Patent Description:
<CIT> discloses an ultra wideband radar system for detecting moving objects comprising an antenna, which may be scanned in at least one dimension, and a signal processor wherein the signal processor includes a scan combiner that combines scan information in accordance with a candidate trajectory for the moving object.

<CIT> discloses: Identification of the tee-off bay from which a golf ball landing on a golf-range target originated, is made by calculating an estimate of flight duration of the descending ball as a function of the measured angle of descent in elevation, and, in respect of each ball launched from the bays, comparing this estimate for a match with a measured interval between the launch of the respective ball and descent of the descending ball.

<CIT> provides an integrated sports assessment and information disclosure, applicable to most sports, designed to measure, calculate, derive, and analyze the resultant sport ball movement and ball-orientation characteristics in order to provide an assessment of the player's performance and the circumstances surrounding the conduct of the sports action.

<CIT> discloses a golf ball tracking system, which includes a distributed sensor and processor system adapted to simultaneously track the trajectories of multiple golf balls hit by one of more golfers. The system is adapted to keep track of the location of the golfers to enable the allocation of shots to the correct golfer.

<CIT> discloses a method simulating a run which is a distance between a landing point and a final arriving point using an initial condition of a hit ball and an actually measured falling condition.

<CIT> discloses a system, device and method for an anti-missile system generally including a ground-based sensor array generating tracking data of a guided missile tracking a target. A control node in communication with the ground-based sensor array generates targeting data from the tracking data. A phased array directed-energy unit in communication with the control node radiates the guided missile with microwave radiation based on the targeting data received from the control node, where the microwave radiation disrupts an electronic component of the guided missile such that the guided missile discontinues tracking the target.

In particular, a system for tracking multiple projectiles comprises a first radar device aimed so that a field of view of the first radar device covers at least a portion of a target area into which projectiles are to be launched from a plurality of launch locations and a processor receiving data from the radar and identifying from the data tracks of a plurality of projectiles, the processor determining for each projectile track identified a specific one of the launch locations from which the projectile was launched and providing to the launch location associated with each projectile data corresponding to a trajectory of the projectile.

According to the invention, the system of further includes a second radar device aimed so that a second field of view of the second radar device covers at least a portion of the target volume including a portion of the target volume outside the first field of view as well as an overlap portion of the target volume also included in the first field of view.

According to an example, the device associated with each location includes a screen displaying the data.

According to the invention, for each of a plurality of time frames, the processor receives from the first radar device a radar signal and calculates from this radar signal projectile data including position and speed values for each projectile identified.

According to an exemplary embodiment, for each time frame, the processor refers to data from at least one prior time frame and determines for each projectile identified, whether the projectile data correlates with an existing trajectory and, when the projectile data correlates with an existing trajectory, the processor updates the existing trajectory with which the current projectile data correlates to include the current projectile data.

According to an exemplary embodiment, when the current projectile data for an identified projectile does not correlate with an existing trajectory, initiating a new trajectory.

According to the invention, for each trajectory the processor compares an initial projectile position to known launch locations and, if the initial projectile position matches a known launch location, the processor assigns this launch location to the trajectory.

In this case, preferably, when the initial projectile position for a trajectory does not match a known launch location, the processor, based on the trajectory, extrapolates backward in time from the initial projectile position to a launch location for the projectile.

According to an exemplary embodiment, the multiple projectiles are golf balls being launched in a driving range and wherein the processor compares launch locations to known locations of a plurality of hitting bays from which golf balls are hit into the driving range, with each hitting bay being identified by the processor as a single launch location so that any golf balls launched from any location within a hitting bay are identified as originating from that hitting bay and provides to a device associated with the hitting bay the data corresponding to a trajectory of the projectile.

According to an exemplary embodiment, the system further includes a third radar device aimed so that a third field of view of the second radar device covers at least a portion of the target volume including a portion of the target volume outside the first and second fields of view as well as an overlap portion of the target volume also included in one of the first and second fields of view.

According to an exemplary embodiment, the first radar device is positioned at a first end of the target volume at which the launch locations are located with the first field of view extending into the target volume from the launch locations toward a far end of the target volume, the second radar device is positioned on a first lateral side of the target volume facing the first end of the target volume and including a first portion of launch locations including a first location adjacent to the first lateral side, the third radar device is positioned on a second lateral side of the target volume facing the first end of the target volume and including a second portion of launch locations including a second location adjacent to the first lateral side.

