U.S. patent application number 11/398400 was filed with the patent office on 2007-10-11 for projectile targeting analysis.
This patent application is currently assigned to The United States of America as Represented by the Secretary of the Navy. Invention is credited to Richard Christopher Hebb, Rocco Portoghese, Edward John Purvis, James Earl Purvis.
Application Number | 20070238073 11/398400 |
Document ID | / |
Family ID | 38575732 |
Filed Date | 2007-10-11 |
United States Patent
Application |
20070238073 |
Kind Code |
A1 |
Portoghese; Rocco ; et
al. |
October 11, 2007 |
Projectile targeting analysis
Abstract
An exemplary embodiment of the invention relates to determining
aimpoint relative to a target located within a firing range. The
target can be either fixed or moving, and if the target is moving
then it can be mounted on tracks or controlled by servomechanisms.
In addition to aimpoint, predicted projectile effects and personnel
performance can be calculated for evaluation and for training. The
firing range is mapped so that placement of infrared emitters is
associated with specific targets. Placement of the emitter external
to the target perimeter produces accurate results so long as the
emitter is within the field of view of a camera mounted upon the
projectile launcher. The invention results in large firing ranges
with the ability to place targets wherever desired without
decreasing aimpoint measurement accuracy.
Inventors: |
Portoghese; Rocco; (Winter
Park, FL) ; Hebb; Richard Christopher; (Orlando,
FL) ; Purvis; Edward John; (US) ; Purvis;
James Earl; (Seville, FL) |
Correspondence
Address: |
Eliot Abolafia
Deflorez Building Code 11.3
12350 Research Parkway
Orlando
FL
32826-3275
US
|
Assignee: |
The United States of America as
Represented by the Secretary of the Navy
|
Family ID: |
38575732 |
Appl. No.: |
11/398400 |
Filed: |
April 5, 2006 |
Current U.S.
Class: |
434/21 |
Current CPC
Class: |
F41G 3/2605 20130101;
G01S 5/163 20130101; F41G 3/2661 20130101; F41G 3/323 20130101 |
Class at
Publication: |
434/021 |
International
Class: |
F41G 3/26 20060101
F41G003/26 |
Claims
1. A system for determining a location vector for an aimpoint
relative to a target located within a firing range, comprising: a.
the target having a perimeter further defining a centroid for
locating the target; b. an near infrared emitter, placed within the
firing range, the emitter being further placed outside the
perimeter of the target and the emitter being associated with the
centroid for determining the angular offset between the target and
the emitter; c. an emitter controller for wirelessly controlling
the illumination sequence of the emitter; d. a projectile launcher
for testing; e. a digital camera having a lens, the camera
adjustably mounted on the projectile launcher for alignment of the
camera optical axis with the projectile launcher site line, the
camera field of view encompassing the emitter, and the camera being
mapped to derive the angular offset between the image formed by the
emitter emission from the target centroid position; f. a sensor
responsive to the projectile launcher for detecting triggering
events when the projectile launcher is fired; g. communication
means for transferring information between the computer and each of
the sensors, emitter, camera; and h. a system computer for
receiving inputs from the emitter, the camera and the sensor for
controlling the emitter controller, and for determining the
aimpoint vector at the triggering event.
2. The system of claim 1 wherein the sensor comprises a
microphone.
3. The system of claim 1 wherein the camera includes of an array of
photonic detectors sensitive to near infrared light.
4. The system of claim 3 wherein the camera further includes a
filter for blocking non near infrared light and permitting near
infrared light to pass through the filter.
5. The system of claim 1 wherein the near infrared emitter
comprises a halogen lamp and a filter for blocking non near
infrared light.
6. The system of claim 1 wherein the communication means comprises
relay radios.
7. The system of claim 1 wherein the field of coverage is between
10 meters and 100.
8. The system of claim 1 wherein the emitter is located between 50
meters and 1000 meters from the camera lens plane.
9. The system of claim 1 wherein the computer includes a computer
program for calculating the fall of the shot.
10. The system of claim 9 wherein the computer program calculates
the aerodynamic effects of air velocity upon the fall of the
shot.
11. The system of claim 9 wherein the computer includes a computer
program for calculating the effects of the projectile launcher
burst.
12. The system of claim 1 including a video recording means
controlled by the system computer for capturing visual and
projectile launcher event information.
13. The system of claim 12 wherein the visual and projectile
launcher event information is captured within the audio portion of
the recording;
14. The system of claim 12 wherein the video recording means
comprises a digital videocassette recorder.
15. A system for determining a location vector for an aimpoint
relative to a moving target located within a firing range,
comprising: a. the moving target having a perimeter further
defining a centroid for locating the target; b. an near infrared
emitter, placed within the firing range, the emitter being further
placed outside the perimeter of the moving target and the emitter
being associated with the centroid for determining the angular
offset between the target and the emitter; c. an emitter controller
for wirelessly controlling the illumination sequence of the
emitter; d. a projectile launcher for testing; e. a digital camera
having a lens, the camera adjustably mounted on the projectile
launcher for alignment of the camera optical axis with the
projectile launcher site line, the camera field of view
encompassing the emitter, and the camera being mapped to derive the
angular offset between the image formed by the emitter emission
from the target centroid position; f. a sensor responsive to the
projectile launcher for detecting triggering events when the
projectile launcher is fired; g. a downrange controller for
controlling the position of the moving target, wherein the computer
is responsive to output from the downrange controller for
determining the aimpoint vector at the triggering event; h.
communication means for transferring information between the
computer and each of the sensors, emitter, camera; and i. a system
computer for receiving inputs from the emitter, the camera, the
downrange controller and the sensor for controlling the emitter
controller, and for determining the aimpoint vector at the
triggering event.
16. The system of claim 15 wherein the moving target is movably
mounted on tracks.
17. The system of claim 15 wherein the downrange controller is
provided with capacity to store up to 60 seconds of motion.
18. The system of claim 15 wherein the sensor comprises a
microphone.
19. The system of claim 15 wherein the camera includes of an array
of photonic detectors sensitive to near infrared light.
20. The system of claim 19 wherein the camera further includes a
filter for blocking non near infrared light and permitting near
infrared light to pass through the filter.
21. The system of claim 15 wherein the near infrared emitter
comprises a halogen lamp and a filter for blocking non near
infrared light.
22. The system of claim 15 wherein the communication means
comprises relay radios.
23. The system of claim 15 wherein the field of coverage is between
10 meters and 100.
24. The system of claim 15 wherein the emitter is located between
50 meters and 1000 meters from the camera lens plane.
25. The system of claim 15 wherein the computer includes a computer
program for calculating the fall of the shot.
26. The system of claim 25 wherein the computer program calculates
the aerodynamic effects of air velocity upon the fall of the
shot.
27. The system of claim 25 wherein the computer includes a computer
program for calculating the effects of the projectile launcher
burst.
28. The system of claim 15 including a video recording means
controlled by the system computer for capturing visual and
projectile launcher event information.
29. The system of claim 28 wherein the visual and projectile
launcher event information is captured within the audio portion of
the recording;
30. The system of claim 28 wherein the video recording means
comprises a digital videocassette recorder.
31. A method for determining projectile launcher aimpoint
comprising: a. selecting the location of a shooter at a firing
line; b. surveying a firing range for determining the location of
target and emitter coordinates; c. calculating the centroid of a
target having a defined perimeter, the target being placed within
the firing range; d. placing emitters on the firing range
externally to the target perimeter; e. associating the target with
the emitter f. mounting a camera sensitive to near infrared light
to the projectile launcher g. calibrating the optical axis of a
camera with the boresight of the projectile launcher; h. mapping
the camera with the target and emitter position i. providing
equipment means for controlling the emitter and for determining and
recording the predicted aimpoint at a triggering event j.
determining the projectile launcher aimpoint at the triggering
event
32. The method of claim 31 further comprising the following when
the target is a moving target: a. providing a downrange controller
for controlling the position of the moving target, wherein the
computer is responsive to output from the downrange controller for
determining the aimpoint vector at the triggering event.
33. The method of claim 31 further comprising determining the fall
of the shot.
34. The method of claim 33 further comprising determining
projectile launcher burst effects.
35. The method of claim 31 further comprising recording the
projectile launcher aimpoint determination data on the equipment
means and providing performance feedback to personnel.
36. The method of claim 31 further comprising preparing an
evaluation report for a projectile from data captured by the
equipment means.
37. A system for determining the contemporaneous position of a
moving target comprising, a movable platform, the target mounted on
the platform, an emitter mounted on the platform, the emitter being
in fixed relationship to the target, a reflector mounted on the
platform the emitter being in fixed relationship to the emitter, a
rangefinder and a downrange controller receiving range information
from the rangefinder wherein the position of the reflector is
determined by the rangefinder and the position of the target
centroid being determined by the target position relative to the
emitter.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to projectile targeting and
more particularly to small projectile trajectory analysis.
[0003] 2. Description of the Related Art
[0004] Determination of aimpoint is well known. Aimpoint is used in
actual field situations to determine a fire control solution.
Aimpoint is also used in training weapons operators to sharpen
their skills and to improve their performance. U.S. Pat. Nos.
4,804,325 and 5,213,503 each of which is incorporated herein by
reference illustrate representative relevant techniques in the
prior art.
[0005] U.S. Pat. No. 4,804,325 discloses a weapons training
simulator that predicts aimpoint and trajectory. The invention uses
a sensor mounted on a weapon to generate a target position signal
based on point sources located within the perimeter of simulated
targets, thereby defining a diffusely illuminated target field. Set
in a real-world environment the aimpoint is determined, using the
output from light emitting diodes (LED's), defining point sources
to a quadrature detector array to create uniform diffuse
sources.
[0006] U.S. Pat. No. 5,213,503 discloses a commercially available
aimpoint infrared spot tracking system that includes a charge
coupled device (CCD) video camera interfaced to a digital frame
grabber operating at standard video rates for use in simulator
training. A lens system images the tracking area (i.e., video
projection screen) onto the CCD imaging sensor. The frame grabber
digitizes each frame of video data collected by the CCD camera.
This data is further processed with digital signal processing
hardware as well as software algorithms to find position
coordinates of the imaged IR spot. The 503' patent uses tracking
system software to allow the aimpoint to be continuously monitored
during a training scenario. For this application a CCD-based
tracking system or similar device utilizing a two-dimensional
position sensing detector (PSD) lateral-effect photodiode provides
the aimpoint position data. The aimpoint analysis of the 503'
patent is limited to a virtual environment with all targets
displayed upon a video projection screen. In particular, an
infrared source is mounted to the weapon and the beam from the
infrared source-is projected onto the screen.
