United States Patent |
6,414,629 |
Curcio |
July 2, 2002 |
Tracking device
Abstract
A tracking system includes a target unit having a GPS receiver, a signal
transmitter to send a signal including a position of the target unit; and a
processor to calculate an optimal time interval for transmission of the signal.
A locating unit has a GPS signal receiver, a compass to provide a reference
direction of the locating unit, a signal receiver to receive the signal sent by
the transmitter of the target unit, a processor to calculate a range and bearing
from the locating unit to the target unit, and an indicator to display the range
and bearing. In certain preferred embodiments, the processor calculates a
confidence level indicating the reliability of the signal being sent.
Inventors: |
Curcio; Joseph A. (Gray, ME) |
Assignee: |
Tektrack, LLC (Gray, ME) |
Appl. No.: |
837979 |
Filed: |
April 19, 2001 |
Current U.S. Class: |
342/357.08 |
Intern'l Class: |
G01S 005/02; H04B 007/185 |
Field of Search: |
342/357.08,357.07,357.09,357,14
|
References Cited
U.S. Patent Documents
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Youhanaie |
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5379045 |
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Gilbert et al. |
342/357. |
5389934 |
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Kass |
342/357. |
5488559 |
Jan., 1996 |
Seymour |
364/449. |
5502446 |
Mar., 1996 |
Denninger |
342/357. |
5554994 |
Sep., 1996 |
Schneider |
342/357. |
5589835 |
Dec., 1996 |
Gildea et al. |
342/357. |
5629678 |
May., 1997 |
Gargano et al. |
340/573. |
5689269 |
Nov., 1997 |
Norris |
342/357. |
5702070 |
Dec., 1997 |
Waid |
244/183. |
5739785 |
Apr., 1998 |
Allison et al. |
342/357. |
5752218 |
May., 1998 |
Harrison et al. |
701/207. |
5781150 |
Jul., 1998 |
Norris |
342/357. |
5784339 |
Jul., 1998 |
Woodsum et al. |
367/134. |
5852401 |
Dec., 1998 |
Kita |
340/521. |
5923294 |
Jul., 1999 |
Bacelon et al. |
342/457. |
6040766 |
Mar., 2000 |
Lubke et al. |
340/438. |
6043777 |
Mar., 2000 |
Bergman et al. |
342/357. |
6049304 |
Apr., 2000 |
Rudel et al. |
342/357. |
6327535 |
Dec., 2001 |
Evans et al. |
342/357. |
Foreign Patent Documents |
0 524 771 |
Jan., 1993 |
EP. |
|
Primary
Examiner: Tarcza; Thomas H.
Assistant Examiner: Mull; Fred H
Attorney, Agent or Firm: Banner & Witcoff, Ltd.
Claims
What is claimed is:
1. A tracking system comprising, in
combination: a target unit having a GPS receiver, a signal transmitter
to send a signal including a position of the target unit, and a processor to
calculate an optimal time interval for transmission of the signal; and a
locating unit having a GPS signal receiver, a compass to provide a reference
direction of the locating unit, a signal receiver to receive the signal sent by
the transmitter of the target unit, a processor to calculate a range and bearing
from the locating unit to the target unit, and an indicator to display the range
and bearing.
2. The tracking system of claim 1, further including a
sensor to detect motion of the target unit, the processor of the target unit
calculating the optimal time interval based on motion of the target unit.
3. The tracking system of claim 2, wherein the sensor is an
accelerometer.
4. The tracking system of claim 1, wherein the processor
of the locating unit calculates a confidence level attributed to the signal sent
by the target unit.
5. The tracking system of claim 4, wherein the
confidence level is displayed by the indicator as a percentage.
6. The
tracking system of claim 1, wherein the processor of the target unit calculates
a confidence level to indicate a reliability of the signal sent by the target
unit.
7. The tracking system of claim 1, wherein the indicator displays
an arrow showing the bearing from the locating unit to the target unit, and the
range from the locating unit to the target unit.
8. The tracking system
of claim 1, wherein the indicator includes a graphical display of relative
positions of the locating unit and the target unit.
9. The tracking
system of claim 1, wherein the signal sent by the transmitter of the target unit
is an RF signal.
10. The tracking system of claim 1, wherein the
locating unit includes a transmitter and the target unit includes a receiver,
the transmitter of the locating unit sending another signal to the receiver of
the target unit to provide data regarding the signal sent from the target unit
to the locating unit.
11. The tracking system of claim 1, wherein the
locating unit includes a speaker to provide the range and bearing via an audible
signal.
12. The tracking system of claim 1, further comprising a water
detector configured to prompt the signal transmitter to send the signal when the
target unit comes in contact with water.
13. The tracking system of
claim 1, wherein the signal includes information in addition to the position of
the target unit.
14. The tracking system of claim 13, wherein the signal
includes data regarding a reliability of the signal sent from the target unit to
the locating unit.
15. The tracking system of claim 13, wherein the
signal includes an identifier unique to the target unit.
16. The
tracking system of claim 13, wherein the signal includes information regarding a
path that the target unit has traveled over a selected period of time.
17. The tracking system of claim 16, wherein the information regarding
the path includes velocity and direction information.
