Abstract:
The disclosed system, device and method for targeting and measurement of stationary target locations in addition to prediction of moving target positions for given weapon intercept times generally includes: a target location system (TLS) configured with a computing device, a GPS receiver, mapping software, calibration software and digital filtering software. Disclosed features and specifications may be variously controlled, adapted or otherwise optionally modified to improve target acquisition and engagement. Exemplary embodiments of the present invention generally provide for improved accuracy of range finders, magnetometers and inclinometers as well as for improved prediction of moving target positions.

Description:
FIELD OF INVENTION 
     The present invention generally concerns targeting devices, targeting methods and precision GPS/INS missile guidance systems; and more particularly, representative and exemplary embodiments of the present invention generally relate to ground-based targeting equipment for the measurement of stationary target locations as well as prediction of moving target positions for a given intercept time. 
     BACKGROUND OF INVENTION 
     Conventional ground-based, man-portable Target Location Systems (TLS) exist in the U.S. Armed Services inventory. Representative examples include the Lightweight Laser Detector and Rangefinder (LLDR) and the Mark VII that are used for measuring stationary target positions. These systems generally use optical instrumentation for focusing and aiming for both night and day operations. They also employ laser rangefinders, magnetometers and inclinometers to measure range, azimuth and inclination. Typically, the operator turns the system on, goes through a relatively elaborate and tedious procedure of calibrating the magnetometer, lets the GPS acquisition complete, lets the camera warm up, focuses the camera on the target, places the crosshairs on the target aim point and pulls the trigger, which initiates the laser rangefinder to engage. The range, azimuth and inclination are then measured and processed in a GPS receiver to estimate target coordinates. The accuracy of the range finders are generally good; however, the accuracies of the magnetometers and inclinometers are marginal at best—generally resulting in large target position errors, especially at long ranges. To accommodate targeting errors, weapons with terminal seekers or weapons with large warheads have been employed. Both of these conventional solutions, however, are unsatisfactory because seekers are complex and expensive, while large warheads generally cause unnecessary collateral damage. 
     Some conventional target location systems that are mounted on specially designed tripods (for slewing and target tracking) have not been fully utilized because they have been designed for acquisition of stationary targets only. Precision attacks against moving targets with GPS guided weapons generally require that the weapons receive accurate data of predicted target position for a particular weapon intercept time with minimum delay. One way of accomplishing this has been to use conventional systems to estimate target velocity, predict target position at a given intercept time and uplink this data to an incoming weapon via a data link for terminal guidance. 
     That notwithstanding, there remains a need to reduce TLS angular errors, to improve target location accuracy, to mitigate the need for elaborate and tedious calibration procedures, to reduce the need for expensive weapons with terminal seekers, and to minimize collateral damage. Additionally, there is a need to more effectively utilize target location systems to conduct precision attacks on moving targets by accurately predicting moving target positions for a given weapon intercept time. 
     SUMMARY OF THE INVENTION 
     In various representative aspects, the present invention provides for targeting and measurement of stationary target locations in addition to predicting of moving target positions for given weapon intercept times. Exemplary features generally include: a target location system (TLS) configured with a computing device, a GPS receiver, mapping software, calibration software and digital filtering software. The present invention further discloses operational targeting procedures for TLS instrument error calibration and target velocity estimation. Systems and methods for improving the accuracy of range finders, magnetometers and inclinometers are provided, as well as for improving prediction of moving target positions. 
     Advantages of the present invention will be set forth in the Detailed Description which follows and may be apparent from the Detailed Description or may be learned by practice of exemplary embodiments of the invention. Still other advantages of the invention may be realized by means of any of the instrumentalities, methods or combinations particularly pointed out in the Claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Representative elements, operational features, applications and/or advantages of the present invention reside inter alia in the details of construction and operation as more fully hereafter depicted, described and claimed—reference being made to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout. Other elements, operational features, applications and/or advantages will become apparent in light of certain exemplary embodiments recited in the Detailed Description, wherein: 
         FIG. 1  representatively illustrates the operation of a Target Location System (TLS); 
         FIG. 2  representatively illustrates the operation of a Real-Time Targeting System (RTTS) in accordance with an exemplary embodiment of the present invention; 
         FIG. 3  representatively illustrates a TLS calibration procedure that uses a pre-surveyed landmark feature and relative-GPS in accordance with an exemplary embodiment of the present invention; 
         FIG. 4  representatively illustrates a TLS calibration procedure that uses a laser designator, a laser guided weapon with GPS/INS and a data link in accordance with an exemplary embodiment of the present invention; 
         FIG. 5  representatively illustrates a TLS calibration procedure that uses a digital map and relative-GPS in accordance with an exemplary embodiment of the present invention; 
         FIG. 6  representatively illustrates a target velocity estimation method using a TLS in accordance with an exemplary embodiment of the present invention; 
         FIG. 7  representatively illustrates a filtering algorithm for a target velocity estimator in accordance with an exemplary embodiment of the present invention; and 
         FIG. 8  representatively illustrates an instrument axis of a TLS and an estimated target velocity axis in accordance with an exemplary embodiment of the present invention. 
     
