Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for
determining the approximate distance between a golf ball and a
target on the golf course such as the golf cup. In particular, the
method and apparatus uses a global positioning satellite receiver
positioned near the golf ball to determine the approximate
location of the golf ball.
2. Description of Related Art
In the game of golf it is important to know as accurately as
possible the distance between the golf ball and the golf cup on the
green. It is sometimes also desirable to know the distance
between the golf ball and a hazard on the hole being played.
Knowing these distances allows proper club selection and allows a
player to formulate a hole management plan. For example, a
player that knows the ball is 11 0 yards from the pin would select
the appropriate club for 110 yards such as a 9 iron or one of the
player's wedges.
Deane Beamon and Jack Nicklaus purportedly pioneered in
professional tournament play the use of books containing yardage
calculations. Most PGA professionals and serious amateurs now
use course yardage books to determine the distance between the
ball and the golf cup or a hazard on the hole being played.
Yardage books are significantly more accurate than guessing the
distance based on a visual inspection.
A significant drawback to the use of yardage books is the fact that
the book must be prepared prior to the round of golf. Such
preparation is inconvenient for most amateur play in recreational
golf. Even when a yardage book is prepared, account must be
made for the location of the tee markers, the location of the golf
cup on the green for the particular day, and the position on the
hole being played.
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There are several alternatives to yardage books for determining the
distance from the ball to the golf cup. Most courses mark the hole in
some form with approximate distances to the middle of the green.
For example, many courses mark the sprinkler heads with distance
to the green, while other courses plant trees or post a marker at the
100 or 150 yard position from the middle of the green. Some
courses have buried low power location beacons along their fairways
and a receiver carried by the golfer receives the nearest beacon
signal and indicates the distance of the beacon.
There are several disadvantages to known techniques for distance
determination on golf courses. First, they are all have varying
degrees of inaccuracy. Typically the distances follow some unknown
line in the fairway and are calculated to the middle of the green.
Inaccuracies of more than 10 yards are common which unfortunately
can be the difference between a 6 foot putt and a sand trap. Second,
most known techniques slow play by requiring the player to consult
his yardage book or walk around searching for a distance marker
and walking off the distance from the marker to the ball. Third,
most techniques do not give an indication of the distance to most, if
not all, of the hazards. For example, it is important to know the
distance the ball needs to travel to carry a trap or water hazard in
front of the green.
Therefore, a method and apparatus which could accurately and
quickly determine the position of a ball and the distance between the
ball and features on the hole being played, such as the golf cup on
the green, the preceding cart, or a hazard would contribute to lower
scores and faster play. Such a method and apparatus would be
particularly advantageous if it also accounted for distance between
the ball and an obstacle or hazard.
SUMMARY OF THE INVENTION
The problems outlined above are generally solved by the method
and system of the present invention for determining distance on a
golf course. The invention provides a good approximation of the
distance from a golf ball to a feature, such as the golf cup ,hazard, or
preceding golf group. Preferably the system includes a visual
display of the golf hole being played, including the location of the pin
on the green, the bunkers protecting the green, the hazards on the
hole, as well as a digital readout of the distance from the ball to the
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golf cup. In an enhanced version the display includes a light pen or
pointing device (finger or pen for pressure sensitive screen) allowing
the player to mark positions on the hole layout. This gives the player
the ability to determine distance between the ball and a marked
position (a water hazard for example) or distance between a mark
and the cup.
Broadly speaking, the method of the present invention includes the
steps of positioning a global positioning satellite system (GPS)
receiver on the hole being played, determining a position of the
remote receiver using the global positioning satellite system, and
displaying the distance from the remote receiver to the feature using
the position of the remote receiver. Normally the receiver is
positioned proximate the golf ball, but alternatively a mark may be
made at the ball's approximate location.
The apparatus generally includes a GPS receiver that is positionable
on the golf hole. For example, the apparatus might be mounted on a
golf cart and the cart may be driven close to the ball. The apparatus
also includes a position determining means and a display.
Preferably, the determining means is a microprocessor associated
with the GPS receiver that calculates an apparent position of the
receiver. Alternatively, the determining means may be a
microprocessor at a base station and the GPS receiver simply relays
or repeats the GPS signals to the base station. The display preferably
shows a graphic representation of the hole layout, and in a preferred
form is light responsive or pressure sensitive, such as a pen input or
touch sensitive display. A distance grid is preferably displayed with
its origin at the GPS receiver or alternatively, a mark location.
