Patent Publication Number: US-8988284-B2

Title: System and method for tracking lost subjects

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. Non-provisional application Ser. No. 12/541,379, filed Aug. 14, 2009 and entitled “System and Method for Tracking Lost Subjects,” which itself claims priority and is entitled to the filing date of U.S. Provisional application Ser. No. 61/088,948, filed Aug. 14, 2008 and entitled “System and Method for Tracking Lost Persons.” The contents of the aforementioned applications are incorporated by reference herein. 
    
    
     INCORPORATION BY REFERENCE 
     Applicants hereby incorporate herein by reference any and all U.S. patents and U.S. patent applications cited or referred to in this application. 
     BACKGROUND OF THE INVENTION 
     1. Field Of the Invention 
     Aspects of this invention relate generally to tracking systems and related methodologies, and more particularly to a system and method for tracking lost subjects using GPS triangulation techniques. 
     2. Description of Related Art 
     By way of background, children, adults with challenged mental capacity, and pet animals can easily wander off from their intended location either by disorientation, distraction, theft or kidnapping. Parents and guardians are concerned now more than ever with the increase of kidnappings and foul play on the part of children. Foul play can happen anywhere including the home, parks and forests, schools, public shopping malls, etc. Adults or persons with mental impairments such as Alzheimer&#39;s or other mentally challenged persons may not have the capacity to understand boundary limits and are at risk of wandering off without proper supervision. Cats and dogs may also be lost or stolen and cannot find their way back to their homes. With increasing concerns regarding theft, kidnapping, foul play or mental impairments, there is a need for a tracking system and alerting mechanism that incorporates a convenient transponder and receiver that is readily available, portable, convenient and easy to use. Such technology may also find beneficial use in military applications and other such contexts where quickly and easily determining the locations of people or equipment is desired. 
     The following art defines the present state of this field: 
     U.S. Pat. No. 5,914,675 to Tognazzini discloses a portable emergency locator device which includes a global positioning system (GPS) receiver generating location data and a wireless telephone transceiver for transmitting the location data as digital data to a called station during a two-way voice conversation via a wireless telephone network (cellular, PCS, or satellite). The emergency locator device can be implemented as a conventional wireless telephone having interfaces for receiving the location data from an external GPS receiver and vehicle status data from external vehicle control systems. The data received from the interfaces is stored in an internal memory for transmission to the called station in response to an emergency event trigger 
     U.S. Pat. No. 6,014,080 to Layson, Jr discloses a tamper resistant body-worn tracking device to be worn by offenders or potential victims for use in a wireless communication system receiving signals from a global positioning system (GPS). The tracking device directly communicates spatial coordinates to multiple remote sites. The tracking device is an enclosed case worn on a limb of a person. The case contains a battery, a signaling device, and a circuit board containing a field programmable gate array, a wireless data modem, a conventional GPS receiver, and a matched filtering GPS receiver. 
     U.S. Pat. No. 6,339,397 to Baker discloses a portable self-contained tracking unit which includes an enclosure attached to a mounting plate, with a hollow interior cavity housing a GPS receiver, a microprocessor and a transmitter. The GPS receiver will receive tracking data and the microprocessor will process the tracking data into a data packet. The transmitter transmits the data packet to a remote receiving station, for transmission to a central database. Photoelectric cells are mounted on the enclosure to recharge batteries which provide power to the electrical components of the tracking unit. The enclosure is designed with a pair of vertically oriented side panels which are generally orthogonally oriented so that the solar panels mounted on the side panels will maintain a favorable solar incidence angle during a wide range of orientations. The transmitter is a cellular telephone with an antenna mounted within the enclosure but spaced a distance from the metal mounting plate and electrical components approximately one-quarter wavelength of the operating frequency of the transmitter. The enclosure is formed of a radio frequency and optically transparent material, so that the antenna and the solar panels may be housed within the hollow interior cavity of the enclosure. In the method of the invention, tracking data is periodically transmitted via cellular phone to a cellular service provider, thence to a data service bureau which sends the data over the Internet to the database of a central server computer. The central server computer will decode the information and provide an interface and value added products such as maps and reports for customers via a web page on the Internet. 