18. The tracking
system of claim 13, wherein the signal includes data regarding a projected path
of the target unit.
19. The tracking system of claim 13, wherein the
signal includes a predetermined test signal known by the locating unit.
20. The tracking system of claim 1, further including an accelerometer
to detect motion of the locating unit.
21. A tracking system comprising,
in combination: a target unit having a GPS receiver, and a signal
transmitter to send a signal including a position of the target unit; and
a locating unit having a GPS signal receiver, a compass
to provide a reference direction of the locating unit, a signal receiver
to receive the signal sent by the transmitter of the target unit, a
processor to calculate a range and bearing from the locating unit to the target
unit and a confidence level attributed to the signal sent by the target unit,
and an indicator to display the range, bearing and confidence level.
22. The tracking system of claim 21, wherein the confidence level is
displayed as a percentage.
23. The tracking system of claim 21, wherein
the indicator displays an arrow showing the bearing from the locating unit to
the target unit, and the range from the locating unit to the target unit.
24. The tracking system of claim 21, wherein the indicator includes a
graphical display of relative positions of the locating unit and the target
unit.
25. The tracking system of claim 21, wherein the locating unit
includes a speaker to provide the range and bearing via an audible signal.
26. The tracking system of claim 21, further comprising a processor to
calculate an optimal time interval for transmission of the signal.
27.
The tracking system of claim 26 further including a sensor to detect motion of
the target unit, the processor of the target unit calculating the optimal time
interval based on motion of the target unit.
28. The tracking system of
claim 27, wherein the sensor is an accelerometer.
29. The tracking
system of claim 21, further comprising a water detector configured to prompt the
signal transmitter to send the signal when the target unit comes in contact with
water.
30. The tracking system of claim 21, wherein the signal includes
information in addition to the position of the target unit.
31. The
tracking system of claim 30, wherein the signal includes an identifier unique to
the target unit.
32. The tracking system of claim 30, wherein the signal
includes information regarding a path that the target unit has traveled over a
selected period of time.
33. The tracking system of claim 32, wherein
the information regarding the path includes velocity and direction information.
34. The tracking system of claim 30, wherein the signal includes data
regarding a projected path of the target unit.
35. The tracking system
of claim 30, wherein the signal includes a predetermined test signal known by
the locating unit.
36. The tracking system of claim 21, further
including an accelerometer to detect motion of the locating unit.
37. A
system to transmit the location of an object or individual associated with the
system comprising, in combination: a GPS receiver to determine a
position of a device; a signal transmitter to send a signal including
the position of the device; and a processor to calculate an optimal time
interval for transmission of the signal.
38. The system of claim 37,
further including a sensor to detect motion of the device, the processor
calculating the optimal time interval based on the motion of the device.
39. The system of claim 38, wherein the sensor is an accelerometer.
40. The system of claim 37, wherein the processor calculates a
confidence level attributed to the signal.
41. The system of claim 37,
wherein the signal sent by the transmitter is an RF signal.
42. The
system of claim 37, wherein the signal includes information in addition to the
position of the device.
43. The system of claim 42, wherein the signal
includes an identifier unique to that transmitter.
44. The system of
claim 42, wherein the signal includes data regarding a reliability of the
signal.
45. The tracking system of claim 42, wherein the signal includes
information regarding a path that the target unit has traveled over a selected
period of time.
46. The tracking system of claim 45, wherein the
information regarding the path includes velocity and direction information.
47. The tracking system of claim 42, wherein the signal includes data
regarding a projected path of the target unit.
48. The tracking system
of claim 42, wherein the signal includes a predetermined test signal known by
the locating unit.
49. The system of claim 37, further comprising a
water detector configured to prompt the signal transmitter to send the signal
when the target unit comes in contact with water.
50. A tracking system
to track the location of an object in water comprising, in combination:
a target unit having a GPS receiver to determine a position of the
target unit, a sensor to detect motion of the target unit, a processor to
calculate when the target unit is proximate a crest of a wave, a signal
transmitter to send a signal including the position of the target unit when the
target unit is proximate a crest of a wave; and a locating unit having a
GPS signal receiver, a compass to provide a reference direction of the locating
unit, a signal receiver to receive the signal sent by the transmitter of the
target unit, a processor to calculate a range and bearing from the locating unit
to the target unit, and an indicator to display the range and bearing.
51. The tracking system of claim 50, wherein the sensor includes an
accelerometer.
52. The tracking system of claim 50, wherein the
processor of the locating unit calculates a confidence level attributed to the
signal sent from the target unit to the locating unit.
53. The tracking
system of claim 52, wherein the confidence level is displayed by the indicator
as a percentage.
54. The tracking system of claim 50, wherein the target
unit includes a water detector that prompts the signal transmitter to send the
signal when the target unit comes in contact with water.
55. The
tracking system of claim 50, wherein the signal includes information in addition
to the position of the target unit.
56. The tracking system of claim 55,
wherein the signal includes an identifier unique to the target unit.
57.
The tracking system of claim 55, wherein the signal includes information
regarding a path that the target unit has traveled over a selected period of
time.
58. The tracking system of claim 57, wherein the information
regarding the path includes velocity and direction information.
59. The
tracking system of claim 55, wherein the signal includes data regarding a
projected path of the target unit.