According to an exemplary embodiment, the second and third fields of view overlap so that the entire first end of the target volume is within at least one of the second and third fields of view.

According to an exemplary embodiment, the processor receives position data from a device associated with a user and identifies a location of the device as a known launch location.

According to an exemplary embodiment, the position data received by the processor is GPS data from a mobile device.

According to an exemplary embodiment, the processor identifies as known launch locations for each of a plurality of devices logged in as users of the system.

According to an exemplary embodiment, when the processor identifies a projectile as potentially associated with a known launch location, the processor sends to the device associated with the known launch location trajectory information for the projectile and a request to the user of the device to confirm that the projectile is associated with the known launch location.

According to an exemplary embodiment, the first radar device is a continuous wave Doppler radar.

The exemplary embodiments may be further understood with reference to the following description and the related appended drawings, wherein like elements are provided with the same reference numerals. The exemplary embodiments relate to a device, a system, and a method using radar to track multiple projectiles being launched from multiple launching locations as the projectiles move through an area and identifying the launching location from which each projectile was launched. Depending on the physical size on the launch areas as well as practical issues like line-of-sight blockage for a first radar device, it is desirable to have one or more additional radar devices in the system to increase the coverage of the volume being covered by the system. It is preferable to cover the entire range of launch areas, so that the launched projectiles can be acquired shortly after launch by the system, to enable association of projectile trajectories and related data to individual launch locations. Although exemplary embodiments detailed herein describe the tracking of golf balls, those skilled in the art will understand that any sports balls or even non-sports related projectiles may be tracked with the system in the same manner.

<FIG> shows a first system <NUM> for tracking an object according to the exemplary embodiments. The first system <NUM> includes three radar devices <NUM>, <NUM>', <NUM>" distributed around a target area into which projectiles are to be launched. In the embodiment of <FIG>, the system <NUM> is a system for tracking golf balls hit into the target area (driving range <NUM>) from a plurality of launch locations (hitting bays <NUM>) distributed along a first end <NUM> of the driving range <NUM>. Each radar unit may, for example, be a continuous wave Doppler radar emitting microwaves at X-band (<NUM>-<NUM>) emitting approximately <NUM> milliWatts EIRE (Equivalent Isotropic Radiated Power), thus being suitable for complying with FCC and CE regulations for short range intentional radiators. Any type of continuous wave (CW) Doppler radar may be used, including phase or frequency modulated CW radar, multi frequency CW radar or a single frequency CW radar. Current pulsed radar systems are limited in their ability to track objects that are close to the radar device. However, the distance an object must be from these pulsed radar systems has decreased over time and is expected to continue to decrease. Thus, these types of radar may soon be effective for these operations and their use in the systems of the invention described below is also contemplated. Throughout the application, the tracking of objects is described based on the use of Doppler frequency spectrums. As would be understood, these Doppler frequency spectrums refer to the data from continuous wave Doppler radar. If a pulsed radar system were employed similar data would be calculated based on a time required for the pulse to return to the radar after reflecting off an object. Any other type of radar capable of three-dimensionally tracking objects similar to those described herein may also be used.

