Abstract:
A process for initiating maritime radio communication, directed toward the recipient vessel&#39;s location, and exclusive of all other vessels outside the geographically-defined box. An airborne electro-optical or infrared sensor detects the presence of vessels in the maritime domain. Established geolocation techniques are employed to determine the approximate geographical location (latitude and longitude) of the target vessel. The derived geographical location of the target vessel is used to encode a Digital Selective Calling (DSC) Geographical Area Call, in the Very High Frequency (VHF) band, for the purpose of establishing radio communications. The process allows for geographically selective communications without previous knowledge of the target vessel&#39;s Maritime Mobile Service Identity (MMSI) and without the target vessel&#39;s assistance in determining its geographical location.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    No Federal funding was used in the research or development of this invention. 
       REFERENCE TO SEQUENCE LISTING, TABLE, OR COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
       [0003]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 340/825.341 Communications, electrical. Digital and selective based on the geographical location (latitude and longitude) of the receiving maritime vessel. This process facilitates radio communication and has applications in maritime search and rescue, collision avoidance, port security, and maritime domain awareness. 
         [0005]    2. Description of Related Art 
         [0006]    Digital Selective Calling (DSC) is an integral part of the Global Maritime Distress Safety System (GMDSS). Geographical Area Calling is one of many types of DSC calls. DSC protocols for Geographical Area Calls are set forth in the International Telecommunications Union&#39;s ITU-R M.493 (series). Vessels with DSC-capable radios, if properly interfaced with a Global Positioning System (GPS) receiver, will process incoming Geographic Area Calls when the vessel is within a prescribed geographical “box,” defined in latitude and longitude by the calling party&#39;s encoded DSC transmission. If outside this defined geographical box, a vessel&#39;s radio will not process the incoming Geographical Area Call and nothing will be heard by the operator. The Federal Communications Commission (FCC) requires that all marine radios manufactured after June, 2000 have at least minimal DSC capabilities. 
         [0007]    Numerous maritime port surveillance systems exist that utilize optical sensors to detect and track vessels. The problem with these systems is the inability to directly establish radio communications with any vessel the optical sensor detects. A broadcast on the Very High Frequency (VHF) distress frequency, channel 16, is generally the only means to establish radio communications with subject vessels. The present invention defines a process that combines established DSC Geographical Area Call formatting with existing geolocation technology using Electro-Optical (EO) or Infrared (IR) sensors in a unique way to enable geographically selective radio contact with any DSC-capable vessel. 
         [0008]    Hiraoka [US 2009/0079590 A1] discloses a method to display the location of a vessel based on received DSC or Automatic Identification System (AIS) transmissions from the vessel. The method described by Hiraoka requires that the subject vessel make its position known by actively transmitting positional reports via DSC or AIS radio transmissions. In Hiraoka, the subject vessel is a willing and active participant in determining its geolocation. The present invention defines a process in which the subject vessel&#39;s position is determined without that vessel&#39;s knowledge or participation. Furthermore, this invention describes a process where radio communications are established without the subject vessel broadcasting its position via DSC or AIS transmissions. The present invention has no requirement that the subject vessel will assist the sender in determining its geolocation. 
         [0009]    Sundoro [US 2010/0099386 A1] describes a method of storing and transmitting a pre-recorded voice message to a selected vessel after radio communications are established using a DSC Individual Call. A DSC Individual Call achieves the desired selectivity by encoding the subject vessel&#39;s Maritime Mobile Service Identity (MMSI) in the DSC transmission. A MMSI is a 9-digit identification number, similar to a telephone number, and unique to a specific vessel or group of vessels. Only the subject vessel&#39;s DSC radio will decode the sender&#39;s DSC Individual Call transmission. The process described in Sundoro does not require that the sender determine the geographical location of the subject vessel, only that its MMSI is known and that the subject vessel is within range of the DSC transmission (roughly 20 miles depending on antennae heights and transmit power). The present invention employs a completely different type of DSC call; the Geographical Area Call. A DSC Geographical Area Call achieves the desired selectivity by encoding the subject vessel&#39;s approximate position (latitude and longitude) in the transmission. Only installed DSC radios within the designated “call box” will decode the transmission. The present invention does not require knowledge of the subject vessel&#39;s MMSI to establish radio communications. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    The present invention defines a process that combines DSC Geographical Area Call functionality with existing geolocation techniques using a EO/IR sensor systems in a unique way to enable selective radio contact with vessels equipped with a DSC radio. EO/IR sensors mounted on an aerial platform detect vessels in the maritime environment. Video images of a subject vessels and the vessel&#39;s geographical location, in latitude and longitude coordinates, are sent to a processor and displayed on a Human/Machine Interface (HMI) display. Upon receiving a user command from the HMI, either manually entered or when operating in autonomous mode, the Geographically Selective Maritime Messaging (GSMM) module formats a DSC Geographical Area Call encoded with the subject vessel&#39;s estimated latitude and longitude coordinates in accordance with International Telecommunications Union formatting protocol. The DSC Geographical Area Call sequence modulates a VHF carrier frequency and is transmitted over the air. The subject vessel&#39;s DSC radio, being within the prescribed “call box,” will decode the transmission and alert the vessel&#39;s radio operator that a caller is attempting to establishing radio communications. Selectivity is accomplished as the entire process is transparent to operators of vessels outside of the geographical call box since their DSC radios will not decode the transmission or provide an audible alert. In summary, this invention defines a process for initiating radio communications with selected vessels without prior knowledge of the subject vessel&#39;s MMSI and without the subject vessel&#39;s assistance in determining its geographical location. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a functional block diagram of the overall Geographically Selective Maritime Messaging (GSMM) process 
           [0012]      FIG. 2  is a block diagram of the GSMM module 
           [0013]      FIG. 3  is a block diagram of the aerial sensor platform 
           [0014]      FIG. 4  is the Human Machine Interface (HMI) display screen 
           [0015]      FIG. 5  is a flow diagram of the preferred embodiment of the process of the invention 
           [0016]      FIG. 6  is the format of a DSC Geographical Area Call (From ITU-R M.493) 
       
    
    
     INDEX TO THE REFERENCE NUMERALS 
       [0000]    
       
           1  Geographically Selective Maritime Messaging Module 
           2  Aerial Sensor Platform 
           3  Very High Frequency (VHF) Radio Transceiver 
           10  Target Display Processor 
           11  Human Machine Interface (HMI) 
           12  HMI Display 
           13  DSC Geographical Area Call Processor 
           20  Camera, Electro-Optical or Infrared sensor 
           21  Global Positioning System (GPS) Receiver and antenna 
           22  Target Position Processor 
           100  Target Display Video 
           101  Target Geographical Location Information, Latitude/Longitude 
           110  User Commands 
           120 - 124  Target Vessels 
           130  DSC Geographical Area Call—Audio Tones 
           200  Target Video 
           201  Geolocation Data—Azimuth and Laser Range Finder (LRF) 
           210  Geolocation Data—Latitude/Longitude of Aerial Sensor Platform 
           211  Geolocation Data—Altitude of Aerial Sensor Platform 
           220  Geolocation Data—Latitude/Longitude of Target 
       
     
       DETAILED DESCRIPTION OF THE INVENTION 
       [0037]    A process described that employs the derived geographical coordinates of OE/IR sensed maritime vessels to initiate radio communications through pre-formatted digital packets. Although all equipment shown in the figures will be described in detail to provide context, only the Geographically Selective Maritime Messaging Module  1  is essential to the process for which a patent is sought. The aerial sensor platform  2  and VHF radio  3  are ancillary equipment and not essential to the process for which a patent is being sought. 
         [0038]    The aerial sensor platform  2  can be any elevated structure or airframe comprised of Electro-Optical or Infrared sensing equipment  20 , Global Positioning System (GPS) receiver and antenna  21 , and target position processor  22 . Aerial sensor platforms  2  include, but not limited to, unmanned aerial vehicles (UAV), aerostat, blimp, or tower structure. The aerial sensor platform  2  provides an unobstructed view of the surrounding maritime environment below. The EO/IR sensor  20  provides raw video  200  of detected vessels to the Target Display Processor  10  of the GSMM Module  1 . The EO/IR sensor  20  also provides a signal  201  to the Target Position Processor  22  for the purpose of determining the approximate geographical position, in latitude and longitude, of objects in the sensor&#39;s field of vision. Signal  201  consists of the azimuth angle of the sensor&#39;s lens and Laser Range Finder (LRF) measurement to the target vessel. The aerial sensor platform&#39;s onboard GPS receiver  21  provides the platform&#39;s own geographical position, in latitude and longitude, as signal  210  internally to the Target Position Processor  22  for the purpose of target vessel geolocation. The GPS receiver  21  also provides signal  210  externally to the Target Display Processor  10  of the GSMM Module  1  for the purpose of displaying the aerial platform&#39;s geographical position on the HMI Display  12 . The GPS receiver  21  also provides signal  211 , altitude or height above ground, internally to the Target Position Processor  22  for the purpose of target vessel geolocation. Since the location and altitude of the aerial sensor platform are known, as well as azimuth angle and range to the target vessel, by applying mathematical formulas the target vessel&#39;s geographical location can readily be determined. In other words, if two sides (platform altitude and distance to target) of a triangle are known, the length of the third side can be determined. This is the function of the Target Position Processor  22 . The target vessel&#39;s derived geographical location, in degrees of latitude and longitude, is provided as an output of the Target Position Processor  22  as signal  220  to the Target Display Processor  10  of the GSMM Module  1 . 
