CA2228549A1 - Locating systems and methods for determining the locations of individuals over a geographical area - Google Patents
Locating systems and methods for determining the locations of individuals over a geographical area Download PDFInfo
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- CA2228549A1 CA2228549A1 CA 2228549 CA2228549A CA2228549A1 CA 2228549 A1 CA2228549 A1 CA 2228549A1 CA 2228549 CA2228549 CA 2228549 CA 2228549 A CA2228549 A CA 2228549A CA 2228549 A1 CA2228549 A1 CA 2228549A1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/003—Transmission of data between radar, sonar or lidar systems and remote stations
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/06—Systems determining position data of a target
- G01S13/46—Indirect determination of position data
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/87—Combinations of radar systems, e.g. primary radar and secondary radar
- G01S13/878—Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/06—Systems determining position data of a target
- G01S13/46—Indirect determination of position data
- G01S2013/466—Indirect determination of position data by Trilateration, i.e. two antennas or two sensors determine separately the distance to a target, whereby with the knowledge of the baseline length, i.e. the distance between the antennas or sensors, the position data of the target is determined
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- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Position Fixing By Use Of Radio Waves (AREA)
Abstract
A locating system for determining the locations of individuals over a geographical area, e.g.
skiers over a ski region, has transmitter units distributed over the area and operable to broadcast radio ranging signals, and individual mobile transceiver units with receivers for receiving the ranging signals, transceiver unit processors responsive to the ranging signals for relaying the ranging signals as transceiver output signals and a transmitter for broadcasting the transceiver output signals. Communication units are distributed over the area and each have a receiver for receiving the transceiver output signals and a processor responsive to the transceiver output signals for computing the locations of the mobile transceiver units and outputting location signals representing the locations of the mobile transceiver units to a master station including an output device for displaying the locations of the mobile transceiver units.
skiers over a ski region, has transmitter units distributed over the area and operable to broadcast radio ranging signals, and individual mobile transceiver units with receivers for receiving the ranging signals, transceiver unit processors responsive to the ranging signals for relaying the ranging signals as transceiver output signals and a transmitter for broadcasting the transceiver output signals. Communication units are distributed over the area and each have a receiver for receiving the transceiver output signals and a processor responsive to the transceiver output signals for computing the locations of the mobile transceiver units and outputting location signals representing the locations of the mobile transceiver units to a master station including an output device for displaying the locations of the mobile transceiver units.
Description
LOCATING SYSTEMS AND METHODS FOR DETERMINING
THE LOCATIONS OF INDIVIDUALS OVER A GEOGRAPHICAL AREA
The present invention relates to locating systems and methods for determining the location of any one of a plurality of mobile units over a geographical area and is useful in particular, but not exclusively, for determining the locations of a large number of individual skiers in a skiing area.
Numerous systems have previously been proposed for locating and monitoring the positions of mobile units over predetermined areas.
For example, United States Patent No. 5,218, 344, issued June 8, 1993 to James G. Ricketts, discloses a method and system for monitoring personnel in an institution such as a correctional facility, hospital, school, military installation or the like which includes a computer connected with one or more stationary transceivers in a defined area of the facility, and a portable transceiver unit worn by each individual who is to be monitored. The computer sends command signals to the stationary transceivers, which broadcast interrogation signals to the portable units. Each portable unit is configured to respond only to interrogation signals unique to that individual, and upon decoding an interrogation signal incident thereon, broadcasts a response signal to the stationary transceivers.
The stationary transceivers relay corresponding data to the computer, where the data is analyzed to provide an indication of the number, location and identity of the individuals. The portable transceiver units may have an emergency alarm button which may be actuated by the individual in the event of an emergency.
The portable units may comprise wrist units, each of which can be configured to transmit at a time determined by an interrogation signal imposed on it, either immediately upon receiving the interrogation signal or a predetermined time after receiving the signal. Further, each wrist unit can be configured to generate its own signal or it can modulate a signal
THE LOCATIONS OF INDIVIDUALS OVER A GEOGRAPHICAL AREA
The present invention relates to locating systems and methods for determining the location of any one of a plurality of mobile units over a geographical area and is useful in particular, but not exclusively, for determining the locations of a large number of individual skiers in a skiing area.
