Abstract:
An Internet based personal tracking system for tracking the position of a portable location unit by a remote user comprising a web host connected to the Internet having a computer storage medium, a portable location unit having a processor for receiving geo-position information, and generating geo-position data representing the position of said location unit, a transceiver included in said location unit for transmitting said position signal to said web host in response to a call signal being received from said web host, a power supply for supplying power to said processor and said transceiver; and a computer program residing on said web host having an input module for receiving a tracking request signal from the remote user via the Internet, a processing module for processing said tracking request signal, and a communication module for initializing communication with said location unit in response to tracking said request signal, and a location module for outputting said call signal to said location unit and for receiving said geo-position data from said location unit; and a display module for outputting said position dataset to the remote user via the Internet for display of the location unit&#39;s position at the remote user&#39;s site.

Description:
This application claims the benefit of Provisional Application Ser. No. 60/118,913, filed Feb. 5, 1999, and 60/153,350, filed Sep. 10, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a system and method for tracking multiple individuals from multiple remote locations on a concurrent basis, specifically receiving and displaying at a remote location the geo-position of an individual received through a communications network, and a personal location unit which can be carried by an individual or object to be tracked. 
     BACKGROUND OF THE INVENTION 
     Personal safety has become of utmost is the upmost concern in today&#39;s society. Unfortunately, there is an ever growing risk of abductions and kidnaping. The location of lost and missing persons, elderly individuals, persons with decreased memory capacity such as Alzheimers patients, or persons in danger or in emergency situations has become a major national problem. The advent of wireless devices for personal communication, such as cellular telephones, has helped lessen this problem. However, communication with these devices can typically only be initiated by the individual carrying the device. It is often desirable for concerned persons to be able to find the location of another person who may not be carrying a cellular phone. For example, a concerned parent may wish to know the location of a lost child or perhaps a lost family member with a medical condition such as Alzheimer&#39;s disease. Children subject to custody battles are often abducted and need to be located. Alzheimer&#39;s patients who wander away from locations without the ability to find their way home need to be located. 
     GPS tracking systems have become increasingly popular for navigation of airplanes, ships, boats, automobiles, and other objects. The GPS tracking systems, which navigate off of fixed satellites, are often used in automatic control systems for controlling the guidance of airplanes, ships, boats, and the like. 
     Heretofore, various personal alarms have been provided which utilize GPS tracking systems in the event of an assault, medical emergency, or any other intrusive wrongdoing. For example, U.S. Pat. No. 5,712,619 discloses a GPS personal alarm using GPS technology and cellular phone technology to transmit the users longitudinal and latitudinal position to a monitoring station which relays the users position to the proper authorities. The system employs an unique housing structure and plunger extending through the housing structure which triggers the alarm, among other things, to cause a position signal to be emitted. 
     U.S. Pat. No. 5,742,233 discloses a signaling system which comprises a portable signaling unit, a remote alarm switch device, a central dispatch station, and a wireless communication system such as a cellular telephone, and a GPS tracking system. The remote alarm switch device is provided by a bracelet worn by the person. The signaling unit is also worn by the person. If the bracelet becomes removed from the person, the signaling unit is activated. The system uses a rechargeable lithium battery as a power source. 
     Various other GPS tracking systems for personal use are noted in the above two patents. However, a problem exists in there prior art devices because of the power required by portable devices. Even in the case of a rechargeable lithium battery, as disclosed in U.S. Pat. No. 5,742,233 above, there is a chance that the power source may be low when an alarm signal is needed from the device. The prior art devices have tended to be relatively complicated and power hungry. 
     The previous GPS devices have been designed to be initiated by the individual carrying the positioning device and not a remote user requesting the location of the individual. Neither are the systems capable or designed to handle a large number of concurrent tracking requests as they are primarily designed to notify emergency authorities such as police or 911 operators. 