As seen in <FIG> and <FIG>, the first radar device <NUM> is positioned behind the hitting bays <NUM> facing the target area <NUM>. The radar device <NUM> is positioned such that most of the projectile trajectories launched from the hitting bays <NUM> will be inside the field of view <NUM> (beam coverage) of the device <NUM> without any blockage from buildings and other structures. For a multi floor facility with hitting bays <NUM> on different levels this means that the radar device <NUM> is typically positioned either a) centered on façade of the hitting bays between the hitting bay floors, or, alternatively, b) on the roof of the hitting bays. Depending on the number of hitting bays horizontally and the field of view <NUM>, it might be preferred to position the radar device <NUM> in alternative b) approximately <NUM> - <NUM> behind the front of the hitting bays <NUM> and approximately <NUM> above the highest hitting bay floor. In this exemplary embodiment, the field of view <NUM> of the radar <NUM> extends outward from the hitting bays <NUM> and encompasses the radar devices <NUM>' and <NUM>" therein as well as the entire portion of the driving range <NUM> that extends beyond the radar devices <NUM>', <NUM>" (the portion of <NUM> further from the hitting bays than the radar units <NUM>', <NUM>"). The radar device <NUM>' is on the right hand side of the driving range <NUM> (when looking toward the hitting bays <NUM>) aimed inward toward the radar device <NUM> so that a field of view <NUM> of the radar device <NUM>' includes a first portion of the hitting bays <NUM> (including all of the hitting bays <NUM> to the right of the radar device <NUM> as well as a portion of the driving range <NUM> in front of the radar device <NUM>' extending from the right hand limit <NUM> of the driving range <NUM> to extend across a centerline <NUM> of the driving range <NUM>. In this exemplary embodiment, the radar devices <NUM>' and <NUM>" are positioned at the right and left hand limits <NUM>, <NUM>, respectively, approximately <NUM> meters from the hitting bays <NUM>. However, those skilled in the art will understand that any other positions for the radar devices <NUM>, <NUM>', <NUM>" may be selected so long as the fields of view <NUM>, <NUM>, <NUM> cover the entirety of the target area to avoid blind spots in which trajectory data would not be available.

Similarly, the radar device <NUM>" is on the left hand side of the driving range <NUM> aimed inward toward the radar device <NUM> so that a field of view <NUM> of the radar device <NUM>" includes a second portion of the hitting bays <NUM> (including all of the hitting bays <NUM> to the left of the radar device <NUM> as well as a portion of the driving range <NUM> in front of the radar device <NUM>" extending from the left hand limit <NUM> of the driving range <NUM> to extend across a centerline <NUM> of the driving range <NUM>. As would be understood by those skilled in the art, the fields of view <NUM> and <NUM> overlap in an area <NUM> including a central one of the hitting bays <NUM> to ensure that all of the hitting bays <NUM> are within a field of view <NUM>, <NUM> of one of the radars <NUM>', <NUM>". In addition, this arrangement ensures that the entire area of the driving range <NUM> is within one of the fields of view <NUM>, <NUM>, <NUM> so that each projectile can be tracked throughout its entire trajectory (limited to portions of trajectories that are within the driving range <NUM>).

As would be understood by those skilled in the art, a projectile may move through different areas during its flight such as a first area solely within only one of the fields of view <NUM>, <NUM>, <NUM> to an area covered by more than one field of view <NUM>, <NUM>, <NUM> (e.g., overlap area <NUM>) and then into an area within only a different one of the fields of view <NUM>, <NUM>, <NUM>. As the projectile moves from one field of view to another, the system <NUM> must continuously associate tracking data for an initial part of the trajectory from a first one of the radar devices <NUM>, <NUM>', <NUM>" associated the corresponding field of view <NUM>, <NUM>, <NUM> with tracking data corresponding to a later part of the trajectory from a second one of the radar devices <NUM>, <NUM>', <NUM>" corresponding to the field of view <NUM>, <NUM>, <NUM> which the projectile has entered. For example, a golf ball launched from the fourth hitting bay <NUM> from the right hand limit <NUM> along trajectory line T toward the centerline <NUM> first enters the field of view <NUM> of the radar device <NUM>'. The ball will then pass into the overlap area <NUM> and from there enters a portion of the driving range <NUM> that is solely within the field of view <NUM> of the radar device <NUM>. For an initial part of the trajectory, the system <NUM> will have data corresponding to the trajectory only from the radar device <NUM>'. For a second part of the trajectory, the system <NUM> will have data corresponding to this trajectory from radar devices <NUM>, <NUM>' and <NUM>". Thereafter, the ball may pass through an area in which fields of view <NUM> and <NUM> overlap before entering the area solely within the field of view <NUM>. The method by which the system <NUM> correlates the trajectory data from the various radar devices <NUM>, <NUM>', <NUM>" to generate a complete trajectory (e.g., from launch to landing) will be described in more detail below.

