WO2006122416A1

WO2006122416A1 - Satellite-enabled remote location monitoring device with two-way distress signal capability

Info

Publication number: WO2006122416A1
Application number: PCT/CA2006/000812
Authority: WO
Inventors: Tom Tessier; Leonard Netser
Original assignee: Surelinx Incorporated
Priority date: 2005-05-17
Filing date: 2006-05-17
Publication date: 2006-11-23
Also published as: CA2507718A1

Abstract

A portable tracker device and a method of transmitting a distress signal using a tracker device is provided. The portable tracker device is able to, in response to a user initiating a distress signal, transmit a location of the tracker device and a distress indicator over a satellite communication infrastructure to a remote computer. The device waits for an acknowledgement from the remote computer and upon receiving the acknowledgement, informs a user that the distress indicator was received. The method comprises having a user initiate a distress signal on the tracker device and transmitting a location of the tracker device and a distress indicator over a satellite communication infrastructure to a remote computer. The remote computer upon receiving the transmission, transmits an acknowledgment to the tracker device, and in response the tracker device informs the user that the distress indicator was received.

Description

SATELLITE-ENABLED REMOTE LOCATION MONITORING DEVICE WITH TWO-WAY DISTRESS SIGNAL CAPABILITY

This invention is in the field of remote position tracking equipment and more specifically in the field of GPS enabled devices capable of transmitting data to a remote location.

BACKGROUND

The Global Positioning System (GPS) of medium-earth orbit (MEO) satellites has allowed people to accurately pinpoint their position using a GPS radio frequency receiving device ("GPS module") that uses triangulation to determine it's position by precisely measuring the time delay of coded radio frequency signals from a number of GPS satellites simultaneously in view of the GPS module.

By combining wireless transmitting capabilities and a control module with a GPS module, devices have been constructed that allow position coordinates determined by the GPS module to be transmitted to a remote location, so that the position of the device can be determined or even tracked over time from a remote location.

In these sorts of applications the main focus is to simply be able to locate a vehicle when desired to check on its progress. The remote tracking devices transmit the location of the vehicle and in well populated areas, can usually access a wireless infrastructure utilizing terrestrial antennas mounted on towers and other structures that are readily available to transmit the information. These remote tracking devices are seldom out of comrminication with either enough GPS satellites to determine its position or a terrestrial wireless communication infrastructure to transmit position data to a remote location. With the focus on monitoring a number of remote devices, problems with transmission of data or temporary loss of a transmissions are fairly rare in weil populated areas, and while they may be irritating usually not terribly problematic for these applications.

However, when the remote tracking device is used to relay its position and track the progress of the remote tracking device in a remote, sparsely populated location, the focus is not one of merely monitoring the location of the remote tracking device, but also the device becomes a vital safety system, hi situations where the remote tracking devices are used for monitoring people in remote locations, these devices are not only used to keep tabs on the location of the remote tracking device but may serve as a very vital component of a rescue mission if the user of the remote tracking device requires help. The capabilities of the remote tracking device may mean the difference between successfully rescuing a person in an emergency situation in a remote location and not being able to locate and rescue that person in time.

m these situations, the remote tracking devices may be the only link between the operator of the remote tracking device and other people. While providing a device that simply transmits data related to the position of the device may be suitable for relatively well populated areas where there is unlikely to be a significant lack of contact with anyone else, this functionality alone may not be sufficient where really remote conditions are involved and contact between parties is almost non-existent except through the device.

in addition, while a person may be fairly confident that transmissions by the remote tracking device will be timely received in more populated areas, this is hardly the case in more remote areas where timely transmission of data is hardly guaranteed due to a lack of radio coverage by terrestrial antennas. In more remote locations and especially northern locations, substantial wireless communication coverage is usually only available using a low earth orbit (LEO) satellite communication system. In order for a satellite to receive a transmitted signal, the satellite must be visible to the transmitting device. A commercial communication system employing LEO satellites in circular orbits generally have orbital periods on the order of approximately 100 minutes. Therefore, for an observer on the ground, LEO satellites come in and out of view at a relatively rapid rate in comparison to medium-earth orbit satellites, with orbital periods of 6-12 hours, and geostationary earth orbit satellites, with a period of exactly one day and appear stationary in the sky to an observer on earth. This means that the LEO satellites will come in and out of view of a particular point on the earth at a fairly rapid rate. Constellations of LEO satellites need a relatively high number of satellites in order to provide coverage that will completely cover the earth at any time. Nearly alt LEO communication satellite constellations do not provide 100% earth coverage. Most systems are designed with the best coverage being focused at mid-latitudes. Therefore, there will not always be constant, uninterrupted communication abilities over the satellite network, a problem which becomes a significant constraint in remote locations, notably high northern and southern locations.