60. The tracking system of claim 55,
wherein the signal includes a predetermined test signal known by the locating
unit.
61. The tracking system of claim 48, further including an
accelerometer to detect motion of the locating unit.
62. A method of
tracking a target unit from a locating unit comprising the steps of:
receiving a GPS signal at a target unit to determine a location of the
target unit; receiving a GPS signal at a locating unit tracking the
target unit to determine a location of the locating unit; calculating an
optimal time interval for transmission of a signal from the target unit to the
locating unit, the signal including the GPS location of the target unit;
transmitting the signal from the target unit to the locating unit during
the optimal time interval; calculating a range and bearing from the
locating unit to the target unit.
63. The method of claim 62, further
comprising the step of displaying the range and bearing from the locating unit
to the target unit.
64. The method of claim 62, further comprising the
step of calculating a confidence level attributed to the signal sent from the
target unit to the locating unit.
65. The method of claim 62, wherein
the target unit includes a sensor to detect motion of the target unit and the
optimal time interval is calculated based on the motion of the target unit.
66. The method of claim 65, wherein the sensor is an accelerometer.
67. The method of claim 62, wherein the locating unit includes an
accelerometer to detect motion of the locating unit.
68. A tracking
system comprising, in combination: a tracking unit having a GPS
receiver, a signal transmitter to send a signal including a position of the
tracking unit, a signal receiver configured to receive a signal sent by a
transmitter of at least another tracking unit, a processor configured to
calculate a range and bearing from the tracking unit to at least another
tracking unit and a confidence level attributed to a signal sent by at least
another tracking unit, a compass to provide a reference direction of the
tracking unit, and an indicator configured to display the range and bearing to
at least another tracking unit.
69. The tracking system of claim 68,
wherein the processor is configured to calculate an optimal time interval for
transmission of the signal.
70. The tracking system of claim 68, further
including a sensor to detect motion of the tracking unit, the processor
calculating an optimal time interval for transmission of a signal based on
motion of the tracking unit.
71. The tracking system of claim 70,
wherein the sensor is an accelerometer.
72. The tracking system of claim
68, wherein the confidence level is displayed by the indicator as a percentage.
73. The tracking system of claim 68, wherein the indicator is configured
to display an arrow showing the bearing from the tracking unit to at least
another tracking unit, and a range from the locating unit to at least another
tracking unit.
74. The tracking system of claim 68, wherein the
indicator is configured to include a graphical display of relative positions of
the tracking unit and at least another tracking unit.
75. The tracking
system of claim 68, wherein the tracking unit includes a speaker to provide the
range and bearing via an audible signal.
76. The tracking system of
claim 68, further comprising a water detector configured to prompt the signal
transmitter to send the signal when the tracking unit comes in contact with
water.
77. The tracking system of claim 68, wherein the signal includes
data regarding a reliability of the signal sent by the tracking unit.
78. The tracking system of claim 68, wherein the signal includes an
identifier unique to the tracking unit.
79. The tracking system of claim
68, wherein the signal includes information regarding a path that the tracking
unit has traveled over a selected period of time.
80. The tracking
system of claim 79, wherein the information regarding the path includes velocity
and direction information.
81. The tracking system of claim 68, wherein
the signal includes data regarding a projected path of the tracking unit.
82. The tracking system of claim 68, wherein the signal includes a
predetermined test signal.
Description
INTRODUCTION
The present invention is directed to a tracking
device, and, more particularly, to a device for tracking an individual or an
object, having improved reliability.
BACKGROUND
Personal
tracking devices have been found to be extremely useful in locating lost objects
and, more importantly, missing persons. Such tracking devices typically use a
network of Global Positioning Satellites (GPS) in low earth orbit that broadcast
precise timing signals from on-board atomic clocks. Using triangulation
formulas, a device that picks up signals from several satellites simultaneously
can determine its position in global coordinates, namely latitude and longitude.
A device with a GPS receiver has a 24 hour a day line-of-sight view to a
sufficient number of satellites at any spot on the earth such that a person with
a GPS receiver is able to determine their own longitude and latitude to within
several meters, as well as their elevation. However, the fact that an individual
knows their own position in longitude and latitude does not help others find
them without extremely precise topographical or geophysical maps, which also
show longitude and latitude. Furthermore, the degree of precision in position
determination is then only accurate to the resolution of the maps on hand and to
the degree of accuracy provided by the GPS hardware.
Dead-reckoning is
well known as a method of guiding ships, whereby the known velocity and
direction of travel of a ship from a known position is used to calculate the
current position of the ship. However, the further the ship moves away from the
known position, the less accurate the dead-reckoning position becomes. Adverse
weather conditions can also erode the accuracy of navigation by dead-reckoning.
With a GPS receiver and a very accurate map, a ship can be guided with a
suitable degree of precision. However, due to the possibility of military uses
of the GPS system by adversaries, the GPS timing signals broadcast by the
satellite network for commercial use are intentionally made less accurate than
GPS signals that are encoded for military uses. These timing and position errors
are known as Selective Availability (SA), and reduce the accuracy of civilian
users of the GPS signals. This reduced accuracy may not be suitable for tracking
objects and individuals, and, therefore, can erase the benefits of the GPS
technology.