     U.S. Pat. No. 6,819,258 to Brown discloses a system for tracking a person from a system subscriber who affixes a location unit to the person to be tracked, wherein the location unit calculates the location of the person at any given time. The system includes a web host connected to a wide area web network, such as the Internet, the web host includes a computer readable medium and is accessible by the subscriber from a remote computer terminal. A computer program resides on the web host for receiving a tracking request from the subscriber and transmitting a tracking call to the location unit carried by the person. The computer program includes instructions embodied in computer readable code for automatically transmitting the tracking call, receiving location data from the location unit in response to the tracking call, and transmitting the location data to the subscriber&#39;s terminal where the current location of the person is displayed. 
     U.S. Patent Application Publication No. US2005/0017900 to Grimm discloses a tracking unit for assisting in the recovery of stolen monies or other property which includes a housing containing a GPS receiver for receiving GPS signals from overhead satellites, a cellular phone transceiver, a microprocessor, and a battery. Following a theft, the microprocessor activates the cellular phone transceiver to dial the telephone number of a central monitoring station. The microprocessor obtains location data from the GPS receiver and transmits the location data, along with identification information, to the central monitoring station. The tracking unit also includes a separate, conventional RF beacon transmitter for allowing authorities to home-in on the tracking unit within a large building or other structure, either after the GPS signals are lost, or after the location of the tracking unit is localized to a specific building or area. 
     U.S. Patent Application Publication No. US2005/0020274 to Ursini discloses a child locating device that is compact and portable. It has a multitude of stealth, placement, and deployment applications. It can be disguised on a child&#39;s wrist, as a bracelet, pendant, watch, ankle bracelet, pocket item, attached to clothing, worn in hair, or in or on a shoe. The device is activated via internet and/or dialing software. The GPS software then tracks from many locations. Locations include home, office, car, or on foot. The system deploys and tracks from a variety of devices, laptop computer, personal computer, or a hand held computer. It combines hardware, GPS software, telephone line, cellular, and internet into a complete child locator. 
     U.S. Patent Application Publication No. US2006/0170588 to Chang discloses a tracking method for a cell phone with a positioning device and a system thereof. The longitudinal and latitudinal coordinates of a tracked end in a global positioning system (GPS) are sent to a cell phone of a tracking end via a short message service (SMS). After decoding the short message contents, the longitudinal and latitudinal coordinates are displayed in a geographic information system (GIS) installed in the cell phone. 
     U.S. Patent Application Publication No. US2006/0176216 to Hipskind discloses an apparatus and methods for tracking an object. The apparatus and methods provide for GPS tracking, and can include a communication system that transmits the position of the object to a central database. Software can track the object and provide updates as to the position, speed, course, and other items of interest. 
     U.S. Patent Application Publication No. US2006/0223518 to Haney discloses a system for exchanging GPS or other position data between wireless devices for purposes of group activities, child location monitoring, work group coordination, dispatching of employees etc. Cell phones and other wireless devices with GPS receivers have loaded therein a Buddy Watch application and a TalkControl application. The Buddy Watch application communicates with the GPS receiver and other wireless devices operated by buddies registered in the users phone as part of buddy groups or individually. GPS position data and historical GPS position data can be exchanged between cell phones of buddies and instant buddies such as tow truck drivers via a buddy watch server. Emergency monitoring services can be set up with notifications to programmable individuals in case an individual does not respond. Positions and tracks can be displayed. TalkControl simplifies and automates the process of joining talk groups for walkie talkie services such as that provided by Nextel. 
     U.S. Patent Application Publication No. US2007/0099626 to Lawrence et al. discloses a system and method for determining and communicating the precise location of an individual and/or a motor vehicle in real-time. As an example, a tracking system is disclosed that includes a Global Positioning System (GPS) receiver, a cellular phone, and a processing unit. The GPS receiver, cellular phone and processing unit are arranged as a single, compact tracking unit. The processing unit receives precise location information (e.g., latitudinal and longitudinal coordinates) for the tracking unit from the GPS receiver. A cellular phone capable of receiving text messages (e.g., and/or voice messages) can be used to call the cellular phone of the tracking unit, which responds (e.g., to an authenticated call) by transmitting a text message (e.g., or synthesized voice message) including the precise coordinates of the tracking unit. Thus, either with or without the knowledge of the individual carrying the tracking unit or driving the motor vehicle containing the tracking unit, the system is capable of providing the exact location of the individual and/or motor vehicle to another at any point in time. 
