12) and a keyboard (14) to enable the instructor either to modify firing exercises already stored by the computer or to build up a new exercise by entering details of locations of guns, positions and types of targets, type of ammunition, wind speed and direction etc.

Description

SPECIFICATION Artillery Fire Control Training Equipment This invention relates to artillery fire control training equipment and is more particularly concerned with simulation equipment for the training of observers in the direction of artillery fire.

According to the present invention, artillery fire control training equipment comprises an optical projector for projecting a picture of a target area terrain, a computer which is arranged to store information as to the terrain topography of a picture projected by said optical projector and to compute upon inititation of a simulated firing sequence the position of shell bursts in the projected picture and the time of occurrence thereof, an electro-optical projection system (e.g. a television projector) for superimposing transient effects (e.g. shell bursts) in the projected terrain picture under the control of said computer, and control unit having manually-operable means to enable a simulated firing sequence to be initiated.

The electro-optical projection system may conveniently also be arranged to superimpose a moving target or targets on to the projected terrain picture.

Preferably the equipment has a permanent store which is adapted to store data (e.g. location of "guns", location of "targets", type of ammunition, etc.) in respect of a plurality of simulated firing exercises and the control unit has provision to enable an instructor to select any such exercise whereupon the data appropriate to that exercise is passed to and temporarily stored by a data store of the computer. To enable an instructor to modify such an exercise or to generate a new exercise, the control unit preferably has a visual display unit and a plurality of further manually-operable means, the arrangement being such that by operation of these means details of an exercise as stored by said computer data store may be displayed on the visual display unit and changed as required.

The equipment may include binoculars through which trainee observers may view the projected terrain picture, the binoculars having graticule markings to enable angular measurements to be made. If in a particular installation the trainee observers are not all situated the same distance from the terrain picture, the equipment preferably includes binoculars with different spacing of the graticule markings which are appropriate to the distance from the terrain picture so that angular measurements made by trainee observers with the aid of the binoculars are largely independent of the position of the observers.

One embodiment of simulation equipment in accordance with the present invention for training Forward Observation Post personnei in directing artillery fire on to targets observed visually will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows diagrammatically an isometric view of a classroom fitted with the equipment, Figure 2 is a block diagram of the equipment, Figure 3 is a plan view of an instructor's keyboard, Figure 4 shows five typical symbols which may be projected on to the screen of the equipment, and Figure 5 shows the circuit diagram of the video signal generator of the equipment in more detail.

Referring now to Figure 1 of the accompanying drawings, the equipment comprises two optical slide projectors 1 and 2 (only one of which is used at any time) and each of these projectors is arranged to project on to a screen 3 a colour picture of the target area in which simulated firing is to occur. Up to thirty trainee observers sit at desks 4, which are arranged in five rows, so as to view the picture projected on to the screen 3. Simulation of transient visual effects, such as shell bursts and smoke clouds, and moving targets, such as tanks, are superimposed on the picture projected on to the screen 3 by means of two television-type projectors 5 and 6 each of which is arranged to cover half the screen 3. Audio effects are provided by means of four loudspeakers 7, 8, 9 and 10.The equipment also includes an instructor's unit 11 which has a visual display unit 12 (with a cathode ray tube type of display) and two keyboards 1 3 and 14, the keyboard 13 being of special form as will hereinafter be described and the keyboard 14 having a plurality of alpha-numeric keys.

By means of the keyboard 13, the instructor is able to select any one of up to six target area pictures for projection by the projector 1 (or 2) and any one of up to six "firing" exercises. The necessary control signals for that purpose are supplied by a digital computer 1 5 and the interconnections between that computer and other items of the equipment are shown in Figure 2 of the accompanying drawings.

Referring now to Figure 2, an interface unit 1 6 is connected between the computer 1 5 and peripheral items (including the instructor's unit 11) which are controlled by the computer or to which the computer is required to respond. The necessary programs for controlling the computer 1 5 and data in respect of the terrain of the target area pictures which may be projected are permanently stored by a "floppy disc" store 17. Upon a particular target area picture and a particular exercise having been selected by the instructor, the relevant computer programme and data are automatically copied into a core store 18 of the computer 1 5 in known manner.At the same time signals are supplied over a lead 1 9 to the slide projector 1, say, to cause the appropriate slide to be selected for projection.