The system <NUM> includes data processing system <NUM> which, as would be understood by those skilled in the art, may include one or more computers coupled to the radar devices <NUM>, <NUM>' and <NUM>" either via a wired or wireless connection. In one embodiment, the data processing system <NUM> includes separate computers <NUM>, <NUM>' and <NUM>", each of which is associated with a corresponding one of the radar devices <NUM>, <NUM>', <NUM>" as well as a central computer <NUM> that coordinates data from the three computers <NUM>, <NUM>', <NUM>". However, those skilled in the art will understand that all of the operations described below can be performed by a single computer or on any number of computers with the various tasks distributed among the computers in any desired fashion.

In one exemplary embodiment, each of the computers <NUM>, <NUM>' and <NUM>" defines its own three-dimensional radar coordinate system relating to data from its corresponding radar device. The central computer <NUM> then defines a universal coordinate system into which the central computer <NUM> translates the tracking data formatted in the respective radar coordinate systems as this data is from each of the computers <NUM>, <NUM>', <NUM>". This permits the central computer <NUM> to track all objects moving through the space in the fields of view <NUM>, <NUM> and <NUM> and to plot the trajectories of these objects relative to the driving range <NUM>. Those skilled in the art will understand that the universal coordinate system may be made identical to one of the radar coordinate systems to simplify calculation. However, it may be desirable to define the universal coordinate system based on permanent physical features present in one of the fields of view <NUM>, <NUM>, <NUM> so that the system <NUM> may be recalibrated with reference to these permanent physical features. For example, the universal coordinate system may be based on a horizontal first axis extending from a center of a central one of the hitting bays <NUM> to a center of an endline of the driving range <NUM>, a second horizontal axis perpendicular to the first axis and a third axis extending vertically through an intersection of the first and second axes.

The central computer <NUM> will also follow the trajectory of each object backward to identify the hitting bay <NUM> from which each object was launched. Thus, in the case of the driving range <NUM>, each shot can be linked to its hitting bay <NUM> and the individual golfers may be provided with data on their shots (e.g., via a screen at each hitting bay <NUM>) even when balls are being launched from multiple hitting bays <NUM> at nearly the same time. In addition, the central computer <NUM> provides to each of the computers <NUM>, <NUM>', <NUM>" all data regarding all of the objects being tracked so that each of the radars devices <NUM>, <NUM>', <NUM>" can search for objects entering its respective field of view <NUM>, <NUM>, <NUM>, respectively, at known locations (i.e., locations at which current trajectories will enter one of the fields of view <NUM>, <NUM>, <NUM>). Each of the computers <NUM>, <NUM>' and <NUM>" may then translate this data from the central computer <NUM> into its own radar specific coordinate system so that each object can be continuously tracked even as these objects pass through the different fields of view <NUM>, <NUM>, <NUM>. Those skilled in the art will understand that, alternatively, the central computer <NUM> may perform the translation and provide the data to each of the computers <NUM>, <NUM>', <NUM>" in its respective coordinate system.

The flow chart of <FIG> shows a method <NUM> of operation implemented by the computers <NUM>, <NUM>', <NUM>" which method is repeated at each time interval for which measurements are taken. For example, in an exemplary system, each computer <NUM>, <NUM>', <NUM>" may perform the method of <FIG> every <NUM> (or <NUM> times per second). Although the method will be described only in regard to the computer <NUM> and the radar device <NUM>, those skilled in the art will understand that the same steps will be performed by the computers <NUM>', <NUM>" in regard to data from the radar devices <NUM>' and <NUM>".

For each time interval, in step <NUM> the computer <NUM> receives data from the radar device <NUM> and, in step <NUM>, calculates the Doppler frequency spectrum (see <FIG>), for example, by using a fast fourier transform for all of the channels of the radar device <NUM> in a known manner. In step <NUM>, the computer <NUM> uses known techniques to identify local intensity maxima from the Doppler frequency spectrum creating peaks representing objects moving through the field of view <NUM> of the radar device <NUM>. As would be understood by those skilled in the art, for each Doppler frequency peak, 3D position and other data (velocity, signal to noise ratio, etc.) for an object represented in the radar data are calculated for the identified peak. In the following, a peak is considered including corresponding 3D position, velocity, signal to noise ratio and other characteristics for the given object at that point in time. In step <NUM> the computer <NUM> forwards to the central computer <NUM> data corresponding to the identified peaks represented in the coordinate system of the radar device <NUM>. As would be understood by those skilled in the art, in an alternate embodiment, the computer may translate the data corresponding to the identified peaks into the universal coordinate system before forwarding this data to the central computer <NUM>.