U.S. Pat. No. 5,781,150 to Norris discloses a tracking
device having an RF transmitter and an RF receiver, each of which have a
built-in GPS receiver. The transmitter sends its GPS position via an RF signal
to the receiver, which in turn calculates the position of the transmitter
relative to that of the receiver. The receiver then displays range and bearing
information regarding the transmitter's location with respect to the receiver.
Norris is limited in that such a device provides no information
regarding the reliability of the RF signal sent. Additional problems are
encountered when using such a GPS system in a man-overboard situation. A radio
transmitter that relies on "line of sight" from its antenna to a receiver for
reliable transmission is subject to potential signal loss when operated at the
surface of the sea. Waves can obscure the direct line of sight of the antenna,
and may tend to submerge the transmitting antenna. This is particularly true for
a transmitter that is worn or carried by a person floating on the surface of the
water. Transmission of a signal, such as an RF signal, can be obscured by waves,
and the transmitter can be subject to immersion, resulting in wasted energy and
signal loss. This results in shortened transmitter battery life and decreased
transmission reliability.
It is an object of the present invention to
provide a tracking device that reduces or wholly overcomes some or all of the
difficulties inherent in prior known devices. Particular objects and advantages
of the invention will be apparent to those skilled in the art, that is, those
who are knowledgeable or experienced in this field of technology, in view of the
following disclosure of the invention and detailed description of preferred
embodiments.
SUMMARY
The principles of the invention may be used
to advantage to provide a tracking device for locating lost individuals or
objects that can increase the chances that a signal sent by a transmitter of the
lost object is received by a device tracking the lost object. Additional
embodiments of the present invention can provide an increased level of
confidence that the location indicated for the individual or object is accurate.
In accordance with a first aspect, a tracking system includes a target
unit having a GPS receiver, a signal transmitter to send a signal indicating a
position of the target unit, and a processor to calculate an optimal time
interval for transmission of the signal. A locating unit has a GPS signal
receiver, a compass to provide a reference direction of the locating unit, a
signal receiver to receive the signal sent by the transmitter of the target
unit, a processor to calculate a range and bearing from the locating unit to the
target unit, and an indicator to display the range and bearing.
In
accordance with a second aspect, a tracking system includes a target unit having
a GPS receiver and a signal transmitter to send a signal indicating a position
of the target unit. A locating unit has a GPS signal receiver and a compass to
provide a reference direction of the locating unit. A signal receiver receives
the signal sent by the transmitter of the target unit. A processor calculates a
range and bearing from the locating unit to the target unit and a confidence
level to indicate a reliability of the signal sent by the target unit. An
indicator displays the range, bearing and confidence level.
In
accordance with another aspect, a system to transmit the location of an object
or individual associated with the system includes a GPS receiver to determine a
position of a device. A signal transmitter sends a signal indicating the
position of the device. A processor calculates an optimal time interval for
transmission of the signal.
In accordance with yet another aspect, a
tracking system to track the location of an object in water includes a target
unit having a GPS receiver to determine a position of the target unit. A sensor
detects motion of the target unit, and a processor calculates when the target
unit is proximate a crest of a wave. A signal transmitter sends a signal
indicating the position of the target unit when the target unit is proximate the
crest of a wave. A locating unit has a GPS signal receiver and a compass to
provide a reference direction of the locating unit. A signal receiver receives
the signal sent by the transmitter of the target unit. A processor in the
locating unit calculates a range and bearing from the locating unit to the
target unit. An indicator displays the range and bearing from the locating unit
to the target unit.
In accordance with a further aspect, a method of
tracking a target unit from a locating unit includes the steps of receiving a
GPS signal at a target unit to determine a location of the target unit,
receiving a GPS signal at a locating unit tracking the target unit to determine
a location of the locating unit, calculating an optimal time interval for
transmission of a signal from the target unit to the locating unit, where the
signal includes the GPS location of the target unit, transmitting the signal
from the target unit to the locating unit during the optimal time interval, and
calculating a range and bearing from the locating unit to the target unit.
In accordance with yet a further aspect, a tracking system includes a
tracking unit having a GPS receiver and a signal transmitter to send a signal
including a position of the tracking unit. A signal receiver is configured to
receive a signal sent by a transmitter of at least another tracking unit. A
processor is configured to calculate a range and bearing from the tracking unit
to at least another tracking unit and a confidence level attributed to a signal
sent by at least another tracking unit. A compass provides a reference direction
of the tracking unit, and an indicator is configured to display the range and
bearing to at least another tracking unit.
From the foregoing
disclosure, it will be readily apparent to those skilled in the art, that is,
those who are knowledgeable or experienced in this area of technology, that the
present invention provides a significant advance. Preferred embodiments of the
tracking device of the present invention can provide increased reliability of
signal transmission from a transmitter to a receiver, and increased confidence
in the accuracy of the signal being sent. These and additional features and
advantages of the invention disclosed here will be further understood from the
following detailed disclosure of preferred embodiments.
BRIEF
DESCRIPTION OF THE DRAWINGS
Preferred embodiments are described in
detail below with reference to the appended drawings.
FIG. 1 is a
schematic representation of a prior art personal tracking system shown in use in
a man-overboard situation.