     U.S. Pat. No. 6,788,200, RE40,879, RE41,087, RE41,102, and RE41,122 to Jamel et al. are directed to a locator unit contained within footwear providing a method for GPS position determination and transmission of said location determination data to a central monitoring station which disseminates the data through the use of proprietary software, wireless communications, land based wire systems and the Internet. 
     The prior art described above teaches various types of tracking devices, each of which providing a GPS receiver built into the tracking device itself. However, the prior art fails to teach a tracking system or method that utilizes triangulation between a GPS-equipped receiver, such as a cell phone or the like, a transponder located with the subject to be tracked, and at least one satellite/tower in order to locate the transponder based on, or relative to, the GPS coordinates of the receiver. Aspects of the present invention fulfill these needs and provide further related advantages as described in the following summary. 
     SUMMARY OF THE INVENTION 
     Aspects of the present invention teach certain benefits in construction and use which give rise to the exemplary advantages described below. 
     The present invention solves the above-described problems by providing a system and method for tracking lost subjects. In sum, a transponder is configured for sending and receiving signals to a receiver, such as a cellular phone, a computer, a portable electronic or computing device, or other wireless communication device over a typical wireless network. In use, proprietary software is installed in the receiver that can then be used to synchronize the receiver with the transponder. Then, when the location of the transponder, and hence the subject that is to be tracked and that is located with the transponder, is to be determined (for example, as when a child is separated from his/her parents or has been abducted), based on triangulation between the receiver, the transponder, and the satellite or broadcast tower, and knowing the location of the receiver based on its inherent GPS capabilities, the precise location of the transponder is thus determined, which information can then be displayed on the receiver 
     A primary objective inherent in the above described system and method of use is to provide advantages not taught by the prior art. 
     Another objective is to provide such a system that utilizes triangulation between a GPS-equipped receiver, such as a cell phone or the like, a transponder, and at least one satellite/tower in order to locate the transponder based on, or relative to, the GPS coordinates of the receiver. 
     A further objective is to provide such a system that does not require the transponder itself to have GPS capabilities, thereby reducing its size, power requirements, and expense. 
     A still further objective is to provide such a system that is compatible with a wide range of cell phones, computers, portable electronic or computing devices, and similar receivers. 
     A still further objective is to provide such a system that allows for various user interfaces or software applications depending on user selections and receiver type. 
     A still further objective is to provide such a system that allows a single receiver to monitor and track a single transponder, a single receiver to monitor and track multiple transponders, multiple receivers to monitor and track a single transponder, or multiple receivers to monitor and track multiple transponders. 
     A still further objective is to provide such a system wherein the one or more receivers are synchronized with or have access for monitoring or tracking purposes to the one or more transponders through a secure connection. 
     Other features and advantages of aspects of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of aspects of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawing illustrates aspects of the present invention. In such drawing: 
         FIG. 1  is a schematic diagram of an exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The above described drawing figures illustrate aspects of the invention in at least one of its exemplary embodiments, which are further defined in detail in the following description. 
     In more detail regarding the exemplary embodiment of the present invention, then, with reference to  FIG. 1 , there is disclosed a system and method for monitoring and tracking the position of a subject, such as a child, pet or other item of value. The system preferably comprises a transponder  10  and a GPS-enabled receiver  50 . 