Some current LEO satellite communication systems have satellite visibility gaps of 15 minutes or longer where no service is available to users. Additionally, because satellite communication relies upon line of sight with the transmitting device, in areas with limited view of the sky such as gorges or other areas, this time is extended even further because the transmitting device would have to wait until a satellite is in view of its limited sight; in very sheltered locations, satellites have to pass directly above the transmitting device before they can communicate, thus severely restricting the minutes per day of satellite communication capability.

A remote (racking device that is suitable for monitoring the progress of a vehicle, object or person through a relatively populated area with good terrestrial wireless communication infrastructures, will often not be sufficient for tracking personnel in remote locations where the remote tracking device must not only be able to provide remote monitoring of the personnel, but must also form a vital piece of emergency search and rescue equipment.

SUMMARY OF THE INVENTION It is an object of the present invention to address deficiencies in the prior art.

In one aspect of the invention is provided. The portable tracker device comprises: a positioning module operative to determine the global position of the device; a data communication module operative to transmit data over a wireless communication infrastructure; a control module operatively coupled to the positioning module and the data communication module. The control module is operative to, in response to a user initiating a distress signal: transmit location data, using position data received from the position module, and a distress indicator to the data communication module to transmit the location data over the wireless communication infrastructure to a remote computer; wait for an acknowledgement from the remote computer, transmitted over the wireless communication infrastructure, that the distress indicator was received by the remote computer; and in response to receiving the acknowledgement, indicate to the user that the distress indicator was received.

In another aspect of the invention a method of transmitting a distress signal using a tracker device is provided. The method comprises: having a user initiate a distress signal on the tracker device; in response to the user initiating a distress signal on the tracker device, transmitting a location of the tracker device and a distress indicator over a wireless communication infrastructure to a remote computer; in response to receiving the location of the tracker device and the distress indicator, the remote computer transmitting an acknowledgment over the wireless communication infrastructure to the tracker device; and in response to receiving the acknowledgment, the tracker device indicating to the user that the distress indicator was received.

The tracker device is a remote device that can be transported with a person or object and can determine its position and transmit its location to location remote from the tracker device allowing the tracker device to me monitored by remote personnel.

The data communication module is operative to transmit data packets from the tracker device and receive incoming data packets.

In one embodiment of the invention, the programming of the tracker device can be altered remotely. The data communication module can receive data that can alter the programming of the tracker device on the fly without requiring any action from the user of the tracker device. Parameters such as the interval between times of transmission of data packets containing location data by the tracker device can be altered remotely without requiring the tracker device to be taken in for servicing or an on-site visit made for servicing.

In a further embodiment of the tracker device, an I/O interface module can be provided in Che tracker device comprising inputs and outputs to the tracker device. The I/O interface module can be attached to sensor inputs, outputs and/or other interfaces to be connected to the tracker device. Any inputs can be monitored by the control computer and the control computer can implement a pie-programmed action when certain conditions are met; by either transmitting a message that a pre-condition has been met, prompting an output to address the pre-condition, or both.

In normal operation, the tracker device transmits location data to a remote server which can then be transmitted to a τemote device such as a personal computer, PDA, fax, phone, etc. to inform the user of the τemote device of the location of the tracker device.

In addition, data packets originating from either the remote device or the remote server can be transmitted back to the tracker device, such as sending a message to the user of the tracker device by providing the tracker device with a screen capable of displaying text or activating some other means of conveying this acknowledgment to the user of the track device.

In addition to providing monitoring of the tracker device when it is located or moving in remote locations, the tracker device can also further serve as a vital emergency tool greatly enhancing the success of a search and rescue mission that might have to be performed to assist a user of the tracker device in a remote location. The tracker device is equipped to send an alert data packet, containing the last set of coordinates of the tracker device, to the central server to alert operators at the central server that the user of the tracker device is in trouble or needs assistance. The user of the tracker device instigates the alert data packet, typically by opening the tracker device and flicking a switch, or pressing a button on the tracker device.