For each time interval, the central computer <NUM> receives the data generated by the computers <NUM>, <NUM>', <NUM>" in step <NUM> and performs the method <NUM> of <FIG> to track all of the projectiles within the fields of view <NUM>, <NUM>, <NUM> determined to be relevant (e.g., for a driving range, all projectiles determined to be golf balls in flight). For example, as would be understood by those skilled in the art, moving items which do not follow the patterns associated with ballistic flight (example, birds) can be detected and eliminated from the analysis. In step <NUM>, the central computer <NUM> receives data from each of the computers <NUM>, <NUM>', <NUM>" for the current time interval and, in step <NUM>, converts this data to the universal coordinate system. In step <NUM>, the central computer <NUM> determines whether each peak represented in the data can be assigned to an existing trajectory or whether a new trajectory should be initiated. This process is more clearly illustrated by the method <NUM>.

As shown in <FIG>, for each time interval the central computer <NUM> analyzes each of the peaks received from all of the radars <NUM>, <NUM>', <NUM>" to determine if the peak N matches an existing track M. As would be understood by those skilled in the art, a track is a time sequence of <NUM>-dimensional positions and other trajectory data associated with a moving object. In step <NUM> the central computer <NUM> compares the peak N to each existing track to determine whether the peak N matches any of the existing tracks. Those skilled in the art will understand that the central computer may determine whether a peak represents a new point on an existing trajectory by comparing the new position and velocity data to data from existing tracks (e.g., by comparing data from the peak to that for each track from one or more prior time intervals) to determine whether the new data is consistent with prior velocity and position data for any of the tracks. That is, if the central computer <NUM> determines that a distance between a prior ball position and the new peak is equal to (within a certain tolerance) a distance that which would have been traversed by the ball of an existing track M at its prior velocity and this distance is consistent with a direction of the prior velocity, this peak will be assigned to this prior trajectory M. If the peak N matches an existing track M, the method proceeds to <NUM>. If the new peak N is not consistent with any existing trajectory, it will be assigned as the initial point for a new trajectory and the method proceeds to <NUM>.

In method <NUM> as shown in <FIG>, for each Track M the central computer <NUM> determines whether the track is associated with a specific one of the hitting bays <NUM>. In step <NUM>, if the Track M is not associated with a hitting bay <NUM>, the central computer <NUM> associates the Track M with a hitting bay <NUM> in step <NUM> by, for example, moving back in time along the Track M to an initial point at one of the hitting bays <NUM>. Alternatively, if an initial point of the Track M is not at one of the hitting bays <NUM> (e.g., the ball was not picked up until it had travelled a distance from its launch), the specific hitting bay <NUM> may be identified by extrapolating back in time (e.g., continuing the Track M back in time along a path consistent with its later trajectory) until the Track M reaches one of the hitting bays <NUM>. The central computer <NUM> then, in step <NUM>, calculates launch data for the ball associated with Track M and forwards the data to the hitting bay Q <NUM> associated with this Track M. The method then proceeds to step <NUM>. As would be understood by those skilled in the art, the data forwarded to the hitting bay <NUM> (or other location) associated with the launch location of a Track M may include graphic data illustrating a flight path of the ball from one or more perspectives, tabular data concerning variables such as launch speed, average speed, launch angle relative to the horizontal, spin rate, spin axis, distance covered, maximum height, etc. In addition, this data may be provided to a device associated with the hitting bay Q <NUM> (or any other location) associated with the launch location. For example, this device may be a screen displaying the data, a mobile device associated with a user located at the launch location, etc..