     For example, U.S. Pat. No. 5,712,619 provides for a personal alarm system in the event of an emergency where the wearer initiates an emergency signal. In the event of an emergency the wearer pulls a pin and the unit makes a cellular call to a monitoring station and transmits the position of the unit. The monitoring station sends the information to the proper authorities such as emergency personnel. 
     The devices shown in U.S. Pat. Nos. 5,914,675 and 5,742,233 also can transmit GPS information in response to an emergency trigger initiated by the wearer. Once initiated, the device transmits a distress signal for detection by rescue teams. 
     The device of U.S. Pat. No. 5,835,907, again, will collect and transmit the global position of an individual to emergency services or another location once an emergency button has been activated in the device. This device will also periodically transmit GPS information to a database for later retrieval. Again, the tracking process is initiated by the unit. 
     The cellular switching system of U.S. Pat. No. 5,388,147 is a telephone switching system which is responsive to an emergency call from a cellular phone user. The particular cellular phone has the capability to transmit geo-position information to the switching system which can be forwarded to emergency authorities. 
     Thus, while the prior art has provided devices to allow one to determine their present geographical location, and has provided personal devices which may be triggered by a person to send a signal containing his location to a public service entity, the prior art has not provided a tracking system which allows initiating and determining a person&#39;s position by a concerned person from a remote location. In particular, a system which does not rely upon an individual to initiate a distress signal. 
     Moreover, the prior art has not provided a satisfactory personal tracking system which allows for the concurrent use by a large number of remote concerned persons to track a large number of individuals. Such a need exists to allow remote lay personnel such as parents, relatives, or other concerned parties to determine the position of children, the elderly, and Alzheimer&#39;s patients, etc., without relying upon official authorities. 
     Accordingly, it is an object of this invention to provide a tracking system initiated by a concerned user to determine the geographic position of an individual. 
     Another object of this invention is to track an individual from a remote location without alerting the individual, or others who may be holding the person captive. 
     Yet another object of this invention is to provide a tracking system allowing a multitude of remote users to concurrently track a multitude of individuals. 
     Yet another object of this invention is to provide a personal tracking system using a web host connected to the Internet to allow a vast multitude of concerned users to track individuals concurrently. 
     Accordingly, an object of the present invention is to provide a personal location unit employing a wireless communication and GPS system which is simplified and reliable for use in a remotely activated tracking system. 
     Another object of the invention is to provide a simple and reliable location unit which automatically answers an inquiry and transmits a position signal without an audio component thus requiring low power. 
     Another object of the present invention is to provide a simplified and reliable personal emergency location unit employing wireless and GPS technology wherein a back-up battery source is provided having a shelf life which is sufficient to power the device for a single emergency signal in the case of an emergency. 
     SUMMARY OF THE INVENTION 
     The above objectives are accomplished according to the present invention by providing a web host connected to the Internet wherein the web host has a position receiving module for receiving the global position of a personal location unit carried by an individual having a unique unit code and system access number. The web host includes an interface module allowing remote users access to the web host through the Internet and retrieve the geo-position of a tracked individual. By using the Internet, the web host is made available to literally millions of individuals allowing a multitude of concerned users to track individuals concurrently. 
     The personal location unit receives global position information from the GPS system and transmits this information to the web host upon request. Requests to and from the personal location unit are made possible through a wireless communications network. The personal location unit contains a wireless transceiver for accomplishing communication. The personal location unit also includes a position receiver for receiving position data and a processor for calculating the present global position. 
     Advantageously, the location unit may include a GPS chip carried within an enclosure for reading information from a global positioning satellite system and generating tracking information signals. A processor/modem chip included in the unit receives the tracking signals and generates personal position signals representing the latitude and longitude, or other coordinates, of the person. A transceiver included in the unit receives the position signals and transmits the position signals to a remote station automatically in response to a call being received from the remote station. The processor/modem chip automatically controls the transceiver to transmit the position signal in response to answering the call from the remote station or user, and then hang up. Quite advantageously, the position signal includes a digital signal containing digital data only, and no audio or sound signal. The digital position signal includes a small digital record which includes personal code data identifying a person to which the device is assigned, latitude data, and longitude data. The digital record may also include any necessary protocol data. The small digital record of the position signal requires only a very low power for generation and transmission. In particular, this allows for operation using a miniature auxiliary power source as a back-up power source. 