Numerous systems have previously been proposed for locating and monitoring the positions of mobile units over predetermined areas.
For example, United States Patent No. 5,218, 344, issued June 8, 1993 to James G. Ricketts, discloses a method and system for monitoring personnel in an institution such as a correctional facility, hospital, school, military installation or the like which includes a computer connected with one or more stationary transceivers in a defined area of the facility, and a portable transceiver unit worn by each individual who is to be monitored. The computer sends command signals to the stationary transceivers, which broadcast interrogation signals to the portable units. Each portable unit is configured to respond only to interrogation signals unique to that individual, and upon decoding an interrogation signal incident thereon, broadcasts a response signal to the stationary transceivers.
The stationary transceivers relay corresponding data to the computer, where the data is analyzed to provide an indication of the number, location and identity of the individuals. The portable transceiver units may have an emergency alarm button which may be actuated by the individual in the event of an emergency.
The portable units may comprise wrist units, each of which can be configured to transmit at a time determined by an interrogation signal imposed on it, either immediately upon receiving the interrogation signal or a predetermined time after receiving the signal. Further, each wrist unit can be configured to generate its own signal or it can modulate a signal
-2-incident upon it. Any of the well-known modulation techniques can be used, for example frequency shifting, delaying the incident signal by a fixed amount of time, applying a frequency or phase modulation to the incident signal or multiplying the incident signal frequency. If the wrist units generate their own signals, then the transceivers need only S receive these signals and need not be capable of generating signals.
However, if the wrist units modulate or modify signals incident upon them, then the transceivers can generate the signals which are incident upon the wrist units. In the latter instance, the transceivers can function like a radar system. In this manner, location information can be derived by correctly processing the signals received at the transceiver.
The present invention is based on an appreciation of the fact that in situations where it is required to monitor the locations of a large number of mobile units, for example up to 10,000 skiers, it is very desirable or even essential that each mobile unit should be inexpensive and, therefore, of uncomplicated implementation.
With this consideration in mind, the present invention is based on the concept that processing of signals by the mobile units should be minimized and that such processing should, instead, be effected at a relatively smaller number of processing stations.
According to the present invention, a locating system for determining the locations of mobile units over a geographical area has transmitter units distributed over the geographical area and operable to broadcast radio ranging signals. The mobile units are each provided with a receiver for receiving the ranging signals, a transceiver unit processor responsive to the ranging signals for outputting transceiver output signals representing the ranges of the respective mobile transceiver unit from the transmitter units and a transmitter for broadcasting the transceiver output signals.
Communication units distributed over the geographical area are provided with receivers for receiving the transceiver output signals and processors responsive to the transceiver output signals for outputting location signals representing the locations of the mobile transceiver
However, if the wrist units modulate or modify signals incident upon them, then the transceivers can generate the signals which are incident upon the wrist units. In the latter instance, the transceivers can function like a radar system. In this manner, location information can be derived by correctly processing the signals received at the transceiver.
The present invention is based on an appreciation of the fact that in situations where it is required to monitor the locations of a large number of mobile units, for example up to 10,000 skiers, it is very desirable or even essential that each mobile unit should be inexpensive and, therefore, of uncomplicated implementation.
With this consideration in mind, the present invention is based on the concept that processing of signals by the mobile units should be minimized and that such processing should, instead, be effected at a relatively smaller number of processing stations.
According to the present invention, a locating system for determining the locations of mobile units over a geographical area has transmitter units distributed over the geographical area and operable to broadcast radio ranging signals. The mobile units are each provided with a receiver for receiving the ranging signals, a transceiver unit processor responsive to the ranging signals for outputting transceiver output signals representing the ranges of the respective mobile transceiver unit from the transmitter units and a transmitter for broadcasting the transceiver output signals.