If, in step <NUM>, the Track M is associated with a specific hitting bay Q <NUM>, the method proceeds to step <NUM>. In step <NUM> the central computer <NUM> determines whether the ball has landed. For example, if the Track M has proceeded upward along an arc, peaked and then continued to descend along an arc and in the current time interval the height of the ball is the same or higher in the previous time interval, the central computer <NUM> determines that the ball has landed. Alternatively, the computer <NUM> may make this determination based on a comparison between an elevation of the ball and a known elevation of the surface at the current location of the ball. If the central computer <NUM> determines in step <NUM> that the ball has landed, the Track M is terminated in step <NUM> and final data is calculated in step <NUM> and forwarded to the user in the identified hitting bay Q <NUM>. If, in step <NUM> the central computer <NUM> determines that the ball has not yet landed, in step <NUM> the Track M is smoothed (e.g., filtered to reduce noise) and in step <NUM> the updated smoothed Track M is provided to the user in the hitting bay Q <NUM> associated with the Track M. Those skilled in the art will understand that this information may also be forwarded to any number of hitting bays <NUM> as desired. For example, if multiple hitting bays <NUM> are involved in a competition, all of the Tracks associated with these hitting bays <NUM> may be provided to all of these hitting bays <NUM>. For Tracks M that have not been terminated, the process repeats for the next time interval.

<FIG> show a method for dealing with situations where two or more balls are close enough together in time and Doppler frequency that one or more of the tracks is obscured by another of the tracks. Specifically, as seen in <FIG>, in this example, Track T1 for a ball <NUM> crosses a Track T2 for ball <NUM> and the Track for T1 interrupts the Track T2 for a period of time represented by the gray area <NUM> in each of <FIG>-. The Tracks T1 and T2 overlap in the perspective of <FIG> for the time range <NUM> so that, when the two tracks diverge after this overlap <NUM>, the computer dedicated to the radar generating the data may not be able to determine immediately which of the later Track portions a and b is associated with T1 and which is associated with T2. However, when the data included in the Tracks T1 and T2 is broken down to show the paths of the balls <NUM> and <NUM> over time as shown in <FIG>, it becomes clear that the portion a is a continuation of Track T1 while the portion b is a continuation of the Track T2. That is a comparison of the travel represented by the portions a and b with the initial portions of the Tracks T1 and T2 makes clear to which track the portions a and b should be assigned. As would be understood by those skilled in the art, the system may also compare other parameters such as, for example, the velocity represented by the initial portions of the Tracks T1 and T2 with the velocity represented in portions a and b to enhance the accuracy of the selection.

<FIG> and <FIG> show a system <NUM> for tracking a plurality of objects according to a further exemplary embodiment. The system <NUM> includes four radar devices <NUM>, <NUM>', <NUM>", <NUM>‴. Similar to the system <NUM>, each of the radar devices <NUM>, <NUM>', <NUM>", <NUM>"' is coupled to a corresponding computer <NUM>, <NUM>', <NUM>", <NUM>"', respectively, and each of these radar computers is connected to a central computer <NUM> in the same manner as described above in regard to system <NUM>. The radar devices <NUM>" and <NUM>‴ are positioned in the same manner as the radar devices <NUM>' and <NUM>" of the system <NUM> while the radar device <NUM> has been replaced in system <NUM> with the two radar devices <NUM>, <NUM>'. Each of the radars is located behind the hitting bays <NUM> of the driving range <NUM> and positioned similarly to the radar <NUM> except that, instead of being located on a centerline <NUM> of the driving range <NUM>, the radar device <NUM> is offset from the centerline <NUM> toward a right edge <NUM> of the driving range <NUM> while the radar device <NUM>' is offset from the centerline <NUM> toward a left edge <NUM>. Thus, the fields of view <NUM>, <NUM>, <NUM>, <NUM> of radar devices <NUM>, <NUM>', <NUM>", <NUM>"', respectively, overlap in a manner similar to the fields of view <NUM>, <NUM>, <NUM> of the radar devices <NUM>, <NUM>', <NUM>", respectively, of system <NUM>. The central computer <NUM> of the system <NUM> coordinates with the computers <NUM>, <NUM>', <NUM>", <NUM>‴ in the same manner as the central computer <NUM> communicates with the computers <NUM>, <NUM>', <NUM>" to track projectiles moving between the various fields of view. The four radar device arrangement of system <NUM> provides a more complete coverage of the area of the driving range <NUM> and the hitting bays <NUM> than in system <NUM> but otherwise operates similarly.