     Preferably, a main power supply supplies power to the GPS chip, the processor/modem chip, and the transceiver during normal operation. However, an auxiliary power supply may be provided for supplying power to the processor/chip and transceiver to transmit the position signal when the main power supply is insufficient to transmit the signal. 
     The above objectives are further achieved, quite advantageously, by utilizing web host computer program embodied in a computer readable medium running on a web host. The program provides instructions for the receiving of a concerned user&#39;s request, validating the input, requesting the location from a personal location unit, receiving the location or position data, and supplying a user readable format such as a map or street address to the remote user. The web host is able to provide this function to a multitude of users since each concerned user has a unique access code which is associated with a unique personal location unit number. Thus, a large number of concerned user&#39;s requests can be processed concurrently. 
     To track an individual, the concerned user accesses the web host through the Internet or other multi-user network through the user&#39;s terminal. The concerned user requests the web page of the tracking system by accessing a domain name such as www.satcel.com. An initial or home page is displayed at the user&#39;s terminal, and the user is asked to enter an access number and personal unit code. This input is received by the web host program and validated. Once validated, the web host program sends a location request to a location module embodied in the web host program to determine the global position of a personal location unit. The location module initiates a cellular phone call to begin wireless communication with the personal location unit through a wireless communication module embodied in the program, and requests the global position from the personal location unit. The location unit automatically answers the call receives global position information from GPS satellites, transmits the position information back to the wireless communication module ,then hangs up. The communication module passes the information to either the location module or a format module. If the location module receives the global coordinates the information is passed to the format module embodied in the web host program. The format module formats the global coordinates in a user readable format such as a graphical map, street address, or position coordinates. The format module is capable of formatting both raw satellite data as well as longitude, latitude, and altitude position coordinates passed by the personal location unit and thereby not requiring a specific data format from the personal unit. The user readable global position information is then passed to the display module embodied in the web host program so that the concerned user can retrieve the global position information in a format readable at the user&#39;s terminal. Therefore, the global position of the individual carrying the personal location unit is available for display on the concerned user&#39;s terminal allowing the user to know the global position of the individual in real-time. 
     To perform the tracking function of the present invention for millions of users, the web host program includes a network interface module allowing the web host to form a connection with remote user terminals. In the preferred embodiment, the connection interface provides a connection to either an Internet service provider (ISP) or directly to the Internet backbone. By being connected to the Internet, the web host is accessible to the millions of potential remote users presently connected. Each concerned user can concurrently access the web host, initiate a tracking request, and receive geo-position date of an individual. 
     The display module included within the web host program also provides any concerned user accessing the web host with a plurality of viewable pages of the web site. For example, when the concerned user first accesses the web host, the home page is displayed on the user&#39;s screen. 
     Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is made to the attached drawings, wherein elements having the same reference numeral designations represent like elements throughout and wherein: 
         FIG. 1  is a diagram representing the interrelations of the location unit, web host, and remote user terminal; 
         FIG. 2  is a diagram of the components of a location unit; 
         FIG. 3  is a process flow diagram for illustrating the steps of a remote user tracking an individual; 
         FIG. 4  is a diagram of the general components of computer readable instructions residing on the web host; 
         FIG. 5  is a diagram of the modules contained with the computer readable instructions residing on the web host; 
         FIG. 6  is a diagram representing the interrelations of the location unit and base station. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The detailed description which follows may be presented in terms of program procedures, modules, and objects, executed on a computer or a network of computers which are a set of computer readable instructions. These procedural and modular descriptions and representations are the means used by those skilled in the art to most effectively convey the substance of their work to others skilled in the art. An object or module as herein described is generally a self-consistent sequence of steps leading to desired results. These steps are those requiring physical manipulations of physical quantities. Usually, these quantities take the steps of electrical or magnetic signals capable of being stored, transferred, combined, compared or otherwise manipulated. More specifically, an object or module is a section of computer readable code which is designed to perform a specific task or tasks. Actual computer executable code need not be contained with one file or one storage medium to constitute an object or module. Objects or modules generally receive input and provide output. The objects or module may receive information passed by another calling object or module and may output information to the calling object. A web host is computer hardware capable of creating and processing computer readable instructions and is not limited to a single computer. For example, mass storage, network communications, and main processing could be executed by three physically separate computers and would still constitute a web host. Therefore, the term “web host” is not intended to be limited to a single computer. Packets are electronic messages or information together with an Internet address which are sent as one unit. A datagram is a complete message and can be sent in many or one separate packet. With these terms in mind, the preferred embodiment is described in more detail. 
     Referring to the drawings, the invention will now be described in further detail. This invention provides an Internet based personal tracking system, designated generally as A, for tracking a position of an individual  10  in possession of personal location unit  12  of FIG.  1 . The tracking system includes a web host B connected to the Internet  14  through network connection device  15 . A computer program runs on web host B and receives input from a concerned user  16  through the user terminal  17 . Web host B receives input from location unit  12  through cellular network  22  and modem  20  representing the global position data for individual  10 ; and makes the position data accessible by concerned user  16  through user&#39;s terminal  17 . Web host B has a connection  13  to the Internet  14  allowing a multitude of concerned users  16  to access web host B. Each concerned user has a connection  18  to the Internet allowing access to the web host. In addition to a connection with the Internet, web host B has a communication connection  19  for connecting the web host to a modem  20 . Modem  20  allows web host B to initiate cellular calls to call a personal location unit  12 . When dialing cellular numbers, modem  20  connects to a cellular network  22  through a phone line  21 . The web host can then transmit and receive data from personal location unit  12  through cellular network  22  allowing for location unit  12  to send its global position data to web host B. 
     In order to provide the functionality required for a concerned user to track an individual, location device  12  may be a GPS based device using digital cellular communications. As best can be seen in  FIG. 2 , location unit  12  may include a GPS chip  28  carried within an enclosure for reading information from a global positioning satellite system. Global position satellites  36   a - 36   c , generate signals  37  which are received through an antenna  35  of unit  12  and forwarded to GPS chip  28 . GPS chip  28  passes the information to a processor  34 . Processor  34  then may calculate latitude, longitude, and altitude of the device and, therefore, of the individual. Once calculated the position information is transmitted to a cellular network  22  by a wireless transceiver  26  using a wireless communication antenna  32 . Memory  33  may be included within personal unit  12  to hold a number of previous position readings which can be used to show the prior path or track of the location unit and tracked individual, as disclosed in the above application. Processor  34  is programmed to control location unit  12  on stand-by, automatically answer a position inquiry from a concerned user, poll the GPS chip and received GPS position information, transmit the position information to the host, terminate the call, and return to stand-by. 
     While personal location unit  12  may be powered by a stackable power supply  30 , a back-up battery system  31  may also be provided which has an extended shelf-life. Stackable power supply  30  may include stackable thin film batteries as have been recently developed for the cellular market. In the event that the stackable power supply  30  fails, an individual can still activate key  25 . Once key  25  is activated, back-up power supply  31  enables location unit  12  to transmit its current GPS location to cellular network  22  even though stackable power supply  30  is fully exhausted. Therefore, the individual can transmit the current location in the event the key is activated. 
     Since the personal unit  12  only receives location requests and transmits GPS data, the powers required are significantly less than the traditional cellular phone. With this advantage as well as eliminating the need for voice communication, location unit  12  can require less power and be significantly smaller than the traditional cellular phone. However, if an individual does not wish to take advantage of these improvements, any device with wireless communication and global positioning features may be used such as the GPS/Cell-phone Navtalk marked by Garmin. 