Communication units distributed over the geographical area are provided with receivers for receiving the transceiver output signals and processors responsive to the transceiver output signals for outputting location signals representing the locations of the mobile transceiver
-3-units. A master station is connected by signal channels to the communication units and includes an output device for representing the locations of the mobile transceiver units.
The mobile transceiver units are not required to process the ranging signals so as to determine the locations of the mobile transceiver units but, instead, transmit to the communication units data corresponding to the ranging signals received by the mobile transceiver units from the transmitter units. This data is then processed by the transceiver output signal processors at the communication units to compute the locations of the mobile transceiver units and corresponding location data is then passed from the communication units through the signal channels to the master station.
Since it is not necessary to incorporate into the mobile transceiver units any means for computing the mobile transceiver unit locations, the mobile transceiver units are simple and inexpensive.
The present invention will be more readily apparent from the following description of an embodiment thereof when taken in conjunction with the accompanying drawings, in which:-Figure 1 shows a diagrammatic plan view of a geographical area provided with a locating system according to the present invention;
Figure 2 shows a block diagram illustrating four separate components of the locating system of Figure 1;
Figure 3 shows a block diagram of one of a plurality of transmitters included in the locating system of Figure 1;
Figure 4 shows a block diagram of a mobile transceiver unit forming one of the components of the locating system of Figure 1.
The mobile transceiver units are not required to process the ranging signals so as to determine the locations of the mobile transceiver units but, instead, transmit to the communication units data corresponding to the ranging signals received by the mobile transceiver units from the transmitter units. This data is then processed by the transceiver output signal processors at the communication units to compute the locations of the mobile transceiver units and corresponding location data is then passed from the communication units through the signal channels to the master station.
Since it is not necessary to incorporate into the mobile transceiver units any means for computing the mobile transceiver unit locations, the mobile transceiver units are simple and inexpensive.
The present invention will be more readily apparent from the following description of an embodiment thereof when taken in conjunction with the accompanying drawings, in which:-Figure 1 shows a diagrammatic plan view of a geographical area provided with a locating system according to the present invention;
Figure 2 shows a block diagram illustrating four separate components of the locating system of Figure 1;
Figure 3 shows a block diagram of one of a plurality of transmitters included in the locating system of Figure 1;
Figure 4 shows a block diagram of a mobile transceiver unit forming one of the components of the locating system of Figure 1.
-4-Figure 5 shows a block diagram of one of a plurality of communication towers in the locating system of Figure 1; and Figure 6 shows a block diagram of a master station included in the locating system of Figure 1.
Refernng firstly to Figure 1 of the accompanying drawings, which shows a diagrammatic plan view, i. e. a map, of a geographical area containing a locating system according to the present invention, the locating system, as illustrated, has five transmitters 10. In the present embodiment, this geographical area is a ski resort. From these transmitters 10, ranging signals are transmitted, as described in greater detail below, to mobile transceiver units 12, which in the present case are carried by skiers, any one of which may be in motion over the illustrated geographical area or may be stationary. From the mobile transceiver units 12, data corresponding to the ranging signals is transmitted to communication towers 14, where this data is processed to determine the locations of the mobile transceiver units 12.
From the communication towers 14, data representing the mobile transceiver unit locations is passed over land lines 16 (Figure 2) to a master station 18, at which information is displayed, for example by means of a video display or a printer output.
Figure 2 shows a block diagram showing one each of the transmitters 10, the mobile transceiver units 12 and the communication towers 14, with the latter connected by land lines 16 to the master station 18.
Figure 3 illustrates in greater detail one of the transmitter units 10. As shown in Figure 3, the transmitter unit 10 has a GPS (global positioning system) timing receiver 20 provided with an antenna 22 for receiving GPS timing signals from GPS satellites. The timing receiver 20 is connected to a microprocessor and controller 24. The processor and controller 24 is connected by land lines 26 to the master station 18 and is also connected to a spread signal processor 28 which, in turn, is connected to a ranging transmitter 30 which, from an -S-antenna 32, broadcasts spread spectrum ranging signals identifying the respective transmitter unit 10 and including timing data from the timing receiver 20 and ranging codes.
