US-12618975-B2 - Targeting

US12618975B2US 12618975 B2US12618975 B2US 12618975B2US-12618975-B2

Abstract

A targeting method comprising the steps of determining a bearing to a target from an observer using first and second independent techniques; comparing the bearings as determined by the first and second independent techniques and determining whether the bearings are accurate; and if the bearing is deemed to be accurate; measuring a range from the observer to the target; and calculating the position the target based on the verified bearing and range from the observer's position. The bearing can be measured by using a magnetometer, and cross-checked or verified using calculations based on three-dimensional satellite cartography data. The range to the target can be cross-checked, as can the position and viewpoint of the observer.

Inventors

Charles Forsberg

Assignees

TELEPLAN FORSBERG LIMITED

Dates

Publication Date: 20260505
Application Date: 20200323
Priority Date: 20190321

Claims (20)

1 . A targeting method, comprising: determining a verified bearing to a target from an observer using first and second independent techniques to obtain a first bearing measurement and a second bearing measurement, respectively; comparing the first bearing measurement and the second bearing measurement as determined by the first and the second independent techniques to determine whether the verified bearing is accurate; and if the verified bearing is deemed to be accurate, measuring a range from the observer to the target; and calculating the position of the target based on the verified bearing and range from the observer's position characterised by: obtaining the first bearing measurement by using a laser range finder comprising an image capture device and a compass or magnetometer to measure a bearing to three or more features within an image captured by the image capture device; obtaining the second bearing measurement by using three-dimensional satellite cartography data including elevation data to identify features in the three-dimensional satellite cartography data that correspond to the said three or more features in the image captured by the image capture device, calculating the position, pan/tilt and roll angles of the laser range finder based on the subtended angles between the three or more features within the captured image and checking that the bearing measurements correspond by comparing the first bearing measurement determined by using the laser range finder with the second bearing measurement calculated from the three-dimensional satellite cartography data, to check that the difference between the two sets of data is smaller than a predetermined value.
2 . The targeting method of claim 1 , comprising the steps of determining a bearing to a target from an observer using three or more independent techniques.
3 . The targeting method of claim 1 , further comprising: determining a position of an observer using first and second independent techniques; comparing the observer's positions as determined by the first and second independent techniques and based on the comparison, determining whether the observer's position is accurate; and if the observer's position is deemed to be accurate; measuring the bearing to the target from the observer; measuring the range to the target from the observer; and calculating the position the target using the verified position of the observer, the verified bearing and the range measurement.
4 . The targeting method of claim 1 , further comprising: determining a range from an observer to a target using first and second independent techniques; comparing the ranges as determined by the first and second independent techniques and determining whether the ranges are accurate; and if the range is deemed to be accurate; measuring the bearing to the target from the observer; and calculating the position the target based on the verified range and verified bearing from the observer's position.
5 . The targeting method of claim 1 , wherein the first and second independent techniques are different techniques.
6 . The targeting method of claim 1 , wherein one of the bearing verification techniques comprises using a magnetometer integrated into the sighting device.
7 . The targeting method of claim 1 , the bearing verification technique additionally comprises capturing a “field of view” image through a range finding device, the “field of view” image containing three or more identifiable features within a single image, picking-out features within the image, which have x and y pixel displacements relative to the centre pixel of the range finding device, and based on the relative pixel positions within the image and a calibration for aberrations in the lens, calculating the subtended angles both in azimuth and elevation to obtain the position, pan/tilt and roll angles of the range finding device based on the subtended angles between the features within the field of view and thereby calculating the bearings to the identifiable features within the field of view.
8 . The targeting method of claim 7 , comprising picking out four or more random, but identifiable features within the field of view; measuring the subtended azimuth and elevation angles between them; transposing the points of interest onto three-dimensional satellite cartography data, calculating the position and orientation of the range finding device with reference to the three-dimensional satellite cartography data, and scaling the angles within the field of view to actual, true bearings.
9 . The targeting method of claim 8 , further comprising the step of identifying a target within the image by placing a cursor upon it, and interpolating between the previously-determined bearings to obtain a true bearing from the observation point to the target.
10 . The targeting method of claim 9 , further comprising comparing a directly-measured bearing to the target with the bearing calculated from the three-dimensional satellite cartography data, and checking that they are close enough to one another to be deemed accurate.
11 . The targeting method of claim 1 , the bearing verification technique further comprises overlaying augmented reality markers in the field of view of a range finding device, the positions of the augmented reality markers being calculated from a measured location of the user and three-dimensional satellite cartography data, the verification being performed by observing whether the augmented reality markers displayed in the field of view align with objects to which they correspond in the actual field of view.
12 . The targeting method of claim 11 , further comprising the step of freezing the overlaid augmented reality markers relative to the field of view, moving the field of view so as to align the augmented reality markers with the objects to which they correspond in the actual field of view, and unfreezing the overlaid augmented reality markers.
13 . The targeting method of claim 11 , further comprising the step of capturing video or photographic imagery containing the actual field of view and as seen by the user through the range finding device.
14 . The targeting method of claim 3 , wherein one of the techniques for determining the position of the observer comprises using a GPS receiver on the observer's person or nearby, the GPS receiver being configured to receive latitude, longitude and elevation or similar coordinates, which define the observer's position.
15 . The targeting method of any of claim 3 , wherein one of the techniques for determining the position of the observer comprises the observer standing at a fixed position relative to a known, mapped landmark.
16 . The targeting method of claim 15 , wherein mapped landmark is a landmark on a three-dimensional map, which contains a plan view of the terrain in addition to an elevation map, which shows the elevation of objects/features on the map.
17 . The targeting method of claim 16 , wherein the verification of the position of the observer comprises triangulation by the observer taking bearings and ranges to a number of features within view, which correspond to identifiable features in the three-dimensional map satellite cartography data.
18 . The targeting method of claim 17 , wherein the range and bearing to object within the observer's field of view are obtained by taking photographs through a laser rangefinder type device, and wherein the captured photography data is optionally recorded for future reference/cross-checking purposes.
19 . The targeting method of any of claim 4 , wherein one of the techniques for determining the range to a target is measured using a laser rangefinder type device.
20 . The targeting method of claim 4 , wherein one of the techniques for determining the range to a target comprises using three-dimensional satellite cartography data containing elevation information about terrain contours and contours corresponding to object heights in the terrain, determining the position of the user within the three-dimensional satellite cartography map and a bearing to the target, the method further comprising tracing a ray from the calculated observation point within the three-dimensional cartography model to the target along a straight line corresponding to the azimuth and elevation of the bearing, extending that line through the three-dimensional satellite cartography image infinitely, and determining a first point from the observation point that the superimposed line impinges on the three-dimensional “surface” within the three-dimensional satellite cartography map, calculating a distance between that point and the determined observation point.