[0007] Live testing is generally performed to determine the path of
projectiles by physically tracking the projectile path (hereafter
the "fall of shot") from the nozzle exit to the actual end-point of
the projectile path, which could be the location at detonation. In
particular, aimpoint analysis is the focus of testing when
experimenting with new weapon sights or fire control systems. As
used in this specification weapon and projectile launcher are used
interchangeably.
[0008] There are several disadvantages to live testing including
technical obstacles to tracking the projectile. For example,
ballistic radar is the technology most commonly used to track the
fall of shot, but radar cannot track sub-sonic rounds. In addition,
measuring the fall of shot by any method cannot separate system
error from user error, round-to-round dispersion or environmental
error. Furthermore, live testing typically requires the expenditure
of large numbers of projectiles: this can become expensive
especially with prototypes. Finally, measuring the fall of shot
captures only a snapshot of the result of the projectile's
flight.
[0009] In addition to live fire testing, small arms weapons
simulators are used extensively for training. During training, it
is important for a simulator to replicate the environment that a
shooter could encounter. In the real world, targets may be either
stationary moving. In training operators, determining the time
required to acquire the target, engage the target, and manipulate a
fire control system as well as other projectile launcher-handling
data are useful. In training, it is also important to minimize the
expenditure of ammunition while maximizing the training benefits.
Especially important is determining the accuracy of the shooter so
that the shooter can improve his or her skill. A need exists to
measure a shooter's aimpoint and to predict the impact of the
projectile from the projectile launcher aimpoint.
[0010] Therefore, there is a need for determining aimpoint that
allows the small arms testing community to separate the aimpoint of
a projectile launcher from the actual fall of shot in physical
testing environments. In addition, there is a further need to
determine aimpoint for training weapons operators.
BRIEF SUMMARY OF THE INVENTION
[0011] It is an object of the invention to track aimpoint.
[0012] It is another object of the invention to calculate the
predicted trajectory rather than the actual trajectory of the
projectile.
[0013] It is a further object of the invention to compute the
difference between the actual aimpoint and the aimpoint required to
hit the target: user error.
[0014] It is still another object of the invention to be able to
modify the calculated projectile path to incorporate system error
dispersion, and external effects to determine the probability of a
hit or contact (P(h)).
[0015] It is yet another object of the invention to capture the
aimpoint at the moment of dry-fire.
[0016] It is further an additional object of the invention to
predict the effects of the projectile in the impact zone.
[0017] It is a final object of the invention to collect digitized
video of the projectile launcher's aimpoint during the aiming
procedure to evaluate the shooter's aiming performance.
[0018] In order to accomplish the above objects, in accordance with
a first aspect of the present invention there is provided an
aimpoint tracking and data collection system for projectiles during
live fire testing or training events. The exemplary embodiment uses
infrared reference emitters and a projectile launcher-mounted
camera system to measure aimpoint relative to predefined targets on
a live testing or training range. Calculated aimpoint angles may be
used in conjunction with a ballistics model to predict a
projectile's miss distance at the plane of the intended target. In
addition, if the projectile is from a weapon then the effects may
be incorporated to predict the impact.
[0019] The system according to the first aspect may further include
moving targets.
[0020] The system according to the first aspect may further include
a computer program for performing coordination and control of the
equipment and calculations. The calculation may further include the
effects of external conditions such as wind on the trajectory.
[0021] In a second aspect of the present invention a method for
determining projectile launcher aimpoint is disclosed. The method
comprises surveying a firing range for determining the location of
target and emitter coordinates, calculating the centroid of a
target having a defined perimeter, the target being placed on the
firing range, placing fixed infrared emitting sensors on the firing
range wherein the sensors are located external to the target
perimeter, selecting the location of the shooter at a firing line,
mounting a camera to the projectile launcher, calibrating the
optical axis of a camera with the boresight of the projectile
launcher, mapping the camera with the target and emitter position,
providing equipment means for controlling the emitter and for
determining the predicted aimpoint at a triggering event,
determining the projectile launcher aimpoint at the triggering
event, and outputting the measuring projectile launcher aimpoint at
the triggering event.
[0022] These and other features and advantages of the present
invention may be better understood by considering the following
detailed description of certain preferred embodiments. In the
course of this description, reference will frequently be made to
the attached drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0023] Referring now to the drawing wherein like elements are
numbered alike in the several FIGURES:
[0024] FIG. 1 is a perspective view of an exemplary embodiment
illustrating the location of components of the present
invention;
[0025] FIG. 2 is a signal flowchart of an exemplary embodiment of
the present invention;
[0026] FIG. 3 is a signal flowchart for the emitter controller of
the present invention;
[0027] FIG. 4 is a signal flowchart for the downrange controller of
the present invention;
[0028] FIG. 5 is a signal flowchart for the system interface box of
the present invention; and
[0029] FIG. 6 is a flow diagram of the software for controlling the
illustrative embodiment of the present invention;
[0030] FIG. 7 is a software program flowchart of the System
Interface Box (SIB);
[0031] FIG. 8 is a software program flowchart of the Emitter
Controller (EC);
[0032] FIGS. 9a, 9b, and 9c, sheets 1, 2, and 3 respectively are a
flow diagram of the software for controlling the illustrative
embodiment of the present invention;
[0033] FIG. 10 is a plan view illustrating a firing range showing
the mathematical relationships for fixed targets, emitters and a
projectile launcher, and includes the boresighting relationship
between the projectile launcher aimpoint and the camera optical
axis;
[0034] FIG. 11 is a plan view of a firing range showing the
sightline and the sightline intersection with the moving target
path plane indicating the mathematical relationship between the
sightline and the moving target at shot fired time.
[0035] FIG. 12 is a plan view illustrating a track mounted moving
target with attached emitter illustrating the target, shot, and
round trajectories, along with equations for calculating the
coordinates at the time of the round intercept with the target path
plane.
DETAILED DESCRIPTION OF THE INVENTION
[0036] In the following detailed description of the preferred
embodiment, reference is made to the accompanying drawings in which
is shown by way of illustration a specific embodiment whereby the
invention may be practiced. It is to be understood that other
embodiments may be utilized and changes may be made without
departing from the scope of the present invention.
[0037] Referring to FIG. 1 and FIG. 2, an exemplary embodiment a
projectile launcher aimpoint tracking system is shown generally at
10. A camera 12 is affixed to a mount 14, and the mount is affixed
to a projectile launcher such as a rifle 16. Stationary targets 18
or moving targets 20 including both stationary and moving infrared
emitters 24, respectively along with emitter controllers 22 are
located in a firing range. A firing range is a volume where targets
are located and can include an entire battle theatre. Infrared
emitters 24, typically LED's or optically filtered halogen lamps,
are located downrange as references for the determination of target
location. The associated emitter controller 22 controls each
infrared emitter and receives signals from the system interface box
28 or a downrange controller 25 which communicates with the emitter
controller by radio transmission. A computer 26 provides the
overall control of the system with interfaces provided though a
system interface box 28, each being mounted in a rack 30. Radio
transmitters 32, relays 34 and receivers 36 along with connecting
cables 38 provide communication connections between system
components. Sensors that detect projectile launcher related events,
for example but not limited to firing, lasing, etc. include one or
more of a microphone 40a, a powered sensor 40b, or a normally open
switch 40c to provide input to the system interface box 28. In
addition a video recorder 42, for example a videocassette recorder,
digital recorder, digital compact disk recorder, etc., receives and
stores the camera video and event information, including
information from the trigger sensors.
[0038] The projectile launcher mounted camera 12 views the
live-fire range from the perspective of the projectile launcher
bore sight. Both the camera and its lens 44 are removable and may
be replaced with a different camera and or different lens for each
test depending upon the test objectives. Typical variables for
selecting the camera and lens are the camera size, resolution,
required field-of-view, and mounting requirements. For example,
small-bore projectile launchers require a small, light camera to
minimize interference with operator control and a narrow
field-of-view to maximize angular resolution per video pixel. As a
further example, a wider field-of-view is required if the targets
are dispersed over a wide firing range, such as battle theatre, for
example 30 degrees as opposed to a narrow target range, for example
8 degrees.
[0039] In the exemplary embodiment, the camera 12 is an ELMO CCD
(charged coupled device) Black and White Camera, model ME4111R that
does not have the typical near-infrared blocking filter installed
(although other suitable cameras are commercially available, for
example, a small rectangular 1/2'' format camera with an electronic
high speed shutter manufactured by Panasonic that can have its
near-infrared blocking filter removed). The image pick-up device is
a 1/2 inch interline-transfer CCD with 768 H.times.494 V effective
picture elements (pixels). The camera typically consists of a
camera head with lens, a camera control unit (CCU) and an
interconnecting cable. The CCU is powered by 12 VDC from either a
battery or an AC adapter. The camera is operated in the standard
NTSC mode with a vertical frequency (field) of 59.94 Hz, horizontal
frequency (line) of 15.734 kHz and provides a composite video
output.
[0040] The Elmo camera uses an Elmo lens mounting and two lenses,
having focal lengths of 24 mm and 36 mm. The Panasonic camera uses
standard C mount lenses and a single 35 mm lens along with two
focal length adapters to provide a 1.5.times. and or 2.times. focal
length products. Using the adapters, the 35 mm lens can be modified
to provide 52.5, 70, and 105 mm focal lengths by using combinations
of the adapters.
[0041] The camera mount 14 is adjustable permitting the camera lens
optical axis to be aligned roughly with the projectile launcher
bore sight line. A software managed boresight process is used for
fine aligning the angular offset of the camera optical axis from
the projectile launcher boresight line. After the camera is roughly
aligned, the remaining angular and linear camera axis offset from
the sightline is recorded and used in subsequent projectile
launcher aimpoint error calculations. In particular, when viewing
targets at any distance, the angular and linear offsets of the
camera optical axis from the sightline is corrected via the
software calculations to remove effects upon the aimpoint
measurement accuracy thereby eliminating the need for optical
corrective algorithms.
[0042] It is to be appreciated that in the illustrated embodiment
the field coverage must provide for the camera 12 imaging of a
target's reference emitter 24 when the projectile launcher 16 is
sighted on a target 18, 20. This requirement originates from the
need to mark the reference emitter when a projectile is fired at
the target. From this field of coverage it is to be further
appreciated that the field coverage is optimally between 10 meters
and 100 meters at the target distance thereby permitting location
of the emitter outside of the perimeter of the target so long as
the emitter is within the field of camera coverage.
[0043] A titler 46, located in the operator station main rack 30,
overlays text onto the incoming camera video and transmits the
result to the VCR 42. The titler is responsive to the system
computer 26 through an RS232 interface and provides output signals
to the system computer through the RS232 interface and to the VCR
through an RS170 video interface. The system computer provides
commands to the titter to overlay test data onto the camera video
for correlation to events of interest occurring during the
test.