When the instructor subsequently presses the Fire key 1 9 (see Figure 3 of the accompanying drawings) of the keyboard 1 3, the selected exercise commences and the desired visual and audible effects of the simulation are produced in real time. For the visual effects, video signals are supplied to the projectors 5 and 6 by a video signal generator 20 at the appropriate times as the raster of those projectors is scanned (by frame and line time-base circuitry which is not shown). As to the audible effects, the appropriate audio signals are supplied by audio signal generators 21 and 22 and are passed through amplifiers 23 and 24 to either the loudspeakers 7 and 8 (in respect of shell bursts and "hostile" fire) or the loudspeakers 9 and 10 (in respect of the sound of flight of a projectile).To add realism to the simulation, general battlefield sounds (i.e. wind, tank noises, etc.), are supplied by a casette tape recorder 25 which is under the direct control of the instructor, the audio signal supplied by the recorder 25 being fed into the amplifier 23.

The visual effects to which references have previously been made may be in respect of a simulated shell burst (either a ground burst, an air burst with shrapnel or a "hidden" ground burst), a simulated smoke burst with subsequent development of a smoke cloud drifting with the wind, or a synthetic target which may be a tank, machine gun flashes or anti-tank gun flashes. In each case the appropriate pre-programmed "symbol" shapes are held in the computer store 18 and when required for use are automatically transferred, along with position and size information, to the signal generator 20 which supplies the appropriate video signals to the projectors 5 and 6. The symbols appear on the screen 3 as a bright shape with a slight bluish tint and are of sufficient brightness to swamp out that area of the optically projected terrain picture.

Thus, when the instructor sets up the next exercise on his control unit 11 and presses the Fire key 19, the computer 1 5 automatically decides which symbol shapes and sizes are required, their position on the screen and their switch on and switch off times. In the case of smoke, the computer 1 5 continuously determines the required shape and position as the smoke expands and drifts with wind speed and direction nominated by the instructor.

To use synthetic targets, the instructor nominates the symbol shape required, its position in grid co-ordinates and, in the case of moving tanks, their speed and direction. Because the computer 1 5 already knows the terrain topography data, the moving tanks are continuously positioned to drive over or behind any contours which are reievant to their track or to the observer's view point. The tank shape and aspect also changes automatically with range and heading changes though these particular changes occur in steps rather than as a continuous variation. Enemy machine gun or anti-tank gun fire appear at the positions defined by the instructor as flash symbols at pre-determined rates of fire.

Synthetic symbols as displayed on the screen 3 are composed of groups of rectangular picture elements whose width is 1/512 of the . ster width and whose height is one raster line. Hence, on the screen one rectangular element is 2.34 mil wide and 1.55 mil high in terms of the terrain picture scaling. (One mil is equivalent to an object size of one metre at one thousand metres range).

The basic symbol shapes are transferred from the computer 1 5 and held in a store (not shown in Figure 2) of the video signal generator 20 as a block of elements 1 6 widex 1 6 high. Hence, symbol shapes are made up of the required elements from this 1 6x 16 matrix. Having defined the symbol's basic shape, its size can be increased in steps by multiplying both axes of the 1 6x 16 matrix by factors of 1, 2, 4 or 8 by computer command. The position at which the symbol appears on the screen is controlled by the computer 1 5 to a resolution of 1 mol laterally and one raster line (1.55 mil) vertically.

Examples of five typical symbols which may be projected on to the screen 3 by the projections 5 and 6 are shown at Figure 4 of the accompanying drawings, the individual symbols providing simulations as follows:- Figure 4(a)-An airburst Figure 4(b)-An impact burst Figure 4(c)-A burst cloud appearing from behind an obstruction Figure 4(d)-Shrapnel Figure 4(e)-A tank at 400 metres It will be noted that all the symbols as projected are made up of rectangular elements (as previously described) and are as shown by the full lines 26, 27, 28, 29 and 30 in Figure 4 but, as far as each of the symbols (a), (b), (c) and (e) are concerned, the apparent shape seen by a trainee observer is that of the dotted lines 26A, 27A, 28A and 30A.

