Abstract:
A radar system includes a memory device operable to store radar-return data characterizing at least one geographic region, a database including a set of chart data representing fixed landmarks associated with the at least one geographic region, and a processor coupled to the memory device. The processor is configured to obtain from the memory device multiple sets of the radar-return data corresponding to successive scans of the at least one geographic region, perform correlation processing among the multiple data sets to yield a first correlated data set, perform correlation processing between the first correlated data set and fixed-landmark chart data associated with the at least one geographic region to yield a second correlated data set, and process the second correlated data set to remove said fixed-landmark chart data therefrom and yield a third data set representing scanned objects that are not fixed landmarks.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Commercial marine radar systems are required to provide automated radar target detection and tracking of 100 targets (e.g., objects that have not been previously identified and/or charted) or more. The ability to discriminate between targets and fixed navigation objects is of great concern. It is particularly valuable to detect those targets that have, or appear to have, no apparent motion. 
       SUMMARY OF THE INVENTION 
       [0002]    In an embodiment, a radar system includes a memory device operable to store radar-return data characterizing at least one geographic region, a database including a set of chart data representing fixed landmarks associated with the at least one geographic region, and a processor coupled to the memory device. The processor is configured to obtain from the memory device multiple sets of the radar-return data corresponding to successive scans of the at least one geographic region, perform correlation processing among the multiple data sets to yield a first correlated data set, perform correlation processing between the first correlated data set and fixed-landmark chart data associated with the at least one geographic region to yield a second correlated data set, and process the second correlated data set to remove said fixed-landmark chart data therefrom and yield a third data set representing scanned objects that are not fixed landmarks. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]    Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings. 
           [0004]      FIG. 1  illustrates an exemplary system formed in accordance with an embodiment of the present invention; 
           [0005]      FIG. 2  illustrates conceptually the functionality of a memory device according to an embodiment; and 
           [0006]      FIG. 3  is a flowchart illustrating the functionality of the system of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0007]    Embodiments of the invention employ processing of 2-D radar reflectivity data to detect and identify objects in a geographic region that are not fixed, or not otherwise known, landmarks. As used in this description, the term “landmark” should be interpreted to include fixed navigation aids, such as buoys, as well as geological objects, such as land masses. An embodiment provides a solution to the problem of discerning between a vessel or floating hazard and a fixed or otherwise known landmark, such as a navigation buoy, when the vessel or floating hazard has no velocity relative to the observing radar, as well as providing a direct way of allowing a radar to provide identification information for detected navigation items. 
         [0008]    This approach differs from existing target detection and tracking concepts for marine radar in that it uses a motion-compensated marine-chart database as a distinctive memory layer to provide known locations of objects within a navigable waterway and use successive memory layers to retain detailed radar images of the surrounding water and land masses directly “above” or indexed to the motion stabilized marine chart database. 
         [0009]    The layered 3-D memory lends itself to more advanced processing among the stored image layers for reduction of clutter due to sea state or rain, and avoidance of collisions at sea with either known fixed objects or other floating threats that are not included by a database. 
         [0010]      FIG. 1  illustrates a system according to an embodiment, as well as a suitable operating environment in which an embodiment of the invention may be implemented. The operating environment is only one example of a suitable operating environment and is not intended to suggest any limitation as to the scope of use or functionality of the invention. 
         [0011]    The invention may be described in the general context of computer-executable instructions, such as program modules, executed by one or more computer processors or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Typically the functionality of the program modules may be combined or distributed as desired in various embodiments. 
         [0012]    The system/operating environment illustrated in  FIG. 1  typically includes at least some form of computer readable media, which may be associated with one or more processors and/or memory devices. Computer readable media can be any available media that can be accessed by one or more components of such operating environment. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media. Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by one or more components of such operating environment. Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Combinations of the any of the above should also be included within the scope of computer readable media. 
         [0013]    Embodiments of the invention include a system and computer program product for classifying a target as a vessel or floating hazard (as opposed to a fixed and/or known object such as a navigation buoy) when the radar target or floating hazard has no relative velocity to the observing radar and provides a direct means of allowing a radar to provide identification information for detected navigation items, as well as providing navigation and location verification of the vessel (not shown) on which the system is implemented.  FIG. 1  illustrates an exemplary system  10  formed in accordance with an embodiment of the present invention. The system  10  includes a radar antenna  12  and a scan motor and angle indicator assembly  14  operable to provide an indication of the azimuth angle of the antenna. The system  10  further includes a radar transceiver  16 , a radar-signal processor  18 , a memory device  20 , a radar navigation processor  22 , a radar detection processor  24 , a ship heading indicator  26 , a marine chart database  28 , a GPS receiver  30 , and a radar display device  32 . The memory device  20  may include or be a component of a three-dimensional buffer processing system, such as, or similar to, the RDR-4000 weather radar system manufactured by Honeywell®, including its volumetric buffer technology. 