In a preferred form, the apparent location of the GPS remote receiver
is adjusted with an error correction to achieve a corrected location.
The difference between the corrected location and the stored location
of a feature such as the golf cup is calculated to determine the
approximate distance between the ball and the cup. The location of
the golf cup is preferably close to the actual location of the current
placement of the cup on the green, but may be a nominal location,
such as "middle" of the green or "front" of the green.
The error correction is determined by positioning a GPS receiver at a
reference location having a known position. The GPS receiver
determines an apparent position using the available global
positioning satellites in view. The error correction is calculated
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based on the difference between the apparent position and the
known position. The error correction is preferably broadcast
periodically for use by the remote GPS receivers used by the golf
players. Preferably, the position of the golf cups on the greens are
determined by placing a GPS receiver in or near the cup (e.g. before
play by the greens keeper), determining an apparent position, and
applying the error correction to obtain the golf cup position stored
for use during play.
In the preferred embodiment, a base station is placed at the known
position to continuously calculate and transmit the error correction.
The remote receivers are optionally configured to periodically
transmit their position to the base station so that the course marshal
can continuously monitor the progress of play.
In an alternative form, the remote receiver is used to calculate an
error correction for its own use. For example, a remote receiver
mounted on a golf cart would be driven onto a placard designating a
known location on each hole. The apparent GPS position of the
remote receiver over the placard is compared with the known
position to calculate an error correction for use during play.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 schematically illustrates the display of the preferred
embodiment of the remote unit;
Figure 2 is a block diagram of a remote unit including a GPS receiver
in accordance with the present invention;
Figure 3 is a block diagram of the base station in accordance with the
present invention;
Figure 4 is a block diagram of a cup locator unit used to locate the
position of each golf cup on the respective green;
Figure 5 is a schematic of the packet radio network used to transmit
the error correction;
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Figure 6 is a flow chart depicting the operation of the calibration
sequence for determining the error correction;
Figure 7 comprises the flow charts illustrating the operation of a
remote unit in accordance with the system of the present invention,
where
Fig. 7A is a flow chart of the calibration sequence,
Fig. 7B is a flow chart of the method for determining the
corrected position of the remote unit,
Fig. 7C depicts the method for determining the distance from
the cup to the mark A, and
Fig. 7D shows the flow chart for the method for determining
the distance marks A and B;
Figure 8 depicts the layout of an alternative embodiment of the
control panel of the remote unit;
Figure 9 is a block diagram describing an alternative embodiment of
the remote unit which includes an internal calibration mechanism;
Figure 10 is a schematic of an alternative embodiment of the remote
unit display showing a golf hole layout;
Figure 11 illustrates the pro shop monitor of the preferred
embodiment; and
Figure 12 is a block diagram depicting an alternative system where
the remote units act as repeaters.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention utilizes a global positioning satellite system,
such as Navstar or Glonass (GPS) to determine the approximate
distance from a golf ball to hole features, such as the cup or pin on
the green of the golf hole being played. GPS is a spaced based
system of satellites which can provide to an infinite number of
receivers accurate three dimensional position (i.e. horizontal location
and altitude), velocity, and time. A general understanding of GPS is
useful to appreciate the operation of the present invention.
Numerous books and articles are available on GPS operation and
theory. See e.g., GPS - A Guide to the Next Utility, Trimble
Navigation (incorporated by reference for background).
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THE GLOBAL POSITIONING SATELLITE SYSTEM
The GPS system is an umbrella of satellites circling the earth
passively transmitting signals. Each satellite has a very accurate
atomic clock which is periodically updated. A GPS receiver with an
accurate clock can identify a satellite and determine the transit time
of the signal from the satellite to the receiver. Knowing the transit
time and knowing that the speed of light is 186,000 miles per second
enables a calculation of the distance from the satellite to the receiver.
The signal carries with it data which discloses satellite position and
time of transmission, and synchronizes the aircraft GPS system with
satellite clocks.
If a GPS receiver can locate 3 or 4 satellites it can determine its
distance from each satellite. The intersection of these 3 or 4 spheres
enables a precise location of the receiver (and some compensation for
timing errors in the receiver's internal clock). The GPS system
should have 21 satellites and 3 spares once the system is fully
deployed. Currently about 14 satellites are deployed, giving
reasonable satellite coverage worldwide for most of the day.