[0044] Referring to FIG. 2 and FIG. 5 The digital video recorder 42
is a typical, commercially available cassette unit, but may
alternately be a digital recorder that utilizes other media such as
digital disks or internal hard disks. In the exemplary embodiment,
the digital recorder is mounted in the operator station main rack
30. During testing, the recorder, records the video from the camera
12, the titler 46, as well as the main and auxiliary trigger events
from the system interface box 28 on the left and right audio analog
channels. This input is first transmitted to a tone generator 50
for the trigger and then to the videocassette recorder 42. The
near-infrared CCD image of the live fire range is also output from
the video recorder 42 via an RS170 video interface to the system
computer's frame grabber board for marking the emitter centroid
relative to the projectile launcher sightline. In this manner, the
marking of the emitter can be performed immediately after an event.
Alternately, the marking of the emitter may be performed during
post-test processing, where the videocassette recorder provides
recorded event data and test video to the system computer and the
computer's frame grabber board to be described hereinbelow.
Microphone sensor 40a inputs representing the trigger events
recorded on the left and right audio channels are received by the
VCR. The sensor signals 40a, 40b, 40c are also outputted to the
system interface box 28 main and auxiliary audio inputs for trigger
event re-generation.
[0045] The frame grabber (not shown) is a commercially available
Matrox Orion board that decodes the composite video from the CCD
camera 12, described hereinabove, and digitizes the image to a 640H
by 480V pixel format. All measurements of the emitter 24 centroid
are made on video frames digitized by the frame grabber. The
10-nanosecond jitter of the Matrox Orion board, which equates to
less than ten percent of a pixel width, has minimal effect on the
emitter centroid measurement and the resulting system error.
[0046] As is well known in the art, the targets 18, 20 are those
typically used for live fire ranges. The targets previously used
have been E-silhouettes. Other targets may be used; the only
consideration is that there is a defined target centroid. The
targets are attached to supports that hold the targets in
position.
[0047] Referring again to FIG. 1, both fixed targets 18 and moving
targets 20 are illustrated in the exemplary embodiment. Each moving
target is mounted on a track 52 and responds to signals from the
system computer 26 to traverse a portion of the firing range
through a preprogrammed path when commanded by the computer.
Alternatively, a dedicated preprogrammed target motion controller
(not shown) can control each target using servomotors. In yet
another variation the target motion controller is able to respond
to contemporaneous operator commands using servomotors. Mounting
the moving targets on tracks simplifies the calculation of location
within the firing range by the downrange controller (to be
described hereinafter). In alternative embodiments, the location of
the moving target is transmitted through alternate means, for
example a multiplexed optical signal from a rangefinder or a global
positioning system.
[0048] The exemplary embodiment includes the implementation of a
moving target 20 measurement subsystem. The goal of the moving
target measurement subsystem is to provide the 3D coordinates of
the moving target and emitter centroids at the time that a shot is
fired (to determine the projectile launcher sightline angles
relative to the target center) and at the time of the terminal
position of the fired projectile (where it intersects the target
path plane, hits the ground, or air bursts) to differentiate the
location of the moving target and the projectile at the time the
projectile reaches its terminus or intersects the target. The
location of the moving targets' centroid, like the fixed targets'
centroid, is determined with reference to the infrared emitters'
centroid.
[0049] The infrared emitters 24 (IR's) are located on the firing
range and are used in conjunction with the projectile
launcher-mounted CCD camera 12 to determine where a projectile
launcher 16 is aimed relative to targets 18, 20 located on the
range. In the exemplary embodiment, the emitters for fixed targets
18 are mounted to upright posts 54 that have been driven into the
ground to rigidly fix the emitter position. Preferably, the ability
to support live fire operations is provided by placing the emitters
to one side of the target to minimize the possibility that an
emitter will be struck by a projectile. The emitters are located on
the range such that the camera 12 can sense the emitter during the
projectile launcher aiming process. The camera does not need to
sense the target so long as the emitter associated with the target
under fire is in the camera's field of view and is identified as
the target reference emitter in the system computer program
software. The system computer 26 defines the target's reference
emitter 24 via a target-emitter database.
[0050] The emitters 24 are halogen light sources that are optically
filtered using an RG780, or generally equivalent, filter to block
visible output while allowing near-infrared output to pass through.
"Near infrared" is commonly defined as the region of the
electromagnetic spectrum wavelength between 0.77 to 1.4 microns.
The RG 780 Filter makes the emitter output invisible to a shooter,
but provides near infrared for the CCD camera 12 to detect. The CCD
camera is also optically filtered, preferably using an RT830 filter
(or general equivalent) to optimize detection of near-infrared
output. The filter blocks most of the visible wavelengths but
passes near-infrared radiation that corresponds to the emitter
output and is within the CCD's near-infrared response. The diameter
of the infrared emitter 24 aperture is typically 50 millimeters,
with smaller or larger sizes used for nearer or farther emitter
positions.
[0051] The emitters used in the illustrated embodiment have angular
output profiles that range from a 10-degree symmetrical cone to a
45-degree horizontal by 10-degree vertical compressed cone shape.
Considering only the physical size of the emitter aperture, the
calculated angular, size of the emitter presented to the CCD camera
12 varies as a function of distance from the camera. The emitter
subtends a relatively small angle at the 50-meter range and the
angle reduces linearly as the range increases. In the exemplary
embodiment, 50 meters is the closest planned range to an emitter,
while 1000 meters is the maximum range to an emitter although
closer and further ranges are within the contemplation of the
illustrated embodiment. In general, an emitter placed at a further
range will present itself as a smaller object in the CCD camera
image and would allow a more precise location to be derived from
the emitter marking/location process. If an emitter subtends less
than a pixel when imaged on the CCD camera, marking the emitter
centroid will be difficult due to an inability to determine the
emitter shape. However, the image of the emitter sensed by the CCD
sensor is actually larger, due to a phenomenon known as blooming.
Blooming will become important as the angular size of an emitter
aperture falls below the angle covered by a pixel.
[0052] Because of blooming, the physical size of the emitter 24
aperture does not provide a direct relationship to angular size in
the CCD camera 12 image. In the exemplary embodiment, high output
emitters are used to provide sufficient near-infrared output to
overcome ambient radiation from the sun. This high output increases
blooming. During actual live fire testing, captured images of the
emitter at various ranges show larger angular sizes depending on
the ambient illumination level and the emitter range.
[0053] IR emitters 24 are commonly available along with power
sources. A portable 12V power source may be used, for example a
battery (not shown). The portable battery power source combined
with the radio controlled emitter controllers, described
hereinafter, advantageously provide for remote placement of the
emitters within a live fire test range while maintaining
communication with the system computer 26. As is well known, a DC
generator or powered inverter may also used to power the
emitters.
[0054] An emitter controller 22 controls each emitter 24. The
emitter controller communicates with the computer using a broadcast
radio antenna 32 and receiver antenna 36 although other types of
communication links, for example microwave, wide area wireless
network, telephonic network etc. are well known in the art.
[0055] Referring to FIG. 3, the emitter controller includes a
Zworld BL1800 microprocessor 56. A 3.686 kHz resettable TX/RX clock
58 provides timing to the BL1800 microprocessor upon initiation of
an enable signal from the microprocessor. A radio transceiver 60
connected to the microprocessor handles radio communications. The
transceiver is a TEC T400 as is well known to those of skill in the
art. The microprocessor sends a signal to the emitter power control
circuit 64 to turn the emitter on and off. An ID select circuit 66
is provided to enable each emitter controller to be set to a unique
ID, allowing radio broadcast commands to be addressed to specific
controllers. A battery level detector circuit 68 is provided to
monitor the battery charge state. Auxiliary circuits provide status
LEDs and an override switch 70. The override switch is provided to
allow a user at the emitter controller to cause the controller to
power its attached emitter without recourse to radio commands, a
feature useful during system setup or test.
[0056] In the exemplary embodiment, the emitters 24 are placed in
relation to the firing range to provide a coordinate reference. In
this arrangement the need to locate the IR's within close proximity
to or at the fixed targets 18 is eliminated so long as the distance
vector from the emitter to the target is known. The IR's are
therefore generally located external to targets within the firing
range but can also be located within the target boundary. The
downrange placement of the IR's takes advantage of the high
resolution of the camera 12 in order to render the optic and
alignment errors negligible for determination of the aimpoint
position vector. The Lens Mapping Procedure within the system
computer software to be described hereinbelow is used to provide
the microRadiansperPixel_H and microRadiansperPixel_V values
associated with a particular CCD camera 12 and lens 44 combination
that will be mounted to a projectile launcher 16 under test.
[0057] Referring to FIG. 4, the downrange controller 22 consists of
a Zworld BL1800 microprocessor 80, a RIEGL LD90-3100-VLS-FLP
rangefinder 82, a TEC T400 radio transceiver 96, and a custom
circuit board containing an array of control and interface
circuits. The transceiver controls radio communications. A 3.686
kHz resettable TX/RX clock circuit 86 provides timing for radio
communications. The SIB and all DRC's are tied together through a
hardwired dual-channel current loop and RS485 channel. The two
channels of the current loop are used by the SIB to send time
critical signals, while the RS485 serial channel is used for bulk
data transfer. All hardwired connections to the DRC are
optoisolated, protecting the DRC from potentially damaging
transient voltages. The current loop channels are isolated by the
custom isolation circuit 94. The RS485 serial channel is isolated
by a B&B Electronics 485OPIN optoisolator 102. Either the SIB,
through the current loop, or the DRC's internal microprocessor 80
may enable the 2 kHz Laser Trigger Clock 84. The Laser Trigger
Clock in turn causes the range finder 82 to gather range data at 2
kHz. Data from the rangefinder is downloaded to the microprocessor
for analysis and storage through a RS232 channel. An ID select
circuit 100 provides each DRC with a unique address.
[0058] Referring again to FIG. 1, a downrange controller 25 is
positioned at the end of each moving target's track 52 in order to
monitor the location of the moving target 20. When enabled, the
DRC's rangefinder takes 2000 range samples per second. The DRC's
microprocessor averages groups of ten samples so that range data is
recorded 200 times per second. Repetitive samples are discarded so
that only motion is recorded. Each controller is provided with
capacity to store up to 60 seconds of motion. The present
embodiment has a capacity for 16 individually addressed downrange
controllers, although it is within the contemplation of the present
embodiment to include additional controllers. A DC supply, for
example a battery (not shown), powers each controller 25, although
it is within the contemplation of the invention to use other power
sources including inverters, fuel cells and DC generators.
