Golf course yardage and information system

Claims

What is claimed is:

1. A player position determining and course management system for a golf course, having a plurality of roving units for use by players in playing the course, each roving unit having a differential global positioning system (DGPS) RF transmitter/receiver (transceiver) for operation in conjunction with a land-based stationary DGPS receiver and with a plurality of GPS satellites continuously orbiting the earth and transmitting GPS satellite signal information for use in determining the relative position of and distance between objects on the earth, said system comprising:

in each roving unit DGPS RF transceiver:

a central processing unit (CPU) including a data processor for executing various tasks ranging from fastest execution of a task to slowest execution of a task on a schedule of priorities of task completion,

real-time means for controlling the processor to give the tasks priority ranging from fastest execution of a task with highest priority to slowest execution of a task with lowest priority, and if CPU throughput remains available after the lowest priority task is executed by the processor, for causing the processor to execute remaining tasks pending receipt of a task interrupt, and

means for precisely timing functions of said system including modulating means utilizing a common digital modulation technique for digitally modulating data transmitted to and from all of the roving DGPS RF transceivers of the system in a Federal Communications Commission (FCC) authorized frequency spectrum.

2. The system of claim 1, in which:

said modulating means utilizes phase shift keying (PSK).

3. The system of claim 1, in which:

said modulating means utilizes frequency shift keying (FSK).

4. The system of claim 1, in which:

said roving DGPS RF transceivers of the system utilize a variable length network.

5. The system of claim 1, in which:

said means for precisely timing functions includes means in said roving DGPS RF transceivers of the system employing, with the stationary DGPS receiver, a pulse-per-second output to inform a user that a measurement of the user's transceiver position is valid.

6. The system of claim 5, in which:

said means in said roving DGPS RF transceivers of the system includes means for receiving a pulse-per-second output from the stationary DGPS receiver as an interrupt into said processor to inform the system as to when time commenced for a valid measurement of a user's transceiver position.

7. The system of claim 1, in which:

each of said roving units is a golf cart.

8. The system of claim 1, in which:

each of said roving units is a hand-held unit.

9. In a ball position determining and course management system for a golf course, including a base station for course management and a plurality of roving units for golfers during play of the course, each of the base station and the roving units being adapted to operate on a differential global positioning system (DGPS) with RF transmitter/receivers (transceivers) in conjunction with a plurality of earth-orbiting GPS satellites that transmit GPS satellite signal information for use in determining the relative position of and distance between objects on the earth, the improvement in said system comprising:

timing means in said base station and each of said roving units for precisely timing the functions of said system, said timing means including transmitting means in the base station for transmitting a pulse per second (pps) signal to each roving unit, said timing means also including interrupt means in each roving unit responsive to receipt of the pps signal transmitted by said transmitting means for resetting a real-time clock interrupt counter in the respective roving unit.

10. The system of claim 9, in which:

said interrupt means is responsive to receipt of the pps signal to reset the real-time clock interrupt counter to 1 in a count of 2.sup.n where n is an integer at least equal to 8, whereby a real-time clock interrupt runs asynchronously with the pps signal so that 2.sup.n interrupts occur every second.

11. The system of claim 10, in which:

said interrupt means includes system timing means with said real-time clock responsive to said interrupts from the pps signal for indicating when the next time message is valid, for counting the number of 2.sup.n task interrupts received up to the point in time that the time message containing the valid time is received to obtain a count, and for incrementing from that count to maintain precise timekeeping in the system.

12. The system of claim 9, in which:

said timing means includes

message means at the base station for creating a message to indicate a time at which a given pps of the pps signal was valid, together with range and range rate differential correction information, and

said interrupt means at each roving unit includes

means for receiving said message to indicate the precise GPS time that was valid when the given pps occurred, and

means for counting the number of 2.sup.n interrupts received since the given pps occurred to synchronize the system to that time, so that time is maintained accurate to 1/2.sup.n second.