There are basically two types of GPS receivers - P (precision) code
and C/A (coarse availability) code. P code is for government use only
and requires specialized equipment. C/A code receivers are
becoming widely available with the continuing deployment of GPS
satellites. One difficulty with C/A code receivers is that the
government from time to time intentionally degrades the satellite
signals - so called "selective availability." With selective availability
turned on horizontal accuracy is on the order of 50 - 100 meters.
With selective availability disabled horizontal accuracy can improve
to around 15 meters.
FIRST EMBODIMENT
Turning to the drawings, the system of the present invention
includes a remote unit 10, base station 12, and cup locator 14. A
remote unit 10 accompanies the golfer during the round - for
example mounted on the golf cart.
As shown in Figure 2, the remote unit 10 include a packet radio
system 20, a GPS antenna 21 and receiver 22, a CPU 24, storage 25, a
display 26, and a control device 28. The GPS receiver 22 is
preferably the multi-channel receiver such as the SV-6 Model made
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by Trimble Navigation of Sunnyvale, California. Other commercially
available substitutes are acceptable such as made by Magellan or
Rockwell/Collins. The antenna 21 is either remote or internal to the
receiver 22, but in any event is mounted on the golf cart for an
upward look angle for optimum GPS signal reception.
As shown in Figure 2, the remote unit 10 includes a CPU 24, control
device 28, nonvolatile memory storage 25, as well as the radio
interface 20 and GPS engine and antenna 22, 21. In the preferred
remote unit, the CPU 24, memory storage 25, and display 26 are
integral, such as the PDA or pen tablet referenced above, and are
collectively referred to as the display 26. The memory storage 25
includes the internal RAM and the PCMCIA cards incorporated with
such a PDA or pen tablet. Of course integration or segregation of the
components of Figure 2 is a simple matter of design choice.
The display 26 of the preferred embodiment, illustrated in Figures 1
and 2, is a pen input display. The pen input display 26 is mounted
on the golf cart and permits the user to directly input commands
with the control device or pen 28. Preferably, the pen display 26 is a
Personal Digital Assistant (PDA) such as the Apple Newton.
Alternatively, the pen display 26 may comprise a pen tablet
computer, either monochrome or color, such as made by Fujitsu, IBM,
Toshiba, and others.
As can be seen in Figure 1, the display 26 includes: a depiction (i.e.,graphic representation) of the layout of the hole l l l; option buttons
112-114; and indicators l lS-117. An icon 118 represents the
location of the remote unit (cart) 10 on the hole being played. A grid
119 comprising distance arcs and distance symbols (50-300 yards in
Fig. l) is overlaid on the hole layout l l l. The option buttons 112
- 114 allow access to other functions and the indicators 115 - 117
display as labeled.
ln Figure 2, the packet radio system 20 is conventional, and includes
modem 34, radio interface 36, and radio 38 (including an antenna,
not shown). The radio system 20 is bi-directional in that it can
receive error correction and other information as well as transmit
present position and messages back to the base station 12. A PAC-
COM, Inc. (Orlando, Florida) packet radio modem 2400 baud for use
with any commercial half duplex radio is believed preferable for the
modem 34.
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As an alternative to the bi-directional radio system 20 of Figure 2~
the radio system 20 may be uni-directional for simply receiving an
error correction (or other message) broadcast to all remote units 10,
e.g. over FM frequencies. The ACTT receiver chip set made by Seiko
is believed preferably. The ACTT chip combines most of the
components of the radio system 20 on a single, low cost, low power
chip which is currently only a receiver. This alternative is
particularly suited for hand-held remote units 10 (vice cart
mounted) .
Figure 3 illustrates the base station 12, which is desirably placed in
or near the pro shop. The base station 12 includes a calibration
section 40 which comprises a GPS receiver 42 and antenna 44. The
calibration section 40 continuously determines apparent position of
the antenna 44 and feeds this information to CPU 46. The CPU is
conventional, such as a 486 type personal computer operating a 66
MHz. The control device 47 preferably includes a mouse and a
standard keyboard.
The course geography database 48 is similarly connected to the CPU
46 and stores course information such as hole layout and the present
position of the cups on the greens for the day. A monitor 50 is
coupled to CPU 46 and is useful not only for initialization, but also is
selectable to display the present position of all the remote receiver
units 10 on the course. The base station 12 includes a packet radio
system similar to Figure 2 coupled to the CPU 46, and comprises
modem 52t interface 54, radio 56 and radio antenna 58.
The monitor 50 is capable of displaying the golf course 130 as shown
in Figure 11. The remote units (carts) 10 are shown on the various
holes and represented as "plus" icons in Figure 11 color coded as
shown. The "$" symbol represents a service request as shown, such
as a cart requesting beverage service.