     In the exemplary embodiment, the transponder  10  is embedded within an article (not shown) that is configured to be worn by the subject. Where the subject is a child, the article may be such items as shoes, clips, pins, buttons, chains, pants, shirts, etc. Where the subject is a pet, the article may be a collar or any other type of pet accessory. Thus, the article itself may be any conceivable item, now known or later developed, that is wearable by a person, pet or other item of value, so long as the article allows for the transponder  10  to be embedded therein, carried therewith, or securely affixed thereto. In an alternate embodiment, the transponder  10  is affixed directly to the subject. In a further alternate embodiment, the transponder  10  is configured as a stand-alone device that may simply be placed in a pocket, purse, bag, or other item to be worn, carried, or otherwise co-located with the subject being tracked. It will thus be appreciated that the transponder may take a number of physical forms and attendant sizes and shapes without departing from the spirit and scope of the invention. Preferably, the transponder  10  in any form is relatively small, whether to be embedded or incorporated in some item to be worn, both for functional and aesthetic reasons, or to be packaged within a case as a stand-alone device to be carried in a pocket, purse, etc., such case thus preferably being the size of a lipstick or dental floss container, though not necessarily so. 
     The GPS-enabled receiver  50  is preferably a cellular phone, smart phone or other such wireless communication device now known or later developed, to be maintained by a user (not shown), such as a parent, babysitter or other guardian. In alternate embodiments, the receiver  50  may be a PDA, tablet computing device, personal computer, whether laptop or desktop, or any other electronic device, now known or later developed, having GPS capabilities. After installing the necessary software onto the receiver  50 , such as a mobile phone application, the receiver  50  is synchronized with the transponder  10  and configured for monitoring and tracking the location of the transponder  10 , and thus the subject, as further discussed below. 
     In the exemplary embodiment, the receiver  50  is incorporated with cellular phone technology, which enables the user, among other things, to program a specific and unique transponder code, allowing the receiver  50  to synchronize and communicate with that particular transponder  10 . Alternatively, during a pairing sequence or routine, the receiver  50  automatically acquires and stores the unique transponder code associated with each transponder  10  to which the receiver  50  is to be synchronized. 
     With the receiver  50  and transponder  10  synchronized, the user can effectively remotely activate the system, as when the subject cannot be located or the user is merely curious as to the subject&#39;s current whereabouts, by inputting the unique transponder code into the synchronized receiver  50 . The receiver  50  then sends out a signal to be received by the transponder  10 , which then sends a reply message back to the receiver  50 . Alternatively, the receiver  50  is able to automatically monitor and track the subject when the transponder  10  exceeds a prescribed perimeter boundary option if desired. In such a situation, the receiver  50  warns its holder, i.e., the user, of the safe distance compromise, digitally determines distance in feet or meters, or other measurement units, and utilises a directional finder arrow to guide the user in the direction of the transponder  10 , much like a compass. The receiver  50  is able to display or audibly announce the distance away and direction of the transponder  10  and triangulate to a cell quadrant like GPS. Once within that quadrant, the receiver  50  may give more specific signalization utilizing, but not limited to, the compass arrow and distance described above. In an alternate embodiment, the data corresponding to the transponder location is instead presented graphically as on a map, such as by having the software installed on the receiver  50  configured to interface with either a proprietary map software application or a third-party software application such as Google® or Yahoo!® maps. As such, the receiver  50  would be able to locate or graphically display the position of the transponder  10  and thus the subject on a map. In a further alternate embodiment, navigational coordinates or directions of the transponder  10  relative to the receiver  50  may be presented on the display of the receiver  50  or by some other method now known or later developed. It will be appreciated by those skilled in the art that one or more such display method or any other method now known or later developed or any combination thereof may be employed in conjunction with the present invention. 
     The receiver  50  can also optionally activate a network tracking sequence by sending the transponder code associated with the lost or “out of bounds” transponder  10  to other “subscribing” receivers  90 , as by a text message or the like. As such, it will be appreciated that a single transponder  10  may be tracked by multiple receivers  50 ,  90  according to aspects of the present invention and as further explained below. 