[0059] Referring again to FIG. 2 and FIG. 5, trigger event sensors
40a, 40b, 40c, are used to initiate the aimpoint vector
determination sequence. Three types of sensors are available for
the initiation function, and include a microphone, a powered
sensor, and a switch. Each trigger event sensor provides output to
the system interface box SIB 28 and to the VCR 42.
[0060] The microphone 40a generates a trigger event by detecting
fire by listening for projectile launcher recoil and outputs an
analog signal. The microphone is a standard commercial microphone
having a sensitivity of 6 dB although higher and lower
sensitivities will function in the embodiment. The microphone is
mounted on, or near, the projectile launcher such that the
diaphragm of the microphone responds to the initiating sound of the
projectile launcher firing.
[0061] The powered sensor 40b is any digital sensor that requires
external power. The power sensor is provided with +5VDC from the
system interface box (SIB) 28. The SIB generates a trigger event
when the powered sensor digital output goes high. Powered sensors
include Hall Effect sensors to detect the motion of some projectile
launcher part or an accelerometer to detect the shock of the
projectile launcher recoil. The powered sensor is mounted on the
projectile launcher such that the sensor is responsive to the
movement or acceleration of the sensed component.
[0062] The switch 40c is a normally open switch that completes a
circuit when closed. The SIB 28 generates a trigger event when the
switch is closed or pressed. The switch is used to detect a
preselected physical projectile launcher operation, such as a
trigger pull or a button press, or may be a hand switch held by the
operator, test director or system operator.
[0063] When the particular microphone 40a, power sensor 40b or
switch 40c is used, the associated output signal is sent to a
glitch detector with lockout timer 110. The lockout timer provides
a period after each trigger event during which further trigger
events are ignored. The glitch detector output is sent to the
Zworld BL 1800 microprocessor 112 within the SIB 28, alerting the
microprocessor of the trigger event. The glitch detector output is
also sent to a trigger tone generator 50. The trigger tone
generator produces a short burst of audio line level tone that is
recorded by the system video recorder 42, marking the trigger event
on the video recording.
[0064] The BL 1800 microprocessor 112 of the SIB 28 serves as a
general interface between the downrange and firing line hardware,
including the emitter controllers 22 and downrange controllers 32,
the trigger event sensors 40a, 40b, 40c, the VCR 42 and the system
computer 26. The TEC T400 radio transceiver 120 handles radio
communications.
[0065] The SIB 28 communicates to the system computer 26 through
three channels: RS232 serial, parallel digital, and RS485 serial.
General communication between the SIB and the system computer are
passed through the RS232 serial channel. The parallel digital
signals are used to transmit time critical communication. The
digital signals from the system computer are received by the SIB
through a Data Translations STP68 interface board 124. Signal
conditioning circuitry 122 turns two of the digital signals into
the dual-channel current loop that joins the RS485 serial channel
in hardwire linking the SIB and all of the DRC's. The current loops
transmit time-critical events to the DRC's while the RS485 serial
channel allows for bulk data transfer. A Keypad 114 and a Matrix
Orbital LK2204-25 LCD display 116 allow the user to interact with
the SIB, monitor its status, issue commands, and run test
functions.
[0066] The system computer 26 is a typical commercially available
PC capable of running software embodied on the computer media. In
the exemplary embodiment the computer includes a Windows 2000.TM.
or higher operating system. PC requirements in the exemplary
embodiment are at least 128 MB of RAM and a 733 MHz Pentium III
processor or equivalent although the system will run on other
platforms. A CDROM drive or equivalent means, for example, an
external memory device or Internet download capability is required
for software installation. As is well known, the PC contains a
memory device such as a hard disk, a microprocessor and input
device and output devices. Preferably, the output devices include
both a display screen and a printer. To accept the software and
databases, the memory device, for example the hard disk, preferably
should have a capacity of at least 10 GB free hard drive space for
program operation and data storage. However, the memory requirement
may vary and depends upon the expected size of the database. As is
well known in the art, memory can be selected to match the database
or increased by installing a higher capacity disk drive.
Software Control
[0067] The software for controlling the equipment that comprises
the illustrative embodiment will now be described. It is to be
appreciated that the software can be expressed in many forms by
those skilled in the art and only the necessary functions will be
described herein. The software provides control among downrange
hardware, operation station hardware and firing line hardware.
SIB Program
[0068] Referring to FIG. 6, the compiled code in the Zworld BL 1800
microprocessor 112 (See FIG. 5) automatically initiates at system
power up 150. At initialization 152 variables and arrays are
created and the digital I/O system is initialized with outputs set
to their default startup states. The main loop is started 154 and
repeats until the system is powered down. The main and auxiliary
trigger pulse digital inputs are polled 156 to check for hardware
detection of projectile launcher events. The system computer is
alerted 158 to a hardware detected projectile launcher event by
raising the trigger flag. Then the main and auxiliary triggers
reset digital inputs are polled 160 to determine if the system
computer commands the main or auxiliary trigger flags to be lowered
162. The main or auxiliary trigger flags are lowered as commanded
by the system computer. The RS232 serial buffer serving
communications to the LCD display is polled 164 to determine if a
keypad key press has been received. In the Handle Key press 166
step the program responds appropriately to the key press. The RS232
serial buffer serving communications to the system computer is then
polled 168 to determine if a computer command has been received. In
the ping steps 170, 172, the computer determines whether a ping is
received. All commands from the system computer other than a ping
are meant for the emitter controllers via the radio link and the
command bytes are placed in the outgoing queue 174. In the bytes in
outgoing queue 176, the program determines if there are any
computer commands waiting to be sent to the emitter controllers via
the radio link. The SIB radio transceiver's received signal
strength indicator line is polled 178 to determine if another
unit's transceiver is currently transmitting. Then, all computer
command bytes in the outgoing queue are sent to the emitter
controllers via the radio transceiver 180. The bytes from the
outgoing queue are cleared after being sent 182. Next the SIB radio
transceiver's received signal strength indicator is polled to
determine if another unit's transceiver is currently transmitting
184. If another unit is transmitting, incoming radio messages are
received 186 and the system responds as appropriate 188 to the
received radio message. Finally, the main loop ends 190 and repeats
in the start step 154.
Emitter Controller (EC) Program
[0069] Referring to FIG. 7, the emitter controller program will now
be described. The compiled code resident in the emitter Zworld
BL1800 microcontroller 56 (See FIG. 3) is initiated upon powerup
202. At initialization 204 variables and arrays are created and the
digital I/O system is initialized with outputs set to their default
startup states. The two digital inputs of the EC's 2-position DIP
switch are polled to determine the controller's ID tens digit, and
the four digital inputs of the 10-position rotary switch are polled
to determine the controller's ID ones digit 206. The status LEDs
are flashed to indicate the emitter identification number; the LEDs
are cycled a number of times equal to the tens digit, then flashed
a number of times equal to the ones digit 208.
[0070] The main loop starts 210 and repeats until power down. The
program queries whether there are any bytes waiting to be sent to
the system computer via radio link 212. In a responses allowed step
214, the EC settings are queried to determine if radio responses
have been disabled by system computer command. Radio responses may
be disabled to prevent confused radio traffic when many EC's are
deployed. The program pauses for a duration determined by the
emitter ID number 216, 218, 220. This pause will prevent the EC's
from attempting to transmit simultaneously, as well as causing them
to respond to broadcast commands in numerical order. The EC radio
transceiver's received signal strength indicator line is polled to
determine if another unit's transceiver is currently transmitting.
Next, in the "Bytes in outgoing queue" step, the waiting messages
in the outgoing queue are broadcast via the EC's radio transceiver
222. The outgoing queue is cleared 224 after the waiting messages
are sent. The EC's set ID is checked 226. Then the EC determines
its battery state 228 through two onboard voltage comparators,
dividing the range of battery voltages into three categories: good,
warn and critical. If manual override functionality has not been
disabled by the system computer 230 the manual override switch
state is polled and if "on" the manual override flag is set 232.
The EC then polls the radio transceiver's RSSI line to determine if
another unit's transceiver is currently transmitting 234. In steps
236 through 240 incoming bytes are received and the message
transmitted by the bytes is handled. Appropriate responses, if any,
are placed in the outgoing queue. The program polls whether the
emitter manual override flag has been raised 242. If the flag is
raised then the emitter is turned on 244 and the emitter status LED
is flashed steadily 246, indicating that the emitter is on due to
manual override, and the main loop ends. If the manual override
flag is not raised, the program polls whether the emitter flag is
raised 248. If the flag is raised then the emitter and the emitter
status LEDs are turned on 250 and the main loop ends. If neither
the manual override nor the emitter flag are raised, the emitter
and emitter status LED are turned off 254, the emitter status LED
turns off 256 and the main loop ends 258.
Downrange Controller Program
[0071] Referring to FIG. 8, on powerup 262 the compiled code
resident in the downrange controller Zworld BL 1800 microcontroller
80 starts and runs. Variables, states and settings are initialized
264. The hardware ID is checked 266 by polling the four digital
inputs of the DRC's 16 position rotary switch to determine the
unit's ID number. The handle temp function 268 uses onboard sensors
to determine the DRC's current internal temperature. The DRC's fan,
defroster, and/or heater are then activated as needed to keep the
unit's internal temperature within tolerance limits.
[0072] The main loop 270 is then started and repeated until
shutdown. Once every 15 seconds a subset of commands within the
main loop is performed 272 wherein the hardware ID lines are
checked and the DRC ID number is ascertained 274, the handle
temperature routine performed 276, and the check battery voltage
routine is performed 278 thereby ending 280 the periodic check
cycle. When this main loop periodic subset is completed, the main
loop functions are performed.
[0073] Each pass 282, the main loop begins by checking the state of
Trigger1 284. Trigger1 is a current loop passing through the SIB
and all of the DRC's. When Trigger1 is active, all rangefinders
will begin ranging and sending data to their microcontrollers. If
Trigger1 is active, the DRC then determines if the system computer
has enabled the DRC for recording 286. If the DRC is enabled for
recording, the microcontroller will begin processing and recording
the incoming data from the rangefinder 288. The rangefinder will
continue to range until Trigger1 returns inactive. The
microcontroller will continue to record data from the rangefinder
until the rangefinder until no more data is forthcoming or a full
sixty seconds of data. Once all data has been recorded the DRC will
disable itself 292 for recording if the system computer has placed
it in disable after record mode. Disable after record mode 292
prevents new data from being accidentally overwritten before the
data can be downloaded to the system computer. If the DRC is in the
disabled after record mode then no further rangefinder data will be
recorded until the DRC is again enabled by a system computer
command. If Trigger1 is not active but rangefinder data has been
received 294 the data can be discarded. The RS485 serial buffer
serving the communications with the system computer is then polled
298 to determine if commands have been received. If so, the
microprocessor acts appropriately 300, 302. Any responses to the
system computer are placed in the outgoing queue 304. The
microprocessor next checks the outgoing queue. If the queue
contains any bytes, they are sent to the system computer through
the RS485 serial channel and the queue is cleared 306, 308. The
RS232 serial buffer serving communications with the keypad/display
unit is polled to determine if a keypad keypress has been received
310. Appropriate responses to any keypresses are generated 312 and
the main loop ends 314.