Referring now to Figure 5 of the accompanying drawings, the video signal generator 22 comprises an image data store 31 which receives and is arranged temporarily to store digital information received from the computer 1 5 in respect of symbols to be displayed. The information supplied by the computer in respect of each symbol image to be projected characterises the symbol in question, the size multiplication factor, the required video signal level and the position on the screen 3 at which the image is to be projected. There are also provided a plurality of symbol generators 32 (Only three of which are shown in the drawing) and each of these generators is arranged to supply video signals in respect of a different symbol. Video signals supplied by the generators 32 under the control of information stored by the data store 31 and timing signals supplied by a timing signal generator 33 are combined with a synchronising signal supplied by the timing generator 33 by means of a video output store 34 which passes the required video signal to the projectors 5 and 6. It will be noted that this arrangement enables the parameters of any particular symbol image to be changed while it is being projected.

The audio signal generator 21 (Figure 2) may conveniently comprise a plurality of separate generators each of which is arranged to supply an audio signal in respect of a different sound (e.g. a shell bursting, fire from an anti-tank gun, fire from a machine gun, etc.,). As required, each of these separate generators is rendered operative by an initiating signal received from the computer 1 5 which also supplied information as to the required level of audio signal. Operation of the audio signal generator 22 for the purpose of simulating the sound of flight of a projectile is similarly initiated by a signal received from the computer 1 5 but, in this case, the computer 1 5 also provides information as to the levels of audio signals to be supplied to the loudspeakers 9 and 10 so as to give a stereo effect.

As previously implied, the instructor's interface with the equipment under consideration is through the unit 11 (Figures 1 and 2). The visual display unit 12 and the keyboards 13 and 14 enable him to select a pre-recorded exercise (as stored by the store 17), to modify such a selected exercise, and to set-up a new exercise.

The information available to the instructor is presented on the visual display unit 1 2 is three separate alpha-numeric pages which are subsequently referred to as PAGE 1, PAGE 2 and PAGE 3 and are called up by pressing the appropriate one of three keys 35, 36 and 37 of the keyboard 13 (Figure 3). By moving a visible marker or cursor over a page displaced on the screen of the display unit 12, the instructor is able to select from a predetermined series of options and to enter information into the computer store 1 8 by operation of the keyboard 14. Movement of the cursor is effected by pressing arrowed keys 38 to 41 of the control keyboard 13, the resulting movement being in the direction indicated by the arrow.By repeated application of the appropriate arrowed keys 38 to 41 , the cursor can be moved to any position on the screen thus enabling individual parameters to be changed quickly.

The normal presentation on the screen of the display unit 1 2 is of white characters on a black background. The cursor appears as a white rectangle containing black characters, thus providing an isolated "attention-getter" within the total picture. During option selection, the cursor rectangle is the same length as the word selected and is one character in height. When entering numerical data, the cursor rectangle is one character in length in the position of the next digit to be entered.

The three separate pages for display by the unit 12 will now be considered in more detail. Firstly PAGE 1, which enables the instructor to make selections of terrain and exercise and gives the location of guns, is as follows:- TERRAIN EXERCISE 1 1 2 2 3 3 4 4 5 5 6 6 BATTERY LOCATION AND LAYOUT BATTERY BATTERY2 LOCATION E xxxxx E xxxxx N xxxxx N xxxxx ALTxxxx ALTxxxx LAYOUT GUN 1 xxxxxxxxxxx xxxxxxxxxxx GUN 2 xxxxxxxxxxx xxxxxxxxxxx GUN 3 xxxxxxxxxxx xxxxxxxxxxx GUN 4 xxxxxxxxxxx xxxxxxxxxxx In practice, the several x's in PAGE 1 as shown above would be replaced by numerals to give the eastings, northings and altitude of each battery and the disposition of the individual guns in each battery, the latter information being the range and bearing of each gun from a reference point for the battery. Although for simplicity, only two batteries of four guns each are shown, the equipment may handle up to four batteries each of eight guns with PAGE 1 extended accordingly.

