GB1605209A

GB1605209A - Weapon locating apparatus

Info

Publication number: GB1605209A
Application number: GB2638568A
Authority: GB
Original assignee: EMI Ltd
Current assignee: EMI Ltd
Priority date: 1969-06-04
Filing date: 1969-06-04
Publication date: 1983-11-02

Description

(54) "IMPROVEMENTS RELATING TO WEAPON LOCATING APPARATUS" (71) We, EMI LIMITED, formerly ELECTRIC & MUSICAL INDUSTRIES LIMITED, a British Company, of Blyth Road, Hayes, Middlesex, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to weapon locating apparatus in which radar is used to detect the position of a projectile from a weapon, and in response to the observed positions of the projectile its trajectory is calculated and extrapolated so as to provide an indication of the likely location of the weapon from which the projectile was fired.

Figure 1 of the drawings shows a weapon A such as a mortar which fires projectiles such as mortar bombs along a trajectory represented by the dashed line B so that the mortar bombs land at position C. A weapon locator D observes a mortar bomb at a plurality of positions such as E, F and G along its trajectory and computing means associated with radar apparatus in the locator responds to the observed positions of the mortar bomb to produce equations relating to the estimated trajectory of the mortar bombs.However, if it is assumed that the mortar is located at the same height as the locator D, points at this height being represented by the dotted line H, then the position estimated by the locator for the mortar will be the point J where the trajectory B crosses the line H so that fire directed at the mortar A in response to the instructions from the locator D will in fact land at a position indicated by the arrow K. In order to overcome this disadvantage in a known weapon locator, the locator is provided with means for feeding as an input signal the estimated altitude of the mortar above the locator, an initial value of the altitude being taken from a map of the region using the altitude of the terrain at the point K.In response to this altitude instruction the locator will indicate that the weapon lies at the point L, and as the point L lies beneath the surface of the ground indicated by the line M the altitude input to the locator is updated to that of the ground immediately above the point L, that is at the point N. In this way successively closer approximations to the position of the mortar A are produced. It will however be appreciated that the operation described above is time consuming and prone to error.

It is an object of the present invention to provide an improved weapon locator in which the time taken to locate the weapon is reduced.

According to the present invention there is provided a weapon locator including radar means for observing the position of a projectile from a weapon at several points along its trajectory, computing means responsive to said radar means to provide a series of estimated positions for said weapon dependent upon different estimated heights along the trajectory, means for producing a representation of the actual heights of a region which includes said estimated positions and means for superimposing on said representation said estimated positions, whereby the location of said weapon can be identified on said representation as the position at which the estimated and actual heights coincide.

In order that the invention may be fully understood and readily carried into effect it will now be described with reference to the drawings accompanying the Provisional Specification of which: Figure 1 illustrates the problem with which the invention is concerned as has been described above, Figure 2 shows in diagrammatic form one example of a weapon locator according to the invention, and Figure 3 shows another form of display from a weapon locator according to another example of the invention.

In Figure 2 a radar apparatus indicated by the block 1 provides a plurality of signals representing the position of a projectile at a number of points along its trajectory, which signals are applied to a computer indicated by the block 2. The radar 1 may use continuous tracking or track-while-scan techniques to observe the projectile and signals may be fed from the computer 2 to the radar 1 to assist in this. An output from computer 2 is fed to a projection cathode ray tube 3 to produce a bright spot at a position representing the location of the weapon. This bright spot is focussed by a lens 4 on to a screen 5 on which a display is produced, the bright spot being indicated by the point 6.Means 7 is provided for entering into the computer 2 an estimate of the height of the weapon relative to the locator which as can be seen from Figure 1 will have the effect of moving the position of the point 6 on the display 5.

In the absence of adjustment by the means 7 the point 6 corresponds to the point J. The means 7 may be arranged to receive the height above sea level of the weapon and includes switches, for example, for entering the height above sea level of the locator itself, so that the computer in the locator can respond to both heights. An optical film or slide projector 8 is provided coupled to the computer 2 and is caused to display on the screen 5 a contour map of the region in which the weapon lies.

The slides for the projector 8 are arranged in such a way that a particular one of the slides is selected by the computer 2 and the scan of the cathode ray tube 3 is arranged so that the bright spot 6 appears at the correct position on the map displayed on the screen 5.