         [0039]    The GSMM Module  1  shown in  FIG. 2  is the essence of the present invention. The Target Display Processor  10  accepts inputs  200 ,  210 , and  220  from the Aerial Sensor Platform  2  and outputs the composite signal labeled Target Display  100  to the Human Machine Interface (HMI)  11 . Target Display Signal  100  consists of an icon representing the aerial sensor platform&#39;s position and an icon representing the target vessel&#39;s position overlaid on an electronic nautical chart. Video of the target vessel is also supplied as part of the composite Target Display Signal  100  to the HMI  11  and displayed on HMI Display  12 . Target Display Processor  10  also outputs the target vessel&#39;s geographical location, in degrees latitude and longitude, to the DSC Geographical Area Call Processor  13 . If enabled by User Command signal  110 , the DSC Geographical Area Call Processor  13  will encode the target vessel&#39;s geographical position into a DSC Geographical Area Call sequence as specified by ITU-R M.493 (series). The DSC Geographical Area Call sequence  130  is sent to a VHF radio  3  where it modulates a carrier frequency and is transmitted over the air with an effective range of approximately 25 nautical miles. 
         [0040]    DSC protocols and call formatting are set forth in ITU-R M.493 as follows: The DSC system is a synchronous system using characters composed from a ten-bit error-detecting code. The first seven bits of the ten-bit code are information bits. Bits  8 ,  9  and  10  indicate, in the form of a binary number, the number of B elements that occur in the seven information bits, a Y element being a binary number 1 and a B element a binary number 0. The order of transmission for the information bits is least significant bit first but for the check bits it is most significant bit first. Time diversity is provided in the call sequence as follows: Apart from the phasing characters, each character is transmitted twice in a time-spread mode; the first transmission (DX) of a specific character is followed by the transmission of four other characters before the re-transmission (RX) of that specific character takes place, allowing for a time-diversity reception interval of 33⅓ ms for VHF radio-telephone channels. The classes of emission, frequency shifts and modulation rates are as follows: Frequency modulation with a pre-emphasis of 6 dB/octave (phase modulation) with frequency-shift of the modulating sub-carrier for use on VHF channels. Frequency-shift between 1300 and 2100 Hz; the sub-carrier being at 1700 Hz; the frequency tolerance of the 1300 and 2100 Hz tones is ±10 Hz; the modulation rate is 1200 Baud; the index of modulation is 2.0±10%. 
         [0041]    ITU information specific to the Geographical Area Call: Geographical area entry DSC equipment should be provided with means for transforming a geographical area specified by the user as a center point and a range to the corresponding Mercator area call format specified. The transformation of the entered range and center-point should result in the minimum rectangular area that encompasses the entered data. 
         [0042]      FIG. 6  from ITU-R M.493.11 depicts how a desired geographic “call box,” encompassing the subject vessel, is formatted and digitally encoded. When such a Geographical Area Call is transmitted, only those DSC-capable radios located within the boundary of the call box will decode the transmission and alert the operator by ringing. The transmission will be transparent to all vessels outside the boundary of the call box. ITU-R M.493 only allows for call box resolution in one degree increments, or roughly 60 miles per side. This is not practical since the call box would encompass many unintended vessels. One method to address this shortcoming is by reducing the transmitter output power and employing radiation pattern beamforming techniques with directional antennas. ITU M.821 allows for a DSC expansion sequence, which improves resolution to one minute increments, or about one mile per side. 
         [0043]    The receiving DSC radio, upon receiving and decoding the Geographical Area Call on 156.525 MHz (Ch. 70), alerts the radio operator that another party is attempting to initiate radio communications. Per ITU-R M.493, the receiving DSC radio automatically tunes to a pre-determined frequency for follow-on voice communications. Channel 70 is designated by the Federal Communications Commission (FCC) as a “digital messaging only” frequency; no voice communications are permitted. 
