Abstract:
A method for displaying attitude, heading, and navigation data on a single display is described. The method comprises configuring the display with terrain data, overlaying the terrain display with a compass rose display, and superimposing an attitude direction indicator with the compass rose display, the attitude direction indicator referenced to a center of the compass rose.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to the configuration of aircraft cockpit displays, and more specifically, methods and apparatus for displaying attitude, heading, and terrain data. 
   Historically, pilots have had to use a combination of displays while flying. An attitude indicator (ADI) displays pitch and roll information for the aircraft. A horizontal situation indicator (HSI) displays compass heading and an alignment of the aircraft with certain navigational aids. A navigational display, sometimes referred to as a lateral map, provides a pilot with terrain information, waypoints, airports and other navigational aids. This multiple display arrangement requires the pilot to constantly scan multiple display units and to mentally integrate the information to provide or augment situational awareness. 
   In addition to the technologies described above, other advanced technology aircraft and flight deck automation, most of which provide a display to the cockpit, may tend to increase workload for the flight crew. Therefore, while the advanced technology provides higher or safer performance for an aircraft, flights crew&#39;s responsibility for correct and timely performance of those activities may not be reduced. The crew&#39;s oversight of flight deck activities may become more difficult as additional concurrent activities are performed and monitored by the same or a fewer number of people. 
   A controlled flight into terrain (CFIT) is a type of accident that can be difficult for a pilot or flight crew to avoid as it involves mental integration of multiple displays, for example, ADI, HSI and navigation displays. However, a CFIT can be avoided if the pilot has a proper mental picture or “situation awareness” of the aircraft&#39;s current position, trajectory, and other flight parameters in relationship to the terrain. 
   BRIEF SUMMARY OF THE INVENTION 
   In one aspect, a method for displaying attitude, heading, and navigation data on a single display is provided. The method comprises configuring the display with terrain data, overlaying the terrain display with a compass rose display, and superimposing an attitude direction indicator with the compass rose display, the attitude direction indicator referenced to a center of the compass rose. 
   In another aspect, a unit for displaying a navigational display is provided. The unit is configured to display a terrain, overlay a portion of the terrain display with a compass rose, and superimpose an attitude direction indicator with the compass rose. The attitude direction indicator is referenced to a center of the compass rose. 
   In still another aspect, a visual display format for a navigational system is provided. The visual display format comprises a terrain display, a compass rose overlaying a portion of said terrain display, and an attitude direction indicator superimposed with said compass rose, said attitude direction indicator referenced to a center of said compass rose. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram illustrating connectivity between aircraft sensors and displays associated with the sensors. 
       FIG. 2  is an illustration of an attitude direction indicator (ADI) display. 
       FIG. 3  is an illustration of a horizontal situation indicator (HSI) display. 
       FIG. 4  is an illustration of a navigational display. 
       FIG. 5  is an illustration of a combined ADI, HSI, and navigational display. 
       FIG. 6  is an illustration of a combined ADI, HSI, and navigational display illustrating a zero pitch and roll. 
       FIG. 7  is an illustration of a combined ADI, HSI, and navigational display illustrating a negative pitch and a zero roll. 
       FIG. 8  is an illustration of a combined ADI, HSI, and navigational display illustrating a negative pitch and roll. 
       FIG. 9  is a block diagram illustrating an integrated display presentation system for dynamically displaying terrain situation awareness information, attitude and heading in an aircraft environment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As described above, avoiding controlled flights into terrain (CFITs) is difficult. Occurrences of CFITs can be lessened if the pilot has a proper mental picture or “situation awareness” of the aircraft&#39;s current position in relationship to the terrain. To lessen the risks of a CFIT, the below described methods and apparatus describe an integration of both strategic and tactical terrain awareness information on a single display, as well as basic attitude information. Specifically, the integration of terrain and attitude and navigation and basic aircraft parameters (e.g., airspeed, altitude, and vertical speed) onto a single display is believed to provide a solution to help reduce occurrences of CFIT. The combination of information formally presented in separate horizontal situation indicator, navigation, and attitude indicator displays into a single display is thought to facilitate operator decoding of the attitude of the vehicle as well as ground track and relative position to terrain landmarks. 
     FIG. 1  is a block diagram of a navigation and flight control system  10  illustrating connectivity between aircraft sensors and displays associated with the sensors. Specifically, a horizontal situation indicator (HSI) sensor  12  provides sensor data relating to a compass heading and alignment of the aircraft to an HSI processor  14 . HSI processor  14  provides digital data relating to the compass heading and alignment of the aircraft to a HSI display  16  and also to a mission computer  20 . 