The alert data packet is transmitted with as little delay as possible to the remote server where it is flagged as an alert data packet and used to alert an operator of the remote server to the distress situation of the user of the tracker device. The operator can then acknowledge receipt of the aiert data packet and this acknowledgment is transmitted back to the tracker device.

Once an operator has been alerted to the distress signal from the tracker device, the location and the alert status of the tracker device can be forwarded to a remote device to inform the operator of the remote device of the distress situation and provide the last set of coordinates of the tracker device. A rescue mission can then be instigated using the last known coordinates of the tracker device.

In addition to receiving alert data packages and forwarding and storing received location data from a tracking device, the remote server can also monitor the incoming data packets from a tracker device to ensure that data packets are being received at approximately expected intervals. If a data packet is expected from a tracker device and a significant time has passed, suggesting it is not a standard delay in transmission, the centra! server can send a data packet to the tracker device querying whether there is a problem and if no acknowledgment is received, taking further steps such as informing the operator of the remote device that no data packets have been received from the tracker device within the expected time and even preparing a rescue mission.

DESCRIPTION OF THE DRAWINGS

While the invention is claimed in the concluding portions hereof, preferred embodiments are provided in the accompanying detailed description which may be best understood in conjunction with the accompanying diagrams where like parts in each of the several diagrams are labeled with like numbers, and where:

Fig. 1 is a schematic illustration of a tracker device, in accordance with the present invention; and

Fig. 2 is a schematic illustration of a personnel tracking and monitoring system incorporating the tracker device of Fig. 1, in accordance with the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Fig. 1 schematically illustrates a tracker device 10 comprising: a GPS module 12; a GPS antenna 13; a data communication module 14; a transmitter/receiver antenna 15; a control module 16 and an input/output interface module 18. The tracker device 10 is a remote device that can be transported with a person or object. The tracker device 10 can determine its position and transmit tnis location data to a remote location, allowing the location of a tracker device 10 to be determined at the remote location.

The GPS module 12 is a GPS receiver operative to receive global positioning satellite signals using the GPS antenna 13 and process these signals into location and other data.

The data communication module 14 is a transmitter/receiver operative to transmit data packets from the tracker device 10 and receive data packets. Although this data communication module 14 could be operative to transmit and receive data over any wireless infrastructure system such as a cellular telephone system with terrestrial antennas or some other system, in one embodiment of the invention it is contemplated that the data communication module 14 would be a satellite data communication operative to transmit data via satellite communication system such as the Orbcomm™ satellite system.

The control module 16 controls the operation of the tracker device ]0 and is in communication with the GPS module 12, data communication module 14 and I/O module 18. The control module 16 receives location data from the GPS module 12 and can store this data. Additionally, the control module 16 is operative to assemble and format data packets at determined intervals and transmit these assembled data packets using the data communication module 14 over the wireless infrastructure. The control module 16 can also receive incoming data packets from the wireless infrastructure using the data communication module 14. In addition, the control module 16 controls the general operation of the tracker device 10 such as activating and deactivating the GPS module 12 and controlling the mode of operation of the tracker device 10 (i.e. receiver on, unit on low-power sleep, etc.).

Optionally, the programming of the control module 16 can be altered remotely. The data communication module 14 can receive data that can alter the programming of the control module 16 allowing the programming of the control module 16 to be altered remotely. Parameters such as the interval between times of transmission of data packets containing location data by the tracker device 10 can be altered remotely without requiring the tracker device 10 to be taken in for servicing or an on-site visit made for servicing. Also, the programming of the tracker device 10 can be altered remotely without requiring the user of the tracker device 10 to have to make any changes to the tracker device 10 by him or herself.

The I/O interface module 18 can be attached to sensor inputs, outputs and/or other interfaces to be connected to the tracker device 10. Any inputs can be monitored by the control module 16 and the control module 16 can implement a pre-programmed action when certain conditions are met. The I/O interface module 18 can also allow the attachment of a number of outputs that allows the control computer 16 to provide outputs when pre-determined conditions are met. For example, a temperature sensor could be connected to the I/O interface module 18 to monitor the temperature of the contents of a container the tracker device 10 is attached to. If the temperature of the contents of the container drops below a specified level or exceeds a specified level, the control module 16 can transmit a message back to the central server 110 to alert people to the detected condition and provide an output through the I/O interface module 18 that will activate a backup environmental control.