13. The system of claim 9, in which:

said timing means includes means for synchronizing the base station and all roving units to GPS time within an interval on the order of microseconds, to dispense with direct base synchronization, whereby all roving units on a network comprising the system require initialization only to indicate when they are allowed to transmit, and thereafter, each may transmit in its own unique, specific time slot asynchronous of direct base timing control.

14. The system of claim 13, in which:

means are provided for eliminating the need for the pps signal from the GPS receiver at the base station to be synchronized to GPS time in integer seconds, by maintaining the accuracy of the pps to the millisecond level despite the system only requiring timing to about one thousandth of a second, so that it is immaterial to proper operation that synchronization exists on some GPS receivers and not on others.

15. The system of claim 9, further including:

variable length network means having a circular frame cycle with a predetermined number of frames of message packets, the number of frames being set by the base station according to system network load demand, so that when relatively few roving units are on the course only a relatively small number of unique frames need be maintained by the base station to provide a higher update rate of roving unit state message packets to the base station, attributable to a need for fewer unique frames to be transmitted before the network returns to frame 0.

16. The system of claim 15, in which:

the variable length network means includes mean for quantizing a predetermined number of additional roving units that may be accommodated by an increase in the network size, with only integer frames allowed to be added or subtracted.

17. The system of claim 16, in which:

the variable length network means includes a variable length structure of the packets for setting the number of frames at 16 to continually enhance network efficiency, and to quantize at 16 the number of additional roving units that may be accommodated by an increase in the network size, whereby, with only integer frames allowed to be added or subtracted, the fastest unique roving unit position updates are provided to the base station every second when not more than 16 roving units are on the course, and the slowest updates are given every 16 seconds when more than 240 roving units are on the course.

18. The system of claim 9, in which:

each of said roving units is a golf cart.

19. The system of claim 9, in which:

each of said roving units is a hand-held unit.

20. The system of claim 9, in which:

errors in the real-time clock are calibrated despite drift in a crystal oscillator of the base station and each roving unit attributable to temperature differences, by commencing said count each time a pps is received at the respective roving unit, up to 2.sup.n counts until the next pps is received, with the real-time clock running at 2.sup.n Hertz, to indicate whether the clock is running slow or fast and the amount by which it is slow or fast according to the count reached when the next pps is received, to permit precise calibration of the base station to the roving unit real-time clock every second, to maintain one millisecond timing accuracy of the system.

21. A system for determining the location of each of a plurality of dispersed objects in transit, and for administering the disposition of each of said objects, said system including a base station for administration and a plurality of remote stations associated with said objects while in transit, each of the base station and the remote stations being adapted to operate on a differential global positioning system (DGPS) with RF transmitter/receivers (transceivers) in conjunction with a plurality of earth-orbiting GPS satellites that transmit GPS satellite signal information for use in determining the relative position of and distance between targeted points on the earth, said system comprising:

timing means in said base station and each of said remote stations for precisely timing the functions of said system including transmitting means in the base station for transmitting a pulse per second (PPS) signal to the remote stations, said timing means further including interrupt means in each remote station responsive to receipt of the PPS signal transmitted by the base station transmitting means for resetting a real-time clock interrupt counter in the respective remote station, whereby to synchronize the timing between the base station and the remote stations and to dispense with the need for direct base synchronization such that all remote stations on the system require initialization only to indicate when they are allowed to transmit in a specific time slot asynchronous of direct base station timing control.

22. The system of claim 21 wherein the base station includes a monitor for displaying the location of all remote stations in real time such that the remote stations can be observed while in transit.

23. The system of claim 22 wherein said monitor is a high resolution color graphic monitor capable of displaying full-color advertisements.

24. The system of claim 21 wherein the base station includes means for transmitting a text message to selected remote stations thereby providing information to said remote stations.