       FIG. 4  illustrates the basic components of web host program C for providing functionality to this invention. The web host program comprises a set of computer readable instructions embodied in a computer readable medium located on the web host. To initiate a tracking request, the program receives a datagram  60  generated by user terminal  17  sent to web host B. Datagram  60  includes an unique access code  60   a  and an unique unit code  60   b  supplied by the concerned user. The program includes as interface module  61  which includes the instructions necessary for terminal  17  to communicate with web host B. Interface module  61  passes request datagram  60  to a process module  64 . Process module  64  includes can include a set of instructions for receiving datagram  60 , validating the access and unit codes, and requesting and receiving the position data for making the same available to the concerned user, as more fully described below. 
     As best can be seen in  FIG. 5 , processing module  64  includes an input module  74  for receiving tracking request datagram  60 . There is a validation module  76  having instructions for receiving the access code and determining if the access code is valid and whether processing can continue. There is a location module  78  which receives unit code  60   b  for further processing if the processing continues. Location module  78  includes a set of instructions for initiating wireless communication through a wireless communication module  80 . Wireless communication module  80  includes instructions for polling personal location unit  12  by making a cellular phone call through modem  20 . Connected wireless communication module  80  sends a position request datagram  81  which received by transceiver  26  of personal unit  12 . Wireless communication module  80  also includes the instructions for receiving and processing position data and forwards this data to a format module  82 . The format module includes instructions which create position information  66  and provides a user readable representation of the position of individual  10  such as a map display or position coordinates. A display module  84  includes a set of instructions to create a datagram containing user position information  66  to be accessed by the concerned user&#39;s terminal  17 . Network interface module  72  includes instructions for receiving position information  66  and allowing the concerned user to know and/or display the global position of the individual being tracked. Location unit  12  responds to position request datagram  81  by determining its global position through satellites  36   a - 36   c  ( FIG. 2 ) and temporary stores this global position information. The position data  62  is then transmitted back through modem  20  to wireless communication module  80 . 
     OPERATION 
     In use, concerned user  16  can discover the global position of individual  10  by accessing web host B through terminal  17  connected to web host B by the Internet. To do this, the concerned user enters a domain name for web host B such as www.satcel.com in step  40  of FIG.  3 . When the remote user enters a domain name, a datagram is created at terminal  17  and transmitted across the Internet, from the concerned user to the web host, which contains the Internet addresses of the user. At this point, the concerned user enters a tracking request which includes a system access number  60   a  and a personal unit code  60   b  which is unique to personal unit  12 , at step  42 . A datagram is created containing the concerned user&#39;s input and sent to the web host. Upon receiving the remote user&#39;s request, the web host initiates communication with the personal location unit at step  44  by initiating a cellular telephone call to the personal location unit. The personal location unit may answer the call without any action by the individual nor with any notification to the individual. The web host sends a small compressed digital packet requesting the global position of the personal location unit. Such a packet need only include a single character or two, as disclosed in the above application. 
     Once communication with the personal location unit is initiated, the web host requests position data from the personal unit at step  46 . The personal location unit then polls GPS satellites for determining its global position at  48 . The GPS satellites transmit the location data and the personal location unit receives the data at step  50 . The personal location unit then constructs a packet containing the global position data and sends the packet back to the web host. The web host receives the position data and stores the information at  52  either in permanent or temporary memory. At this point, cellular communication may be terminated. At  54 , the web host formats the global position of the individual based upon the stored position data. The results of the formatting would be a map display, street address or position coordinates. Once this formatting is complete, the web host makes the global position information available to the concerned user at  56 . The web host, associating the personal location unit number and concerned user&#39;s Internet address, constructs datagram  60  ( FIG. 4 ) containing the individual&#39;s position. This datagram is sent to the concerned user&#39;s terminal across the Internet. The concerned user receives the datagram and a display of the global position of the individual is created at the concerned user&#39;s terminal. Once the initial map is displayed the user has the option to zoom in or out on the position of the tracking unit. 