The I/O interface module 18 can also be used to control an external device remotely through a serial connection.

Fig. 2 is a schematic illustration of an overall system using the tracker devices 10 where the wireless infrastructure is a satellite communication system. The system comprises: tracker devices 10; global positioning satellites 50; communication satellites 100; a gateway station 105; a data network 107; a remote server 110; and a remote terminal 120. The tracker device 10 determines position data using the GPS satellites 50 and transmits location data based on this position data to the remote server 110, allowing a person using the remote terminal 120 to access this location data.

In normal operation, each of the tracker devices 10 will receive signals from the global positioning satellites 50 and from these signals determine position data. Each tracker device 10 logs this position data and at predetermined intervals the tracker device 10 generates a data packet containing location data and attempts to transmit the data packet using the transmitter/receiver antenna 15 to the communication satellites 100.

The communication satellites 100 are typically low-earth orbit satellites to allow the tracker devices 10 to operate in a wider range of areas and remote locations where other wireless infrastructures may not be available. Using low-earth orbit satellites allows data transmitted to the communication satellites 100 to be transmitted with lower powered transmitters and low-cost antennas, but because of the orbits of the communication satellites 100, the satellites iOO are not always in communication with the tracker devices 10. This is especially true in many remote and high-latitude locations. The tracker devices 10 transmit location data to the communication satellites 100 using a store and forward method. If a communication satellite 100 is not in view, the tracker devices 10 store the data packets in memory until a communication satellite 100 comes into communication with the tracker device 10. Once the communication satellite 100 has come into communication with tracker device 10 the tracker device 10 will forward or transmit the data packet to the communication satellite 100.

Once a data packet has been transferred to a communication satellite 100, the communication satellite 100 transmits the data packet to a gateway station 105. Again, the communication satellite 100, because of its orbit, is not always in communication with a gateway station 105. The data packet is typically transmitted to the gateway station 105 in a store and forward method, where the communication satellite 100 stores the data packet until the communication satellite 100 is in communication with a gateway station 105 and then transmits the data packet to the gateway station 105.

Generally, although not necessarily, the tracker device 10 can be operative to implement an acknowledge-or-retransmit algorithm to ensure successful transmission of the data packets. When a data packet is received by the gateway station 105, the gateway station

105 can transmit an acknowledgement of receipt back through the communication satellites 100 to the tracker device 10. The tracker device 10 will wait after transmitting a data packet for this acknowledgment of receipt by the gateway station 105. If no acknowledgment of receipt is received by the tracker device 10, the tracker device 10 will attempt to retransmit the data packet and can continue to do so until an acknowledgment of receipt by the gateway station 105 is received by the tracker device 10.

From the gateway station 105, the data packet is transmitted over a data network 107 to a central server 110. The central server 110 parses the data packets and identifies the tracker device 10 that transmitted the data packet. The central server 110 can then store the different locations of each tracker device 10 at different times and build a history of locations the tracker device 10 has been located over time.

Although Fig. 2 illustrates the system using a low earth orbit satellite system as the wireless infrastructure being used to transmit data packets from the tracker devices 10 to the central server 110, it is contemplated that other suitable wireless communication infrastructures capable of transmitting data from the tracker devices 10 to the remote server 110 could be used. For example, the tracker devices 10 and remote server 110 could be communicating through a cell phone wireless network, high frequency (HF) short wave (approximately 1-60 MHz) radio repeater network utilizing atmospheric reflection of signals to communicate over the horizon or other such applicable system.

A remote device 120 can then be used to access the appropriate logged data in the remote server 110 for access by a person using the remote device 120. The remote device 120 can be a cell phone, pager, fax or other device where an operator of the remote device 120 can be quickly notified of the position of the tracker device 10. Alternatively, the remote device 120 could be a personal computer, PDA or other device in communication with the remote server 110 over a TCP/IP connection or wireless network and the location information could be forwarded to the remote device 120 in an email or through a specific program running on the remote device 120. The remote server 110 can communicate a last position of the tracker device 10 to the remote device 120 or a number of past locations. In one embodiment, the remote device 120 has a map client that can display the locations of a tracker device 10 overlaid on a map displayed on the remote device 120.