System Computer Program
[0074] The system computer program comprises a main program and two
threads, the frame grabber and the event detection thread. A
process events process captures data for later analysis, but the
process also executes in real time.
[0075] Referring to FIG. 9a main program is illustrated at 300. The
program starts 302 by initializing data structures 304 entered into
databases 306, 308, 310. The data is collected from the on-site
survey 312, the lens mapping procedure, 314 and from the test plan
and ballistic models 316. After the data structures are
initialized, the program initiates communication linkage and
verification with the system hardware through wires and radios
along with its internal communications 318. The event detection and
frame grabber threads are initialized and placed in a suspended
state 320. The computer display shows the main menu 322 whereby the
operator selects either the capture or analyze modes 324. In the
capture mode filenames are assigned and new data files are opened
and initialized for the event 326. In the analyze mode the data is
analyzed 336a. The detection processing mode is selected for either
live processing 330, 332, 334, 336b or post system processing. 338,
340, 342. During Live Processing, data from a single event is
captured and immediately analyzed at 336b. For Post Processing,
where a large amount of data is to be captured sequentially, the
data are recorded and analyzed later via AnalyzeData( ) at 336a.
The System Interface Box (SIB) turns on the default emitter for the
selected target after a target is selected 329 or 337. The event
detection sequence initiates when an event is selected at 330 or
338 and the video recorder is started.
[0076] Referring to FIG. 9b, the thread for monitoring event
detection ports on the SIB hardware is shown at 350. Following
initialization, the event detection circuits are reset 354 and the
event counters are initialized 356. The event detection loop starts
360. The video recorder status is checked 362 and the detection
thread is suspended if the video recorder is off 364. If the video
recorder is operating, the video frames from the projectile
launcher-mounted camera are recorded on the digital video recorder.
If Live Processing mode was selected 366, then the video frames are
also input into a computer memory buffer configured as a six second
first in first out (FIFO) memory buffer 368. If an event has
occurred 370 then the event detector circuits are reset 372 and
event data are processed 374. If an event has not occurred, then
the burst timer is checked 380 and the burst count is incremented
if the burst timeout has passed 382. If not in the burst mode, or
after events are processed 372, 374, the event detection loop is
restarted 360.
[0077] Referring to FIG. 9c, the process for analysis of event data
is illustrated at 400. The process handles the selection, display,
and marking of the emitter locations for event images stored in the
FIFO buffer by the video frame grabber. User controls for
displaying, marking, and saving marking data are provided 404. An
event is selected from the available events 410. The data related
to an event is used to find and display the video frame for the
event 412. The operator verifies the event occurrence and emitter
marking, and the marked event data is saved 414. The marked emitter
data is used with the target and emitter coordinate data provided
via the survey process to determine aimpoint performance 416.
Aimpoint data for the target and event of interest is saved 418 and
combined with the ballistics model to provide flyout of the round
towards the target. The operator may then select another event to
be analyzed, or return to the previous process 420, 422.
[0078] A projectile dynamics model as is well known in the art is
included for both training and testing. The dynamics model
calculates the fall of the shot. Such testing may include
modifications to the projectile launcher site or triggering
mechanisms. The projectile dynamics model may include aerodynamic
drag effects as well as lift and gravity forces upon the
projectile. Wind and other shocks encountered by the projectile are
also included in the dynamics model. Such modeling is well known in
the art including the aerodynamic effects of lift and drag caused
by the exogenous aerodynamic forces.
[0079] In addition to the dynamics model, a projectile burst effect
model, the development of which is well known in the art may be
included. Burst effects are correlated to the actual projectile
parameters, for example, the quantity of explosive, the fracture
characteristics of the casing and the effects of proximity
devices.
Setup and Operation
[0080] The operation of the invention will now be described.
Range Survey
[0081] First, a survey of the firing range is performed. The system
uses survey equipment to measure the three-dimensional coordinates
of the targets, reference emitters and shooting position. Since all
of the subsequent calculations are based upon these measurements,
the accuracy of these coordinates bounds the accuracy of the
system.
[0082] The scenario objectives, whether testing or training, are
factored into the design of the range. The location of the firing
line is determined along with placement of downrange hardware
consisting of rangefinders and IR's, thereby defining the range and
available targets. The static emitters preferably should be placed
within 20 mils of the targets but may also be placed further from
the target with acceptable loss of accuracy. Next, a static target
survey is performed in which range data for the shooter, static
targets, and emitter three-dimensional coordinates within the live
fire range are determined along with ground plane elevation at each
target.
[0083] Equipment used to survey live fire test ranges typically
includes theodolites, transits, laser range finders and global
positioning systems. The exemplary embodiment uses a survey that
incorporates a theodolite angular measurement device with a laser
rangefinder to provide azimuth, elevation, and range to a
retro-reflective marker with an option to calculate and output
three-dimensional coordinates. Typically, measurements are
referenced to geodetic coordinates. In the exemplary embodiment, a
relative reference method is used by defining a local coordinate
system origin (defined as (0, 0, 0)) that coincides with a
predefined shooter position. The target and emitter coordinates are
measured relative to the shooter position. Regardless of the
measurement method, the desired results are coordinates reported in
Northing, Easting, and Elevation coordinates (n, e, h).
[0084] Survey equipment, under ideal circumstances, can supply
accuracies on the order of at least + or -1 mm. The uncertainty in
the target and reference emitter position can increase to + or -0.1
meter (for each) due to additional errors that can occur during
subsequent target and reference emitter placement. Preferably, the
target and reference emitters will be positioned before the survey.
The target and reference emitter coordinates will then be obtained
by surveying to their centers. Even with the survey performed after
target and emitter placement, the best achievable uncertainty in
their placement is considered to be + or -0.01 meters (for each).
Therefore, with respect to the total uncertainty error the survey
contributes + or -0.01 meters for each of the shooter position,
target position and emitter position.
[0085] Communication and control connections are made between the
operation station (comprising the system computer 26 and the SIB
28) and the firing line and downrange hardware. Some connections
are made through cables and other connections are made through
radio means (including radio relays). After controls are
established, the components are set to their specific addresses for
communication with the SIB. In particular, the trigger events are
established and each camera is associated with each projectile
launcher. It is important that the location of each target and IR
emitter within the range be precisely determined. With this range
data determined the Input Files are input into the computer.
Surveyed Target and Emitter Coordinates
[0086] The targets and emitters are located on the firing range at
specific northing, easting, and elevation coordinates provided by
survey. The accuracy of the target and emitter positions depends on
when the survey is preformed relative to placing the targets and
emitters on the range. One method is to survey and mark the desired
positions on the ground, followed by the later placement of the
targets and emitters. Adding measured elevation offsets to the
ground survey positions give the final coordinates of the targets
and emitters. Using this method, estimated errors in the
coordinates range from + or -50 mm to + or -100 mm.
[0087] In the exemplary embodiment, targets and emitters are
located by securely positioning the targets on the firing range at
the approximate ranges desired, and then surveying directly to the
target and emitters. If surveying is performed after placement, the
coordinates of the targets and emitters should fall within + or -10
mm or better. Recording measured offsets of the target centroids
from the ground are used to evaluate projectile ground impact in
the immediate area of the target.
[0088] During aimpoint analysis, when marking the location of the
emitter relative to the pixel coordinates, the centroid of each
emitter is located by visual interpolation. Marking precision is
increased by allowing for sub-pixel marking via a zoom function
(implemented in the system software). The zoom function magnifies
the area of the image that contains the emitter signature.
Sub-pixel marking precision is the inverse of the zoom factor
chosen; a zoom factor of 4 provides sub-pixel precision of 0.25
pixels. Marking of the emitter centroid is performed by noting the
horizontal and vertical dimensions of the emitter image in pixels.
The location of the emitter centroid is determined by dividing
these dimensions in half.
Correspondence between the Shooting Range and CCD Camera Image
[0089] Referring to FIG. 10, the geometry of the shooter, emitter
and target measurement process is illustrated. The shooter,
emitter, and target geometry forms a long, narrow triangle with the
shooter at the apex and the emitter and target located downrange at
the other triangle vertices. Equations describing the angles from
the reference emitter to the target are shown along with the sight
line-emitter angles with reference to the CCD camera image.
[0090] The shooting position will preferably be located beforehand
by having the surveyor place a marker at the defined shooting
position on the ground. The accuracy of the shooting position
coordinates would follow the best-case coordinate accuracies of +
or -10 mm.
[0091] With the shooter, emitter and target positions ascertained,
the process for finding the sightline to target aimpoint angles is
performed. The process consists of four basic steps: 1) Using the
3D coordinates of the shooter, emitter, and target, calculate the
emitter and target angles (vertical and horizontal) relative to a
line parallel to a reference (northing) axis. 2) Calculating the
emitter to target angles by subtracting the emitter angles from the
target angles. 3) Measuring the sightline to emitter angles by
marking the emitter centroid on the CCD image captured when a shot
is fired and correct for boresight angular errors. 4) Using the
calculations made from survey coordinates and the calculations made
via the CCD measurements for the particular shooter, target, and
emitter combination, calculating the sightline to target angles by
subtracting the emitter to target angles from the sightline to
emitter angles.
Lens Mapping
[0092] The Lens Mapping Procedure will now be described. The lens
mapping is preferably performed onsite after setup of the equipment
to ensure that the lens mapping accurately reflects the camera and
lens settings. During lens mapping, the location of an emitter in
the camera image is used in finding the angular offset of the
emitter from the camera's optical axis, and subsequently the
angular offset from the projectile launcher's line of sight. In
order to determine the angular offsets, camera and lens
combinations are mapped to determine the angle represented by each
pixel of the camera's imaging device. Locating the camera and lens
at a known distance in millimeters from a target calibrated in
millimeters, and capturing the resulting image comprise camera/lens
mapping. The captured image (in digital format) is examined to
determine the relationship between the pixels and the calibration
target markings. The LMP is a function of the system computer
software and is used to provide the microRadiansperPixel_H and
microRadiansperPixel_V values associated with a particular CCD
camera and lens combination that will be mounted to a projectile
launcher under test during a scenario. The microradians per pixel
across the field of view of the camera/lens combination are
calculated from the relationship of the pixels to the linear target
markings, and the known distance from the camera lens to the
target. In the preferred embodiment a standard camera faceplate
format of 1/2'' is typically used although 1/4'', 1/3'' and 2/3''
formats as well as nonstandard formats are suitable.