PAGE 2 is concerned primarily with firing parameters and the locations of targets as follows:- BATTERY BATTERY2 BURSTTIME xx xx DECENT ANGLE xxxx xxxx DISPERSION ZONE Rxxx Hxxx Rxxx Hxxx OFFSET Exxxxx Exxxxx Nxxxxx Nxxxxx TIME OF FLIGHT xx xx DISPLAYED TARGETS TYPE POSITION COURSE SPEED TARGET 1 Exxxxx Nxxxxx xxxx xx TARGET 2 Exxxxx Nxxxxx xxxx xx TARGET 3 Exxxxx Nxxxxx xxxx xx WIND SPEED xx WIND DIRECTION xxxx On PAGE 2, BURST TIME specifies the length of time a shell burst symbol is required to appear after detonation. DECENT ANGLE specifies the descent angle (in milliradians) of a shell relative to the horizontal.DISPERSION ZONE gives the range variation (R) in metres of impact or air busts due to variations in trajectory and the height variation (H) in metres of air bursts due to variations in time fuse characteristics. OFFSET enables the instructor to offset the burst point for a firing (as otherwise specified on PAGE 3) in terms of eastings and northings. TIME OF FLIGHT is the time calculated by the computer 1 5 between the instructor pressing the FIRE key 1 9 and the instant at which the appropriate burst symbol is projected by the projector 7 or 8.

Under DISPLAYED TARGETS on PAGE 2, there is given details of up to six targets which are required to be displayed by means of the projectors 7 and 8 with their positions and, in the case of moving targets, their courses (in mils) and speed (in kilometers per hour) from the initial positions indicated. The identity of each target (i.e. the symbol to be displayed) is indicated in letters under the heading TYPE, e.g. TANK APC (for armoured personnel carrier), MGUN (for machine gun) and A TANK (for anti-tank gun).

PAGE 3 displays details of a particular exercise as follows:- BATTERY1 BATTERY2 NO. OF GUNS REQUIRED x x TARGET LOCATION GRID Exxxxx Exxxxx Nxxxxx Nxxxxx ALT xxxx xxxx OR TARGET NO x x AMMUNITION TYPE DISTRIBUTION OF FIRE GUN NUMBERS TO FIRE x x CORRECTIONS LEFT/RIGHT xxx xxx ADD/DROP xxx xxx UP/DOWN xxx xxx In PAGE 3, as in PAGE 1 and PAGE 2, the several x's are replaced by numerals. If there is an entry against TARGET NO., it is, of course, the number of one of the targets specified on PAGE 2. Against AMMUNITION TYPE is shown the appropriate type of ammunition in words, e.g., "HE" for high explosive, "MTSQ" for mechanical time super quick, "SMK" for smoke and "ILLUM" for star shells, for each battery (which again is only shown as two in number for simplicity although, in practice, there may be provision for four batteries).Against DISTRIBUTION OF FIRE appears the required distribution, e.g. PARALLEL or CONVERGE, for each battery. The number of the gun (see PAGE 1) in each battery is shown against GUN NUMBERS but if all the guns of a battery are to be fired '0' is inserted here.

Alterations in bearing and range with respect to an observer are given as LEFT/RIGHT and ADD/DROP corrections while for MTSQ variations in the height of burst above ground are given as UP/DOWN corrections. (A re-run of a firing sequence with such corrections incorporated may be effected by the instructor reoperating the key 1 9 after entering the corrections on PAGE 3).

It is convenient now to describe further the manner in which the instructor enters information on PAGES 1, 2 and 3. After selecting the appropriate page for display by means of one of the keys 35 to 37, the instructor moves the cursor (by operation of the keys 38 to 41) to the point in the display at which an entry is to be made and presses a further key 42 of the keyboard 1 3. Required numeric entries are then made by means of the keyboard 14 and the result is displaced at the bottom of the displayed page to enable it to be checked. Assuming the displayed information is correct, the key 42 is pressed again whereupon the information is transferred to the computer 1 5 for use in a subsequent firing exercise and appears in the display at the cursor selected position.If, however, the information is wrong, it may be deleted by operation of a key 43 of the keyboard 1 3.

The procedure just described is followed for entering types of target on PAGE 2 but, in that case, it is merely necessary to press a single key of the keyboard 14 according to the code 1 =a tank, 2=four tanks, 3=an APC, 4=four APC's, 5=machine gun and 6=anti-tank gun. Upon pressing the key 42 of the keyboard 1 3 for the second time, the appropriate legend appears in the displayed page at the cursor-marked position. Similarly ammunition types and distribution of fire are entered on PAGE 3 by using a single digit numeric code.