Data packets originating from either the remote device 120 or the central server 110 can be transmitted back through the system to a tracker device 10. A data packet can be sent by the remote unit 120 to the remote server 110, the remote server 110 will in turn forward the return data packet back to the gateway station 105 where it will be transmitted to a communication satellite 100 and routed back to the tracker device 10.

With the provision of a screen, text messages or other message content can be transmitted to a tracker device 10 from either a remote device 120 or a remote server 110, allowing a user of the remote device 120 to communicate simple messages to the tracker device 10.

The tracker device 10 is operative to send a distress signal to the remote server 110 so that a user of the tracker device 10 can notify someone of an emergency situation. A user of the tracker device 10 can instigate the distress signal by selecting a distress signal on the tracker device 10. When the user instigates this distress signal, tracker device 10 will transmit location data identifying the immediate position of the tracker device 10 to the remote server 110 with an indicator that the data packet is a distress alert. This indicator could be the use of a special address at the remote server 110 so that the data packet is given priority processing status or it could be an indicator in the data field of the data packet identifying the urgency of the distress data packet that the remote server 110 upon parsing the alert data packet will forward the information to an operator for immediate attention.

Generally, although not necessarily the user of the tracker device 10 will instigate the distress signal by opening the tracker device and flicking a switch or pressing a button. Typically, the tracker device 10 will provide an indication to the user of the tracker device 10 that a distress signal has been instigated, such as by lighting a red indicator light on the device tracker 10.

When a distress signal is selected by the user of the tracker device 10, the tracker device 10 will assemble a special alert data packet and transmit the alert data packet to the first communication satellite 100 in sight. The alert data packet is then transmitted from the communication satellite 100 to the first gateway station 105 where it is then transmitted over the data network 107 to the remote server 110. Once the alert data packet is transmitted to the central server 110, the remote server 110 can alert operators monitoring the remote server 110 to the alert data packet. The remote server 110 then sends an acknowledgment data packet back through the data network 107, the gateway station 105, the communication satellite 100 and back to the tracker device 10 that transmitted the alert data packet. The tracker device 10 upon receiving the acknowledgment data packet will alert the user that the distress signal has been received and acknowledged, typically by lighting a light on the tracker device 10 so that the user knows his or her transmission has been successful and help is on its way.

The remote server 110 can also forward an alert message to a remote device 120 to notify the operator of the remote device 120 of the distress message and provide the last position of the tracker device 10. Wireless communication infrastructures, and especially satellite communication infrastructure in high latitude locations, can not guarantee a short duration of time until the transmission of data packets or even guarantee transmission of a data packet. Typically, without some sort of acknowledgment of receipt, a person transmitting a distress signal can only transmit the distress signal and hope that it gets through and help is sent. By providing a system that provides an acknowiedgment that the distress signal has been received the person in distress will be informed that his or her distress signal has been received by the proper parties. Alternatively, if an acknowledgment is not received by the tracker device 10 the tracker device 10 can continue to attempt to retransmit an alert data packet until an acknowledgment is received. Additionally, if person does not receive an acknowledgment he or she can try to take further proactive steps to get help, such as moving the tracker device 10 to a different location that may be more accessible to the satellite communication system 100.

In one embodiment of the invention, the tracker device 10 indicates the acknowledgement of the distress signal by the central server 10 by lighting an alert τeply light, such as a coloured light, on the tracker device 10 so that the user of the tracker device 10 knows the acknowiedgment has been received by the trackeT device 10.

The remote server 110 can also monitor the incoming data packets from the tracker devices 10 to track whether data packets from each of the tracker devices 10 are being received on approximately the expected intervals. Each tracker device 10 will have a predetermined interval in which the tracker device 10 is expected to transmit a data packet comprising location data. Especially when the wireiess infrastructure is a satellite communication system, there could be some significant delay of time between the tracker device 10 attempting to transmit a data packet so the central server 110 so the remote server 110 would have to account for a reasonable delay in receiving an expected data packet from a tracker device.

