Abstract:
A display system is provided for a vehicle. The system includes a first data source configured to provide low resolution terrain data; a second data source configured to provide high resolution terrain data; a processing unit coupled to the first data source and the second data source, the processing unit configured to receive the low resolution terrain data and high resolution terrain data, to integrate the low resolution terrain data and the high resolution terrain data into a common three-dimensional view that includes graphical elements representing both the low and the high resolution terrain data, and to supply display commands associated with the low and the high resolution terrain data; and a display device coupled to the processing unit and configured to receive the display commands and operable to render the common three-dimensional view to thereby allow simultaneous viewing of the low and the high resolution terrain data.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0001]    This invention was made with Government support under W91215-10-C-0003 awarded by USASOC Technology Application Program Office. The Government has certain rights in the invention. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention generally relates to aircraft display systems and methods and, more particularly, to systems and methods that display images representing terrain data. 
       BACKGROUND 
       [0003]    Computer generated aircraft displays have become highly sophisticated and capable of displaying a substantial amount of flight management, navigation, and control information that gives flight crews more effective control of the aircraft and a reduction in workload. In this regard, electronic displays, such as Heads-Up Displays (HUDs) and Heads-Down Displays (HDDs), are used in aircraft as Primary Flight Displays to display important flight management, navigation, and control information to flight crews. For example, the Primary Flight Display can combine critical flight instrumentation (e.g., altitude, attitude, heading, airspeed, vertical speed instruments) and primary engine instrument indicators into a single, readily interpretable display. 
         [0004]    Some Primary Flight Displays may provide a 3D, synthetic perspective view of the terrain surrounding the aircraft, including man-made and natural terrain. Examples include Synthetic Vision Systems (SVSs). These images are typically based on pre-loaded and predetermined terrain data from a database or terrain data from a sensor system. Storing and processing large amounts of this terrain data may be difficult, especially at a level of detail desired for a synthetic display. 
         [0005]    Accordingly, it is desirable to provide systems and methods with improved rendering of terrain data on a visual display, such as, for example, a Primary Flight Display, similar electronic aircraft displays, and other types of electronic displays. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention. 
       BRIEF SUMMARY 
       [0006]    In accordance with an exemplary embodiment, a display system is provided for a vehicle. The display system includes a first data source configured to provide low resolution terrain data; a second data source configured to provide high resolution terrain data; a processing unit coupled to the first data source and the second data source, the processing unit configured to receive the low resolution terrain data and high resolution terrain data, to integrate the low resolution terrain data and the high resolution terrain data into a common three-dimensional view that comprises graphical elements representing both the low resolution terrain data and the high resolution terrain data, and to supply display commands associated with the low resolution terrain data and the high resolution terrain data; and a display device coupled to the processing unit and configured to receive the display commands and operable to render the common three-dimensional view to thereby allow simultaneous viewing of the low resolution terrain data and the high resolution terrain data. 
         [0007]    In accordance with another exemplary embodiment, a method is provided for displaying multi-resolution terrain data. The method includes receiving low resolution terrain data from a first data source; receiving high resolution terrain data from a second data source; blending the low resolution terrain data and the high resolution terrain data into a field of view (FOV); and producing display signals for the FOV 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
           [0009]      FIG. 1  is a functional block diagram of an aircraft display system in accordance with an exemplary embodiment; 
           [0010]      FIG. 2  is a schematic representation of a visual display with integrated high and low resolution terrain data in accordance with an exemplary embodiment; 
           [0011]      FIG. 3  is a flowchart describing a method for displaying images representing integrated high and low resolution terrain data in accordance with an exemplary embodiment; and 
           [0012]      FIG. 4  depicts an exemplary image of the visual display rendered by the aircraft display system of  FIG. 1  in accordance with an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. 
         [0014]    Broadly, exemplary embodiments described herein provide visual display systems and methods for aircraft. More specifically, the visual display systems and methods display images of terrain data integrated from a first data source with low resolution terrain data and a second data source with high resolution terrain data. 