FIG. 2 is a block diagram showing the
components of a personal tracking system in accordance with the present
invention.
FIG. 3 is a plan view of a preferred embodiment of a
graphical display of the personal tracking system of FIG. 2.
FIG. 4 is a
plan view of an alternative embodiment of a graphical display of the personal
tracking system of FIG. 2.
FIG. 5 is a block diagram showing the
components of a personal tracking system in accordance with an alternative
embodiment of the present invention.
FIG. 6 is a block diagram showing
the components of a personal tracking system in accordance with yet another
alternative embodiment of the present invention.
FIG. 7 is a block
diagram showing the components of a personal tracking system in accordance with
a further alternative embodiment of the present invention.
The figures
referred to above are not drawn necessarily to scale and should be understood to
present a representation of the invention, illustrative of the principles
involved. Some features of the tracking device depicted in the drawings have
been enlarged or distorted relative to others to facilitate explanation and
understanding. The same reference numbers are used in the drawings for similar
or identical components and features shown in various alternative embodiments.
Tracking devices as disclosed herein, will have configurations and components
determined, in part, by the intended application and environment in which they
are used.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
A prior
art personal tracking device 2 is shown in FIG. 1 in a man-overboard situation.
A first individual 4 having a GPS device 6 is shown at the crest of a wave. A
second individual 8 having a GPS device 6 is shown at the trough of a wave. GPS
devices 6 include a transmitter that sends a signal 10, e.g., an RF signal, to a
GPS device 12 on a ship 14. GPS device 12 has a receiver to receive the signals
10 sent by GPS devices 6. Each of the GPS devices ascertains its longitudinal
and latitudinal position by acquiring signals from GPS satellites 16 that orbit
the earth. A problem with such a prior art tracking device is that much of the
signal 10 transmitted by second individual 8 is obstructed by waves.
Additionally, the signal can further be diminished when the individual and their
transmitter are submerged.
A tracking system 3 in accordance with a
preferred embodiment of the present invention is shown in FIG. 2. Tracking
system 3 includes a target unit 18 and a locating unit 20. Target unit 18 is
associated with the object or person to be located, while locating unit 20 is
used to search for and locate the target unit. Target unit 18 and locating unit
20 each have a GPS receiver 22 that receives signals 23 sent by GPS satellites
16. Target unit 18 has a processor 24 that calculates its position using known
triangulation and/or quadrangulation techniques based on signals 23 received
from GPS satellites 16. A transmitter 26 of target unit 18 sends a signal 28 to
a receiver 30 of locating unit 20 indicating the position of target unit 18.
Signal 28 may be, for example, an RF, an IR, a VHF signal, or any other suitable
line of sight signal. Target unit 18 is typically powered by a battery 31.
In certain preferred embodiments, locating unit 20 can track multiple
target units 18. In such a case, signal 28 from target unit 18 may include an
identifier, e.g., a serial number, unique to that particular target unit, so
that locating unit 20 can differentiate between different target units.
Alternatively, signal 28 can be transmitted on a preselected frequency, known by
locating unit 20 to be associated with that particular target unit. Other
methods of identifying a signal 28 associated with a particular target unit 18
will become readily apparent to those skilled in the art, given the benefit of
this disclosure.
Since target unit 18 has no way of knowing if signal 28
is being received by a locating unit 20 or is falling on deaf ears, target unit
18 preferably sends signal 28 during times of predicted high reliability for
transmission of the signal, in order to conserve battery power and improve the
reliability of the tracking system. In certain preferred embodiments, target
unit 18 has a sensor 32 that provides data regarding the motion of target unit
18. Processor 24 uses the data from sensor 32, and through the use of an
algorithm determines a time of predicted high reliability for the transmission
of signal 28, as illustrated in FIG. 7. In a preferred embodiment, sensor 32 is
an accelerometer that provides data regarding the instantaneous acceleration of
the targeting unit and its direction of travel. An accelerometer can be used,
for example, when target unit 18 is floating on the surface of a body of water,
such as in a man-overboard rescue scenario. In such a scenario, not only will
target unit 18 move with the wind and currents, it will also ride up and down
along the surface of waves. Processor 24, therefore, can use inertial data from
the accelerometer to determine when target unit 18 is at or near the crest of
the wave, thereby determining an optimal time interval for transmission of
signal 28 to receiver 30. In this manner, the transmission of signal 28 is much
more likely to be received by locating unit 20 than if signal 28 was sent when
target unit 18 is at the bottom, or near the bottom, of the trough of the wave.
This transmission process is known as parametric filtering with dynamic
tuning, since target unit 18 relies on sensing components, e.g., sensor 32, to
improve the reliability of transmissions, and this tuning of the transmission
process is done continuously on a real-time basis by processor 24. Thus, target
unit 18 knows where it is at all times through data from GPS receiver 22, and
also knows where it is heading and how fast it is moving in a given direction
through data from sensor 32.
In certain preferred embodiments, target
unit 18 could incorporate additional information in signal 28 in addition to the
instantaneous location of target unit 18. Processor 24 could incorporate
historical information in signal 28 including, for example, location, drift
direction and velocity of target unit 18 over a certain prior period of time.