The Cup Locator 14 is illustrated in Figure 4 and as can be seen is
nearly identical to the remote unit of Figure 2. A CPU 60 is coupled
to a GPS receiver 62 which includes an antenna 64. Memory 66 is
coupled to CPU 60 and stores the location of each cup as the cup
locator 14 is moved from green to green. The location of each cup
may alternatively be transmitted to the base station 12 using modem
68, radio interface 70, and radio 72.
OPERATION
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Figure 5 illustrates schematically the operation of the system of the
present invention. The cup locator unit 14 (Fig. 4) is transported
from green to green when the location of the cups are changed. The
greens keeper positions the cup locator unit 14 over the new cup and
allows a few seconds for the GPS receiver 62 to determine an
apparent cup location. The longer the greens keeper permits
acquisition the more samples are obtained and accuracy is increased.
The first cup might take several minutes while the GPS receiver 62
consults its almanac and locates the satellites in view, a so-called
"cold start." Determining the location of the cups should take only a
few seconds to determine an apparent location once the GPS receiver
62 has operated for several minutes. Because the GPS receiver of
Figure 4 is a C/A code receiver, its accuracy is about 15 meters
(selective availability disabled) with a worst accuracy of about 100
meters .
The greens keeper switches an "enter" pad (not shown) and hole
number for each cup. Preferably, the timing signals from the 4 - 10
satellites in view are stored in memory 66 of the cup locator.
Accuracy is improved by letting the cup locator 14 acquire multiple
samples of each satellite timing signal. The apparent cup locations
are downloaded and stored in a course geography database in the
storage 48 of Figure 3. Additionally, the course layout is stored in
the database 48. After the cup apparent locations are downloaded
an error correction is applied to obtain a corrected position for each
cup. The corrected position is preferably transmitted over the
packet radio system to update the memory 25 of each remote unit
10 before play.
In the preferred embodiment, the uncorrected or apparent cup
locations are loaded into the base station computer 46 for so-called
"post processing" error correction. That is, using conventional
differential techniques, the timing signal for each satellite for each
apparent location is compared with the same satellite timing signal
for the apparent position of the base station. In this fashion, a very
accurate correction for each timing signal for each satellite can be
computed at the base station for the time the apparent cup locations
were acquired. Each apparent cup location may have associated with
it many (e.g. 4- l O) satellite timing signals. Correcting these timing
signals gives very accurate cup locations. Conventional surveying
differential correction can achieve cup locations with an accuracy of
2134~3~
several centimeters by looking at carrier phase and other known
parameters. It is believed that simple position correction of the
timing signals will achieve accuracies on the order of .25 meter
which is believed sufficiently accurate for the present application.
See e.g., Differential Correction, by Trimble Navigation (incorporated
by reference for background).
Correcting the apparent cup locations as accurately as possible is
advantageous. Without correction, the following error are present:
satellite clock error; receiver error; atmospheric/ionispheric errors;
selective availability errors (if enabled); and ephemeris errors.
Because these errors change over time, it is necessary during post
processing to apply the timing signal corrections for the time the
apparent cup locations were acquired.
Alternatively, the apparent position of the respective cup is
transmitted to the base station and also stored in memory 66. As
shown in Figure 4, the modem 68 receives the digital information
representing the cup number and apparent location and modulates
an analog signal with the digital information. The modulated signal
passes through interface 70 to radio 72 where it is transmitted to the
base station 12. Figure 5 shows schematically the passage of the
radio transmission over the packet network to the base station 12.
Typically, the greens keeper would return to the base station after
the cups are changed and verify that the cup information had been
transmitted correctly - if not, the cup information stored in memory
66 would be downloaded to the base station 12.
In this alternative, the calibration system 40 operates to calculate
and apply an error correction to the cup apparent locations as they
are received over the packet radio system at the base station 12.
These corrected cup locations are stored in the course geography
database for later use. In this alternative method, the error is
minimized by minimizing the time between acquisition and
application of the error correction. By transmitting apparent cup
location over the packet network and immediately applying an error
correction, all GPS receivers are primarily observing the same
satellites and have the same errors. Of course the post processing
method of the preferred embodiment is more accurate.