In the operation of the apparatus shown in Figure 2 an operator viewing the display on the screen 5 notes the height set in by the input means 7 and compares it with the height indicated on the contour map 5 at the point of the bright spot 6. If these two heights are the same then the spot 6 clearly indicates a likely location of the weapon at ground level. On the other hand, if the height indicated by the input means 7 differs from the height indicated by the map displayed on the screen 5 at the bright spot 6 then the height set on the input means 7 is adjusted to tend to bring the two heights to equality so that the bright spot 6 correctly indicates a likely location for the weapon.

Figure 3 shows a modified form of display which could be produced on the screen 5 in which a line 10 is produced on the display indicating the locations of the weapon for a range of different heights and a crossing line 11, or other indication is moved along the line 10 in dependence upon the adjustment of the height set in the input means 7.

Instead of using a projection cathode ray tube and a screen 5 as shown in Figure 2 a direct viewing cathode ray tube may be used with a rear optical port through which the slide or film may be projected by projector 8 to produce an image on the screen of the cathode ray tube.

The height set in by the means 7 may be indicated adjacent to the display or, preferably, adjacent to the spot 6 (Figure 2) or cross line 11 (Figure 3) on the display, which can readily be accomplished by arranging that the cathode ray tube 3 produces a display of the appropriate cyphers under the command of the computer 2. Rapid comparison of the height set In by the means 7 and the contour height is facilitated by such arrangements.

In order to accommodate large differences in the height of the weapon relative to the locator the projector 8 may be provided with slides or films of maps on different scales of which finally a relatively small area map is displayed on a fairly large scale on the screen 5 so as to assist in the accuracy of the estimation of the location of the weapon.

Preferably the operation time of the computer 2 in response to adjustments to the height set-in by the input means 7 is sufficiently rapid that to the operator the movement of the bright spot 6 or the crossbar 11 appears to be directly linked to the input means. When the corrected location of the weapon as estimated by the computer 2 is determined a numerical display or print out may be provided indicating the location.

In yet another alternative arrangement a light pen is provided coupled to the computer in such a way that the light pen can be placed at a position along the line 10 shown in Figure 3 and the computer can produce an output indicating the height of the trajectory at the position indicated by the light pen and the light pen may be moved along the line 10 until the height indicated by the computer is equal to the height indicated by the contour map at the position of the light pen on the display. In a further alternative the line 10 of Figure 3 may be provided with markings for different heights.

The speed at which correction of location in dependence upon the altitude of the terrain is accomplished in accordance with this invention is dependent on the speed of the assimilation of the contour information by the operator, and this can be enhanced in a number of ways, apart from the use of a high display brightness and resolution. For example, the contour map may be displayed in colours together with a scale indicating the heights associated with the different colours.

The slide or film of the map of the area may be shaded in density in dependence on the contour heights and the spot 6 focussed on the slide or film so that the light transmitted by the slide or film is proportional or inversely proportional to the height of the ground at the point indicated by the spot 6, and a photo-multiplier placed to receive the transmitted light. The photo-multiplier will produce a signal representing this height which can be used in an analogue or digital servo mechanism automatically to move the spot 6 to a point at which the height of the ground and height of the point of the trajectory are equal.

In addition to its use for locating enemy weapons the locator can also be used to determine the position of fall of shots from friendly weapons.

WHAT WE CLAIM IS: 1. A weapon locator including radar means for observing the position of a projectile from a weapon at several points along its trajectory, computing means responsive to said radar means to provide a series of estimated positions

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Claims

**WARNING** start of CLMS field may overlap end of DESC **.

4 on to a screen 5 on which a display is produced, the bright spot being indicated by the point 6. Means 7 is provided for entering into the computer 2 an estimate of the height of the weapon relative to the locator which as can be seen from Figure 1 will have the effect of moving the position of the point 6 on the display 5.

In the absence of adjustment by the means 7 the point 6 corresponds to the point J. The means 7 may be arranged to receive the height above sea level of the weapon and includes switches, for example, for entering the height above sea level of the locator itself, so that the computer in the locator can respond to both heights. An optical film or slide projector 8 is provided coupled to the computer 2 and is caused to display on the screen 5 a contour map of the region in which the weapon lies.

The slides for the projector 8 are arranged in such a way that a particular one of the slides is selected by the computer 2 and the scan of the cathode ray tube 3 is arranged so that the bright spot 6 appears at the correct position on the map displayed on the screen 5.