Description

This invention relates to targeting, and in particular, but without limitation, to improvements in and relating to targeting systems and methods with improved veracity and cross-checking. Targeting systems are used in a range of both military and civilian applications for ascertaining the precise position of an object in space. This can be accomplished in a number of ways, such as by using GPS positioning, or by more conventional methods, such as magnetic range and bearing from the observer's instrument (10) to the target (18) or triangulation from the observer's instrument (10) to a known reference point (and therefore reference bearing) and the target (18). One known problem with GPS positioning is that GPS systems can be “spoofed” relatively easily, and if targeting is based solely on GPS positioning, it is potentially error prone—especially in hostile situations. However, as targeting is used by the military to position ordnance, errors in the coordinates given can lead to misses, an incorrect target being hit, and/or unacceptable collateral damage. When targeting errors occur, there is often a need for a detailed after-the-event investigation, which no existing targeting system can provide with adequate veracity. Existing targeting systems generally involve the use of a “observer”, that is to say, an actual person located somewhere near the intended target, who calculates the position of the target using trigonometry and/or triangulation. The observer is located at a known position, and a rangefinder and compass (which are often both incorporated into a single laser rangefinder/scope type device) are used to measure a bearing and range to the target. Where greater accuracy is needed, the observer can move to other known positions, and take further bearings and range measurements, so as to reduce the size of the “cocked-hat” so produced by the triangulation method. The existing observer system relies on taking line-of-sight measurements to the target being taken. Clearly, there is potential for error when using the known observer method. First, if the observer's position is inaccurate, or just incorrect, then the bearings and distances measured by the observer will be from an incorrect origin, thereby rendering the entire procedure inaccurate. Second, if the observer measures the bearing incorrectly, even by +/−1 degree, at a range of 2 km, the error in position can be as much as 35 m. Third, if the observer erroneously ranges an object that is located in front of, or behind the intended target, then large range errors can occur. The situation is illustrated, schematically, in FIGS. 1 and 2 of the drawings, which are schematic oblique and plan views, respectively, of a hypothetical terrain. An observer is located at point 10 and is observing a view down a valley (as indicated by the contour lines in FIG. 2) towards a building 12, which is the intended target. Between the observer 10 and the target 12 there is a bridge 14. A chimney 16 is located behind the target 12. Using a laser rangefinder, the observer 10 sights 18 the centre of the target building 12 and records the bearing 20 and distance 22. From the origin of the measurement, namely the observer's position 10, the location of the target 12 on the map (FIG. 2) can be plotted. However, if the observer is in a different location 100 to where s/he thinks s/he is, then the bearing 120 and/or distance 122 measurements will be incorrect. Further, if when sighting the target building 12, the observer accidentally ranges the bridge pier 24 by mistake, then the range to target will be completely wrong. Likewise, if the observer intends to target the chimney 16, but accidentally ranges the building 12 in front of it, even though the bearing measurement may be within acceptable limits, the range measurement will be too short. The problem is not restricted to errors in the plane of the map (e.g. in FIG. 2) because if the observer intends to target, for example, a vehicle 30 crossing the bridge 14, then the elevation of the target 30 also needs to be considered. Any error in the range measurement could result in missing the target completely—with ordnance landing in the valley below the vehicle 30, rather than striking the bridge 14 or vehicle 30 itself. The foregoing hypothetical example illustrates the problem, and to confound matters further, due to the potential for errors at each stage of the targeting procedure, there is no way to know which measurements were incorrect, or indeed if the correct target was actually spotted. A need exists for a solution to one or more of the above problems, which aspects of this invention aim to provide. According to a first aspect of the invention, there is provided a targeting method comprising the steps of: determining the bearing to a target from an observer using first and second (or more) independent techniques; and comparing the bearings as determined by the first and second independent techniques and determining w