[0093] To begin the lens mapping process, the particular camera and
lens that are suitable for the field of view and range are selected
for the aimpoint measurement task. The selection of a specific lens
is dependent on both the camera selected (due to the camera image
format used and also due to the lens mounting requirements) and on
the focal length needed to provide a suitable field of view for the
downrange targets. As an example and not by way of limitation,
focal length lenses from f=24 mm to f=100 mm can be used in
combination with CCD image formats of 1/2 in. and 1/3 in. When
using the same focal length lenses for the 1/2 in. and 1/3 in.
formats, the field of view (FOV) for the 1/3 in CCTV format is less
than the FOV for the 1/2 in. CCTV format because of the difference
in the physical size of the image of the image surface. However,
since the number of pixels is the same for the two image formats
(768h.times.494v), the 1/3 in. format provides a higher angular
resolution at the expense of a smaller field of view. In the
exemplary embodiment, the field coverage must provide for the
camera's imaging of a target's reference emitter when the
projectile launcher is sighted on the target. This requirement
originates from the need to mark the reference emitter when a shot
is fired at a target.
[0094] It is too be appreciated that each scenario will have its
own particular requirements, and each scenario should be analyzed
to determine what field coverage is required. In the exemplary
embodiment, field coverage falls between 10 meters and 100 meters
although larger fields are within the contemplation of the present
invention. Smaller field coverages lead to higher system
measurement resolution, but the emitters will need to be closer to
the targets. Larger field coverages will reduce the measurement
resolution, but will allow larger target to emitter separations and
will help to ensure that the emitter will be visible when a shot is
fired.
[0095] After the camera and lens are selected the camera is mounted
to a tripod and placed near the planned shooter position. Three
reference emitters are located at a distance from the camera that
approximates the range of the planned scenario targets. The three
reference emitters should be placed in a straight line, preferably
parallel to the horizon. To align the reference emitters, the CCD
camera image is referred to and the spacing is arranged to provide
for all three emitters to be in the camera's FOV when the center of
the camera's FOV is aligned to the left-most emitter.
[0096] For the horizontal lens mapping, the second emitter should
be preferably placed at about 25% of the image width from the image
center towards the right side of the image. The third emitter
should be placed preferably at about 70% of this same width. This
placement of the emitters will allow for the camera to be rotated
90 degrees counterclockwise and the same three emitters to be used
when performing the vertical lens mapping. Using survey equipment,
the 3D coordinates of the camera and the three emitters are
measured and recorded. If desired, the camera can be set to be the
origin with the reference axis defined by the line between the
camera and the left-most emitter. With the camera mounted on a
tripod, the camera is panned and tilted to visually attempt to
align the center of the left-most emitter to be in the center of
the camera image. It is to be appreciated that all three emitters
are operating and are within the camera's horizontal FOV.
[0097] Once these steps are completed the camera and emitter 3D
coordinates are calculated. Although the calculations can be
performed manually, in the preferred embodiment the data is entered
into a software program that is part of the system software. When
the software program is being used the camera and emitter 3D
coordinates are entered. After saving the coordinates, the camera
image is brought up on the computer screen and the process of
performing the fine camera alignment and marking the emitters for
lens mapping is initiated. The mouse cursor is placed over the
emitters and the (pix.x, pix.y) pixel coordinates are viewed on the
screen. The cursor is placed over the E.sub.o and the pixel
coordinates are checked against the center of the CCD image
coordinates. If the emitter is not a center, the camera is panned
and tilted until E.sub.o is at the pixel coordinates for the center
of the image. Next the cursor is placed over the emitter E.sub.2H
and checked if the pix.y value for E2H is the same as E.sub.o. If
the pix.y coordinates are not the same, the camera is rolled about
its axis to make both E.sub.o and E.sub.2H (and also E.sub.1H) have
the same pix.y value.
[0098] For the vertical lens mapping, the camera is rotated 90
degrees counterclockwise and aligned visually so that the left-most
emitter becomes the center emitter within the CCD image with the
remaining emitters being within the camera's vertical FOV. The
adjustment of the camera to properly image the three emitters for
the vertical lens mapping is similar to the horizontal alignment,
except that the pix.x coordinates of all three emitters should be
the same value, which should be the pixel coordinate of the
horizontal center of the image. The camera is panned, tilted, and
rolled to perform the alignment and then mark the emitters in the
same order. After the last emitter is marked for the vertical lens
mapping, the horizontal and vertical tens mapping values will be
displayed and an option for storing the values will be given. Lens
map values are stored with a name that corresponds with the camera
and lens combination used for later retrieval during the live fire
aimpoint scenario.
[0099] The errors that can occur in the camera/lens mapping are:
errors in the camera/lens distance to the target, errors in the
target calibration, and errors in the reading of the pixel
relationship to the target. In measurement of the camera and lens
combination mapping function, standard deviation of the pixel in
terms of angle was determined to be less than 0.15 milliradians
(mrad). This angle is considered to be the lens mapping uncertainty
contributing to total system error. The angular value is constant
and does not change with range.
Camera Mounting and Boresight Calibration
[0100] The camera is mounted to the projectile launcher, preferably
with a rigid mount providing a view of the emitters over the entire
projectile launcher super-elevation range. The linear offsets
(horizontal and vertical) of the camera aperture from the
projectile launcher sight line are measured. The ideal alignment of
the camera for measuring emitter angles would have the optical axis
of the camera lens coaxial with the sightline of the projectile
launcher, and the camera lens located at the surveyed shooter
position coordinates. However, this is not practical for live fire
since the camera must be mounted out of the way of the projectile
path and any projectile launcher operations. The mounting
requirements lead to coordinate offsets and angular deviations of
the optical axis of the lens from the projectile launcher
sightline, which are corrected by the boresight process.
[0101] As can be appreciated by those skilled in the art, the
boresight process provides a set of boresight angles that are used
to correct the subsequent measured emitter to sightline angles
obtained during the firing event. When establishing a boresight to
an emitter geometrical relationship at the boresight range, the
boresight angles derived from the boresight emitter measurement
includes angular deviations between the sightline and the camera
optical axis as well as apparent angular deviations due to the
coordinate offset from the sightline, assuming that the optical
axis to sightline offsets are negligible. However, even small
optical axis to sightline offsets will cause apparent angular
deviations, and their effect should be considered.
[0102] It is to be appreciated that because the coordinate offsets
are constant and the boresight emitter range can vary from the
boresight target range, errors will occur in the aimpoint
calculations as the boresight target range varies. The magnitude of
these errors depends on the offsets and the range difference
between the range to the target and the range to the emitter.
Without correction, the aimpoint angles will only be correct when
the target's emitter is at the boresight range.
[0103] To account for the error that will be introduced for firing
at targets that are at different ranges than the boresight range,
the portion of the boresight angles that is due to the sightline to
camera offset is mathematically subtracted from the aimpoint
calculations. This adjustment is done by calculating the angular
deviations due to the sightline to camera offset at the boresight
range, and then subtracting those angles from the angular
deviations that are due to the camera lens offset at the target
emitter range. This difference is than added to the boresight
angles to produce the boresight correction angles for emitters at
ranges other than the boresight range. As can be appreciated by
those skilled in the art, there will still be some residual errors
after this boresight correction process due to measurement
uncertainty.
[0104] When the CCD camera is preferably rigidly mounted to the
projectile launcher under test, it must be aligned to the
projectile launcher sightline. Some adjustment capability is
provided in the mount to adjust the optical axis of the camera lens
to be approximately parallel to the projectile launcher sightline.
If the optical axis is parallel, there will be a constant linear
offset between the sightline and the optical axis, but no angular
offset. However, the constant linear offset translates into an
angular offset, which reduces linearly with increasing range. Since
the mechanical alignment process is relatively coarse, and
electronic alignment, or boresighting, is performed to find the
residual error for removal during actual aimpoint error
measurements.
[0105] Aiming the projectile launcher at the boresight target and
emitter pair that is placed at a known range performs the boresight
calibration. An expert gunner fires one or more shots (preferably
three) at the boresight target and the boresight emitter centroid
is marked on the CCD image. The shot group is analyzed to verify
proper aiming by the expert gunner relative to the projectile
launcher under test. If acceptable, the average of the shot
grouping is used as the boresight correction values to account for
the remaining angular offset of the optical axis to the sightline.
As can be appreciated by one skilled in the art, the sight settings
remain unchanged after the boresight process is completed.
[0106] The acceptability of the aimpoint errors is dependent on the
projectile launcher under test. For example, an expert M16 gunner
using the iron sights can aim at a well-marked target to within 0.5
milliradians (mrad), while sighting errors for an M203 Quad sight
may be as high as 4 mrad.
[0107] For adjustable sight projectile launchers, for example OICW,
OCSW, MK-19, M203, etc. the adjustable sights cause two additional
concerns caused by the projectile launchers' significant changes in
the sightline to barrel angle relative to changes in the target
range. As is well known in the art, the adjustable sight design is
used to produce super-elevation of the barrel to fly a projectile
to a target. In some cases the elevation angle may be on the order
of 36 degrees.
[0108] The change in the sightline to barrel angle produces a
change in the camera optical axis (OA) to sightline (SL) angle and
offset. The primary concerns are that since the camera is attached
to the barrel, the camera will rotate with the barrel's
super-elevation. Since the camera is attached to the barrel of the
projectile launcher, the camera will rotate with the barrel's
super-elevation. If the barrel is super-elevated more than a few
degrees, the infrared reference emitters may be out of the camera's
field of view (FOV) and the emitter cannot be marked. Second, for
each sightline to barrel angle setting, the coordinate and angular
offsets of the optical axis to the sightline will be different,
requiring a separate compensation for each new sight setting.
[0109] It is within the contemplation of the present invention that
the loss of emitter in the camera's FOV be accommodated by a mount
that provides for indexed angular rotation of the camera to
counteract the super-elevation of the barrel. A selection of
indexed camera rotation angles can be used to keep the emitter
within the FOV for a group of sight angle settings. The number of
camera rotation settings depends on the range of the sight angles
versus the FOV. In an alternate embodiment, emitters can be mounted
at higher elevations on the range so that they are in the FOV when
the projectile launcher is super-elevated.