As shown in Figures 3 and 5, during normal play the base station 12
performs continuous calibration. During calibration, the GPS receiver
42 continuously calculates its apparent position. The antenna 44 is
l O
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placed at a known location. The difference between the apparent
position and the known location is the current error correction. This
technique is known as "differential GPS" and has been applied in land
surveying techniques. Because the satellites are so high compared to
the distance between the cup locator receiver 62 and the calibration
receiver 44, this differential error correction accounts for most of the
possible errors in the system. In the preferred embodiment, the
error correction may comprise a vector or position correction which
is reasonably accurate if the remote units are using the same
satellites as the base station to find apparent position. Alternatively,
the error correction comprises a timing correction or "delta" for the
timing signals of the satellites in view. With an uncorrected accuracy
of 10-15 meters, the calibrated or corrected accuracy is less than 5
meters in all cases, and normally approaches 1 meter accuracy.
When players are on the course, the current error correction is
transmitted periodically to all remote units 10 on the packet radio
network (Fig. 5). Preferably, once every five to fifteen seconds a
small time window (e.g. .5 second) is opened on each remote unit 10
for reception of the current error correction. The flow chart of the
calibration software routine is illustrated in Figure 7A where the
calibrate loop is run every 5-15 seconds.
Turning to Figure 2 the remote unit is preferably mounted on a golf
cart. Current hardware technology dictates a size, weight, and power
requirement that makes golf cart mounting the most feasible.
However, miniaturization should enable an embodiment that is hand
held in the near future.
The remote unit 10 preferably continuously operates to calculate the
distance from the unit 10 to the cup on the hole being played. As
shown in Figure 7B the GPS receiver 22 determines an apparent
position and then reads the current error correction stored in
memory 25. The CPU 24 applies the current error correction to the
apparent position to calculate a corrected position. The corrected
position is compared to the corrected cup location retrieved from
memory 25 and the difference is determined and shown as the
distance to the pin on display 26. In the preferred embodiment the
error correction comprises a number of timing signal corrections for
particular satellites useful during the 15 second calibration loop. The
CPU 24 applies these timing signal corrections to its apparent
position timing signals.
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Use of the display of Figure 1 is matched to the players abilities. If
the player does nothing, the grid 11 9 is displayed every time the
cart (i.e. remote unit) 10 stops and has its origin at the cart. In this
case, both indicators 11 6 and 11 7 display the same number which is
the distance from the cart to the cup location. By looking at the grid,
the player can also tell approximate distances to other features, such
as the distance to carry a hazard or to lay up short of a hazard. The
cart symbol 11 8 is always present and shows the position of the cart
on the hole layout 111. The player need to touch the arrows of the
"Hole" indicator 115 with the pen 28 to increment (or decrement) the
hole being played - i.e. when hole 17 is complete the player touches
the top arrow of indicator 115 to increment and display hole 18.
The preferred embodiment employs a method to determine if the
cart is stopped. If the cart is stopped, the grid 119 snaps onto the
display and the cart (remote unit 10) does not re-transmit its
location to the base station 12 (to reduce bandwidth requirements).
Additionally, when sopped, the GPS receiver 22 may begin averaging
apparent position measurements to obtain a more accurate "apparent
position." The method to determine if the cart is stopped compares
the apparent positions of the cart (typically 2 samples) to the
selective availability error (Derror). If both samples are within 1
meter, then the cart is assumed to be stopped. Selective availability
error (Derror) is believed to be not more than 1 meter per 5 seconds
and although random, if a cart is stopped the 2nd sample would be
within 1 meter of the 1st sample if the cart is stopped. If the 2nd
sample is greater then 1 meter, then the cart is assumed to be
moving and the 2nd sample becomes the new current apparent
position.
If the player chooses to use the expanded features, more options are
available. If the player touches the hole layout 111 with the pen 28
the grid snaps to the location touched and the indicator 11 6 indicates
the yardage to the pin from the apex or origin of the grid. In Figure
1, the player has touched the middle tee box (where the player will
place the ball) to more accurately judge distances to hazards. This
feature is particularly useful for hole, shot planning, or estimating
driving distance. For example, the player might touch the hole
layout 1 11 between the 150 and 200 yard grid arcs to determine a
target 110 yards from the pin for hitting the player's next shot.
Another feature is the icon 120 depicting the nearest cart of the
group playing ahead. As can be seen, the icon 120 is about 230
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yards ahead, so tee-off can safely be made if no club is expected to
approach the 230 yard distance. This ability to determine distance
to the cart ahead speeds up play while preserving game etiquette,
and is particularly useful where the cart ahead cannot be seen, so-
called blind holes. The preferred embodiment simply shows all carts
(remote units) 10 on the hole being played.