    
    
     Elements in the Figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the Figures may be exaggerated relative to other elements to help improve understanding of various embodiments of the present invention. Furthermore, the terms “first”, “second”, and the like herein, if any, are used inter alia for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. Moreover, the terms “front”, “back”, “top”, “bottom”, “over”, “under”, and the like in the Description and/or in the claims, if any, are generally employed for descriptive purposes and not necessarily for comprehensively describing exclusive relative position. Any of the preceding terms so used may be interchanged under appropriate circumstances such that various embodiments of the invention described herein may be capable of operation in other configurations and/or orientations than those explicitly illustrated or otherwise described. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The following representative descriptions of the present invention generally relate to exemplary embodiments and the inventors&#39; conception of the best mode, and are not intended to limit the applicability or configuration of the invention in any way. Rather, the following description is intended to provide convenient illustrations for implementing various embodiments of the invention. As will become apparent, changes may be made in the function and/or arrangement of any of the elements described in the disclosed exemplary embodiments without departing from the spirit and scope of the invention. 
     Target Locating System (TLS) 
       FIG. 1  representatively illustrates the operation of a typical TLS. TLS  10  generally includes range finder  60  and sensor package  50 . Sensor package  50  comprises, for example, a three-axis magnetometer and a two-axis inclinometer. The three axes of the magnetometer are generally mutually orthogonal and measure the magnetic field of the earth in the TLS  10  forward, right and down axis. The inclinometer measures the pitch and roll angles of the TLS. Processor  70  uses rangefinder  60  measurements to compute the TLS  10  to target  30  range (R meas ). The rangefinder&#39;s laser is fired by depressing trigger  80 . Some TLS models may also be suitably configured to query the TLS processor  70  to fire the range finder automatically at a fixed rate. Processor  70  uses the magnetometer measurements and the earth&#39;s geomagnetic field model database to compute the TLS azimuth angle (ψ meas ) with respect to true north. Processor  70  also uses both the magnetometer and inclinometer measurements to compute the inclination angle (θ meas ) of the TLS with respect to local vertical. TLS measurement data  90  is then output on the processor&#39;s  70  output port. 
     After power-up, the TLS operator engages a procedure that calibrates most of the magnetometer sensor errors; however, due to errors in the earth&#39;s geomagnetic field model, the azimuth error is generally accepted as the largest source of targeting error. The magnetic field on the earth&#39;s surface is typically non-uniform and varies due inter alia to an uneven magnetic composition of the earth&#39;s crust. TLS azimuth and inclination errors are on the order of 13 mils (1-σ) and 7.5 mils (1-σ) respectively. These errors generally correspond to a 38 meter horizontal and a 22 meter maximum vertical targeting error when the target is 1 kilometer from the observer, and a 191 meter horizontal and 110 meter vertical targeting error when the target is 5 kilometers from the observer. Such large targeting errors generally operate to handicap the use of conventional TLS&#39;s for urban warfare, where smaller targeting errors are required. Accordingly, there is a need for a ground-based, man-portable system that can substantially reduce the current TLS errors. Moreover, there is a need to expand the role of existing TLS&#39;s by incorporating moving target velocity estimation and position prediction capabilities. 
     Real-Time Targeting System (RTTS) 