[0110] When the geometry of the projectile launcher sightline
versus sight adjustment is ascertained, it would be possible to
boresight at an intermediate sight range, and then to add or
subtract the angular changes in the sightline angles as the sight
is indexed to setting for ranges other than the boresight range.
These sightline angular changes would include both elevation and
azimuth angles since adjustable sights also produce a horizontal
change in the sightline angle to account for the increased effect
of projectile precession with range. In addition to changing the OA
to SL angles, there will also be a change in the optical axis to
sightline offsets that will have to be taken into account.
[0111] In another embodiment for adjustable sight projectile
launchers, a separate boresight for each indexed sight setting,
with its corresponding indexed camera rotation, could be performed.
In effect, each setting of the sight, along with any required
rotation of the camera, would act as an individual fixed sight
projectile launcher. In practice, a family of boresight and OA to
SL offsets would need to be saved for each sight setting that is
planned for use in an experiment or exercise.
[0112] For either of the hereinabove embodiments for adjustable
sight use, the shooter would have to indicate the current indexed
sight setting for the firing event. The software would then use the
boresight and OA to SL offsets for that sight setting via either a
mathematical sightline model or a sight setting lookup table. The
result of using either of these two methods for adjustable sights
in the software will result in not additional uncertainties in
aimpoint measurements.
Moving Target Measurements
[0113] The goal of the moving target measurement system is to
provide the 3D coordinates of the moving target centroid at the
time that a shot is fired (to determine the projectile launcher
sightline angles relative to the target center), and at the time of
the terminal position of the fired round (where it intersects the
target path plane, hits the ground, or air bursts), to
differentiate the location of the moving target and the round at
the time the round reaches its terminus, or intersects the target.
The location of the moving targets' centroid, like the fixed
targets' centroid is determined with reference to the infrared
emitters.
[0114] Moving targets, along with associated emitters and laser
rangefinders are established during setup. The laser rangefinders
are aligned and the downrange controllers are setup. The laser
rangefinder is zeroed at the moving target home or initial
position. Then, the moving target and emitter 3D coordinates at the
home (or initial) position and the end positions are obtained.
[0115] Referring to FIGS. 11 and 12, which depict the target path
plane and identify the target angles from the shooter's position,
the sightline offset angles from the target and the subsequent
sightline angles, the method of calculating the sightline
intersection with the target plane will now be explained. The 3D
coordinates of the moving target and emitter at the time a shot is
fired are found by measuring the target sled offset from the target
sled home position via a rangefinder. This offset is used to
produce a 3D offset relative to surveyed 3D coordinates of the
target and emitter at the home position. The 3D offsets are added
to the home position 3D coordinates to produce the target and
emitter 3D coordinates within the test range coordinate system at
the time of an event. These target and emitter 3D coordinates at
shot fired are used, along with the CCD image pixel coordinates of
the emitter, to produce the sightline offset angles relative to the
target center. Once the target and emitter 3D coordinates within
the test range are found, the calculation of the sightline offset
angles follows the same procedure that is used for static targets
described hereinabove.
[0116] The sightline offset angle is added to the horizontal and
vertical angles of the target within the firing range coordinate
system (derived from the target's surveyed 3D coordinates) in order
to determine the horizontal and vertical angles of the sightline in
the firing range coordinate system. After sightline orientation is
found, the intersection of the sightline with the target path plane
is calculated.
[0117] Once the drop of the round, which is calculated relative to
the sightline, is provided by the ballistics model, the 3D
coordinate of the fired round on the target path plane can be found
by subtracting the drop from the sightline intersection with the
target path plane.
[0118] The moving target setup will now be described. The target
sled moves along a linear track under remote control. Preferably,
motion is provided by an electric motor powered by 12 VDC batteries
although pneumatic, hydraulic or other mechanical drivers that are
well known in the art may provide motion. The target sled can move
in either direction along the track and the target can be popped up
or down. Remote control may be independent of the system computer.
The target track, while not necessarily level, is assumed to be
flat and straight such that it does not cause up and down or left
and right deviations of the target from a straight line of more
than 20 mm. While an assumption of 20 mm may be optimistic, this
assumption allows the target path to be considered as following a
straight line. When the 20 mm assumption does not hold, additional
measurements of the vertical position of the target centroid as the
target moves along the track can be used to increase the vertical
accuracy of the target centroid calculations. The beginning and
ending target sled positions (also referred to as "home" and "end")
are electronically referenced to insure that these positions are
known and repeatable. Sensors are used on the track to detect the
home and end reference positions of the target sled. The target and
emitter centroid positions are measured in 3D coordinates (via
survey to + or -10 mm) for the home and end positions of the target
sled. These 3D target and emitter centroid home and end positions
are defined as T.sub.B & T.sub.E, and E.sub.B & E.sub.E,
respectively. The moving target setup procedure requires that the
rangefinder SetRangefinderZero( ) command be sent at the time of
surveying the target's home position 3D coordinates. Subsequent
rangefinder readings of the target sled position via the
rangefinder will provide the relative target sled offset from the
target home position, T.sub.B. The 3D coordinates of T.sub.B and
T.sub.E, are used to produce a 3D unit vector t.sub.Bt.sub.E by the
linear target offset from the home position of the track. Summing
this offset with the 3D coordinates of the target home position
T.sub.B, provides the 3D coordinates of the intermediate target
position.
[0119] A system emitter is physically attached to the moving target
sled, and the position of the emitter centroid relative to the
target centroid is fixed. The 3D coordinates of the emitter
centroid at an intermediate target position are calculated by
summing T.sub.O with the 3D coordinates of the emitter at the home
position, E.sub.B since the target and emitter are assumed to
follow parallel paths). The 3D coordinates of the target and
emitter centroid at the intermediate target sled position are used
to find the shooter's aimpoint angles (.epsilon..sub.x,
.epsilon..sub.y) relative to the target centroid. The aimpoint
angles produced will be for the aimpoint at the point in time that
corresponds to the video frame used to mark the emitter position.
The target path plane, TPP, is defined as containing the T.sub.B
and T.sub.E points and is constrained to be normal to the firing
range n-e plane by defining a third point on the plane as
T.sub.B'=T.sub.B+(0,0,1). These three points on the target path
plane are used to produce the 3D equation of the target path plane,
which will be used in finding the sightline intersection with the
target path plane.
[0120] During an event, target linear offsets are captured
continuously during target movement and referenced to a event start
time. These offsets and time references are stored during the event
and transferred to the system computer after the completion of the
event. When analyzing the event via the recorded video frames, the
point in time corresponding to the midpoint of the video frame
selected for marking the emitter position, t@MarkedFrame, is used
to retrieve the stored target linear offset for the marked frame.
The point in time when the shot is fired, t@shotFired, is used to
retrieve the target linear offset for when the shot was fired. The
linear offset, d.sub.offset, of the target sled from the home
position for a particular time is provided via an optical
rangefinder that bounces an infrared beam off a retroreflector
attached to the moving target sled. The offset is provided to an
accuracy of + or -10 mm. This is equal to the measurement accuracy
specification of the rangefinder for an average of twenty 2000 Hz
measurements providing a 200 Hz sample output (5 nanosecond). The
linear target sled offset, d.sub.offset is multiplied by the track
unit vector t.sub.Bt.sub.E, to arrive at the 3D coordinate offset
of the target sled, T.sub.O, relative to the home position of the
target sled. Adding T.sub.O T.sub.B, the 3D coordinate of the
target centroid at the home position, produces the 3D position of
the target centroid, T.sub.3D, within the firing range
(T.sub.3D=T.sub.B+T.sub.O). Adding T.sub.O and E.sub.B, the 3D
coordinate of the emitter centroid at the home position, produces
the 3D position of the emitter centroid, E.sub.3D, within the
firing range. (E.sub.3D=T.sub.O+E.sub.B). The location of the
emitter in the CCD camera image will be used to determine the
aimpoint angles (.epsilon..sub.x, .epsilon..sub.y) of the sightline
relative to the moving target centroid at the t@MarkedFrame, time.
These aimpoint angles for the moving target will be calculated
using the same methods as for static targets, except for the fact
that the target and emitter 3D coordinates, T.sub.MF and E.sub.MF,
will be provided via calculations that use the rangefinder and
survey data.
[0121] Referring again to FIG. 1 at shot fired time (SF) time the
3D coordinates of the target T.sub.SF will be found by retrieving
the target linear offset from the rangefinder at the t@shotfired
time. The aimpoint angles (.epsilon..sub.x, .epsilon..sub.y) will
be summed with the angles to T.sub.SF (.theta..sub.e,.theta..sub.h)
to produce the sightline angles, (E.sub.e,E.sub.h), of the
sightline vector, psl.sub.I within the firing range relative to the
surveyed shooter position P. A sightline unit vector is created by
using the sightline angles (E.sub.e,E.sub.h) to find the direction
of the sightline within the firing range. The sightline unit vector
is defined as:
psl.sub.I=(cos(E.sub.e)/|psl.sub.I|,sin(E.sub.e)/|psl.sub.I|,sin(E.sub.h)-
/|psl.sub.I)=(n.sub.psl,e.sub.psl,h.sub.psl)
[0122] Round intercept (RI) is next and the definition of RI
depends on the type of round, either kinetic energy (KE) or high
explosive (HE). For a KE round, the RI occurs when the round either
passes through the target path plane or the round impacts the
ground short of the target. For a HE projectile the RI occurs at
whichever occurs first: the round impacts the target, the round
impacts the ground, or, if fused, the fuse time expires. In any of
the different cases, the sightline angles and the sightline
intersection with the target path plane must be known in order to
define the path of the round. If the round impacts the ground, or
airbursts, the distance from the shooter must also be known to
calculate the 3D coordinate. Additionally, the time-of-flight of
the round at round intercept, TOF.sub.RI, must be known to
determine the target sled offset and to find the target 3D
coordinates, T.sub.RI, at the time of RI.
KE Rounds
[0123] For KE rounds, the ground range to the target path plane in
the n-e plane of the firing range and the sightline elevation angle
determines the time-of-flight of the round unless the round impacts
the ground before the target path plane. In order to determine the
ground range to the target path plane, the sightline vector
intersection, SL.sub.I, to be described hereinbelow, with the plane
of the moving path is calculated. The 3D coordinates of the
shooter, P, and the sightline intersection, SLI, is used to find
the slant range to the target plane, r.sub.TP. The r.sub.RI range
is the corresponding ground range to the target path plane parallel
to the n-e plane of the firing range. The range r.sub.RI is used to
set the maximum range for the ballistics model to fly the round
towards the target path plane. The ballistics model provides the
time-of-flight to round impact, TOF.sub.RI, for the KE round in
use.