The option buttons 112 - 114 allow the player to access "tips" (e.g.
caddie hints), "drinks," and "more" respectively. The tips are just
that - memory storage 25 contains caddie hints for the current
location of the cart. For example, here the hint might state "aim
between the far trap and the green and carry the trap". The "more"
menu allows the player to access other options, such as a scorecard
where the player can enter scores for the round for each player or
food service. If desired, the scores can be transmitted over the radio
network and downloaded to the base station 12 for handicap input
and is particular useful during tournaments. The "drink button
allows the player to order drinks, either for immediate delivery. As
shown in Figure 12, if a player requests immediate food or beverage,
the monitor 130 reflects the request and the delivery person can be
dispatched.
Figure 7C illustrates the flow chart for determining the distance from
the mark "A" to the pin (e.g. Fig. 11), while Fig. 7D depicts the
determination of the distance from mark "A" to mark "B". The
method for determining the distance from the remote unit 10 to the
mark "A" is almost identical to the method of Fig. 7C with the
position of the cart compared to the Mark coordinates instead of the
position of the pin.
The accuracy of determining a distance to a " mark" or between
" marks" is dependent upon screen resolution. There are several
conventional methods for determining distance between marks on a
screen or monitor, with Figs. 7C and 7D illustrating one approach. A
rectangular projection is defined as a grid encompassing the entire
hole being played with the latitude and longitude of an origin (e.g.
Iower left corner) defined. The units of the rectangular projection
are real numbers that correspond to actual distances from the origin.
The pixels on the screen (SP) can be mapped to the rectangular
projection points (RP) as:
RP = m SP + b RP = m SP +b
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where
m = dx m = dy
b = dx - m dS b = dy - m dS
Several methods are available for determining the distance between
the marks or the pin or cart to a mark. In a preferred method, the
mark and coordinates of the cart (for example) are converted to
radians in meters from an origin (such as the prime meridian and
equator) .
Alternatively, the distance form mark A to the cart can be
determined trigonometrically. The distance between the cart and pin
are known and the angle between the cart/pin vector to the cart/
mark vector can be ascertained from the screen. The magnitude of
the cart/mark vector can be determined.
In the preferred embodiment the remote unit 10 calculates and
displays a distance from the unit 10 to the cup (or an arbitrary green
location), it receives a current error correction every 5 - 15 seconds,
and additionally, transmits a current position to the base station
every 5 - 15 seconds. This allows the course marshal or pro to view
the monitor in Figs. 3 and 12 to consider the position of every remote
unit on the course.
SECOND EMBODIMENT
Figure 9 illustrates an alternative embodiment remote unit 80 which
is preferably mounted on a golf cart or hand carried. In the system
of Figure 9 the base station is eliminated as well as the packet radio
system. The remote unit 80 includes a GPS receiver 82, GPS antenna
84, CPU 86, display 88, control device 90, storage 92 and calibration
94. The hardware may be the same as in the preferred embodiment
but for the hand carried remote unit power requirements is a factor
in hardware selection.
1 4
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In particular, the storage 92 similarly contains a course geography
database, but in addition contains the location of a calibration
location for each hole. Such a calibration location is preferably a
placard on the ground in the cart path adjacent the tee box for the
hole being played. In the alternative embodiment, a control device
like Figures 1 or 8 is used with keypad "6" being additionally labeled
with the notation "Calibrate." The calibration box 94 in Figure 9 is
preferably EEPROM and contains the calibration routine of Figure 6.
Of course the calibration routine could alternatively be stored in
Storage 92.
In use, the present position of the cups for each hole is loaded in the
course geography database in storage 92. Preferably the cup locator
of Figure 4 is used with the packet radio system eliminated. The cup
locations are stored in memory 66 and transferred to the remote unit
80. Without calibration and with a C/A code receiver 82, the remote
unit 80 will give distance accuracies within 100 meters (S/A
enabled) and within 20 meters (S/A disabled). Of course technical
improvements in GPS technology might improve on this accuracy to
some degree.
To improve these accuracies a calibration procedure is utilized. The
golfer places the remote unit 80 over a placard in the cart path, calls
up the display for the hole being played, and presses "Calibrate" pad
6. The routine of Figure 6 is initiated, and an error correction is
determined by comparing the current apparent GPS position with the
GPS position stored for the hole placard. This calibrate procedure
gives a reasonably accurate error correction for the duration of play
for the hole. If a player forgets to calibrate for a hole the previous
error correction is simply carried over and applied.