In the present embodiment of the invention, in which the locating system is provided on a ski area and in which, therefore, it may be required to locate, track and monitor the locations of up to l0,000, or even more, skiers at the ski resort to protect the life and health of the skiers, the transmitters 10 are preferably located on towers (not shown) on the tops of the highest mountain peaks in the area of ski slopes. The overall distance between the transmitters 10 may, then, be up to five or ten miles, and is preferably at least two miles.
Each of the transmitters may transmit, as its ranging signal, a ranging code along with a 400 bps identification code, the five transmitters 10 being arranged to transmit in sequence at one-second intervals, so that each transmitter 10 transmits its ranging signal for only 200 msecs each second. The transmitters 10 are solar powered, with sufficient battery backup 1 S and/or diesel backup power generation equipment to ensure that they provide adequate signal levels throughout the ski area. In the present embodiment, the transmitters 10 each have a power of SO to 150 W. By employing such high transmitter power levels, the transceivers 12 may be provided with very simple, inexpensive and relatively insensitive receiver circuits and relatively poor antennas. The sequential transmission of the ranging signals from the transmitters 10 facilitates simple and inexpensive signal processing by the mobile transceiver units 12.
Figure 4 shows in greater detail one of the mobile transceiver units 12. As shown in Figure 4, this mobile transceiver unit 12 has a receiver 34 with a loop antenna 36 for receiving the ranging signals from the transmitters 10. The ranging signals from the transmitters 10 are broadcast on an unused VHF or UHF TV channel with a 6 MHz, 20 dB band width, thus providing a strong, interference-free ranging signal to the mobile transceiver unit receiver 34.
From the receiver 34, the ranging signal is passed to a processor and controller 3 8, provided with a sleep/active clock 40 and outputting to a transmitter 42 provided with an antenna 44.
The present system employs trilateration (or multilateration, when more than three ranging signals are available to the receiver 34) to locate and track the respective skier. Each of the mobile transceiver units 12 may also include a solid state pressure sensor for monitoring local atmospheric pressure to facilitate the trilateration or multilateration computations using a three dimensional earth model rather than a two dimensional flat earth model resulting from trilateration computations which remove user clock error (i.e. clock bias) from measurements containing three ranges.
The mobile transceiver unit 12 requires only a relatively short range, e.g.
500 to 2,000 feet, to the nearest communication towers 14, and transmits transceiver output signals through the antenna 44 in the form of a TDMA (time division multiple access) radio signal containing data indicating the identity of the respective skier and unprocessed spread spectrum ranging data from the ranging signals from the transmitters 10. Since the mobile transceiver unit 10 does not itself compute the location of the respective skier, the transceiver output signal is required to have only a very low data rate, e.g. in the order of 200 bps. For convenience, this transceiver output signal may be broadcast on a ITHF NBFM licenced frequency range for taxis, i.e. 450 to 512 MHz in most countries, since in rural and mountainous areas sharing of these "taxi-cab" frequency channels will not present a problem, particularly since only a low power (e.g. 1050 mW), short-range transmission is required.
The transmitters 10 transmit spread spectrum signals (which are similar to GPS
signals, but not exactly the same! ) on a round robin, time shared, TDMA (or CDMA, if the continuous time, band sharing is used) basis. Each transmitter 10 transmits for exactly 0.2 seconds in a circular, repeating cycle. Thus, no ID is required for each transmitter 10. It is however an option to have a unique ID (or unique spread spectrum Pseudo Noise [PN]
ranging code) for each transmitter 10. The spread spectrum signals repeat many times during the 0.2 second burst, so each transceiver unit has many chances to make "range," or "pseudo range" or "Time of Arnval" (TOA) measurements on each transmitter signal. These TOA
measurements are effected by a correlation technique on the incoming spread spectrum ranging signals, with a time precision of about 25 nanoseconds. Once a mobile transceiver unit "acquires" a transmitter spread spectrum ranging signal, it is now in very good time synchronization with the entire network of transmitters.