This type of historical vector information regarding the path that target unit
18 has traveled over a selected time period can be used by locating unit 20 to
enhance the reliability of the system. Further, processor 24 could calculate a
projected drift path over time based on its recently acquired position
information and the historical information collected, and incorporate this
projection in signal 28.
It is to be appreciated that the data received
from GPS satellites 16 may be accurate enough to be used to determine times of
predicted high reliability. For example, if the GPS data is accurate enough,
processor 24 could use that data to predict when target unit 18 is at or near
the crest of a wave, and send signal 28 at that time. In this case, processor 24
could calculate times of predicted high reliability without the use of
additional components such as sensor 32.
In certain preferred
embodiments, target unit 18 includes a water detector 33. When target unit 18
encounters water, e.g., when an individual falls into a body of water off a
ship, water detector 33 senses the water and activates processor 24, which in
turn sends signal 28 from transmitter 26 as described above. Thus, in a
man-overboard situation, the processor is only activated upon entry into water,
thereby conserving battery power.
The use of water detector 33 is
particularly useful in a situation where an individual wearing a target unit 18
falls overboard from a vessel having locating unit 20. When processor 24 is
initially activated, GPS receiver 22 takes some time to initialize, and,
therefore, cannot include a location in the first signal it transmits upon entry
into the water. Accordingly, signal 28 preferably includes the identifier unique
to that target unit. This allows processor 34 of locating unit 20 to commence
tracking of this particular target unit 18 upon receiving the initial signal
from target unit 18. Since GPS receiver 22 of locating unit 20 is typically
powered on at all times, processor 34 knows its position, and, therefore, the
position of target unit 18 at the time of activation. This provides a starting
point location for the search.
Water detector 33 may be any type of
detector that can detect when the target unit is in water, such as a detector
that activates an electrical contact upon coming into contact with water, a
pressure detector, or a combination of both. Other suitable water detectors will
become readily apparent to those skilled in the art, given the benefit of this
disclosure.
It is to be appreciated that signal 28 can also include, in
addition to the location of target unit 18, an identifier unique to that target
unit 18. Signal 28 could also include other types of data and voice. For
example, medical information regarding an individual wearing target unit 18
could be included in signal 28, providing users of locating unit 20 constant
updates on the lost individual's medical condition. Additionally, transmission
of data from various target units, including their location, health status,
etc., can be relayed in a network configuration, as described further below.
Locating unit 20 has a processor 34 that calculates its position using
known triangulation and/or quadrangulation techniques based on signals 23
received from GPS satellites 16. Locating unit 20 also has an electronic compass
36. Processor 34 then is able to calculate the position of target unit 18
relative to locating unit 20, through a differential GPS measurement, and
provide range and bearing information indicating the position of target unit 18
with respect to locating unit 20. By providing relative range and bearing
information based on a differential GPS measurement, the absolute error of the
location of target unit 18 created by the SA induced error component of the GPS
system is cancelled out. Relative range and bearing is more useful than an
absolute location in a man-overboard rescue scenario, where the rescuers are
primarily interested in knowing the distance and direction to the person in the
water.
Locating unit 20 is powered by power supply 40, which may be an
AC circuit, a battery, or other suitable power source. Locating unit 20 also has
a display 38 that provides a visual indicator of the range and bearing to target
unit 20. A preferred embodiment of a display 138 is shown in FIG. 3. Display 138
provides a user with a visual indicator of the direction toward target unit 18
from the user's vantage point, along with distance information. Display 138 may
be an LCD display, or any other type of display suitable for displaying graphics
and text. In this preferred embodiment, the range and bearing information is
displayed through the use of an arrow 140 that always points in the direction of
target unit 18, and text 142 listing the distance to target unit 18 in a
suitable unit of measure, e.g., meters, yards, etc. Compass 36 in locating unit
20 ensures that arrow 140 will always point in the proper direction, that is,
toward target unit 18. Display 138 may also provide a unit identifier 144 in
text form, identifying the target unit in question when multiple target units
are being tracked. In an additional preferred embodiment, the use of voice
synthesis software in processor 34 and a speaker 143 in display 138 will provide
constantly updated range, bearing and other data information to a user without
requiring the user to constantly look at a monitor.
In certain preferred
embodiments, as illustrated in FIG. 7, processor 34 calculates a value for the
reliability or quality of the transmission of signal 28, referred to herein as a
confidence level or confidence index. Confidence level 145 provides a user with
information from which they can gauge the accuracy of the range and bearing
information displayed. That is, the confidence level is a derived indicator that
predicts to a user how accurately the range and bearing information displayed
reflects the actual data calculated by target unit 18. Confidence level 145 may
be displayed as a percentage, e.g., 95%, or as an integer value in a range,
e.g., from 1 to 10. Confidence level 145 can be calculated in different ways.
Calculation of the confidence level can be done solely by processor 34 of
locating unit 20, or in conjunction with processor 24 of target unit 18.