         [0015]      FIG. 1  depicts a block diagram of an exemplary aircraft visual display system  100  for displaying images with integrated high resolution terrain data and low resolution terrain data. In the exemplary embodiment shown, the system  100  includes a processing unit  102 , a first data source  104 , a flight management system  106 , a display device  108 , and a second data source  110 . Although the system  100  appears in  FIG. 1  to be arranged as an integrated system, the system  100  is not so limited and can also include an arrangement whereby one or more of the processing unit  102 , the first data source  104 , the flight management system  106 , the display device  108 , and the second data source  110  are separate components or subcomponents of another system located either onboard or external to an aircraft. Also, for example, the system  100  can be arranged as an integrated system (e.g., aircraft display system, Primary Flight Display system, a Head Up Display with SVS or EVS as an overlay (or underlay), a “near to eye display” system, or a head mounted display system, etc.) or a subsystem of a more comprehensive aircraft system (e.g., flight management system, navigation and control system, target aiming and control system, collision alert and/or avoidance system, weather avoidance system, etc.). The system  100  can be utilized in an aircraft, such as a helicopter, airplane, or unmanned vehicle. Moreover, exemplary embodiments of the system  100  can also be utilized in spacecraft, ships, submarines, fixed wing and rotor aircraft, such as helicopters, as well as other types of vehicles. For simplicity, embodiments are described below with reference to “aircraft.” 
         [0016]    The processing unit  102  can be a computer processor associated with a Primary Flight Display. Generally, the processing unit  102  receives and/or retrieves flight management information (e.g., from the flight management system  106 ) and landing, target and/or terrain information (e.g., from first data source  104  or second data source  110 ). The processing unit  102  generates display control signals for flight management information, which includes navigation and control symbology such as a zero pitch reference line, heading indicators, tapes for airspeed and altitude, flight path information, RNP information, and any other information desired by a flight crew. As discussed in further detail below, the processing unit  102  additionally receives and integrates terrain data from the first data source  104  and second data source  110 , and generates display control signals based on the integrated terrain data. The processing unit  102  then sends the generated display control signals to a display device (e.g., the display device  108 ). More specific functions of the processing unit  102  will be discussed below. 
         [0017]    The first data source  104  and the second data source  110  are coupled to the processing unit  102  and may be any suitable type of data source and may be the same or different types of data source. As described below, the first data source  104  may include low resolution terrain data, and the second data source  110  may include high resolution terrain data. The low resolution terrain data and the high resolution terrain data may be stored, for example, according to latitude and longitude coordinates. In one exemplary embodiment, the first and second data sources  104  and  110  are disparate data sources. 
         [0018]    The first and second data sources  104  and  110  each include regularly spaced elevation values, not necessarily geometrically or linearly spaced but often regularly spaced in degree space. As suggested by the labels, high resolution data has a higher resolution than the low resolution data. For example, in one exemplary embodiment, low resolution data may include elevation or height field values with post spacings of 3 to 6 arc seconds (90 to 185 meters, respectively), whereas high resolution elevation or height field data may have post spacings of 1 meter or less (for example, BuckEye data) to result in a significant difference in resolution. In one exemplary embodiment, the low resolution data and high resolution data may have spacing differences on the order of 1 to 2 orders of magnitude (e.g., 10× or 100× differences in spacing). Generally, high resolution data and low resolution data refers to lateral spacing. In exemplary embodiments, the high resolution terrain data and low resolution terrain data may be related to one another by a non-integer relationship or an integer relationship. In some embodiments, the high resolution terrain data and low resolution terrain data may have no predetermined relationship other than the differences in resolution between the two data sources  104  and  110 . 
         [0019]    In one exemplary embodiment, the first data source  104  and/or the second data source  110  may be a database with stored data. Such a database may be a memory device (e.g., non-volatile memory, disk, drive, tape, optical storage device, mass storage device, etc.) that can store digital landing, waypoint, and target location as either absolute coordinate data or as a function of an aircraft&#39;s position. The database can additionally include other types of navigation information, such as information used to calculate flight path and determine RNP information. The database can also include, for example, a terrain database, which includes the locations and elevations of natural and man-made terrain. The terrain can include obstacles, such as buildings and vehicles. Obstacle data can be stored together with terrain or in a separate obstacle only database. The geographic locations and height of the obstacles for typical avionics applications can be obtained through survey or through various reporting services. 
         [0020]    As another example, the first data source  104  and/or second data source  110  may include any suitable sensor for detecting terrain and providing data to the processing unit  102  based on the detected terrain. Such a sensor system may include sensors such as radar or forward-looking infrared (FLIR). Other types of imaging sensors may include types such as visible light, millimeter-wave radar, X-band (weather) radar, etc. In one embodiment, the sensor system is a stand-alone system, although in other embodiments, the sensor system can be used to completely or partially verify database. The sensor collected data, after additional verifications, may be later inserted into such databases for future uses. 