The TOA measurements represent the time difference between an arbitrary internal mobile transceiver unit time mark and the initial acquisition time of the transmitter signals. The TOA numbers are scaled, stored, and averaged (or otherwise "filtered") in the processor and controller 38. Since each mobile transceiver unit 12 sequentially locks onto to each transmitter 10 (or sequentially acquires each different ranging code from each transmitter 10, if the CDMA continuous time option is used) and the spread spectrum ranging codes are unique to each transmitter, no ID problem exists. IDs can of course be used if transmitted by the transmitters 10 or if assigned by the processor and controller 38.
However, the position location processing effected at the communication towers 14 counts on the TOA
data being in a regular, cyclic, real-time time-tagged order. If a particular transmitter signal is not received for some reason, then the mobile transceiver unit 12 will either bit stuff a11 zeros or send along the last filtered TOA numbers (with the old time tag).
The number of the transmitters 10 is redundant in the sense that more information is available than needed for a three dimensional position location fix at the communication towers 14. The redundant information is used by the system to provide more precision in altitude measurements, to ensure that skier unit clock bias errors are removed, and to ensure that the best possible geometry for position location is used in the position location fix.
One error arising from the TDMA mode of transmission of the transmitters 10 is that mobile transceiver TOA measurements made from each transmitter are not made simultaneously.
The use of time continuous CDMA would eliminate this error. But, even with TDMA, non-simultaneous transmitter spread spectrum ranging signal transmission, a skier's total motion in one second is in the range of 44 feet, i.e. a number only about twice the TOA time _$_ resolution of the skier's measurement system and in the random noise category as far as other system timing errors are concerned.
The mobile transceiver unit 12 employs an internal replaceable or rechargeable battery as a power source, and a solar cell may, if desired, be provided for extending the battery life.
The communication units 14 are provided on towers, e.g. wooden or metal towers having a height of SO feet or more, distributed throughout the skiing region at distances of a few thousand feet apart, and must have radio line-of site to the primary ski runs and a11 other "in-bounds" areas where skiers are normally permitted to be.
One of the communication units 14 is diagrammatically illustrated in the block diagram of Figure 5 and includes a receiver 50 with an antenna 52 for receiving the transceiver output signals from the mobile transceiver units 12 within range of the respective communication unit 14.
From the receiver 50, these signals are passed to a data processor and mulplexer 54, which also receives GPS timing signals from a GPS receiver 56 and antenna 58.
A data processor 60, which in the present embodiment of the invention is implemented as a remote controlled personal computer, processes data from the data processor and multiplexer to determine the position and tracks of the mobile transceivers and passes this information through the land line 16 to the master station 18.
The communication units 14 may be powered by land line, batteries and/or generators and may each gather raw ranging data from e.g. twenty-five to a hundred mobile transceiver units 12 per second.
A block diagram of the master station 18 is shown in Figure 6, in which an input/output and control processor 62 is shown connected to receive the data from the communication units 14 through their land lines and also data from the transmitters 10 through the land lines 26.
For convenience, the master station 18 can be located near the headquarters of the ski region in accommodation (not shown) suitable for human occupation under all envirionmental conditions.
From the processor 62, the data is passed through a control CPU 64, a database CPU 66 and a "hot standby" CPU 68 to a smart signal muter and secondary controller 70 which, in turn, outputs to a control and status display 72 and a skier safety display 74, which in the present embodiment comprise monitors.
As will be apparent to those skilled in the art, various modifications may be made to the above-described embodiment.
For example, instead of employing the present system for locating skiers, it may be adapted for locating yachts over an area of water or aircraft; for locating wild animals and/or persons in a park; for monitoring lawn mowers and other mobile equipment over a golf course or for monitoring swimmers in a pool or other swimming zone.