[0124] The flight time for a KE round depends upon whether the
round passes through the target path plane or impacts the ground
before the target. Therefore, depending on the outcome,
TOF.sub.RI=TOF.sub.TP (time of flight to the target path plane) or
TOF.sub.RI=TOF.sub.GI (time of flight to ground impact). By setting
the maximum range for the ballistics model to r.sub.RI, the maximum
time of flight from the ballistics model will automatically be
TOF.sub.RI. Using the ballistics of the KE round in use, the drop,
relative to the sightline, of the round at the target path plane is
calculated and used to calculate the 3D coordinate, R.sub.RI, of
the round as it intersects the target path plane. For a KE round,
no consideration is given to the 3D location of the round after it
passes through the target path plane. For this case,
R.sub.RI=SL.sub.I-(0,0,drop).
[0125] For the possibility of a KE round impacting the ground
before the target, R.sub.GI is defined at the 3D coordinate where
the ballistics calculation indicates that the round drops to the
plane of the ground. For this possibility, the time-of-flight of
the round stops at the point of ground impact and the time is
labeled TOF.sub.GI. If the round impacts the ground, then
TOF.sub.RI=TOF.sub.GI and
R.sub.RI=R.sub.GI=(PSl.sub.E(n,e,0)*r.sub.GI)+P(n,e,0), which
results in a 3D coordinate on the ground. The TOF.sub.RI will be
used to determine the moving centroid coordinates, T.sub.RI, at the
time that the round arrives downrange. This is accomplished by
obtaining a target sled offset, d.sub.RI, via the rangefinder at
the shot fired time plus the TOF.sub.RI and repeating the process
for finding the 3D coordinate of the target centroid within the
firing range at the round intercept time, T.sub.RI. Once TRI and
RRI are known, the distance between the two 3D coordinates can be
used to determine whether a hit or miss occurred, based upon the
size of the target.
High Explosive (HE) Rounds
[0126] For HE rounds, the TOF.sub.RI time and the R.sub.RI
coordinate calculations have additional considerations. Airburst HE
rounds are fused for a particular range and the time-of-flight for
an air burst is dependent on the fuse range and the speed of the
round. Since an HE round is still considered active after it passes
the target, the intersection of the round with the target path
plane is only important if the round actually hits the target (in
which case the round is assumed to have exploded). If the round
passes through the target path plane and then air bursts or impacts
the ground, a hit or miss calculation can be performed using the
target and round coordinates to determine if the target was hit. In
case a target hit did not occur, the air burst or ground impact
coordinates are calculated and can be used to find the distance
from R.sub.RI to the target at T.sub.RI. In addition, if the round
impacts the ground before the target path plane, the 3D coordinate
R.sub.GI is also needed to determine the distance from R.sub.RI to
the target at T.sub.RI.
[0127] There are three possible time-of-flights to consider for HE
rounds. The first is the fuse range related, TOF.sub.HE, the second
is the ground impact, TOF.sub.GI, and the third is the target
impact, TOF.sub.TP (note, TOF.sub.TP is the same as the KE round
TOF.sub.TP). For each of these TOF's, there is a related 3D round
terminus coordinate. The first step is to fly the round out using
the ballistics model and the aimpoint angles derived from the
emitter marking at shot fired. If the found is fused, then the
round is only flown out to the fuse range. Then a check is made to
determine if the round air burst or hit the ground. Then another
check is made to determine if the rounds terminal range (for either
air burst or ground impact) is before the target path plane or
after the moving plane. If the terminal range is less than the
range to the target path plane, the round has either hit the ground
or airburst in front of the target path plane. No target impact is
then possible. If the terminal range is greater than or equal to
the range to the target path plane, then the round has either hit
the target, hit the ground, or airburst. Since the determination of
an air burst or ground impact has already been performed, the only
possibility that needs to be checked is whether a target impact has
occurred. The result is that the sightline intercept with the
target path plane must be calculated to determine the TOF.sub.TP to
the target path plane. This is the same calculation described
hereinabove for the KE rounds.
[0128] If TOF.sub.HE is greater than or equal to TOF.sub.TP, then
the 3D positions of the round at TOF.sub.TP, R.sub.TP, can be
compared with the 3D position of the target at TOF.sub.TP,
T.sub.TP, T.sub.TP. |R.sub.TPT.sub.TP| can be used to determine if
a hit or miss occurred, where a hit would occur if the distance
|R.sub.TPT.sub.TP| is less than target radius. If a hit occurred,
then R.sub.RI is set to R.sub.TP and there is no airburst or ground
impact after target path plane. If no target intersection occurs
then the 3D position of the round at either airburst or ground
impact, R.sub.RI is calculated and the distance |R.sub.TIT.sub.TI|
is calculated.
Sightline Intersection with the Target Path Plane
[0129] An important task in the moving target calculations is to
find the intersection of the sightline vector with the target path
plane. The sightline vector is defined by the shooter position P
and the sightline angles (E.sub.e,E.sub.h) into the firing range
(FIG. 11). The target path plane contains the target home and end
positions, T.sub.B and T.sub.E, and is specified to be a vertically
oriented plane parallel to the h-axis.
[0130] The first step in defining the target path plane is to add
an additional point to the beginning and ending target coordinates
T.sub.B and T.sub.E, to make up the required the required third
point for a plane. This third point is created by adding a unit
length vector parallel to the h-axis of the firing range coordinate
system to the T.sub.B coordinate. This point is labeled as T'.sub.B
and is equal to:
T.sub.B(n.sub.TB,e.sub.TB,h.sub.TB)+(0,0,1)=T'.sub.B(n.sub.TB',e.sub.TB',-
h.sub.TB').
[0131] These three points, T.sub.B, T.sub.E, and T'.sub.B, define a
plane that includes the path of the target along the track and is
vertically oriented to be parallel to the elevation axis.
[0132] The equation of the target path plane is produced by using
the coordinates of T.sub.B, T.sub.E, and T'B in calculating the
coefficients for the general form of the equation of a plane,
Ax+By+Cz+D=0. The A,B, and C coefficients are the components of a
vector that is normal to the target path plane, TPP.sub.N. These
coefficients are calculated by taking the cross product of the
vectors T.sub.BT.sub.E and T.sub.BT'.sub.B on the target path
plane, where:
T.sub.BT.sub.E=(n.sub.BE,e.sub.BE,h.sub.BE)=((n.sub.E-n.sub.B),(e.sub.E-e-
.sub.B),(h.sub.E-h.sub.B)
T.sub.BT'.sub.B=(n.sub.BB',e.sub.BB',h.sub.BB')=((n.sub.B'-n.sub.B),(e.su-
b.B'-e.sub.B),(h.sub.B'-h.sub.B)=(0,0,1)
[0133] And the cross product result (A,B,C) simplifies to:
A=e.sub.BE, B=-n.sub.BE, C=0.
[0134] The coefficient D is calculated by taking the negative
determinant of the three co-planar points, T.sub.B T.sub.E and
T'.sub.B, and setting the result to be equal to D.
[0135] Dividing these four coefficients by the length of the vector
TPP.sub.N, |TPP.sub.N|=(A.sup.2+B.sup.2+C.sup.2).sup.1/2, produces
the unit normal vector to the target path plane,
tPP.sub.N=(A/|TPP.sub.N|,B/|TPP.sub.NC/|TPP.sub.N)=(a,b,c) and a
vector magnitude: d=-D/|TPP.sub.N|,
[0136] That is the minimum distance from the origin to the plane.
This unit normal vector tpPN and distance d will be used in finding
the intersection of the sightline vector with the target path
plane.
[0137] The sightline vector is defined by a starting point, the
shooter position P, and set of easting and elevation angles
(E.sub.e,E.sub.h), providing the projection direction into the
firing range coordinates system from P. The general equation for
the sightline vector is: PSL.sub.I=P+(r.sub.TP*psl.sub.I).
[0138] The direction vector of the sightline vector, defined
hereinabove is:
psl.sub.I=(cos(E.sub.e)/|psl.sub.I|,sin(E.sub.e)/|psl.sub.I|,sin(E.s-
ub.h)/|psl.sub.I|)=(n.sub.psI,e.sub.psl,h.sub.psl) and, r.sub.TP is
the unknown distance from the shooter P to the sightline vector
intersection with the target path plane at SL.sub.I.
[0139] The sightline vector intersection, SL.sub.I, with the target
path plane is found by determining the unknown distance r.sub.TP
and then using r.sub.TP in the general equation for the sightline
vector: r.sub.TP=-((tpp.sub.N*P)+d)/(tpp.sub.N*psl.sub.I), is used,
where the numerator is the distance from the shooter at P to the
point on the plane at the minimum distance from the origin and the
denominator is the cosine of the angle between the target path
plane unit vector, tpp.sub.N, and the sightline unit vector,
psl.sub.I. The result r.sub.TP, is the length of the vector
PSL.sub.I, which is used to find the sightline intersection with
the target path plane, SL.sub.I, via the equation:
SL.sub.I=P+(r.sub.TP*psl.sub.I).
[0140] After the scenario has begun, a shooter will align the
projectile launcher site with a target. The center of the lens
image at the trigger event determines the reference for aimpoint.
The infrared sensors illuminate at the trigger event to provide
distance measurements from the aimpoint reference to the fixed IR
emitter or the moving target position as determined by the
downrange controller. With the information that is collected at the
trigger event, the aimpoint and projectile launcher effects are
calculated, preferably using the software resident in the system
computer. Output from the sensors and the camera are integrated
into the VCR with titling for event analysis. The information
collected, including references and calculated aimpoint and
projectile dynamics provide information for training and projectile
launchers testing.
[0141] Error between the actual and predicted aimpoint result from
uncertainties associated with the shooter, target, and emitter
positions. The errors are range dependent and are minor
contributors to the overall error. In addition error associated
with the offset of the CCD camera from the projectile launcher
sightline lens mapping and the emitter marking process can also
produce minor errors and these errors can be minimized through
techniques to be described hereinafter. Finally, the uncertainty
associated with the bore-sight as performed by an expert gunner is
the limiting factor in the cumulative error of the system.
[0142] While preferred embodiments have been shown and described,
various modifications and substitutions may be made thereto without
departing from the spirit and scope of the present invention.
Accordingly, it is to be understood that the present invention has
been described by way of illustrations and not limitation.
[0143] Any element in a claim that does not explicitly state "means
for" performing a specified function, or "step for" performing a
specific function, is not to be interpreted as a "means" or "step"
clause as specified in 35 U.S.C. 112 paragraph 6. In particular,
the use of "step of" in the claims herein is not intended to invoke
the provisions of 35 U.S.C. 112 paragraph 6.
* * * * *