         [0021]    The flight management system  106  is coupled to processing unit  102 , and can provide navigation data associated with the aircraft&#39;s current position and flight direction (e.g., heading, course, track, etc.) to the processing unit  102 . The navigation data provided to the processing unit  102  can also include information about the aircraft&#39;s airspeed, altitude, pitch, and other important flight information. In exemplary embodiments, the flight management system  106  can include any suitable position and direction determination devices that are capable of providing the processing unit  102  with at least an aircraft&#39;s current position (e.g., in latitudinal and longitudinal form), the real-time direction (heading, course, track, etc.) of the aircraft in its flight path, the waypoints along the flight path, and other important flight information (e.g., airspeed, altitude, attitude, etc.). Such information can be provided to the processing unit  102  by, for example, an Inertial Reference System (IRS), Air-data Heading Reference System (AHRS), and/or a global positioning system (GPS). 
         [0022]    The system  100  also includes the display device  108  coupled to the processing unit  102 . The display device  108  may include any device or apparatus suitable for displaying various types of computer generated symbols and information representing at least pitch, heading, flight path, airspeed, altitude, landing information, waypoints, targets, obstacle, terrain, and RNP data in an integrated, multi-color or monochrome form. Using data retrieved (or received) from the flight management system  106  and/or data sources  104  and  110 , the processing unit  102  executes one or more algorithms (e.g., implemented in software) for determining the position of the various types of desired information on the display device  108 . The processing unit  102  then generates display control signals representing this data, and sends display control signals to the display device  108 . The display device  108  and/or processing unit  102  may include a graphics display generator for generating the appropriate graphical elements on the screen of the display device  108 , as discussed in greater detail below. In this embodiment, the display device  108  is an aircraft cockpit, multi-color display (e.g., a Primary Flight Display). 
         [0023]    Although a cockpit display screen may be used to display the above-described flight information symbols and data, any suitable type of display medium capable of visually presenting multi-colored or monochrome flight information for a pilot or other flight crew member can be provided, such as, for example, various CRT and flat-panel display systems (e.g., CRT displays, LCDs, OLED displays, plasma displays, projection displays, HDDs, HUDs, etc.). 
         [0024]      FIG. 2  is a schematic representation of a visual display  200  of integrated high and low resolution terrain data. The schematic representation of the visual display  200  of  FIG. 2  will be described briefly prior to a more detailed description of the method  300  for rendering the display  200 . In one exemplary embodiment, the visual display  200  is rendered with a series of “mesh strips,” each with a number of triangles or polygons that collectively form the terrain and other flight information formed on the display device  108 . The size of the triangles generally corresponds to the resolution of the respective portion of the visual display  200 . In the representation of visual display  200  of  FIG. 2 , the visual display  200  includes a number of low resolution strips  201 - 208  that may be sequentially formed to render the larger field of view (FOV) (or view frustum), defined by boundaries  210 - 213 . As described above, the strips (e.g., strip  201 ) may be formed by triangles or polygons (e.g., triangles  260 - 277 ). As described in greater detail below, one or more portions of the visual display  200  may be formed with a high resolution patch  250  that replaces corresponding portions of the low resolution mesh (e.g., portions of strips  201 - 203 ). Additional details about the visual display  200  will be described with reference to the method  300  of  FIG. 3 , which describes a method for rendering the visual display  200  with integrated multi-resolution terrain data, such as the visual display  200  of  FIG. 2  with the system  100  of  FIG. 1 . 
         [0025]    In one embodiment, the method  300  is used for displaying terrain data in 3D, synthetic view for a Primary Flight Display of an aircraft, such as for example, the system  100  discussed above. As such, the method  300  of  FIG. 3  will be described with reference to the system  100  of  FIG. 1  and with reference the schematic representation of a visual display  200  of  FIG. 2 . 
         [0026]    In a first step  305  of the method  300  of  FIG. 3 , the processing unit  102  determines the boundaries of the field of view (FOV), e.g., the terrain that the pilot or operator is to view from the aircraft. As described above, in a Primary Flight Display, the FOV is the synthetic terrain that surrounds the aircraft as viewed from the cockpit or other vantage point. The boundaries of the FOV may be expressed as latitude/longitude data and transformed into a “real-world” coordinate system relative to the aircraft or an xyz-coordinate system of the display device  108 . In the schematic representation of  FIG. 2 , the boundaries  210 - 213  of the FOV correspond to the edges of the visual display  200 . 