Accuracy is largely dependent on the desires of the golfer. With
Selective Availability disabled (or perhaps with a wide area
differential correction or pseudolite) accuracy within I meter should
be possible on most holes if a calibration is performed every hole. If
the system is calibrated by the pro shop before play, accuracy is
estimated to be quite good (e.g. < 3 meters) for several hours until
new satellites come into view and use.
TH~D EMBODIMENT
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The display 26 of Figure 10 is preferably a 640 x 480 pixel LCD
supertwist, ISA bus compatible display, but other conventional types
of displays are operable. The display depicts the layout of the hole
being played, as well as a distance box 30 and present position icon
33. The CPU 24 is preferably an 8088 CMOS microprocessor operable
at 10 MHz and ISA bus compatible. A control device 28 is coupled to
the display 26 so that the player can optionally position one or two
markers on the hole layout.
Figure 8 illustrates one embodiment of the control device 28. The
four direction keys 110 are used for marking locations on the hole
(see Fig. 10, marks A and B). The twelve function keys 112 operate
to function as labeled. While a pen based control system might be
preferable functionally to the device 28 illustrated in Fig. 8, cost
considerations prompted the choice of the device 28.
The storage 25 is preferably includes nonvolatile memory which
stores a database of the hole layouts, as well as the corrected location
of the cup on each hole. Battery backed-up RAM is preferred, but
other alternatives are operable and offer some advantages, such as a
WORM optical disc coupled to RAM or EEPROM. Volatile memory
stores the current error correction.
Figure 10 illustrates operation of this embodiment. In Figure 10, the
far left space in box 30 shows the distance from the remote unit 10
to the cup. Preferably, the remote unit 10 is placed as close as
possible to the ball so the distance readout in box 30 "CART TO PIN"
is an accurate reflection of the distance of the ball to the pin.
The player can also visually track the progress of the icon 33
-representing the remote unit 10 as the golf cart progresses on the
hole layout from tee 32 to green 101. For shot planning, the player
can mark a location (e.g., "A") on the display 26 using the pointing
device 28. The CPU calculates an approximate distance from the icon
33 to the mark "A" and displays the distance to the player in the
space of box 30 labeled "CART TO A".
For example, Fig. 10 represents a 520 yard par 5 with water 102 on
the left side and in front of an elevated green 101. Trees 103 in the
rough 104 and the fairway 105, as well as a trap 107 in front of the
green are factors. If the player hits to position A and positions the
remote unit 10 near the ball, the far left space in box 30 might read
230. This does not necessarily mean the player hit a 290 yard drive.
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The 230 yard reading is the direct line from the remote unit 10
(adjacent the player's ball) to the cup 106, which is placed at the
front of the green 101. Additionally, the tee markers might have
been placed forward of the nominal 520 yard placard.
The player might mark the display 26 at position B with the pointing
device 28. The far right space on box 30 labeled "B TO PIN" would
read the approximate distance 175. The preferred embodiment is
configured such that if the player marks "B" with the pointing device
28, both the approximate distance from the cup/pin 106 to position B
as well as the approximate distance from "A" to "B" is shown in box
30. This feature allows a player to quickly and effectively consider
his options - for example the player might attempt a fairway wood
from "A" to the green 101 or layup to position B for a wedge to the
length of the green 101.
FOURTH EMBODIMENT
This embodiment is illustrated in Figure 12. The GPS "engine" is
elimin~ted in the remote units. Rather, each remote unit 10
comprises a GPS repeater, such as a Tidget GPS sensor made by
Navsys Corp. of Edinburgh, Scotland. The repeater 120 operates to
receive the GPS raw data timing signals from the GPS satellites,
digitize and compress the timing signals. Preferably, the repeater
120 can be set to look at a certain number of satellites, e.g. 5
satellites. The satellite timing signals are not processed. Instead, the
signals are amplified and periodically relayed to the base station 12.
Different signal processing techniques may be employed if desired,
such as filtering and compressing. The base station collects each
timing signal from the repeaters and processes the timing signals to
determine a location of the repeater.
The base station 12 can employ the amount of processing desired to
the timing signals to improve the accuracy estimation of -the repeater
- commensurate with the time available, the processing load,
accuracy desired, etc. If desired, a distance to the green cup for the
repeater can be transmitted and displayed on the cart of the
repeater.