In the operation of the apparatus shown in Figure 2 an operator viewing the display on the screen 5 notes the height set in by the input means 7 and compares it with the height indicated on the contour map 5 at the point of the bright spot 6. If these two heights are the same then the spot 6 clearly indicates a likely location of the weapon at ground level. On the other hand, if the height indicated by the input means 7 differs from the height indicated by the map displayed on the screen 5 at the bright spot 6 then the height set on the input means 7 is adjusted to tend to bring the two heights to equality so that the bright spot 6 correctly indicates a likely location for the weapon.

Figure 3 shows a modified form of display which could be produced on the screen 5 in which a line 10 is produced on the display indicating the locations of the weapon for a range of different heights and a crossing line 11, or other indication is moved along the line 10 in dependence upon the adjustment of the height set in the input means 7.

Instead of using a projection cathode ray tube and a screen 5 as shown in Figure 2 a direct viewing cathode ray tube may be used with a rear optical port through which the slide or film may be projected by projector 8 to produce an image on the screen of the cathode ray tube.

The height set in by the means 7 may be indicated adjacent to the display or, preferably, adjacent to the spot 6 (Figure 2) or cross line

11 (Figure 3) on the display, which can readily be accomplished by arranging that the cathode ray tube 3 produces a display of the appropriate cyphers under the command of the computer 2. Rapid comparison of the height set In by the means 7 and the contour height is facilitated by such arrangements.

In order to accommodate large differences in the height of the weapon relative to the locator the projector 8 may be provided with slides or films of maps on different scales of which finally a relatively small area map is displayed on a fairly large scale on the screen 5 so as to assist in the accuracy of the estimation of the location of the weapon.

Preferably the operation time of the computer 2 in response to adjustments to the height set-in by the input means 7 is sufficiently rapid that to the operator the movement of the bright spot 6 or the crossbar 11 appears to be directly linked to the input means. When the corrected location of the weapon as estimated by the computer 2 is determined a numerical display or print out may be provided indicating the location.

In yet another alternative arrangement a light pen is provided coupled to the computer in such a way that the light pen can be placed at a position along the line 10 shown in Figure 3 and the computer can produce an output indicating the height of the trajectory at the position indicated by the light pen and the light pen may be moved along the line 10 until the height indicated by the computer is equal to the height indicated by the contour map at the position of the light pen on the display. In a further alternative the line 10 of Figure 3 may be provided with markings for different heights.

The speed at which correction of location in dependence upon the altitude of the terrain is accomplished in accordance with this invention is dependent on the speed of the assimilation of the contour information by the operator, and this can be enhanced in a number of ways, apart from the use of a high display brightness and resolution. For example, the contour map may be displayed in colours together with a scale indicating the heights associated with the different colours.

The slide or film of the map of the area may be shaded in density in dependence on the contour heights and the spot 6 focussed on the slide or film so that the light transmitted by the slide or film is proportional or inversely proportional to the height of the ground at the point indicated by the spot 6, and a photo-multiplier placed to receive the transmitted light. The photo-multiplier will produce a signal representing this height which can be used in an analogue or digital servo mechanism automatically to move the spot 6 to a point at which the height of the ground and height of the point of the trajectory are equal.

In addition to its use for locating enemy weapons the locator can also be used to determine the position of fall of shots from friendly weapons.

WHAT WE CLAIM IS: 1. A weapon locator including radar means for observing the position of a projectile from a weapon at several points along its trajectory, computing means responsive to said radar means to provide a series of estimated positions

for said weapon dependent upon different estimated heights along the trajectory, means for producing a representation of the actual heights of a region which includes said estimated positions and means for superimposing on said representation said estimated positions, whereby the location of said weapon can be identified on said representation as the position at which the estimated and actual heights coincide.
2. A weapon locator according to Claim 1 in which said means for producing a representation includes an optical film or slide projector coupled to said computing means so as to display a map of said region upon the screen of a cathode ray tube.
3. A weapon locator according to Claim 2 in which said means for superimposing comprises means responsive to said computing means whereby a beam of electrons can be focussed on said screen at positions in accordance with estimated positions at different estimated heights of said weapon whereby the location of said weapon can be identified as the position on said map at which the estimated and actual heights coincide.
4. A weapon locator according to any preceding claim in which error signals derived from the difference between the actual heights of said estimated positions on said representation and said estimated heights are used in conjunction with servo-means whereby the position is selected at which the heights coincide.
5. A weapon locator substantially as decribed herein with reference to Figures 2 and 3 of the drawing accompanying the Provisional Specification or modified as herein described.