     The receiver  50  is also preferably capable of storing, in the receiver  50 &#39;s pre-existing memory, vital information regarding the subject, as associated with the respective transponder code, including but not limited to the subject&#39;s physical features, a digital picture, and where the subject is a person, the age, weight, sex, color, clothing last worn, shoe type, model size, and any other uniquely defining characteristics of the subject. Thus, it will be appreciated that the receiver  50  will not only be able to be used as a tracking device but will incorporate technology to wirelessly or otherwise communicate, via Bluetooth® or other wireless communication protocol now known or later developed, the same information and tracking code from the host receiver  50  to other subscribing receivers  90 , thus creating a unique mechanism for multi-tracking capabilities of the pertinent transponder  10 . That is, the quick transmittal of pertinent information to other receivers  90 , as in the exemplary embodiment, enables the notification of numerous people at one time other than by sending them all emails (or in addition to). For instance, if a child is lost at an amusement park, the user can click and broadcast an alert to numerous receivers  90  from the host receiver  50 , even those that the user doesn&#39;t know, without the long arduous task of emailing the information. Other mediums of mass communication, now known or later developed, may be used as well, including social networking websites such as Myspace®, Facebook® and Twitter®, depending on the circumstances. 
     With law enforcement intervention and in coordination with cellular phone services or networks or the like, an “amber alert” message  92  or other emergency “911” message  94 , as illustrated in  FIG. 1 , can be broadcast through wave, cellular or other band to a prescribed local, regional, county, state or other level, thereby alerting the appropriate authorities or other subscribing receivers  90  of a missing person or other emergency. Upon acceptance of the warning by the user, the pre-stored vital information and unique transponder code of the transponder  10  can be broadcast back to the subscribing receivers  90  on the cellular or other network for further action as necessary. In order to ensure that the present system does not become a nuisance or is not overloaded, only the subscribing receivers  90  within the prescribed area, or more specifically within the transponder  10  range capabilities, may become activated. With this “posse” feature, then, if a child is lost in Los Angeles, for example, and the parents or other family and friends think the abductor may live in Fresno and be heading there, one can mass signal those people in the Fresno area and they can opt in or not to see if the child&#39;s coordinates as determined through triangulation are within their locale. In an alternative embodiment, such “opt in” of third-party subscribing receivers  90  can be accomplished more universally at the time of subscription or activation rather than in response to a particular notification. In either case, this “amber alert” opt in could allow for hundreds of “posse” advocates on the lookout for the lost child. Furthermore, it would enable transmission of the pertinent information to the local police department(s), FBI, or other authorities. 
     Relatedly, a further aspect of the present invention as enabled by the synchronization and communication between one or more receivers  50 ,  90  and one or more transponders  10 , and particularly the software installed on the receiver  50 ,  90 , is the creation of effectively an “audit trail” relating to the location over time of the transponder(s)  10  being tracked. It will be appreciated that with each communication sequence between a receiver  50 ,  90  and transponder  10 , actual coordinates of the transponder  10  at a given point in time are determined. By simply configuring the receiver software to capture and log those data sets on the receiver  50  or some other central network facility or computer, a record of the movement of the transponder  10  and hence the subject being tracked can be created. Such a record and the underlying data can then be presented textually, as in a chart, graphically, or in any other such format, and provided to the user or any other authorized parties for purposes ranging from inspection/audit to investigation of criminal activity. It will be appreciated that such a chronology of locations as can be developed according to aspects of the present invention would tell a very clear and helpful story regarding the movement of the subject as known from the location log for the associated transponder  10 . For example, in the case of criminal activity being investigated by law enforcement, by noting the time and location of the transponder  10  (subject) at various points, it would then be known what CCTV cameras or witnesses could be consulted in the hope of obtaining a description or image of a person, vehicle, etc. that could further aid in locating the subject (e.g., abducted person). 
     It will be further appreciated particularly in the context of multiple subscribing receivers  90  having access to the transponder  10  for monitoring and tracking purposes, as described above, that it is desirable that such system have security features and safety precautions built in so as to prevent hacking or other misuse of the system and the information available therethrough for ulterior motives. That is, it is through the unique transponder code and its controlled dissemination that only those authorized to synchronize to or communicate with and thus track a particular transponder  10  are, in fact, able to do so. It will be appreciated that other wireless communication protocols, hardware, and related security measures now known or later developed may be employed in the present invention without departing from its spirit and scope. 