       FIG. 2  representatively illustrates the operation of a Real-Time Targeting System (RTTS) in accordance with an exemplary embodiment of the present invention for stationary and moving targets. RTTS  100  includes a computing device, an imbedded GPS receiver  130  and an externally connected data link radio  150 . The computer comprises a processor  120  and a display  140 . Processor  120  may be adapted to execute software suitably configured for TLS calibration, moving target filtering, target position computation, mapping, modem data linking, and/or the like. The present invention is not limited to a specific computing device platform, but may be configured or otherwise suitably adapted for any type of computer or digital processor. 
     GPS receiver  130  comprises a highly accurate receiver. The present invention is not limited to an imbedded GPS receiver. An externally connected GPS receiver may be alternatively, conjunctively or sequentially used. Data link radio  150  may be any data link suitably configured to transmit targeting data and/or receive weapon position data. In the representatively depicted embodiment, the computer receives the TLS  10  measurement data via cable  110 . The present invention is not limited to the representatively depicted cable  110 , but also may include any data transfer mechanism, such as, for example, wireless system protocols for data transfer from the TLS to the computer. 
     The magnetometer error (or azimuth error) is generally sensitive to the geomagnetic field model and to metallic objects in the local measurement vicinity. Assuming that metallic objects may be avoided, it can be shown that the magnetometer error is a constant over a certain area on the earth&#39;s surface. Specifically, field tests confirm that the TLS measured azimuth and inclination angles have a constant bias error. 
     First Exemplary Method 
       FIG. 3  representatively illustrates the operation of a first TLS calibration method that uses a pre-surveyed landmark feature  210  and a relative GPS technique. TLS  10  measures range to landmark feature  210  as well as azimuth and inclination angle with respect to the earth&#39;s geographic reference. TLS  10  may be calibrated by using a landmark feature  210  (generally, in substantially unobstructed view of the TLS), a portable GPS receiver, a computing device, and software (RTTS)  100  using a procedure described as follows:
     Step 1: select a landmark feature  210  in relatively unobstructed view of TLS  10 ; use RTTS  100  to take a GPS position reading P ref-meas  (Lat ref , Lon ref , Alt ref )  250  of the landmark feature  210  at point P ref    230 ; and store in RTTS-processor  100 .   Step 2: use RTTS  100  GPS receiver to take a TLS  10  self-position reading P obs-meas  (Lat obs , Lon obs , Alt obs )  260  at point P obs    240  and store in RTTS  100  processor.   
     Due to GPS error, both measurements P obs-meas    260  and P ref-meas    250  will have similar offsets, as generally depicted for example in  FIG. 3 . The offset error, however, will generally be within the GPS accuracy budget. It is well-accepted that the relative error of two GPS measurements, taken by the same GPS receiver observing the same GPS satellites, is substantially accurate. The accuracies obtained generally range from several centimeters to 2 meters. This method of surveying is typically termed “Relative Positioning GPS”. The accuracy of this method is improved when the C/A code and the phase of carrier L 1  of the GPS signal structure is used at each epoch of the navigation message, on the order of every 12 to 15 seconds. The accuracy of the TLS angular calibration will depend on the method used for Relative Positioning GPS. Of course, any suitably adapted method may be employed to meet specific operating recommendations or requirements. 
     With reference to  FIG. 3 , even though P obs-meas    260  and P ref-meas    250  have a constant GPS error offset, they are generally geometrically similar to points P obs    240  and P ref    230 , because the GPS measurements P obs-meas    260  and P ref-meas    250  were physically taken at points P obs    240  and P ref    230  respectively.
     Step 3: execute calibration software on RTTS  100  processor to compute the range vector R  270  from point P obs-meas    260  to point P ref-meas    250  as follows:
 