   An attitude direction indicator (ADI)  22  provides sensor data relating to pitch and roll of the aircraft to an ADI processor  24  which provides digital data relating to pitch and roll of the aircraft to ADI display  26  and to mission computer  20 . Navigation sensors  32  provide sensor data regarding terrain location to navigation computer  34 . The sensor data from navigation sensors  32  is correlated with map data that is resident within navigation computer  34  to generate digital terrain data that is forwarded to navigation map display  36  and to mission computer  20 . The digital terrain data includes terrain information, waypoint data, airport data, and other navigational aids. 
   An aircraft also typically includes one or more multi-function displays  40 ,  42 , and  44  which receive data from mission computer  20 . The data displayed by multi-function displays  40 ,  42 , and  44  is typically based upon pilot input received at mission computer  20 , for example, from push buttons (not shown) on multi-function displays (MFDs)  40 ,  42 , and  44 . In other application, a pilot can also interact with MFDs  40 ,  42 , and  44  using a cursor control device. Activation of the push buttons or cursor control device allow a pilot to select which data is to be displayed on each of multi-function displays  40 ,  42 , and  44 . For example, multi-function display  40  can be utilized to display HSI data while multi-function display  42  displays terrain data. While multi-function displays  40 ,  42 , and  44  are typically utilized to display the above described data, aircraft also typically include HSI display  16 , ADI display  26 , and navigation map display  36  (collectively referred to as dedicated displays) to provide backup to multi-function displays  40 ,  42 , and  44 . The dedicated displays may also be somewhat small and inconspicuous as compared to multi-function displays  40 ,  42 , and  44 . This arrangement of dedicated displays and multi-function displays causes the pilot to constantly scan multiple displays and forces him to mentally integrate the information from the individual displays to augment his or her situational awareness. While dedicated displays may not exist in a particular application, exclusive use of multi-functional displays  40 ,  42 , and  44  still only provide data from a single one of HSI, ADI, and navigation data, or at most a combination of HSI and navigation data. 
     FIG. 2  is an illustration of an attitude direction indicator (ADI) display  50 . ADI display  50  provides graphic pitch and roll information of an aircraft to a pilot. Referring to display  50 , a zero pitch reference line  52  separates a positive pitch area  54  and a negative pitch area  56  of the display and grid  58  provides numerical data as to the pitch. In  FIG. 2  a positive pitch of about seven degrees is indicated. A roll grid  60  provides data as to a roll of the aircraft. Display  50  also includes altitude data  62  and airspeed data  64 . 
     FIG. 3  is an illustration of a horizontal situation indicator (HSI) display  70 . HSI display  70  provides graphic compass heading and alignment for an aircraft to a pilot. In addition, HSI display  70  also provides path guidance to a selected navigation source or waypoint. For example, HSI display indicates how many “dots” you are off course (dots equate to a fraction of a degree which is dependent on the type of navigation source) or a lateral math distance off course in miles (dependent upon the type of navigation source or waypoint). Referring to display  70 , compass headings  72  are provided with a zero degree north reference. Display  70  illustrates a heading for the aircraft illustrated on display  70  of 150 degrees, which is generally southeast. 
     FIG. 4  is an illustration of a navigational display  90 . Display  90  includes a rendering of aircraft  92  superimposed over a terrain map  94 . A variety of waypoint and airport locators  96  are also superimposed over terrain map  94 . Many aircraft include terrain awareness equipment which is utilized in navigation of the aircraft from point to point or in navigating to a target. 
     FIG. 5  is an illustration of a combined ADI, HSI, and navigational display  140 . As described above, the ADI, HSI, and navigation map in known systems are presented to a user in three separate displays including dedicated displays, for example, multi-function displays  40 ,  42 , and  44 , or a combination thereof. Combined ADI, HSI, and navigational display  140  merges the three separate displays into a single display format. While described herein as being applied to a pilot and aircraft situation, combined ADI, HSI, and navigational display  140  and similar displays are applicable to other vehicle navigation situations, for example, a ground operator of one or several unmanned air vehicles (UAVs). 
   Combined ADI, HSI, and navigational display  140  provides a top-down look onto a three dimensional rendered section of terrain  142 . Superimposed on terrain  142  is an airspeed indicator  144  and an altitude indicator  146 . Substantially in a center of display  140  is a 360 degree compass rose  148 , which, in one embodiment, includes a translucent, circular attitude indicator ball  150 . In  FIG. 5 , display  140  indicates a heading between 100 and 105 degrees. A displacement of attitude indicator ball  150  from a center  152  of compass rose  148 , as indicated additionally by displacement of a center  154  of attitude indicator ball  150  indicates an amount of deflection in the pitch and roll axes. Additional elements that are contemplated for inclusion on display  140 , but not shown in  FIG. 5  include a course deviation indicator, a current and proposed ground track, and landmark/obstacle data including airports and runways. 