It will be appreciated that when the instructor presses the key 36 of his keyboard 13 (Figures 1 and 3), the PAGE 2 information displayed on the visual display unit 12 (Figure 1) is in respect of the terrain previously selected by means of PAGE 1. Similarly pressing the key 37 causes the PAGE 3 information displayed to be that appropriate to the exercise selected with the aid of PAGE 1.

When either PAGE 2 or PAGE 3 has been selected as aforesaid, the display of simulated targets (including the movement of moving targets) may be initiated by operation of a key 44 of the keyboard 13. A moving target may then be stopped by operation of another key 45 of the keyboard 13 followed by the numeric key of the keyboard 14 corresponding to the single target to be stopped (or the '0' key if all moving targets are to be stopped) and then the key 42. The targets may all be reset to their initial positions by operating the '9' key of the keyboard 1 4 in place of the target number.

In an alternative arrangement, instead of the keyboard 1 3 having three keys 35 to 37 which are operated to call up PAGE 1, PAGE 2 and PAGE 3 respectively, that keyboard may have one key (marked PAGE) and any one of the three pages may be called up for display by operating that key followed by the appropriate numeric key of the keyboard 14.

When a particular terrain has been selected as previously described, the computer store 1 8 (Figure 2) stores information of the topographical heights of the terrain to enable the burst point to be accurately calculated in three dimensional co-ordinates. The terrain is segmented into small areas each being defined by a 1 6-bit word. Eight bits are used to define the height of the centre point of each small area. The remaining eight bits are used for certain specific purposes:- 1. to define the shadow height to ascertain the visibility of the burst point from the observer's position (associated with an impact burst, a concealed burst or a rising smoke cloud).

2. to define particular terrain effects on synthetic tank movement. If a tank is driven towards or behind a wood, it will disappear into the wood rather than driving over the treetops. Similarly, a tank will disappear behind a hill.

For each gun "fired" upon the instructor pressing his fire-control key 1 9 (Figure 3), the computer 1 5 (Figures 1 and 2) effects the following series of calculations: 1. Calculate the required impact point of shell in terrain (X1Y1) using the observer's specified target grid position and corrections, and obtains terrain height (Z,) by a linear interpolation between the known spot heights of adjacent area segments in the stored terrain topography.

2. If an air burst is required, alter Z1 accordingly.

3. Apply random longitudinal and lateral dispersion and instructor's offset to obtain X2, Y2 and2.

In the case of MTSQ, resolves the vertical random dispersion value along the decent and azimuth angles to obtain new values of X2,Y2 and Z2.

(Note: X2, Y2 and Z2 are the co-ordinates of the actual burst point for any angle of descent assuming no intervening terrain feature caused premature termination of the trajectory. This must next be tested).

4. Extend a line towards the battery at the specified descent angle until outside the field of view limits and calculate the co-ordinates of this point on the trajectory.

5. Process terrain data from this point along the trajectory, checking for coincidence between trajectory height and terrain height. The co-ordinates of the point of coincidence (X3, Y3 and Z3) give the actual burst point.

6. Check terrain shadow height data at co-ordinates X3 and Y3 to determine if burst is hidden from the observer's view and choose type of burst symbol to be displayed. If a rising smoke cloud, adjust the Z3 coordinate to define the base height of the cloud. Pass burst symbol data to video signal generator 20.

7. Knowing observer's effective position co-ordinates (which are stored by the computer 15), transform burst position from X2, Y2 and Z2 co-ordinates (or X3, Y3 and Z3 co-ordinates as appropriate) to projected television (screen) co-ordinates which are expressed in TV raster line number for elevation and position along the line for azimuth. Pass this symbol position data to video signal generator 20.

8. Perform time of flight and range calculations to determine the times relative to the pressing of the FIRE key 1 9 at which the burst symbol display is to be switched on and off, the time of initiation of projectile noise, the relative amplitude required from the left and right loudspeakers 9 and 10, the time at which the audio burst detonation is to be triggered and the amplitude of this sound. Output these commands to the signal generators 20, 21 and 22 at the correct times.

Each trainee observer is provided with a pair of binoculars (not shown) for viewing the screen 3 (Figure 1) and these pairs of binoculars each incorporates a graticule scaled to match the screen scaling from the row of desks 4 from which they are to be used. Thus, since, there are five rows of desks 4, the binoculars have graticules with five different types of marking. Each graticule is, in fact, marked in units of 10 milliradians (to +40 milliradians) in azimuth and with markings of 5, 10 and 20 milliradians in elevation.