         [0027]    In a second step  310 , the processing unit  102  determines bounding boxes associated with the high resolution terrain data of the second data source  110 , e.g., the boundaries of high resolution terrain data available to the system  100 . In most exemplary embodiments, the high resolution terrain data of the second data source  110  is limited to more important terrain data, such as static target locations, rendezvous positions, landing areas, the terrain along a planned flight path, or generally “points of interest,” because of processing and storage capacity limitations. The bounding boxes of high resolution terrain data correspond to the geographical extent of the data, e.g., latitude/longitude data and/or extent (width and length) information. The bounding boxes may be a single patch of high resolution terrain data and/or a contiguous patch of sub-patches or noncontiguous patches of high resolution terrain data. 
         [0028]    In a third step  315 , the processing unit  102  compares the bounding boxes of the high resolution terrain data from the second data source  110  to the boundaries of the FOV, and the processing unit  102  determines if any portion of the bounding boxes of high resolution terrain data are within the FOV. If the bounding boxes of high resolution terrain data are not located in the FOV, the method  300  proceeds to step  320 . As such, referring to  FIG. 2 , the processing unit  102  evaluates the bounding boxes of high resolution patches to determine if any patch falls within the boundaries  210 - 213  of the FOV. In the depicted example of  FIG. 2 , the high resolution patch  250  is one such patch that falls within the boundaries  210 - 213 . 
         [0029]    If, however, it is determined that the bounding boxes of the high resolution terrain data is not within the FOV, the method  300  proceeds to step  320 . In step  320 , the processing unit  102  generates a FOV mesh with low resolution terrain data from the first data source  104 . As described above, the low resolution terrain data may be stored according to latitude/longitude and transformed according to the FOV. In the example of  FIG. 2 , the FOV mesh would include the strips  201 - 208  without any high resolution patch (e.g., without high resolution patch  250 ). In step  325 , the processing unit  102  generates display commands based on the FOV mesh of low resolution terrain data for display on the display device  108 . 
         [0030]    Returning to step  315 , if the processing unit  102  determines that the bounding boxes of high resolution terrain data are located within the FOV, in step  330 , the processing unit  102  generates a FOV mesh for such high resolution terrain data, such as the high resolution patch  250  of  FIG. 2 . 
         [0031]    In step  335 , the processing unit  102  determines a starting point for rendering a FOV mesh with the low resolution terrain data. The starting point typically refers to an outer extent or corner of the FOV from which a mesh of the entire FOV may be constructed. For example, in  FIG. 2 , an exemplary starting point  215  may be a lower corner of the boundaries  210 - 213 . 
         [0032]    In step  340 , the processing unit  102  forms a low resolution mesh strip from the low resolution terrain data of the first data source  104 . Typically, the first FOV mesh strip is formed from the starting point of step  335 . As shown in  FIG. 2 , in an initial iteration of step  340 , the first low resolution mesh strip  201  is formed, and in subsequent iterations discussed below, subsequent low resolution mesh strips  202 - 208  may be formed. 
         [0033]    In step  345 , the processing unit  102  determines if there are any intersections between the current low resolution mesh strip and the high resolution patch. As an example, in  FIG. 2 , a portion (e.g., triangles  268 - 272 ) of the first low resolution mesh strip  201  intersects the high resolution patch  250 . 
         [0034]    If there are intersections between the low resolution mesh strip and the high resolution patch, in step  350 , the processing unit  102  removes the portion of the low resolution mesh strip that intersects the high resolution patch. Referring to the example in  FIG. 2 , if the first low resolution mesh strip  201  is the current low resolution mesh strip, triangles  268 - 272  are removed. 
         [0035]    In step  355 , a portion of the high resolution terrain patch replaces the corresponding portion of low resolution mesh strip removed in step  350 . Continuing the example of  FIG. 2  in which the first low resolution mesh strip  201  is the current strip, triangles  268 - 272  are replaced by corresponding portions of the high resolution patch  250 . 