 R   north =(Lat ref −Lat obs )Γ earth-nom  
 
 R   east =cos[Lat obs ](Lon ref −Lon obs )Γ earth-nom  
 
 R   up =(Alt ref −Alt obs )
   

     where Γ earth-nom  is the Earth&#39;s nominal radius. 
     Execute the calibration software again to compute the range magnitude (|R|), azimuth angle (ψ) and inclination angle (θ) as follows: 
     
       
         
           
             
                
               R 
                
             
             = 
             
               
                 
                   R 
                   east 
                   2 
                 
                 + 
                 
                   R 
                   north 
                   2 
                 
                 + 
                 
                   R 
                   up 
                   2 
                 
               
             
           
         
       
       
         
           
             ψ 
             = 
             
               arctan 
               ⁡ 
               
                 [ 
                 
                   
                     R 
                     east 
                   
                   
                     R 
                     north 
                   
                 
                 ] 
               
             
           
         
       
       
         
           
             θ 
             = 
             
               arctan 
               ⁡ 
               
                 [ 
                 
                   
                     R 
                     up 
                   
                   
                      
                     R 
                      
                   
                 
                 ] 
               
             
           
         
       
     
     This is the estimated range, azimuth and inclination angles from the TLS  10  to landmark feature  210 . This data may then be stored, for example, on the RTTS  100  processor.
     Step 4: align TLS  10  crosshairs on the reference point P ref    230  and take measurement. The TLS  10  measures range (R meas ) to reference point P ref , azimuth with respect to true north (ψ meas ) and inclination with respect to local vertical (θ meas ), as generally depicted, for example, in  FIG. 1 .   Step 5: employ RTTS  100  processor to check if the difference between the measured range (R meas ) from step no. 4 and the computed range (|R|) from step no. 3 is less than about 2 meters. If true, then compute the TLS azimuth error (ψ bias ) and inclination error (θ bias ) as follows:
 
ψ bias =ψ meas −ψ
 
θ bias =θ meas −θ
   

     Store the calibration corrections (ψ bias , θ bias ) in RTTS  100  processor and use them to correct subsequent TLS  10  measurements. 
     If the difference between measured range (R meas ) and the computed range (|R|) is more than 2 meters, then perform the calibration process again. 
     Steps 1, 2, and 4 may be performed substantially independently; however, step 3 generally follows steps 1 and 2, and step 5 generally follows steps 3 and 4. 
     The calibration procedure may be repeated for each time there is change in TLS  10  camera sight. The calibration correction for the day sight is generally not used for the night sight, since the day and night sights typically have different bias errors with respect to the axis of the magnetometer and inclinometer. 
     The calibration procedure may be repeated each time TLS  10  is relocated to another position to mitigate the effects of geomagnetic field modeling errors. Additionally, the landmark feature generally should be at least 1 kilometer from TLS  10 . The calibration may be performed in a two to three hour period to ensure that the GPS accuracies are the same for all GPS measurements taken for the calibration. 
     Second Exemplary Method 
     Sometimes it may be impossible to measure the GPS coordinates of a feature in a given landmark. In an alternative method, the GPS coordinates of the landmark feature (first target) may be obtained by guiding a GPS/INS, laser guided weapon to the landmark feature and using a data link to download the weapon GPS coordinates to the RTTS.  FIG. 4  generally illustrates the operation of such an alternative calibration method in a procedure as follows:
     Step 1: select stationary target  30  in clear view of TLS  10  and use TLS  10  to measure range (R meas ), azimuth (ψ meas ) and inclination (θ meas ) as described in step no. 4 of the first exemplary method disclosed vide supra.   Step 2: use RTTS  100  data link to request launch of GPS/INS and data link equipped laser guided weapon  330  against the target  30 . Use TLS  10  laser designator to point laser beam  320  to guide weapon  330  to target  30 . A few seconds before impact, use weapon  330  to download to RTTS  100  processor (via data link) its GPS coordinates, range to target (measured by sensor) and velocity. Store this data on RTTS  100  processor. After visible confirmation that the weapon has successfully hit the intended target, use the last stored weapon GPS coordinates, range to target and velocity to compute weapon GPS coordinates at time of impact. Assume weapon GPS coordinates at impact to be the target coordinates and store coordinates on RTTS  100  processor.   Step 3: use RTTS  100  processor and GPS receiver to determine the self-position of TLS  10  as described in step no. 2 of the first method disclosed vide supra.   Step 4: use RTTS  100  processor to take the target position computed in step no. 2 immediately above and self-position computed in step no. 3 immediately above to compute the range magnitude (|R|), azimuth angle (ψ) and inclination angle (θ) as described in step no. 3 of the first method disclosed vide supra.   Step 5: use RTTS  100  processor to take the data from step no. 1 and step no. 4 immediately above to compute the TLS azimuth error (ψ bias ) and inclination error (θ bias ) as described in step no. 5 of the first method disclosed vide supra. Use the calibration corrections to correct subsequent TLS  10  measurements.   