     While the Internet is the preferred and most expedient method of providing communication between the concerned user and the web host, multi-user networks including Local Area Networks or Wide Area Networks using such communication connections as dial-up, ISDN, Ethernet, token ring, FDDI or other connection methods well known in the art would also provide such a communication connection. Additionally, while cellular communication is the preferred and most expedient method of providing communication between the web host and personal location unit, any wireless communication such as satellites, microwave, or infrared would provide such wireless communication. The position data received by the personal location unit  12  from the GPS satellites  36   a - 36   c  can be converted into the global position of the individual either at the personal unit itself or the raw position date can be passed to the web site and the global position calculated there. Additionally, position date may be derived from sources other than GPS such as GLONASS, Triangulation, or signal strength determination. 
     Referring now in more detail to protective location unit  12  of FIG.  2 . Any suitable GPS  28  chip may be utilized such as a model Superstar (with antenna), available from Canadian Marconi of Quebec, CN. The GPS chip creates tracking signals  23  which included the latitude and longitude of the person wearing locator device  12 . Tracking information signals  23  are transmitted to processor  34 . The processor may any suitable programmable processor. Advantageously, the processor process tracking signals  23  to generate and store personal position signals  100  in memory  33 . Any suitable transceiver device may be utilized. A suitable digital transceiver is available from Motorola of Schaumburg, Ill., Model 650. The transceiver may use either analog or digital lines to transmit a signal. GPS chip  28  reads the tracking signals of the locator device at any desired interval, such as every 30 minutes. The GPS chip is adjustable so that the reading interval may be adjusted as desired. Transceiver device  26  is on standby at all times. The processor stores a predetermined number of the GPS readings, for example, the previous 100 readings in memory  33 . It is advantageous to store a predetermined number of previous readings in the event that a child is abducted and is held inside a building or other environment in which it is not possible to receive satellite signals and obtain GPS readings. In this case, when the locator device is called, a trail of the past 2 days positions will be downloaded to the remote station to help pinpoint the user&#39;s current location. 
     When a position inquiry  102  is received from the remote station in order to determine the position of location unit  12 , the transceiver automatically answers the call and activates processor  34 . Processor  34  is programed to automatically retrieve the personal position signals  100  stored in the memory and transmit the position signals to remote station host B via transceiver  26 . The programming of the processor will be well within the purview of the average artisan in the automatic programming art having been taught the expedients and operation of the present invention. At the remote station, the digital position signals  104  are received by a modem wired to base station computer  58 . The computer is programmed to convert the longitude and latitude signals for the identified location and display the position on the user&#39;s map. 
     In accordance with the invention, digital position signal  104  which is output by location unit  12  is in a special format so that low power requirements are needed to transmit the signal. The signal is purely a data signal and contains no voice or sound. Since there is no voice, the processor  28  outputs only a very small digital position signal  12 . For example, position signal  12  may include a small digital data packet  39 , containing only protocol data  12   a , a personal code number  12   b  identifying the person to whom the locator device is assigned, longitude data  12   c , and latitude data  12   d . Therefore low power is required to transmit the position signals. At the remote station, the digital position signals  12  are received by a modem (not shown) wired to remote station computer  58 . The computer is programmed to convert the longitude and latitude signals for the identified individual, and display the location of the user on a map  38   a.    