Refernng firstly to Figure 1 of the accompanying drawings, which shows a diagrammatic plan view, i. e. a map, of a geographical area containing a locating system according to the present invention, the locating system, as illustrated, has five transmitters 10. In the present embodiment, this geographical area is a ski resort. From these transmitters 10, ranging signals are transmitted, as described in greater detail below, to mobile transceiver units 12, which in the present case are carried by skiers, any one of which may be in motion over the illustrated geographical area or may be stationary. From the mobile transceiver units 12, data corresponding to the ranging signals is transmitted to communication towers 14, where this data is processed to determine the locations of the mobile transceiver units 12.
From the communication towers 14, data representing the mobile transceiver unit locations is passed over land lines 16 (Figure 2) to a master station 18, at which information is displayed, for example by means of a video display or a printer output.
Figure 2 shows a block diagram showing one each of the transmitters 10, the mobile transceiver units 12 and the communication towers 14, with the latter connected by land lines 16 to the master station 18.
Figure 3 illustrates in greater detail one of the transmitter units 10. As shown in Figure 3, the transmitter unit 10 has a GPS (global positioning system) timing receiver 20 provided with an antenna 22 for receiving GPS timing signals from GPS satellites. The timing receiver 20 is connected to a microprocessor and controller 24. The processor and controller 24 is connected by land lines 26 to the master station 18 and is also connected to a spread signal processor 28 which, in turn, is connected to a ranging transmitter 30 which, from an -S-antenna 32, broadcasts spread spectrum ranging signals identifying the respective transmitter unit 10 and including timing data from the timing receiver 20 and ranging codes.
In the present embodiment of the invention, in which the locating system is provided on a ski area and in which, therefore, it may be required to locate, track and monitor the locations of up to l0,000, or even more, skiers at the ski resort to protect the life and health of the skiers, the transmitters 10 are preferably located on towers (not shown) on the tops of the highest mountain peaks in the area of ski slopes. The overall distance between the transmitters 10 may, then, be up to five or ten miles, and is preferably at least two miles.
Each of the transmitters may transmit, as its ranging signal, a ranging code along with a 400 bps identification code, the five transmitters 10 being arranged to transmit in sequence at one-second intervals, so that each transmitter 10 transmits its ranging signal for only 200 msecs each second. The transmitters 10 are solar powered, with sufficient battery backup 1 S and/or diesel backup power generation equipment to ensure that they provide adequate signal levels throughout the ski area. In the present embodiment, the transmitters 10 each have a power of SO to 150 W. By employing such high transmitter power levels, the transceivers 12 may be provided with very simple, inexpensive and relatively insensitive receiver circuits and relatively poor antennas. The sequential transmission of the ranging signals from the transmitters 10 facilitates simple and inexpensive signal processing by the mobile transceiver units 12.
Figure 4 shows in greater detail one of the mobile transceiver units 12. As shown in Figure 4, this mobile transceiver unit 12 has a receiver 34 with a loop antenna 36 for receiving the ranging signals from the transmitters 10. The ranging signals from the transmitters 10 are broadcast on an unused VHF or UHF TV channel with a 6 MHz, 20 dB band width, thus providing a strong, interference-free ranging signal to the mobile transceiver unit receiver 34.
From the receiver 34, the ranging signal is passed to a processor and controller 3 8, provided with a sleep/active clock 40 and outputting to a transmitter 42 provided with an antenna 44.
The present system employs trilateration (or multilateration, when more than three ranging signals are available to the receiver 34) to locate and track the respective skier. Each of the mobile transceiver units 12 may also include a solid state pressure sensor for monitoring local atmospheric pressure to facilitate the trilateration or multilateration computations using a three dimensional earth model rather than a two dimensional flat earth model resulting from trilateration computations which remove user clock error (i.e. clock bias) from measurements containing three ranges.
The mobile transceiver unit 12 requires only a relatively short range, e.g.
