Communications: directive radio wave systems and devices (e.g. – Directive – Including a satellite
Reexamination Certificate
1999-06-16
2001-04-24
Pihulic, Daniel T. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a satellite
Reexamination Certificate
active
06222484
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a system and method for locating a person lost overboard from a vessel. More particularly, the invention concerns a system that is attached to the person at all times while at sea and operates to signal the person's exact location to the vessel or to other rescue vessels.
BACKGROUND OF THE INVENTION
For years persons have been lost overboard and not been able to be located even when near their own ship. Although Emergency Position Indicator Radio Beacons (EPIRBs) have been widely used for decades, they have not been sufficiently small enough to be carried by individuals. Additionally, EPIRBs use radio frequency direction finding and therefore are not very accurate in pin-pointing an individual or even a small boat lost at sea. They are not even very effective for allowing the person's ship to locate the person who has fallen overboard. EPIRBs are typically used by the United States Coast Guard (USCG) service, which continually monitors for EPIRB emergency radio broadcasts and have the ability to determine the location of the EPIRB by Doppler signal processing from the satellite receivers. An EPIRB-determined location is only accurate to within several square miles and can be off as much as thirty square miles.
Other rescue locating devices include mirrors, strobes and lights, whistles flares and other items. These are certainly better than nothing but they are not ideal. In many instances, these devices must be operated by the overboard person who may quickly be overcome and incapacitated by the environment.
More recently, Global Positioning Systems (GPSs) have been used to locate lost persons. GPS systems determine position by receiving signals from a sub-set of the 24 U.S. GPS satellites that are in operation. The signals transmitted by each satellite include a time code, which is synchronized with the time codes transmitted by the other satellites. The GPS system calculates an earth-centered-earth-fixed (ECEF) position for the location where the signals are received, based on the time differences between the signals received from the satellites and the known location of the satellites. ECEF positioning uses a 3-axis coordinate system with the origin located at the center of the earth, and can be translated to a global coordinate-based system (i.e., latitude and longitude).
The GPS satellites are not in geo-synchronous orbits. The location of the satellites are determined from almanac and ephemeris data either downloaded from the ship's host system or from the satellites themselves. Almanac data are good for several weeks and are updated weekly. Ephemeris data are good for about 4 hours and are updated hourly. Almanac data consist of general information regarding all satellites in the constellation and atmospheric data for a determination of RF propagation delays. Almanacs have approximate orbital data parameters for all satellites. The typical ten-parameter almanac describes the satellite orbits over extended periods of time of up to several months and a set for all satellites is sent by each satellite over a period of 12.5 minutes minimally. Signal acquisition time on receiver start-up can be significantly aided by the availability of current almanac and ephemeris data. The approximate orbital data are used to preset the receiver with the approximate position and carrier Doppler frequency (i.e., the frequency shift carried by the rate of change in range to a moving satellite) of each satellite in the constellation. Ephemeris data consist of detailed orbital information for the specific observed satellite. It can take up to 15 minutes to initialize a GPS system if the almanac and ephemeris data are not available or not up to date.
GPS-based locator systems have required individuals to be equipped with a small GPS receiver and a radio to send their latitude and longitude coordinates over the radio. This requires the person to have both devices when lost, which is unusual for most recreational boating situations and typically only occurs with military pilots who are thus equipped. Another approach has been to carry a device that sends an RF emergency signal to the person's vessel or a nearby vessel when overboard, so that the crew on the vessel can broadcast an alert of the overboard situation and give at least the vessel's location with its on-board GPS navigation system when the emergency signal is received. This would provide rescue vessels with the position of the vessel from which the person has fallen overboard, but cannot provide the exact location of the person nor an update of the person's location adrift with the current. A person overboard in heavy sea often cannot be seen even one hundred feet away from a pending rescue vessel. If rescue is not accomplished quickly, that person can easily be lost. Larger ships and sailing vessels typically take time to turn around and retrace their course, so not having an exact location of the overboard person can greatly diminish the effectiveness of the rescue effort. In small sailing vessels often only one person is on watch; if that person falls overboard, it may be hours before it becomes known.
SUMMARY OF THE INVENTION
In accordance with the present invention, a personal emergency location system (PELS) comprises a small battery-powered personal unit adapted to be worn by a person who may have fallen overboard from a vessel having a GPS receiver and processor for determining the person's GPS location coordinates, and an RF transmitter for sending an RF emergency signal of the person's coordinate data to a nearby vessel (such as the person's vessel) within a short range. The PELS personal unit is updated with the most current ephemeris data during a time when the person is inactive on-board the vessel by plugging it into an input module connected with the vessel's GPS system. The person wears the PELS personal unit when on active duty on the vessel. If the person falls overboard, the PELS personal unit is activated to send an emergency signal with the person's location coordinates. The person's vessel or a nearby vessel within a short range can receive the PELS emergency signal, provide a distress acknowledgment, mark the position of the person based on the received emergency signal, and broadcast an alert and emergency signal to other rescue vessels or stations of the person's position.
In a preferred embodiment of the present invention, the PELS personal unit includes a ROM memory for storing a GPS calculation program of machine-readable instructions in order to determine the person's GPS location coordinates to be sent via radio frequency to a nearby GPS-equipped vessel. The RF signal is preferably formatted as a digitized data packet transmitted at 156.525 MHz, meeting all International Maritime Organization (IMO) specifications for digital emergency radio communications.
The PELS system also requires a GPS-based system on-board the person's vessel or a nearby vessel (referred to as the “base station”) that is able to receive the distress signal from the PELS personal unit and provide a distress acknowledgment to it. The base station translates the received personal unit's GPS position into its own navigation program and calculates an intercept vector (range and bearing) to the individual or plots the location of the individual on an electronic chart. The base station can have an emergency communications system which will receive the distress signal and alert the operator with the overboard person's positional information. The base station can perform a “Distress Relay” to other appropriate authorities (as defined by the IMO). Upon receipt of the “Distress Acknowledgment”, the personal unit will enter a standby mode to preserve battery power and enable an acknowledgment-received indication for the distressed individual. This can be done by use of an indicator light(s), audible signal or vibration. The lost person thus knows by the indicator that his distress signal has been received.
T
Seiple Robert B.
Seiple Ronald L.
Chong Leighton K.
Pihulic Daniel T.
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