After a predetermined period of time has passed and the remote server 110 has not received an expected data packet from a tracker device 10, the central server 10 can transmit a message to a remote device 120 indicating that no data packets have been received from the associated tracker device 10 within the expected time frame. Additionally, the last known location of the tracker device 10 can be transmitted to the remote device 120 so that the operator of the remote device 120 can see the last known whereabouts of the tracker device 10.

The remote server 110 can also transmit a distress query to the tracker device 10 to query the user of the tracker device 10 as to whether or not there is an emergency. The remote server 110 can transmits a query data packet to the gateway station 105 which will transmit the data packet to a communication satellite 100 and back to the tracker unit 10. Upon receiving the data packet, the tracker device 10 can alert the user of the device of the received query. If the tracker device 10 is equipped with a screen capable of displaying text, the tracker device 10 could display a message to the user. Alternatively, the tracker device 10 could be equipped with a light that is lit when the tracker device 10 receives the query allowing a user can respond to the query by flicking a switch or pressing a button on the tracker device 10.

There may be a number of reasons that a tracker device 10 could not be transmitting location data to a remote server 110 that do not involve the user of the tracker device 10 being in a distress situation. The tracker device 10 may just not be able to get clear signals from the required number of global positioning satellites 50 and may be unable to determine its position or it could be having problems transmitting to the communication satellites 100. By querying the tracker device 10, this allows the user of the tracker device 10 to indicate that everything is okay and that there is no reason to launch a search and rescue mission.

If the tracker device 10 does not acknowledge the query, operators at either the remote server 110 or an operator of the remote device 120 can begin to launch a rescue mission to find the user of the tracker device 10 using the last known position of the tracker device 10.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all such suitable changes or modifications in structure or operation which may be resorted to are intended to fall within the scope of the claimed invention.

Claims

CLAIMSWhat is claimed is:

1. A portable tracker device comprising:

a positioning module operative to determine the global position of the device;

a data communication module operative to transmit data oveτ a wiτeless communication infrastructure;

a control module operatively coupled to the positioning module and the data communication module, the control module operative to, in response to a user initiating a distress signal:

transmit location data, using position data received from the position module, and a distress indicator to the data communication module to transmit the location data over the wireless communication infrastructure to a remote computer;

wait for an acknowledgement from the remote computer, transmitted over the wireless communication infrastructure, that the distress indicator was received by the remote computer; and

in response to receiving the acknowledgement, indicate to the user that the distress indicator was received.

2. The device of Claim 1, wherein the position module is a GPS positioning module and is operative to determine the global position of the device by receiving global positioning satellite signals and using these global position satellite signals to determine the location of the device.

3. The device of Claim 2, wherein the wireless communication infrastructure is a satellite communication system.

4. The device of Claim 3, wherein the satellite communication system is a network of low earth orbit satellites.

5. The device of Claim 4, wherein the location data and distress indicator are transmitted in a single data packet.

6. The device of Claim 1 wherein the control module is operative to: in response to not receiving the acknowledgment within a predetermined period of time, retransmit the location data and distress indicator to the transmitter receiver module to be transmitted to the remote location.

7. The device of Claim 1 wherein the control module indicates to a user that the acknowledgment has been received by illuminating a light on the device.

8. A method of transmitting a distress signal using a tracker device, the method comprising:

having a user initiate a distress signal on the tracker device;

in response to the user initiating a distress signal on the tracker device, transmitting a location of the tracker device and a distress indicator over a wireless communication infrastructure to a remote computer;

in response to receiving the location of the tracker device and the distress indicator, the remote computer transmitting an acknowledgment over the wireless communication infrastructure to the tracker device; and

in response to receiving the acknowledgment, the tracker device indicating to the user that the distress indicator was received.

9 The method of Claim 8, wherein the wireless communication infrastructure is a satellite communication system.

10. The method of Claim 9, wherein the satellite communication system is a network of low earth orbit satellites.

11. The method of Claim 10, wherein the remote computer in response to receiving the location of the tracker device and the distress indicator transmits a notification to a remote device.

12. The method of Claim II, wherein the location data and distress indicator are transmitted in a single data packet.

13. The method of Claim 8 wherein in response to the tracker device not receiving the acknowledgment within a predetermined period of time, retransmitting the location data and distress indicator to the remote computer.

14. The method of Claim 8 wherein the tracker indicates to the user that the acknowledgment has been received by illuminating a light on the tracker device.