         [0044]    The VHF radio  3  that broadcasts the DSC Geographical Area Call is controlled by the GSMM Module  1 . To initiate a DSC transmission, the HMI  11  sends a transmit enable signal as a User Command  110  through the DSC Geographical Area Call Processor  13  to the VHF radio  3 . The User Command  110  to transmit a DSC Geographical Area Call can be initiated by the HMI  11  either manually by an operator or automatically. 
       BEST MODE OF OPERATION OF INVENTION 
       [0045]    The GSMM process is scalable and easily adaptable to a wide variety of applications. Three manifestations of the GSMM process are outlined here: 
         [0046]    Force protection. In this scenario, the Aerial Sensor Platform  2  is an airborne UAV patrolling the perimeter of a formation of military vessels. The GSMM Module  1  and VHF radio  3  are located aboard one of the military vessels. An operator monitors displayed target vessels on the HMI Display  12  to ensure they do not encroach upon the established security perimeter. If the operator detects a possible Small Vessel Threat (SVT), a User Command  110  is initiated to the DSC Geographical Area Call Processor  13  and a DSC Geographical Area Call  130  sequence is sent to the VHF radio  3  and transmitted on DSC channel  70 , 156.525 MHz. The target vessel&#39;s DSC radio “rings” alerting the operator that someone desires to establish voice communications on a predetermined frequency. Both operators switch to a “working” radio frequency and the GSMM operator communicates that the target vessel has intruded inside the security perimeter. The target vessel backs away from the formation of military vessels. 
         [0047]    Port Security. In this scenario, the Aerial Sensor Platform  2  is a fixed tower or tall building with unobstructed views of a port, harbor, or waterway. The GSMM Module  1  is located in a U. S. Coast Guard Command Center and the VHF radio  3  is part of the Coast Guard&#39;s Rescue  21  communications network. In this configuration, since the aerial platform is fixed the GPS Receiver  21  could be eliminated by manually entering the platform&#39;s latitude, longitude, and altitude information directly into the Target Position Processor  22 . An operator defines geographical boundaries, or “geo-fences,” on the electronic navigational chart using the HMI  11  and HMI Display  12 . An OE/IR sensed vessel crosses the virtual geo-fence and triggers a User Command  110 . The DSC Geographical Area Call Processor  13  receives the command and a DSC Geographical Area Call  130  sequence is sent to the VHF radio  3  and transmitted on DSC channel  70 , 156.525 MHz. The target vessel&#39;s DSC radio “rings” and boater switches his radio to a voice frequency to hear instructions from the Coast Guard. 
         [0048]    Autonomous Operation. In this last scenario, the GSMM Module  1  and VHF radio  3  are physically co-located on the Aerial Sensor Platform  2 , which is a UAV. The EO/IR sensor system scans wide swaths of ocean below while the UAV flies a pre-established flight pattern. The HMI  11  has been programmed to automatically generate User Command  110  and initiate a DSC Geographical Area Call to a target vessel. The onboard VHF radio  3  transmits the call on DSC Channel  70 . The target vessel&#39;s DSC radio rings and the operator shifts to the requested voice frequency to hear a pre-recorded message. 
         [0049]      FIG. 5  is a flow diagram of the preferred embodiment of the invention; a process for selectively initiating radio communications with a maritime vessel equipped with a Digital Selective Calling radio when the vessel is within a geographical area  500 . A Digital Selective Calling radio uses geographical area call formatting as set forth in the International Telecommunications Union&#39;s latest standard in the series designated ITU-R M.493. 
         [0050]    A first step  510  comprises inputting the target vessel&#39;s geographical location, in degrees latitude and longitude, from an optical/infrared sensor system mounted on an aerial sensor platform. A second step  520  comprises displaying the target vessel on a Human/Machine Interface display as a computer icon. The target vessel&#39;s computer icon is displayed at the derived latitude and longitude on an electronic navigational chart. 
         [0051]    An optional step  530  comprises an operator manually selecting a target vessel and sending a user command to the DSC Geographical Area Call processor. Optional step  531  comprises an automated mode of operation wherein a processor is pre-programmed to send a user command to the DSC Geographical Area Call processor without operator intervention. 
         [0052]    Step  540  comprises using a computer processor to format a DSC Geographical Area Call sequence as set forth in ITU-R M.493. The Geographical Area Call “call box” shown in  FIG. 6  is comprised using the target vessel&#39;s geographical location information  510 . 
         [0053]    Step  541  comprises modulating a VHF carrier frequency with the Geographical Area Call sequence  540  and transmitting the signal over the air to the target vessel&#39;s DSC radio. The target vessel&#39;s DSC radio will alert the operator to an incoming Digital Selective Call  542 .