Accuracy of the confidence level is enhanced by having calculations done by
processor 24, however, battery power is consumed more quickly the more processor
24 is used. For example, target unit 18 can send data regarding its calculated
position with respect to a wave, which can be used by processor 34 in
calculating the confidence level. Additionally, as signals are received and
processed by locating unit 20, processor 34 can learn by analyzing the
cumulative data from all the signals that have been received. Processor 34 can
compare data received in a signal with predictions it has made about the
location and/or direction and rate of travel of target unit 18 in order to
evaluate the quality of the signal. Clearly erroneous signals are given very low
confidence levels, while signals that are in concert with predictions made by
processor 34 and previous signals sent by target unit 18 are given higher
confidence levels. Thus, in a search operation, the confidence level will affect
the error range or the +/- range associated with a plotted location of the
target unit 18. Therefore, in a man overboard situation where the confidence
level is low, searchers would be inclined to search a wider area for the lost
individual. When a confidence level is high, however, searchers would be
inclined to move to a pinpointed plotted location on a more direct route at a
higher speed in an attempt to save valuable rescue time.
In other
preferred embodiments, confidence level 145 can be enhanced by including a test
signal in signal 28, known and understood by both target unit 18 and locating
unit 20. Thus, if locating unit 20 receives a signal 28, and the signal includes
a complete test signal, locating unit 20 will assign a high confidence level to
that signal. The test signal can be equivalent to an eye test or hearing loss
test tone. For example, if a sweep tone in discrete transmission power steps is
incorporated in signal 28, locating unit 20 can evaluate the tone and capture
the highest acceptable step of the transmission. This will establish a
quantitative factor representing the strength of the transmitted signal, which
can be translated into a displayed confidence level. In other preferred
embodiments, the sweep tone could be sent at specific time intervals, e.g.,
every sixty seconds, and locating unit 20 can calculate the confidence level
based on the frequency and level of acceptable signals received.
In
certain preferred embodiments, signal 28 can include a variable indicating a
projected time of the next transmission of a signal 28, or a frequency of
transmission variable. Locating unit 20 can then use this information to
evaluate subsequent signals 28 received in order to assist in determining
whether signals 28 have been lost over a particular time period.
At
certain times, target unit 18 may be unable to obtain a valid GPS signal. In
such instances, processor 24 can perform dead reckoning using the data from
sensor 32 and the last known position of target unit 18. The location
transmitted in signal 28 in such a case is, therefore, less accurate than a
GPS-based location. Consequently, it is desirable that the confidence level
calculated by processor 34 of locating unit 20 takes into account that the
location of target unit 18 was produced by dead reckoning. Thus, in certain
preferred embodiments, signal 28 includes an indication that its location is
based on dead reckoning so that the confidence level is calculated properly.
The algorithm or algorithms used to produce a confidence level
constantly evaluate all data received from target unit 18 in order to assign a
confidence level to a particular signal. In addition to displaying this
confidence information, the processing software can be empowered to make a
determination of whether or not to continue to obtain updated data information
from slave devices. In this manner, battery power can be further conserved.
Software can also be utilized to generate range and bearing predictions (i.e.
the software can analyze drifting trends, etc.) in order to fill in the data
blanks that arise from poor data transmission and low confidence factors. In
this manner, the system can maintain an ongoing display of a man overboard
position, even during periods of low signal transmission.
Another
preferred embodiment of a display 238 is shown in FIG. 4, where display 238 is a
graphical display that shows the location of target unit 18 as compared to that
of locating unit 20. In the illustrated embodiment, display 238 takes the form
of a circular display like that of a radar screen, with a center point 240 on
the display representing the location of locating unit 20, and a moving point
242 representing the location of target unit 18 relative to center point 240.
Display 238 also provides text 142 listing the distance to target unit 18, and
confidence level 145.
In certain preferred embodiments, the location
information with respect to target unit 18 may be presented in an alternative
format to reflect the respective confidence level associated with that data. The
range and bearing information, as seen in FIG. 3, may be represented, e.g., as a
dashed line, a colored line, a wider line, a fuzzy line, or any other obvious
variation. With respect to the display depicted in FIG. 4, point 242 may be
represented by a different color, a circle of varying diameter, a cross-hair of
varying size, a fuzzy point, or any other obvious variation to help reflect the
confidence level associated with that data point. This type of alternative
representation provides searchers with a visual indicator that can help them
determine the width and breadth of the search area.
Another preferred
embodiment of a tracking device 103 is shown in FIG. 5, where a transmitter 104
is provided on locating unit 20 to send a signal 106 to a receiver 108 on target
unit 18. Signal 106 can include information such as signal strength, error
checking data, and other confirmation data. Since target unit 18 has the benefit
of knowing that locating unit 20 has received signal 28, target unit 18 can
further conserve battery power by limiting its transmissions. Processor 24 can
interpret the data received from locating unit 20 regarding the strength and
reliability of a previously sent signal, compare these results with its
projection regarding the optimal time interval for sending that particular
signal, and modify its algorithm for calculating optimal transmission times
accordingly. Thus, processor 24 can learn from its environment the best method
to reliably transmit data. Such an embodiment can enhance the accuracy of the
confidence level calculations, since both processors can compare data to
determine how accurate a particular transmitted signal is.