500 to 2,000 feet, to the nearest communication towers 14, and transmits transceiver output signals through the antenna 44 in the form of a TDMA (time division multiple access) radio signal containing data indicating the identity of the respective skier and unprocessed spread spectrum ranging data from the ranging signals from the transmitters 10. Since the mobile transceiver unit 10 does not itself compute the location of the respective skier, the transceiver output signal is required to have only a very low data rate, e.g. in the order of 200 bps. For convenience, this transceiver output signal may be broadcast on a ITHF NBFM licenced frequency range for taxis, i.e. 450 to 512 MHz in most countries, since in rural and mountainous areas sharing of these "taxi-cab" frequency channels will not present a problem, particularly since only a low power (e.g. 1050 mW), short-range transmission is required.
The transmitters 10 transmit spread spectrum signals (which are similar to GPS
signals, but not exactly the same! ) on a round robin, time shared, TDMA (or CDMA, if the continuous time, band sharing is used) basis. Each transmitter 10 transmits for exactly 0.2 seconds in a circular, repeating cycle. Thus, no ID is required for each transmitter 10. It is however an option to have a unique ID (or unique spread spectrum Pseudo Noise [PN]
ranging code) for each transmitter 10. The spread spectrum signals repeat many times during the 0.2 second burst, so each transceiver unit has many chances to make "range," or "pseudo range" or "Time of Arnval" (TOA) measurements on each transmitter signal. These TOA
measurements are effected by a correlation technique on the incoming spread spectrum ranging signals, with a time precision of about 25 nanoseconds. Once a mobile transceiver unit "acquires" a transmitter spread spectrum ranging signal, it is now in very good time synchronization with the entire network of transmitters.
The TOA measurements represent the time difference between an arbitrary internal mobile transceiver unit time mark and the initial acquisition time of the transmitter signals. The TOA numbers are scaled, stored, and averaged (or otherwise "filtered") in the processor and controller 38. Since each mobile transceiver unit 12 sequentially locks onto to each transmitter 10 (or sequentially acquires each different ranging code from each transmitter 10, if the CDMA continuous time option is used) and the spread spectrum ranging codes are unique to each transmitter, no ID problem exists. IDs can of course be used if transmitted by the transmitters 10 or if assigned by the processor and controller 38.
However, the position location processing effected at the communication towers 14 counts on the TOA
data being in a regular, cyclic, real-time time-tagged order. If a particular transmitter signal is not received for some reason, then the mobile transceiver unit 12 will either bit stuff a11 zeros or send along the last filtered TOA numbers (with the old time tag).
The number of the transmitters 10 is redundant in the sense that more information is available than needed for a three dimensional position location fix at the communication towers 14. The redundant information is used by the system to provide more precision in altitude measurements, to ensure that skier unit clock bias errors are removed, and to ensure that the best possible geometry for position location is used in the position location fix.
One error arising from the TDMA mode of transmission of the transmitters 10 is that mobile transceiver TOA measurements made from each transmitter are not made simultaneously.
The use of time continuous CDMA would eliminate this error. But, even with TDMA, non-simultaneous transmitter spread spectrum ranging signal transmission, a skier's total motion in one second is in the range of 44 feet, i.e. a number only about twice the TOA time _$_ resolution of the skier's measurement system and in the random noise category as far as other system timing errors are concerned.
The mobile transceiver unit 12 employs an internal replaceable or rechargeable battery as a power source, and a solar cell may, if desired, be provided for extending the battery life.
The communication units 14 are provided on towers, e.g. wooden or metal towers having a height of SO feet or more, distributed throughout the skiing region at distances of a few thousand feet apart, and must have radio line-of site to the primary ski runs and a11 other "in-bounds" areas where skiers are normally permitted to be.
One of the communication units 14 is diagrammatically illustrated in the block diagram of Figure 5 and includes a receiver 50 with an antenna 52 for receiving the transceiver output signals from the mobile transceiver units 12 within range of the respective communication unit 14.
From the receiver 50, these signals are passed to a data processor and mulplexer 54, which also receives GPS timing signals from a GPS receiver 56 and antenna 58.
A data processor 60, which in the present embodiment of the invention is implemented as a remote controlled personal computer, processes data from the data processor and multiplexer to determine the position and tracks of the mobile transceivers and passes this information through the land line 16 to the master station 18.