     The terminal guidance accuracy of the laser guided weapon should generally be good enough to meet the reference point accuracy requirements. Additionally, the accuracy of the weapon&#39;s terminal ranging sensor and the weapon velocity estimate must be generally good enough to meet these same requirements. 
     Third Exemplary Method 
     As with the second disclosed method, sometimes it may be difficult to measure the GPS coordinates of a feature in a landmark. A third method disclosed herein uses a relative-GPS technique similar to the one disclosed in the first method, except the GPS coordinates of the landmark feature are generally obtained by using a highly accurate Control Image Base (CIB) map. A CIB database contains digital aerial photographic map data of surveyed area. Included with the data is the pre-surveyed and mensurated horizontal plane coordinates (latitude and longitude) of each point on the map. The coordinates of any point on a CIB map may not match up perfectly with the GPS receiver coordinates of the same point on the map. This is due to GPS error and the position error of the CIB map. If the position of one point on a CIB map is calibrated with a GPS receiver, then the GPS position of any point on the CIB map may be determined accordingly. Accordingly, this method may be used to determine the GPS coordinates of a landmark feature. 
       FIG. 5  representatively illustrates the operation of such a method. This method calibrates the TLS  10  azimuth and inclination errors in a procedure as follows:
     Step 1: use RTTS  100  processor and GPS receiver, CIB map  410  and an identifiable feature  440  on CIB map  410 , near forward observer  20  to determine CIB map  410  error. Select a landmark feature  210 , in clear view of TLS  10  and, readily identifiable on CIB map  410 . Select an aim point on landmark feature  210 ; determine corrected GPS coordinates using data generated in step no. 1.   Step 2: use RTTS  100  processor and GPS receiver to determine the self-position of TLS  10 , as described, for example, in step no. 2 of the first method embodiment.   Step 3: use RTTS  100  processor to take the landmark feature position computed in step no. 1 vide supra and the self-position computed in step no. 2 vide supra to compute the range magnitude (|R|), azimuth angle (ψ) and inclination angle (θ) as described, for example, in step no. 3 of the first method embodiment.   Step 4: use TLS  10  to measure range (R meas ), azimuth with respect to true north (ψ meas ) and inclination with respect to local vertical (θ meas ) as described, for example, in step no. 4 of the first method embodiment.   Step 5: use RTTS  100  processor to take data from step no. 3 and step no. 4 to compute the TLS azimuth error (ψ bias ) and inclination error (θ bias ) as described, for example, in step no. 5 of the first method embodiment; use calibration corrections to correct subsequent TLS  10  measurement(s).   
     All specifications and parameter considerations that apply for the first method exemplary embodiment, generally apply to the third method representative embodiment. Additionally, the accuracy of the CIB map  410  should be on the order of about one (1) meter, while the point-to-point position error of objects in the CIB map  410  generally should be on the order of up to about 2 meters. 