25. The system of claim 21 wherein each of said remote stations includes a monitor for displaying the distance from its respective remote station to a specified location marked on the display of the remote station monitor.

26. In a ball position determining and course management system for a golf course, including a base station for course management and a plurality of roving units for use by golfers during play of the course, each of the base station and the roving units being adapted to operate with a satellite-based navigation system for determining the relative position of and distance between objects on the earth, a system network for broadcast communications between the base station and the roving units using message packets, comprising:

variable length network means having a circular frame cycle with a predetermined number of frames of message packets, the number of frames being set by the base station according to system network load demand, so that when relatively few roving units are operating on the system only a relatively small number of frames uniquely identifying the respective roving units need be maintained by the base station to provide a higher update rate of roving unit message packets to the base station, attributable to fewer unique frames needed to be transmitted before the network returns to an initial frame, whereby to enhance the efficiency of the system network.

27. The system of claim 26, including:

timing means in the base station and each of the roving units for precisely timing the functions thereof, the timing means including means for synchronizing the timing of broadcast communications between the base station and all roving units within a predetermined interval to eliminate a need for direct base synchronization thereof, each roving unit having its own unique, specific time slot for broadcast communications to the base station, whereby all roving units on the system network require initialization only to indicate when they are allowed to transmit, and thereafter, each may transmit in the unique, specific time slot allocated thereto, asynchronous of direct base station timing control.

28. The system of claim 26, including:

means enabling roving units that are currently non-operative within the system to enter and operate in the system at will, including arbitration means for minimizing the probability that two or more roving units are attempting to enter the system simultaneously.

BACKGROUND OF THE INVENTION

The present invention relates generally to yardage systems and more particularly to a new and improved golf course yardage and information system.

Before starting play on an unfamiliar or infrequently played course, golfers typically familiarize themselves with the layout of each hole. This gives the golfer the knowledge at the tee box of a particular hole being played, for example, as to whether the hole is a `dog leg left`, a `dog leg right`, or straight; whether any hazards, such as sand traps, bunkers, and water traps, are hidden from view; whether and where the range is posted to calculate yardage from the ball's (and the golfer's) present location to the front of the green, the rear of the green, the pin, a key hazard, or a desired lay up position for the green approach shot.

Customarily, golf courses market informative books on the course in the pro shop, to indicate layout features for each hole and yardage from a few locations along the hole to the center of the green. Also, yardage markers typically are provided at sprinkler heads along the route of each hole, so that the player will know the range from that point to the center of the green. These playing aids provide information on the hole layout and location of hazards, and also allow the golfer, by pacing off yardage from the ball to the nearest sprinkler head, to estimate yardage from the ball to the center of the green. Such measures are by no means precise, but do enhance one's knowledge of the hole, and thereby, an opportunity to improve one's game. They also exact a cost--slowing the pace of play of every golfer behind the one or more who are familiarizing themselves with the course, pacing off yardage, and so forth. Slow play has an adverse effect on the course's daily revenue, as well as on other players' enjoyment of the game.

Various proposals have been made toward improving golf course information systems. The intent of these ostensible improvements has been to reduce the average player's score; to increase enthusiasm and speed of play; and to enhance the player's knowledge of the course regarding every hole, the yardage from the ball or "lie" to the green, the distance and bearing to the pin, and the location of hazards. Proposals have included use of buried electrical wires in various layout configurations about the course for interaction with mobile overland components, or of radio direction finding or triangulation techniques, to inform the golfer of gross features of the course and distances from specific markers to the pin or flag for the hole being played.