     In accordance with the invention, digital position signal  104  which is output by location unit  12  is in a special format so that low power requirements are needed to transmit the signal. The signal is purely a data signal and contains no voice or sound. Since there is no voice, the processor  34  outputs only a very small digital position signal  104 . For example, position signal  104  may include a small digital data record described above. Therefore low power is required to transmit the position signals. At the base station, the digital position signals  106  are received by a modem wired to remote station computer  58 . Therefore low power is required to transmit the position signals. The high power requirements associated with analog sound and voice transmission of full cellular transmissions are eliminated. Means for powering GPS chip  28  processor  34 , and transceiver device  26  may be provided by a miniature rechargeable battery system designated generally as  30 . The rechargeable battery system may be a miniaturized, lightweight version of a lithium ion battery and recharging system such as disclosed in U.S. Pat. No. 5,742,233. For example, transceiver  26  may only require 0.6, or even 0.3, watts. The low power requirements for the system allows redundancy to be built into the system by way of a back-up power supply system  31 , described below, which is sufficient to fire the system for position signal transmission once or twice. 
     In accordance with an advantageous aspect of the invention, a back-up power system, designated as  31 , is provided. Back-up battery  31  may be any suitable battery which has an extended shelf life. An activation switch in the form of a key  25  is provided which normally locks the back-up power supply  31 . The back-up power system  31  allows the processor  34  and transceiver  26  to operate once or twice when the primary power source  30  is completely drained. Once the key  25  has been activated to use the power back-up system, the battery  31  will be fully expended, but a new battery may be inserted after use. Battery  31  may be a suitable watch battery having a shelf life of about one year. 
     While the digital telephone system is preferred, national coverage may not presently exist for digital technology. When national coverage does exist, the digital technology will provide an advanced location system which will have faster and more long distance communication and longer battery life. However, for the present, the wireless communications between the protective location device  12  and the remote station  58  may be had using cellular analog transmissions. Cellular telephone systems currently provide national coverage necessary to allow the location device to function on a national basis. 
     The processor  34  remains in a standby, power reducing mode until one of two events occurs. Either the host or base station makes a call or the emergency key  25  is pressed. In the first case, the remote station sends out a cellular call transceiver  26  and processor  34  answers the call. If the call is to the correct number, i.e. location unit, processor  34  reads the present GPS tracking signal  102 , and transmits the present coordinates via transceiver  26  to the remote station. The personal location device can also transmit previously stored coordinates in memory  33  to the host as described above. For this purpose, processor  34  may be programmed to send either the current position signal, the position history which includes all the stored position signals, or any number of the stored signals in response to a coded inquiry call  102 . Processor may be programmed to send the desired signals depending on a corresponding inquiry signal from the remote station or host. Typically, only the current position signal will be transmitted when key  25  is pulled to activate the system in an emergency. 
     The back-up power supply system provides the redundancy necessary to allow the personal location device to function reliably. The back-up power supply system allows the personal location device to provide location information to the remote station even if the primary power source is drained. While the preferred embodiment is an Internet based system, it is also to use location unit  12  in a personal tracking system as can best be seen in  FIGS. 3 and 4 . The personal location may be worn by a child&#39;s toy such as a stuffed bear  110  by means of a thin, elongated rectangular housing  52  in which the device  12  is housed. Alternately, the personal location unit may be worn by the child when it is not practical or desirable to carry the toy bear  110 . Advantageously, location unit  12  may be placed in a conventional back pack like one typically worn by a child to school. The device may be concealed underneath the child&#39;s clothing or other inconspicuous place so the device may be activated if the child is abducted. 
     If the child is lost, or otherwise encounters an emergency situation, activation switch  25  is turned and activated whereby an emergency GPS signal is transmitted to the remote station to tell the remote station where the child is located. Each personal location device will have a code number which is also transmitted with the GPS signal data so that the remote station knows exactly who the individual is. At that time the remote station will also contain information for contacting a person to be notified in the case of an emergency which may be the parents of the child or other person related to the individual. 
     This application claims the priority of U.S. Provisional Application Ser. Nos. 60/118,983 filed on Feb. 5, 1999 and 60/153,350 filed on Sept. 10, 1999 which applications are hereby incorporated in this disclosure by reference. 
     While a preferred embodiment of the invention has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.