In Figure 12 a preferred embodiment of such a repeater system is
illustrated. Each repeater 120 includes an identification. Each
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repeater 120 is allocated, for example, an 80 millisecond transmit
and a 20 millisecond receive time window. Because the base station
12 and all of the repeaters 120 have accurate GPS timing signals,
such a time window allocation is possible. A repeater 120 receives
timing signals from 4 satellites and stores the signals in a temporary
memory buffer (compressing if desired) for transmission in its
allocated time window. The timing signals include an identification of
the satellite.
The base station 12 receives the timing signals from a certain
repeater 120 in the repeater's allocated timing window. The base
station has already coprocessed a timing correction for each satellite
timing signal, and therefore can apply the correction upon receipt of
the repeater timing signal. The repeaters 120 are receiving the
timing signals from predominantly the same satellites, so the base
station needs to only keep a current correction for a limited number
of satellites. Using the corrected timing signals, the base station can
accurately process the repeater timing signals to derive a location of
the repeater on the golf course.
This embodiment uses the repeater location and compares the
location with a database of golf cup locations (or an arbitrary location
on the green such as center of the green). The difference is the
distance from the repeater 120 to the cup location. This distance is
transmitted to the repeater 120 in the 20 millisecond time window
allocated for that repeater. The distance is displayed on the cart to
give the golfer a distance to the pin estimation.
This embodiment contemplates the use of time windows to avoid the
communication overhead associated with hand shake protocols. With
this method, it is believed that repeaters on 50 carts may transmit
their timing signals and receive a distance to the pin estimation with
an update rate every 5 seconds. From the golfers perspective, a new
distance to the cup estimation is displayed every 5 seconds. In the
pro shop, the position of the carts on the course is refreshed every 5
seconds.
Alternative configurations of this embodiment exist in many forms.
For example, the repeater may take the form factor of a digital pager
and even be hand carried. Additionally, instead of allocating time
windows, the repeater 120 may include a query button which upon
activation by the golfer transmits the latest satellite timing signals
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which are immediately processed and the distance estimation
returned .
It should be readily apparent that a primary advantage of this
embodiment is reduced cost of the remote receiver hardware. A
repeater with a communications link and a simple LED display is all
that is required as the remote unit. Another advantage is the small
size possible and reduced power requirements. Disadvantages are
the processing load required at the base station, a heavy
communications load, and the dependence on the communications
link.
FIFTH EMBODIMENT
With the advent of inexpensive higher resolution displays, this
embodiment contemplates distance estimations from the remote unit
to the golf cup location without the use of GPS or other location
identifier (e.g. Loran or radio triangulation) in the remote unit. A
pen display such as shown in Figure 1 is used, preferably with a
resolution greater than 1020 x 680 pixels. For a 500 yard golf hole
length, this gives about 2 pixels per yard; for a 200 yard golf hole
there are about 5 pixels per yard.
For example on the 500 yard golf hole, the golfer is about 200 yards
from the green and accordingly touches the display with the pen at
the approximate location of the ball on the display. The display
immediately zooms to include the portion of the golf hole from the
green to the designated location plus about 10%. In this example, the
portion of the golf hole display after the zoom is approximately 220
yards. With the new 220 yard display, the golfer can redesignate the
location of the ball on the display with the pen 28. The redesignation
is obviously more accurate because there are now about 5 pixels per
yard. Golfers can be expected to designate their position on a display
within 20 pixels, so the error in designation is within 4 yards.
To improve accuracy, the location of the golf cup on the green is
preferably loaded into a database in the remote unit. That is, a GPS
unit is used to survey the location of the golf cup on the green within
1 yard and this database is loaded whenever the location of the cups
are changed. If center of the green locations are used as nominal cup
locations, accuracy is degraded.
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Alternative Embodiments
Other alternatives are of course possible. By way of nonlimiting
example, the display 26 can be replaced with a simple LED which
only displays distance from the remote unit to the cup. Additionally,
the cup locator unit 14 can be elimin~ted with the greens keeper
simply manually entering the approximate grid coordinates of each
cup into the base station 12. Obviously, if the course does not want
to set in the approximate grid coordinates of each cup, a nominal
grid coordinate, e.g. center or front of the green, can be entered for
each green, but accuracy is obviously reduced. The term "cup
position" or "cup location" should be understood to include a
measured location or a static grid location, such as nominally the
center of the green. The terms "cup" and "pin" are often used
interchangeably in this application. "Global Positioning Satellite
System" includes the U.S. Navstar system, the Russian Glonass, and
future analogous systems, such as the proposed system of the
European Community.