A recent proposal for a position and distance measuring system for a golf course enlists the capabilities of the existing U.S government-sponsored Global Positioning System (GPS) which was established over the last 20 years with space satellites and ground based stations. The GPS system was established as a means for determining distance, range, and position for various governmental purposes, but has become quite useful in many industrial and commercial applications as well. A number of earth-orbiting satellites provide reference points from which to determine the position of a point on or near the earth, using the ground-based receivers. The orbits of these satellites are monitored by the ground station GPS receivers, and the travel times of signals received from the satellites are used to measure distance to each satellite. Each timing signal from a satellite is coded to permit the receiver to determine the elapsed time between launching of the signal from the respective satellite and receipt at the GPS receiver antenna, and thereby to calculate the distance as the product of that elapsed time and the speed of light. Receivers need not be restricted to large ground stations, but are available in portable, mobile and hand-held versions, for a multitude of private navigation, position and distance-measuring systems.

Distance measurements to three GPS satellites can accurately define the position of an object (i.e., that of the GPS receiver, whether of the stationary or portable type) on or near the surface of the earth. A fourth satellite provides a distance measurement that serves to verify clock timing within the GPS system. With several satellites in "view", and through the use of a computer, the GPS receiver theoretically can calculate distances virtually instantaneously with great accuracy. In practice, however, even small errors that typically occur in the calculated measurement of satellite signal travel time from system and natural phenomena severely reduce the accuracy of the distance and position calculations. Error causing phenomena include atmospheric propagation, receiver contributions, satellite ephemeris (transient), and satellite clock. Furthermore, the U.S. Department of Defense (DOD) purposely introduces errors in the satellite signals to deny civilian users fall accuracy. Erroneous measurements of 100 meters or so may be tolerated in many GPS-based measurement systems, but would be unacceptable in a golf course positioning and distance measuring system.

The recently proposed golf course position GPS system employs purely conventional differential GPS, which has found wide use to reduce errors in distance measuring systems. The differential GPS (DGPS) system broadcasts error correction information from a ground receiver of known location in the vicinity of the user. Two GPS receivers are used, one at a known fixed position, so that the difference between that known position and its position calculated from the satellite GPS signal fixes the error in the signal. The fixed position (reference) receiver provides a continuous correction for use by all other receivers, which may be mobile, within its reception area. Knowledge of the error allows all distance and position calculations at the user's receiver to be corrected. Conventional DGPS can reduce errors in position calculations to allow accuracies of within about five meters--quite suitable for most commercial needs, but still unacceptable for a golf course distance measuring system. However, the same conventional DGPS system may be used to determine the location of a golf cart receiver relative to the pin on a hole of a golf course as to determine the location of a ship relative to a land-based point of interest. Weather conditions and terrain have little effect on position determination in the GPS system, and few restrictions are imposed on size or location of a user's receiver.

Details of DGPS are readily available from a number of sources, an example being Blackwell, "Overview of Differential GPS Methods", Global Positioning System, vol. 3, pp. 89-100, The Institute of Navigation, Washington, D.C. (1986). The Blackwell (Stanford Research Institute International) paper details four differential GPS techniques, one of which is virtually identical to the previously proposed GPS-based golf course positioning system.

It is a principal object of the present invention to provide a new and improved golf course yardage and information system utilizing DGPS.

Another object of the invention is to provide such a system having considerably greater accuracy than is available with conventional DGPS.

SUMMARY OF THE INVENTION

Before summarizing the best mode presently contemplated for practicing the golf course yardage and information system of the invention, it bears emphasis that the present invention is not limited to providing distances and information in the context of golf courses. Rather, it may be extended to any number of other consumer, commercial, and industrial applications of satellite navigation and digital communications technology. The present invention will be described in the context of a golf yardage and information system, embodied in what is referred to herein as the PROLINK.TM. (PROLINK is a trademark of Leading Edge Technologies, Inc. of Changler, Ariz., the assignee of the invention disclosed in this patent specification) yardage and course management system (or more briefly, as the `PROLINK system`), but the invention is not limited to use on or for a golf course.

The PROLINK system includes a golf cart-based subsystem, although it may be packaged alternatively or additionally into a hand-held unit carried by the golfer. Both such versions are included within the generic terminology of a mobile unit, a portable unit, or a roving uni