<FIG> and <FIG> show a system <NUM> for tracking a plurality of objects according to a further exemplary embodiment. The system <NUM> includes two radar devices <NUM>, <NUM>'. The system <NUM> is similar to the system <NUM> with the radar devices <NUM> and <NUM>' positioned substantially similarly to the radar devices <NUM>, <NUM>' behind the hitting bays <NUM> of the driving range <NUM>. In the system <NUM>, however, there are no additional radar devices positioned in front of the hitting bays <NUM> as were the radar devices <NUM>", <NUM>"'. Those skilled in the art will understand that the system <NUM> may include a similar arrangement of radar computers coupled to an optional central computer operating in a manner similar to the computers of the system <NUM>. As can be seen in <FIG> and <FIG>, the fields of view <NUM>, <NUM> of the radar devices <NUM>, <NUM>', respectively, overlap while leaving certain portions of the driving range <NUM> uncovered. As will be described below in regards to the system <NUM>, portions of trajectories passing through these uncovered portions of the driving range <NUM> will be extrapolated by the system <NUM> based on the portions of the trajectories detected by the radar devices <NUM>, <NUM>' to identify a specific hitting bay <NUM> from which each ball was launched and to complete the trajectory for each ball to its landing point. The system <NUM> is well suited for golf driving ranges with only a single elevation level of hitting locations. In this case ball trajectories will quickly be inside field of view <NUM> and/or <NUM> without line of sight being obstructed by a building as may be the case in a multi-floor hitting facility. The system <NUM> might consist of one, two or more radars <NUM> depending on the need for covering a specific width of launch area and how far behind the hitting location <NUM> the radar devices <NUM> and <NUM>' can be placed.

As seen in <FIG> and <FIG>, a system <NUM> for tracking a plurality of objects according to a further exemplary embodiment. The system <NUM> includes a single radar device <NUM> positioned so that a field of view <NUM> of the radar device <NUM> includes substantially all of a target area into which projectiles are to be launched. In the embodiment of <FIG> and <FIG>, the system <NUM> is a system for tracking golf balls hit into the target area (driving range <NUM>) from a plurality of launch areas (hitting bays <NUM>) distributed along a first end <NUM> of the driving range <NUM>. The field of view <NUM> of this embodiment includes all of the hitting bays <NUM>. For example, as seen in <FIG> and <FIG>, the radar <NUM> is placed substantially centered on an end line <NUM> of the driving range <NUM> elevated by a desired distance. This type of setup is desirable if sufficient signal-to-noise ratio and positional accuracy can be achieved on the projectile trajectories close to the hitting bays <NUM>, so that the system can still accurately associate each trajectory with a hitting bay in the launch area. If this was a golf driving range, this would typically require that the radar <NUM> should be positioned approximately <NUM>-<NUM> in front of the hitting bays <NUM>. This type of setup would be very suitable for a golf driving range with limited flight distance of the golf ball, e.g. because the golf ball is stopped by a net.

The radar unit <NUM> for this embodiment may, for example, be a higher powered Doppler radar emitting microwaves at X-band and with high enough positional measurement accuracy to ensure accurate association of projectile trajectories with hitting bays. Thus, the system <NUM> operates substantially similarly to the system <NUM> except that each ball will be tracked based solely on data from the radar device <NUM> and there is no need for more than one coordinate system or for any hand-off of tracking from one radar device to another as there was with the system <NUM>. For portions of any ball's flight that are outside of the field of view <NUM>, the computer <NUM> can extrapolate forward or backward in time to estimate the entire trajectory of the ball from launch (e.g., identify a hitting bay <NUM> from which it was launched) to landing. Those skilled in the art will understand that the system <NUM> may still employ a universal coordinate system based on identifiable physical landmarks in the driving range <NUM> in the same manner as described above for the system <NUM>. In this scenario, the coordinate system for the radar device <NUM> may originally be set to coincide perfectly with the universal coordinate system. However, if the device <NUM> is moved at any time, the system <NUM> movement may be measured and any changes in position or aiming may be accounted for with the system <NUM> translating the new radar specific coordinate system (for the device <NUM>) into the universal coordinate system in order to accurately relate measurements from the device <NUM> to positions on the driving range <NUM>.