Further
utility of the aforementioned parametric filtering with dynamic tuning method of
improved radio transmission is achieved in the transmission of a broad range of
communication methodologies. For example, VHF radio transmission while operating
on the surface of the sea can be enhanced through employment of the described
technique. Additionally, the utilization of two-way communications between
transmission stations can further improve signal reliability through the
utilization of the confidence level described above. For example, the addition
of packets of test data to the regular transmission of signals between stations
can allow for error detection and a determination of signal reliability. This
information can then be displayed or otherwise used, i.e., incorporated into a
software algorithm in the processor, in conjunction with the data itself in
order to assign a degree of confidence to the data. In this manner, radio
transmissions on sea and on land can be tested and graded automatically by
processor software intrinsic to the radio devices themselves.
In other
preferred embodiments, multiple units can be networked together, with the
locating unit and each target including a transmitter and receiver, as seen in
FIG. 5, such that each unit is capable of receiving data from any other unit in
the network. In addition, each unit's processor would include software specific
to ascertaining a confidence level to measure the quality, strength, or
reliability associated with transmissions, as well as the computation and
display (or voice synthesis relay) of data relative to multiple unit locations
and conditions in real time.
In certain preferred embodiments, locating
unit 20 may also include a sensor 32, such as an accelerometer. This will allow
locating unit 20 to monitor its movement, and, therefore, perform dead
reckoning. Therefore, in a networked environment with multiple target units, all
the units that are not receiving accurate GPS data can update their
instantaneous location by communicating with other units that are receiving
accurate GPS data. This could be particularly useful in a situation where
certain units are indoors and others outdoors. The outdoor units can then aid in
refining the perceived dead reckoning-based location of indoor units.
In
addition, the incorporation of multiple radio (slave) units into a network that
utilizes an algorithm to calculate a confidence level, along with the dynamic
tuning circuitry described here, further enhances the overall system reliability
of the described method of providing tracking information in a situation where
multiple targets are being tracked. This is accomplished by allowing any device
to act as a relay of data to any other device within the network. By allowing
real time software to process the accelerometer information in each node of the
network and by determining in real time the best possible time to transmit data
within the network, the entire network benefits from the dynamic tuning effect
and is capable of maintaining in real time an overall system, or network,
confidence level. This feature, that is, the networked application of real time
dynamic tuning and assignment of a confidence level has implications that
provide utility to a broad range of communication methodologies.
Another
preferred embodiment is shown in FIG. 6, where a plurality of tracking units 120
are used in a network type configuration. Only two tracking units 120 are shown
here for purposes of clarity, but it is to be appreciated that any number of
tracking units 120 may communicate with one another in such an environment. Each
tracking unit 120 has a GPS receiver 22 to determine its location and an
electronic compass 36. Sensor 32, preferably an accelerometer, provides data
regarding the motion of tracking unit 120 and, therefore, allows each tracking
unit to determine its location by dead reckoning when no GPS signal is
available. Power supply 40 may be any suitable source of power, but is
preferably a battery so that tracking unit 120 can be used anywhere without the
need to be directly tied in to a source of power. Display 38 is used to display
the range and bearing to other tracking units 120, as well as display the
confidence level calculated by processor 34 with respect to signals that are
received from the other tracking units. Transmitter 114 and receiver 130
transmit and receive, respectively, signals 28 exchanged between each of the
tracking units 120. Accordingly, tracking unit 120 can send a signal to, and
receive a signal from, each of the other tracking units 120. In a man overboard
embodiment, each tracking unit can also include a water detector (not shown
here, but seen above in connection with FIG. 2). Thus, each tracking unit 120
has full functionality. That is, each tracking unit can be used as a locating
unit or target unit, and, therefore, can track or be tracked by one or many
other tracking units 120, allowing full networked capability amongst numerous
tracking units.
It is to be appreciated that the devices described
herein, that is, the locating, target and tracking units, may be manufactured as
stand-alone devices. Alternatively, the components of these devices may be
incorporated into existing devices, such as personal data assistants (PDA's),
cellular telephones, and any other suitable wireless devices.
It is to
be appreciated that, although the above discussion is directed primarily to a
man overboard situation, the present invention is suitable for numerous
applications, including land-based situations where tracking individuals, or
property, is desired. Exemplary situations where the present invention can be
utilized include tracking lost children, hospital patients, individuals under
in-house arrest, firefighters, individuals with Alzheimer's disease, and
valuable assets.
The use of a sensor such as an accelerometer in a
tracking system can have many uses. For example, the tracking system can
intelligently detect a fall, accident, etc. of an individual wearing a tracking
system unit. Thus, a tracking system unit worn by a first person, e.g., a skier,
snow machine operator, rock climber, etc., can send a signal to a second person
indicating that the first person could be in danger. Additionally, the use of an
accelerometer in conjunction with a GPS based receiver can be used to monitor
individuals in situations where the individual's access to the GPS signals is
compromised. For example, if a person walks into a building, cave, or other
confined space, and loses reception of GPS signals, dead reckoning can be used
in conjunction with data from the accelerometer to track the location of the
individual as they travel throughout the area where the GPS signal is not
received. This is much more accurate than simply noting the "last known
position" of the individual.
In light of the foregoing disclosure of the
invention and description of the preferred embodiments, those skilled in this
area of technology will readily understand that various modifications and
adaptations can be made without departing from the scope and spirit of the
invention. All such modifications and adaptations are intended to be covered by
the following claims.
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