     Moving Target Position Prediction with TLS Aiding 
     Some of the Target Location Systems (TLS) may be mounted on specially designed platforms that allow for easy azimuth and inclination slewing. These may include damped gimbals that at least partially mitigate oscillations (e.g., aim-point jitter) when the TLS slewing movement stops abruptly. TLS&#39;s equipped with these platforms may be used for estimating target velocity. Additionally, TLS mounted on accurate servo controlled gimbal platforms may be alternatively, conjunctively or sequentially employed. Target velocity may be estimated, for example, by integrating an existing TLS with the Real-Time Targeting System (RTTS). 
       FIG. 6  representatively illustrates the operation of an exemplary process for estimating moving target  510  velocity. TLS  10  may be slewed on a gimbaled platform and its camera used to zoom in on moving target  510 , placing the TLS  10  crosshairs on the moving target centroid. TLS  10  may be slewed substantially continuously on a gimbaled platform to maintain crosshairs ‘on target’ throughout the engagement. This procedure may either be performed manually or a tracking algorithm may be used to track the target substantially automatically and a servo controller may be used to slew the gimbals to maintain the target in the crosshairs of TLS  10  camera sight. The TLS rangefinder may be substantially automatically triggered at regular intervals with the measured time, range, azimuth and inclination angles stored on the RTTS  100  processor. Consecutive TLS measurements may be used to estimate target velocity. As representatively depicted in  FIG. 6 , the laser beam of TLS  10  rangefinder may be adapted to strike obstructions like trees/plants  540 , rocks  530 , poles  520 , and/or the like. Additionally, TLS  10  may miss the target and the laser beam may hit the ground in front of the target or far behind. Such false range returns will generally be rejected to correctly measure the moving target velocity. 
     Target Location System 
       FIG. 7  representatively depicts the operation of a filtering algorithm used for estimating moving target velocities. The processing steps, in no particular order, may be configured as follows:
     Step 1: RTTS  750  processor reads in TLS  10  range (R meas ) azimuth (ψ meas ) and inclination (θ meas ) measurements.   Step 2: RTTS  750  processor uses a Maximum Likelihood Filter  710  to substantially automatically reject false range returns from obstructions in the laser path, such as: trees/plants, poles, and/or the like. The first three TLS  10  range measurements may generally be assumed to be accurate. The Maximum Likelihood Filter  710  uses a priori knowledge of target dynamics to estimate the size of the maximum likelihood range gate. Range measurements outside the expected range limit may then be rejected and the TLS measurements for those time intervals are not provided for subsequent processing.   Step 3: Three independent, two-state Kalman Filters may be used to estimate intermediate variables. Range Rate Estimator  720  may be used to estimate filtered slant-range (R f ) and slant-range rate   
               (       ∂   R       ∂   t       )     .         
Azimuth Estimator  730  may be used to estimate filtered azimuth (ψ f ) and azimuth rate
 