     Again, the transponder  10  can take the shape of, or be incorporated on or in, many convenient forms, including but not limited to straps, clips, pins, wrist bands, necklaces, chains and clothing units such as shoes, so as to be comfortably and discretely worn by the subject. By way of further illustration of aspects of the invention, electronic fabrics can be employed and sewn into military uniforms, helmets, or the like for tracking, wherein the triangulation method and related system of the present invention can also be employed for troop accountability and field monitoring of a brigade. This will allow a central command to see where all the troop personnel are located in a geographic area for strike force maneuvering, etc. Thus, in such an alternate embodiment, it will be appreciated that one or more receivers  50 ,  90  may be configured to track multiple transponders  10 , enabling multiple tracking options. In the specific context of a parent, multiple transponder codes can be entered in the parent&#39;s cell phone or other device corresponding and synchronizing to a transponder co-located or associated with each of the parent&#39;s children. Again, the ability of a single receiver  50  to monitor and track multiple transponders  10  in this manner is both enabled by and a benefit of aspects of the present invention. In an exemplary embodiment, any such clothing units, as, for example, children&#39;s shoes or the uniforms of military personnel, would include electronic built-in transponders  10  that when programmed would indicate the location of the subject. Moreover, continuing with the parent-child example, where each child has multiple pairs of shoes or other articles of clothing or the like equipped with an embedded transponder  10 , or a transponder  10  that is not removable, the parent may need to store in his or her receiver  50  multiple transponder codes associated with such shoes or each child, whereby upon initiating the activation sequence as when one of the children is missing the receiver  50  will “ping” each such transponder  10  that had been previously synchronized with the receiver  50 . When all but one of the activated transponders  10  is at a known safe location or within a safe distance boundary, the one that is not and thus most likely associated with the missing child is quickly and easily determined and tracked according to aspects of the present invention. In the case of a military unit commander, the respective receiver  50  may store hundreds or more unique transponder codes so that such commander can track an entire unit of personnel and assets, for example. In still further embodiments, the transponder  10  may be used in tracking a wide variety of assets, with the transponder  10  capable of being placed within various electronic devices, money bags (in the case of banks), shipping products, motor vehicles, retail goods, etc. Additionally, the transponder could be used for soft criminal tracking, where the criminal does not require an ankle monitor, but rather a government issued shoe or other article to be worn by the criminal, incorporating the transponder  10 , for allowing the criminal&#39;s movement to be monitored as necessary. 
     For shoes, specifically, the transponders  10  may be built into the soles, placed within or under the in-soles, or incorporated into the tongue, toe box, or other part of the shoe as appropriate and will have a life that is equal to or greater than the “wearable” life of typical shoes. Because such self-contained battery transponders  10  are only to be activated when signaled by the receiver  50  in order to generate a unique code path, as explained further below, it will be appreciated that energy or power consumption is minimized and hence battery life is greatly extended, thus enabling the transponder  10  as a whole to outlast the shoe or other item in or on which the transponder  10  is installed. The passive hardware of the transponder  10 , then, essentially consists of a relatively small microprocessor, a transceiver, a memory device separate from or incorporated within the microprocessor for storage of a small amount of identification data, particularly the transponder code through which it is synchronized with the receiver  50 , and a battery as explained above. In further embodiments, though, the battery may be capable of recharging through various means now known or later developed, including but not limited to being recharged through self-generated energy produced by movement of the transponder  10  as it travels with the subject (e.g., vibrational energy). It is also noted that in the event that a child or transponder  10  is found dead or decomposed some time later and the body is unidentifiable, one can look at the “tracking” shoe whereby the police can locate the receiver  50  and thus identifying next of kin. The invention would thus have application with lost or feared dead persons, as effectively the shoe and hence transponder  10  would be the last to be decomposed. A further related aspect would be to configure the transmitter to activate or initiate communication with the receiver when certain conditions are met, such as when the transponder breaches the perimeter boundary that has been set (i.e., the subject being tracked exceeds the selected safe distance) or the transponder is submerged (as when a child has fallen in a pool or other body of water). Once again, the transponders  10  in any such applications may also be stand-alone devices simply worn around the neck or placed in a pocket or bag or other item of persons such as children, the elderly, or soldiers or law enforcement, pets or livestock, or any other subjects to be monitored or tracked according to aspects of the present invention. 