         [0014]      FIG. 2  illustrates conceptually the functionality of the memory device  20  according to an embodiment. A 3-D memory is constructed that includes a “bottom” layer that provides detailed marine navigation chart data that is oriented to the latitude and longitude of vessel location and vessel direction of travel, and includes locations of known landmarks such as drying rocks, islands, navigation buoys and day marks or any other fixed charted object. Successive layers above the chart layer include radar detection data that are collected from successive 360 degree scans at a predetermined time interval Δt by the marine radar antenna  12  that can be conceptually superimposed on the chart layer. While only two scan layers are illustrated in  FIG. 2 , it should be recognized that, advantageously, more than two such layers are retained in the memory, such that a lengthy history of return data can be evaluated according to principles discussed in greater detail below herein. 
         [0015]    The chart data is taken from a marine navigation chart database  28  that may store in memory only the present maximum radar-range extent centered on the present latitude/longitude location of the vessel. 
         [0016]      FIG. 3  is a flowchart illustrating the functionality of the system  10  according to embodiments of the invention. At a step  200 , the GPS receiver provides an indication of the latitude and longitude, and, thus, geographic location, of the vessel on which the system  10  is implemented. As such, a chart appropriate to the indicated location and range extent of the radar may be retrieved from the database  28  to be used for correlation according to principles discussed in greater detail below herein. 
         [0017]    At a step  210 , marine radar detections (radar-return data) are collected for multiple (“N”) consecutive antenna  12  scans of 360 degrees by one or more of the radar navigation processor  22  and radar detection processor  24 . The radar detections are stored in successive layers in the memory device  20  after having been space stabilized by signal processor  18  for the motion of the vessel using latitude and longitude inputs from GPS receiver  30 , and heading, roll, pitch and yaw inputs from a gyroscope (not shown) that is associated with the vessel itself, antenna  12  and/or transceiver  16 . Each 360-degree scan corresponds to one layer of data storage including a conceptual radar image that is superimposed on the marine chart data that is directly “below” it and oriented to the heading of the vessel. 
         [0018]    At a step  220 , scan-to-scan correlation is performed among the N consecutive scans by one or more of the radar navigation processor  22  and radar detection processor  24 . 
         [0019]    At a step  230 , correlation is performed by one or more of the radar navigation processor  22  and radar detection processor  24  between the resulting scan-to-scan correlations and fixed objects on a marine navigation chart corresponding to the geographic location of the radar scans. 
         [0020]    At a step  240 , one or more of the radar navigation processor  22  and radar detection processor  24  determines correlations associated with navigation aids, such as buoys, day marks, etc. 
         [0021]    At a step  250 , one or more of the radar navigation processor  22  and radar detection processor  24  determines correlations associated with geographical landmarks, such as shore lines, large rocks, islets, etc. As such, one or more of the radar navigation processor  22  and radar detection processor  24  can index target returns that match with known landmarks, navigation aids, or other fixed objects and provide identification of those navigation items based on the marine chart database information. 
         [0022]    At a step  260 , the radar detection processor  24  processes the correlation data to remove the correlations associated with the navigation aids and geographical landmarks, such that the resultant correlation data set includes only data indicative of vessels and uncharted potential hazards. As such, the radar detection processor  24  removes radar detections that correspond to the fixed known objects and focuses only on those remaining detections that persist among the successive radar scans to determine eligibility as a target to be tracked. Motion or lack of motion of the detected objects that are not known navigation or geographical features are used to determine, as applicable, the location, velocity and direction of a detected target. 
         [0023]    Alternative approaches may be used, according to embodiments of the invention, to make one or more these determinations by analyzing the relative motion of a detected target. In the first approach, the radar detection processor  24 , in conjunction with the antenna  12  and transceiver  16 , directly measures the component of radial velocity between a detected target and the antenna  12  during the time the target can be observed within the antenna beamwidth. This time frame is determined by the rate of scanning of the antenna  12  and the beamwidth of the antenna. 
         [0024]    In the second approach, the radar detection processor  24  determines the direction of motion and speed of motion of a target by noting the change in location of the target between one scan-to-scan correlation period and the very next scan-to-scan correlation period. By noting the change in location of a detected target over the precise time period between two scan-to-scan correlation periods, and by accounting for the motion of the observing vessel, a very accurate measure of target speed and direction can be obtained by the radar detection processor  24 . 
         [0025]    The display device  32  can then display detected known navigation items and display data associated with such items as provided in the correlated marine chart system, as well as provide details about all detected targets, location, motion and direction. 
         [0026]    At a step  270 , the radar navigation processor  22  determines the location and heading of the vessel based on, for example, a triangulation calculation to the locations of the navigation aids and geographical landmarks previously confirmed by the correlation determinations. 
         [0027]    At a step  280 , the radar navigation processor  22  determines the position of the vessel by triangulating the intersection of relative bearing angles between known navigation aids (e.g., buoys and day marks) and prominent land details. Vessel speed and direction can be obtained by noting the change in position from one triangulation period to the next triangulation period. As such, if data from the GPS receiver  30  becomes unavailable, the system  10  is operable to otherwise provide location and navigation information to the operator of the vessel. 
         [0028]    While a preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.