               (       ∂   ψ       ∂   t       )     .         
Elevation Rate Estimator  740  may be used to estimate filtered inclination (θ f ) and inclination rate
 
               (       ∂   θ       ∂   t       )     .         
These filters generally employ the well-accepted Kalman Filter approach that utilizes measurement time and two consecutive measurements to estimate rates. Each filter may be suitable configured to take into account the system and measurement noise characteristics of the TLS  10  instruments.
 
       FIG. 8  generally illustrates representative coordinate frames of the TLS instruments and the coordinate frame of the estimated velocity vector. With reference to  FIG. 8 , assume that at time t 1 , the moving target is at position  610  and the TLS measured slant-range to a moving target is r 1 , the measured azimuth is ψ 1  and the measured inclination is θ 1 . Also assuming that at the next TLS measurement at time t 2 , the moving target is at position  620  and the TLS measured slant-range to the moving target is r 2 , the measured azimuth is ψ 2  and the measured inclination is θ 2 . 
     Two consecutive measurements may be processed in, for example, the three filters generally depicted in  FIG. 7 , in order to estimate: filtered slant-range and slant-range rate; filtered azimuth and azimuth rate; and filtered inclination and inclination rate. 
     After the filtering process is complete, the RTTS processor computes the velocity vector (V R , V θ , V ψ ) in the TLS slant-range frame as follows: 
     
       
         
           
             
               V 
               R 
             
             = 
             
               
                 ⅆ 
                 R 
               
               
                 ⅆ 
                 t 
               
             
           
         
       
       
         
           
             
               V 
               θ 
             
             = 
             
               
                 R 
                 f 
               
               ⁢ 
               
                 
                   ⅆ 
                   θ 
                 
                 
                   ⅆ 
                   t 
                 
               
             
           
         
       
       
         
           
             
               V 
               ψ 
             
             = 
             
               
                 R 
                 f 
               
               ⁢ 
               
                 
                   ⅆ 
                   ψ 
                 
                 
                   ⅆ 
                   t 
                 
               
             
           
         
       
     
     The vector diagrams in  FIG. 8  generally explain these equations. 
     The RTTS processor computes the target velocity vector (V E , V N , V U ) in the geographic frame as follows: 
     
       
         
           
             
               [ 
               
                 
                   
                     
                       V 
                       E 
                     
                   
                 
                 
                   
                     
                       V 
                       N 
                     
                   
                 
                 
                   
                     
                       V 
                       U 
                     
                   
                 
               
               ] 
             
             = 
             
               
                 [ 
                 
                   
                     
                       
                         cos 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           θ 
                           f 
                         
                         ⁢ 
                         sin 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           ψ 
                           f 
                         
                       
                     
                     
                       
                         cos 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           ψ 
                           f 
                         
                       
                     
                     
                       
                         
                           - 
                           sin 
                         
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           θ 
                           f 
                         
                         ⁢ 
                         sin 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           ψ 
                           f 
                         
                       
                     
                   
                   
                     
                       
                         cos 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           θ 
                           f 
                         
                         ⁢ 
                         cos 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           ψ 
                           f 
                         
                       
                     
                     
                       
                         
                           - 
                           sin 
                         
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           ψ 
                           f 
                         
                       
                     
                     
                       
                         
                           - 
                           sin 
                         
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           θ 
                           f 
                         
                         ⁢ 
                         cos 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           ψ 
                           f 
                         
                       
                     
                   
                   
                     
                       
                         sin 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           θ 
                           f 
                         
                       
                     
                     
                       0 
                     
                     
                       
                         
                           - 
                           cos 
                         
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           θ 
                           f 
                         
                       
                     
                   
                 
                 ] 
               
               ⁡ 
               
                 [ 
                 
                   
                     
                       
                         V 
                         R 
                       
                     
                   
                   
                     
                       
                         V 
                         θ 
                       
                     
                   
                   
                     
                       
                         V 
                         ψ 
                       
                     
                   
                 
                 ] 
               
             
           
         
       
     
     The RTTS processor then computes the predicted target position as follows: 
     
       
         
           
             
               T 
               lat_p 
             
             = 
             
               
                 T 
                 lat_present 
               
               + 
               
                 
                   
                     V 
                     N 
                   
                   ⁢ 
                   Δ 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   t 
                 
                 
                   R 
                   earth_nom 
                 
               
             
           
         
       
       
         
           
             
               T 
               lon_p 
             
             = 
             
               
                 T 
                 lon_present 
               
               + 
               
                 
                   
                     V 
                     E 
                   
                   ⁢ 
                   Δ 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   t 
                 
                 
                   
                     cos 
                     ⁡ 
                     
                       ( 
                       
                         T 
                         lat_present 
                       
                       ) 
                     