     With continued reference to  FIG. 1 , there is again shown an overall schematic of the system and method for tracking lost subjects of the present invention and particularly of the “triangulation” method employed in the exemplary embodiment. Based on triangulation between the receiver  50 , the transponder  10 , and the nearest satellite or broadcast tower relative to the receiver  50 &#39;s geographic location, more generally denoted the network broadcast site  60 , and knowing the location of the receiver  50  based on its inherent GPS capabilities, the precise location of the transponder  10  (distance and direction from the receiver  50 ) is thus determined. 
     As a threshold matter, it is noted that “triangulation” as that term is used herein describes the general method as summarized above whereby knowledge of two fixed points in space (the locations of the GPS-equipped receiver  50  and the network broadcast site  60 ) and of the angular position of the transponder  10  relative to the network broadcast site  60 , the precise spatial location (coordinates) of the transponder  10  relative to the receiver  50  can thus be determined—that is, with information effectively about two sides and an included angle, the rest of the data about the triangle comprising three sides and three vertices or corners can be geometrically determined, including the spatial location of the third vertex (representing the transponder  10 ). As such, it is to be understood by those skilled in the art that “triangulation” as that term is used herein expressly does not include “geodetic triangulation,” which as a discipline or technique of geodesy, the branch of geology that studies the shape of the earth and the determination of the exact position of geographical points and so is concerned with topographical surveying or mapping, was actually a precursor to and in large part has been replaced by GPS techniques for geodesy. 
     Specifically, geodetic triangulation is a technique by which physical datums or markers on the earth&#39;s surface serve as fixed reference points from which angular measurements can be made to then fix or determine other points, as is well known in the art of surveying on a smaller scale. As such, of late, GPS capabilities for determining physical locations based on satellite data have begun to render traditional geodetic triangulation obsolete. By comparison, again, the “triangulation” method of the present invention is not rendered obsolete by GPS technology, but instead employs the GPS capabilities of cell phones or the like to fix a first reference point from which, in conjunction with the satellite or broadcast tower as the second reference point, the third reference point of the transponder, and thus the location of the missing person, pet or thing, is then determined geometrically. As will be appreciated, by taking advantage of the GPS capabilities of a cell phone or the like and configuring such a phone with the necessary software for activating and synchronizing with a transponder and then for “on demand” tracking by calculating the location of the transponder relative to the cell phone, there is disclosed herein a system and method by which current GPS capabilities can be taken advantage of without the cost, size and power requirements of a GPS transceiver in the transponder  10 , or a GPS transceiver being worn on the person, pet or thing being tracked. Thus, it will be further appreciated that the system and method of the present invention is more conducive to widespread commercialization. 
     To summarize, regarding the exemplary system and method for tracking lost subjects of the present invention, as employed in connection with a transponder-receiver set, it will be appreciated that such a transponder  10  is provided for either stand-alone use or installation on or in a clothing article such as a shoe and configured to work in conjunction with a GPS-enabled receiver  50 , such as a cell phone or the like, to track and determine the location of the transponder  10 , and thus the person or missing pet or other item. The receiver  50  is thus able to determine its precise coordinates as by GPS capabilities or the like and, in conjunction with software residing in the receiver  50  and the relay of signals with the transponder  10  through a network broadcast site  60 , is thus able to determine the location of the transponder  10  without having to separately equip the transponder  10  with a GPS transceiver or the like. Thus, the present system and method is able to take numerous forms in conveniently and effectively determining the location of a subject without departing from the spirit and scope of the invention. 
     It should be noted that the various features of each of the above-described embodiments may be combined in any logical manner and are intended to be included within the scope of the present invention. It will also be appreciated by those skilled in the art that the present invention is not limited to the particular geometries and materials of construction disclosed, but may instead entail other functionally comparable structure, now known or later developed, without departing from the spirit and scope of the invention. Furthermore, while aspects of the invention have been described with reference to at least one exemplary embodiment, it is to be clearly understood by those skilled in the art that the invention is not limited thereto. Rather, the scope of the invention is to be interpreted only in conjunction with the appended claims and it is made clear, here, that the inventors believe that the claimed subject matter is the invention.