Claims (22)

Claims

1. Artillery fire control training equipment comprising an optical projector for projecting a picture of a target area terrain, a computer which is arranged to store information as to the terrain topography of a picture projected by said optical projector and to compute upon initiation of a simulated firing sequence the position of shell bursts in the projected picture and the time of occurrence thereof, an electro-optical projection system for superimposing transient effects (for example shell burst) in the projected terrain picture under the control of said computer, and a control unit having manuallyoperable means to enable a simulated firing sequence to be initiated.

2. Artillery fire control training equipment as claimed in Claim 1 in which the electro-optical projection system is a television projector.

3. Artillery fire control training equipment as claimed in Claim 1 or Claim 2 in which the electrooptical projection system is arranged to superimpose one or more moving targets on to the projected terrain picture.

4. Artillery fire control training equipment as claimed in Claim 1, Claim 2 or Claim 3 including a permanent store which is arranged to store data (for example location of "guns", location of "targets", type of "ammunition") in respect of a plurality of simulated firing exercises.

5. Artillery fire control training equipment as claimed in Claim 4 wherein said control unit has provision to enable any one of the plurality of simulated firing exercises to be selected.

6. Artillery fire control training equipment as claimed in Claim 5 in which the control unit comprises a visual display unit and a plurality of manually operable means.

7. Artillery fire control training equipment as claimed in Claim 6 in which, upon operation of one or more of the manually operable means, the visual display unit is arranged to display details of the exercise stored in said computer data store.

8. Artillery fire control training equipment as claimed in Claim 7 in which the data stored in said computer data store may be modified y operation of one or more of the manually operable means.

9. Artillery fire control training equipment as claimed in anyone of Claims 5 to 8 having provision for the data appropriate to the selected exercise to be passed to and temporarily stored by a data store of the computer.

10. Artillery fire control training equipment as claimed in any one of Claims 4 to 9 in which the permanent store comprises one or more floppy disc stores.

11. Artillery fire control training equipment as claimed in any preceding Claim including binoculars through which the projected terrain may be viewed.

12. Artillery fire control training equipment as claimed in Claim 11 in which the binoculars have graticule markings to enable angular measurements to be made.

1 3. Artillery fire control training equipment as claimed in Claim 12 in which the graticule workings have different spacings such that the angular measurements made by observation of the projected terrain picture through the binoculars are largely independent of the distance from said terrain picture of an observer.

14. Artillery fire control training equipment as claimed in any preceding Claim including a plurality of loudspeakers and at least one signal generator controlled by the computer said loudspeakers and at least one signal generator being arranged to provide audio effects (for example the sound of a shell burst).

15. Artillery fire control training equipment as claimed in Claim 14 including means for superimposing pre-recorded background audio effects (for example the sound of moving tank tracks) through the loudspeakers.

1 6. Artillery fire control training equipment as claimed in any preceding Claim in which some or all of the manually operable means are alpha-numerically labelled keys.

1 7. Artillery fire control training equipment as claimed in any preceding Claim in which a video signal generator is provided as an interface between the computer and the electro-optical projection system, said video signal generator being arranged to store data relating to visual effects which are to be projected by said electro-optical projection system.

18. Artillery fire control training equipment as claimed in any preceding Claim in which the visual effects as projected by the electro-optical projection system are made up of one or more rectangular elements.

1 9. Artillery fire control training equipment as claimed in Claim 17 or Claim 1 8 in which said data relating to visual effects is stored as a block or matrix of elements 1 6 high and 1 6 wide.

20. Artillery fire control equipment as claimed in any preceding claim in which the electrosptical projection system comprises two projectors one of said projectors being arranged to superimpose transient visual effects substantially in one half of the projected terrain picture the other of said projectors being arranged to superimpose transient visual effects substantially in the other half of the projected terrain picture.

21. Artillery fire control training equipment as claimed in Claim 9 or Claim 10 in which the details of the exercise stored in said data store are displayed on the visual display unit in a plurality of pages each of said pages being selected by operation of the manually operable means.

22. Artillery fire control training equipment substantially as hereinbefore described with reference to the accompanying drawings. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~