As shown in <FIG>, an exemplary Track T1 of a golf ball leaves a hitting bay <NUM> that is outside the field of view <NUM> at time T0 and enters the field of view <NUM> soon after launch at time Ti. The radar device <NUM> picks up the ball when it enters the field of view <NUM> and tracks the ball until the ball leaves the field of view <NUM> at time Tf. The computer <NUM> generates a trajectory for ball based on data from the radar device <NUM> covering the entire time from Ti to Tf and, based on this trajectory, extrapolates an initial portion of the trajectory T1<NUM> extending from T0 to Ti to identify the hitting bay <NUM> from which the ball was launched. The computer <NUM> then extrapolates the portion T1<NUM> of the trajectory T1 extending from time Tf to time Tl at which the ball lands. The computer <NUM> then assembles the entire trajectory T1 and sends the data corresponding to this trajectory T1 to the hitting bay <NUM> identified as the launch location for the ball. Those skilled in the art will understand that this same extrapolation process may be used in any of the described systems to account for any time during which a ball either leaves the fields of view of the radar(s) or for any time period during which the system loses track of the ball for any reason.

Those skilled in the art will understand that, although the previously described embodiments describe discrete hitting bays <NUM>, the system <NUM> (or any of the other systems disclosed herein) may identify the hitting locations associated with each of the detected projectile tracks. These hitting locations may then be associated with a user of the system associated with each projectile. In the case of a golf driving range, the users may be permitted to hit from any location within a large launch area. Each user may then be associated with a particular location from which balls are being hit by logging into the system (e.g., over WiFi or another wireless network) using an electronic device with location capability. For example, a user may log on to the system using a mobile phone having GPS or any other electronic location system and the system may associate with this device all shots hit from any location that is closer to the current location of this device than to any other logged in device. Alternatively, or in addition, the system may query a device to which it is considering associating one or more shots and ask the user of the device to indicate whether or not he actually took any or all of the indicated shots (Tracks). Based on the user response, the system may then associate future tracks from a given location with this user (user device). Those skilled in the art will understand that this variation may be used with any or all of the previously described systems.

Claim 1:
A system (<NUM>; <NUM>; <NUM>) for tracking multiple projectiles, comprising:
a first radar device (<NUM>; <NUM>, <NUM>') configured to be aimed so that a first field of view (<NUM>; <NUM>, <NUM>; <NUM>) of the first radar device (<NUM>; <NUM>, <NUM>') covers at least a portion of a target volume into which projectiles are to be launched from a plurality of launch locations;
a second radar device (<NUM>'; <NUM>") configured to be aimed so that a second field of view (<NUM>; <NUM>; <NUM>) of the second radar device (<NUM>'; <NUM>") covers at least a portion of the target volume including a portion of the target volume outside the first field of view (<NUM>; <NUM>, <NUM>; <NUM>) as well as an overlap portion of the target volume also included in the first field of view_(<NUM>; <NUM>, <NUM>; <NUM>); and
a processor receiving data from the first radar device (<NUM>; <NUM>, <NUM>') and identifying from the data tracks of a plurality of projectiles, the processor determining for each projectile track identified a launch location from which the projectile was launched and providing to a device associated with the launch location data corresponding to a trajectory of the projectile, wherein, as the projectile moves from one field of view to another, the system (<NUM>; <NUM>; <NUM>) continuously associates tracking data for an initial part of the trajectory from a first one of the radar devices (<NUM>, <NUM>'; <NUM>, <NUM>', <NUM>") associated with the corresponding one field of view with tracking data corresponding to a later part of the trajectory from a second one of the radar devices (<NUM>, <NUM>'; <NUM>, <NUM>', <NUM>") corresponding to the field of view (<NUM>, <NUM>, <NUM>) which the projectile has entered,
wherein, for each of a plurality of time frames, the processor receives from the first radar device (<NUM>; <NUM>, <NUM>') a radar signal and calculates from this radar signal projectile data including position and speed values for each projectile identified,
wherein for each trajectory the processor compares an initial projectile position to known launch locations and, if the initial projectile position matches a known launch location, the processor assigns this launch location to the trajectory, wherein, preferably, when the initial projectile position for a trajectory does not match a known launch location, the processor, based on the trajectory, extrapolates backward in time from the initial projectile position to a launch location for the projectile.