                   
                   ⁢ 
                   
                     R 
                     earth_nom 
                   
                 
               
             
           
         
       
       
         
           
             
               T 
               alt_p 
             
             = 
             
               
                 T 
                 alt_present 
               
               + 
               
                 
                   V 
                   U 
                 
                 ⁢ 
                 Δ 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 t 
               
             
           
         
       
     
     Where, T lat     —     P  is the predicted target latitude at Δt from the present, T lat     —     present  is the estimated latitude at the present time, T lon     —     P  is the predicted target longitude at Δt from the present, T lon     —     present  is the estimated target longitude at the present time, T alt   P  is the predicted target altitude at Δt from the present, T alt     —     present  is the estimated target altitude at the present time, and Δt is the difference between the prediction time interval and the present time. 
     The predicted target position data may then be sent to the weapon via the data link for each time a TLS measurement is received. 
     Moving Target Position Prediction Sensitivities 
     The disclosed TLS aided moving target position prediction method is sensitive to:
     (1) Data latency error: The TLS instrument measurement time uncertainty is a source of error. Improved moving target position prediction accuracy will produce fewer data latency errors;   (2) Update Rate: Velocity is measured by using two consecutive TLS measurements. Many measurements may be rejected due to obstructions in the path of the rangefinder&#39;s laser beam. More TLS measurements (or higher update rates) will ensure improved target velocity accuracy;   (3) TLS jitter: When the TLS crosshairs oscillate from measurement to measurement, this causes the velocity estimate to spike which in turn causes instantaneous errors in computation of target velocity. Smooth motion of the TLS while target tracking is generally recommended to ensure better results. The jitter may be substantially avoided altogether by processing the TLS  10  camera video imagery in a tracking algorithm to track the target accurately and by using a gimbal servo controller to slew the TLS  10  gimbals to accurately center the tracked target in the TLS  10  camera&#39;s crosshairs;   (4) TLS wander: When the TLS crosshairs wanders off target, adding a spurious velocity component, the TLS crosshairs must be centered on the target throughout the engagement to ensure better results. This may be avoided by employing the same or substantially similar TLS  10  gimbal servo pointing method disclosed in exemplary method embodiment no. 3 vide supra;   (5) Target obscuration: When a target disappears behind an object, or when there is a bad weather condition (rain and snow), or when there is smoke—such conditions should be avoided to ensure better results.   

     In the foregoing specification, the invention has been described with reference to specific exemplary embodiments; however, it will be appreciated that various modifications and changes may be made without departing from the scope of the present invention as set forth in the claims below. The specification and figures are to be regarded in an illustrative manner, rather than a restrictive one and all such modifications are intended to be included within the scope of the present invention. Accordingly, the scope of the invention should be determined by the claims appended hereto and their legal equivalents rather than by merely the examples described above. 
     For example, the steps recited in any method or process claims may be executed in any order and are not limited to the specific order presented in the claims. Additionally, the components and/or elements recited in any apparatus claims may be assembled or otherwise operationally configured in a variety of permutations to produce substantially the same result as the present invention and are accordingly not limited to the specific configuration recited in the claims. 
     Benefits, other advantages and solutions to problems have been described above with regard to particular embodiments; however, any benefit, advantage, solution to problem or any element that may cause any particular benefit, advantage or solution to occur or to become more pronounced are not to be construed as critical, required or essential features or components of any or all the claims. 
     As used herein, the terms “comprise”, “comprises”, “comprising”, “having”, “including” or any variation thereof, are intended to reference a non-exclusive inclusion, such that a process, method, article, composition or apparatus that comprises a list of elements does not include only those elements recited, but may also include other elements not expressly listed or inherent to such process, method, article, composition or apparatus. Other combinations and/or modifications of the above-described structures, arrangements, applications, proportions, elements, materials or components used in the practice of the present invention, in addition to those not specifically recited, may be varied or otherwise particularly adapted to specific environments, manufacturing specifications, design parameters or other operating requirements without departing from the general principles of the same.