The communication units 14 may be powered by land line, batteries and/or generators and may each gather raw ranging data from e.g. twenty-five to a hundred mobile transceiver units 12 per second.
A block diagram of the master station 18 is shown in Figure 6, in which an input/output and control processor 62 is shown connected to receive the data from the communication units 14 through their land lines and also data from the transmitters 10 through the land lines 26.
For convenience, the master station 18 can be located near the headquarters of the ski region in accommodation (not shown) suitable for human occupation under all envirionmental conditions.
From the processor 62, the data is passed through a control CPU 64, a database CPU 66 and a "hot standby" CPU 68 to a smart signal muter and secondary controller 70 which, in turn, outputs to a control and status display 72 and a skier safety display 74, which in the present embodiment comprise monitors.
As will be apparent to those skilled in the art, various modifications may be made to the above-described embodiment.
For example, instead of employing the present system for locating skiers, it may be adapted for locating yachts over an area of water or aircraft; for locating wild animals and/or persons in a park; for monitoring lawn mowers and other mobile equipment over a golf course or for monitoring swimmers in a pool or other swimming zone.
Claims (3)
1. A locating device for determining the location of any one of a plurality of individuals over a geographical area, said system comprising:
a plurality of transmitter units distributed over said geographical area and operable to broadcast radio ranging signals;
a plurality of individual mobile transceiver units, said mobile transceiver units comprising receivers for receiving said ranging signals, transceiver unit processors responsive to said ranging signals for relaying said ranging signals as transceiver output signals and a transmitter for broadcasting said transceiver output signals;
a plurality of communication units distributed over said geographical area, said communication units each comprising a receiver for receiving said transceiver output signals and a processor responsive to said transceiver output signals for computing from said ranging signals the locations of said mobile transceiver units and outputting location signals representing the locations of said mobile transceiver units;
a master station; and signal channels connecting said communication units to said master station;
said master station including an output device for representing the locations of said mobile transceiver units.
a plurality of transmitter units distributed over said geographical area and operable to broadcast radio ranging signals;
a plurality of individual mobile transceiver units, said mobile transceiver units comprising receivers for receiving said ranging signals, transceiver unit processors responsive to said ranging signals for relaying said ranging signals as transceiver output signals and a transmitter for broadcasting said transceiver output signals;
a plurality of communication units distributed over said geographical area, said communication units each comprising a receiver for receiving said transceiver output signals and a processor responsive to said transceiver output signals for computing from said ranging signals the locations of said mobile transceiver units and outputting location signals representing the locations of said mobile transceiver units;
a master station; and signal channels connecting said communication units to said master station;
said master station including an output device for representing the locations of said mobile transceiver units.
2. A locating system as claimed in claim 1, wherein said transmitter units each comprise a timing signal source and a transmitter unit processor programmed to output location data representing the location of the respective one of said transmitter units, timing data from said timing signal source and ranging codes in said ranging signals.
3. A locating system as claimed in claim 2, wherein said timing signal source comprises a GPS receiver responsive to satellite-broadcast GPS signals, said transmitter unit processor being programmed to derive said location data from said GPS signals.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2228549 CA2228549A1 (en) | 1998-02-06 | 1998-02-06 | Locating systems and methods for determining the locations of individuals over a geographical area |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2228549 CA2228549A1 (en) | 1998-02-06 | 1998-02-06 | Locating systems and methods for determining the locations of individuals over a geographical area |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2228549A1 true CA2228549A1 (en) | 1999-08-06 |
Family
ID=29409206
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2228549 Abandoned CA2228549A1 (en) | 1998-02-06 | 1998-02-06 | Locating systems and methods for determining the locations of individuals over a geographical area |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2228549A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111638486A (en) * | 2019-03-01 | 2020-09-08 | 阿里巴巴集团控股有限公司 | Positioning method, system and device |
-
1998
- 1998-02-06 CA CA 2228549 patent/CA2228549A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111638486A (en) * | 2019-03-01 | 2020-09-08 | 阿里巴巴集团控股有限公司 | Positioning method, system and device |
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