         [0036]    After step  355 , the method  300  proceeds to step  360 . Similarly, in step  345 , if there are no intersections between the current low resolution mesh strip and the high resolution patch, the method  300  proceeds to step  360 . In step  360 , the processing unit  102  determines if the current low resolution mesh strip completes the FOV. For example, in  FIG. 2 , this does not occur until formation of low resolution mesh strip  208 . 
         [0037]    If the FOV is not complete, the method  300  proceeds to step  340  in which a subsequent low resolution mesh strip is formed adjacent to the previous low resolution mesh strip. Continuing the example above with  FIG. 2 , in step  340 , the second low resolution mesh strip  202  is formed after an iteration with the first low resolution mesh strip  201 . In steps  345 ,  350 ,  355 , and  360 , the processing unit  102  continues to determine intersections between the high resolution patch (or patches), removing portions of the low resolution mesh strips, replacing the removed portions of the low resolution mesh strips with corresponding portions of the high resolution patch, determining if the FOV is completed, and if not, repeating with a subsequent low resolution mesh strip. In  FIG. 2 , these steps result in the formation of low resolution mesh strips  201 - 208 , and replacing portions of those mesh strips  201 - 208 , if intersected, with portions of the high resolution patch  250 , until the boundaries  210 - 213  of the visual display  200  is completed. 
         [0038]    In step  365 , the processing unit  102  generates display signals based on integrated low resolution and high resolution data in the FOV according to steps  305 - 360  and provides the display signals to the display device  108 . The method  300  is repeated for each processing cycle of the system  100  to produce a continuously changing FOV image for the pilot. 
         [0039]    An exemplary visual display  400  is shown in  FIG. 4 . The visual display  400  is an exemplary visual display that may be rendered, for example, by the aircraft display system  100  of  FIG. 1  and the method  300  of  FIG. 3 . 
         [0040]    The visual display  400  shows, among other things, computer generated symbols and graphical elements representing an airspeed scale or tape  404 , an altitude scale or tape  406 , and terrain (e.g., identified generally as element  410 ). Other types of navigation and control symbology or graphical elements, such as a zero-pitch reference line, landing point, and the like may be provided, as necessary or desired. Although the visual display  400  is shown as an egocentric, first-person frame of reference, the visual display  400  can be a secondary, wingman, exocentric, and/or plan or perspective view that enables a viewer to view the aircraft, as well as zoom in and out, including an unmanned vehicle and/or spacecraft. Although the visual display  400  is generally associated with a Primary Flight Display, the display can also be utilized on a multi-function display, Head Up Display, and/or a head mounted display. 
         [0041]    In this embodiment, the terrain  410  is rendered as a three-dimensional, perspective view. The terrain  410  can include any representation of the environment surrounding the aircraft, including flattened terrain. Additionally, the terrain  410  can include a virtual plane selected by a pilot at certain elevation relative to the aircraft and is rendered at that elevation. 
         [0042]    In addition, and as will now be described in more detail, the visual display  400  may selectively render symbology forming part of the terrain  410  that represents low resolution terrain data from the first data source  104  and that represents high resolution terrain data from the second data source  110 . One exemplary method  300  is described above in reference to  FIG. 3  to illustrate how the low resolution terrain data from the first data source  104  and high resolution terrain data from the second data source  110  are blended and displayed. 
         [0043]    As shown in  FIG. 4 , the first portion  420  of the terrain  410  corresponds to the low resolution terrain data of the first data source  104 , and the second portion  430  of the terrain  310  corresponds to the high resolution terrain data. The high resolution terrain data of the second portion  430  is much more detailed and textured as compared to the low resolution terrain data of the first portion  420 . As described above, the system  100  cuts or otherwise removes the low resolution terrain data and splices or patches the high resolution terrain data to provide the second portion  430  within the first portion  420 . This embodiment may be in contrast to a system that down-samples resolutions from a single source of data. 
         [0044]    Typically, the boundary between the portions  420  and  430  is evident from the difference in detail and no further marking of the boundary is necessary. However, in other embodiments, the boundary may be emphasized to the viewer. 
         [0045]    Accordingly, systems and methods for combining high resolution terrain data and low resolution terrain data are provided. The systems and methods provide a display in which places of interest are shown in more detail with the high resolution terrain data while the other areas of the display are rendered with low resolution terrain data. Such a display provides increased situational awareness while enabling efficient processing and storage of terrain data. 
         [0046]    While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.