     FIG. 6  is an illustration of a combined ADI, HSI, and navigational display  200  illustrating a zero degree pitch and zero degree roll. Display  200  also illustrates more defined terrain features  202  than are illustrated on display  140  (shown in  FIG. 5 ). Center  154  of attitude indicator ball  150  is aligned within center  152  of compass rose  148  to indicate the zero degree pitch and zero degree roll of the vehicle associated with display  200 . 
     FIG. 7  is an illustration of a combined ADI, HSI, and navigational display  230  illustrating a negative pitch and a zero roll. Center  154  of attitude indicator ball  150  is directly above center  152  of compass rose  148  to indicate the negative pitch and zero roll of the vehicle associated with display  230 .  FIG. 8  is an illustration of a combined ADI, HSI, and navigational display  260  illustrating a negative pitch and a negative roll (i.e., a roll to the left). Center  154  of attitude indicator ball  150  is above center  152  of compass rose  148  to indicate the negative pitch and is to the right of center  152  of compass rose  148  to indicate the negative roll of the vehicle associated with display  200 . 
     FIG. 9  illustrates, by example and without limitation, an integrated display presentation system  300  for dynamically displaying terrain situation awareness information, as well as attitude and heading reference information, in an aircraft environment embodied as a system block diagram. Display presentation system  300  dynamically displays terrain information as a function of aircraft position, and includes interfaces to subsystems for determining accurate aircraft current position and flight path information, storing and retrieving surrounding terrain data from a digital terrain database as a function of the aircraft current position information, and processing terrain data. 
   Integrated display  140  (shown in  FIG. 5 ) presentation is provided as a set of machine instructions received and operated by display presentation system  300 . The machine instructions include instructions for receiving data from one or more of the instrument information signals available on either an aircraft data bus  302  or another suitable means for providing a real-time electronic signal data source of instrument signals reporting flight parameter information. The instrument signals provide the various signals to integrated display presentation system  300 . A detailed description of the signals available on at least one aircraft data bus  302  is provided by the ARINC Characteristic  429  as published by Aeronautical Radio, Incorporated of Annapolis, Md. Included among the signals provided by the aircraft data bus  302  or other suitable source are signals useful for operating integrated display presentation system  300 , these signals including by example and without limitation, barometric and radio altitude signals, a vertical speed signal, and navigation signals, including GPS altitude, course, heading, latitude and longitude signals, track, and acceleration. While described below as system  300  causing integrated display  140  to be displayed, it is to be understood that integrated display  140  is utilized by way of example only and not meant to exclude displays  200 ,  230 , and  260  or another similarly arranged display format. 
   These signals are used as inputs to an integrated display presentation circuit, which in turn is effective to generate an integrated plurality of display control signals resulting in integrated display  140 . The integrated plurality of display control signals are applied to a display generator  304 , that in turn generates a plurality of display control signals that result in the terrain situation awareness information, attitude information, and heading reference information (e.g., integrated display  140 ) being displayed on cockpit display  306 . 
   A plurality of machine instructions are stored in an onboard memory  308 , which are retrieved and operated by a computer processor  310  to generate the integrated display control signals for generating integrated display  140  or a similarly formatted display. Computer processor  310  is for example, but without limitation, a microprocessor, a digital signal processor, or another suitable processor and may be either a dedicated processor or a processor shared with other onboard equipment. Processor  310  includes inputs coupled to onboard memory  308  to receive machine instructions and inputs coupled to data bus  302  to receive sources of instrument signals reporting flight parameter information. Processor  310  uses data received from a navigation system  312  on the aircraft to provide current information about the altitude, course, heading, track, latitude and longitude and optionally acceleration of the aircraft. The navigation data may be obtained directly from the navigation system, which may include an inertial navigation system, a satellite navigation receiver such as a GPS receiver (shown), VLF/OMEGA, Loran C, VOR/DME or DME/DME, or from the Flight Management System (FMS). 
   Information about the pressure or barometric altitude relative to sea level, vertical speed, and current air speed of the aircraft are available from the navigation system  312 , from an air data computer  314 , an air data and heading reference system (ADHRS) (not shown), or from a barometric altimeter and a barometric rate circuit present on the aircraft. 
   Current altitude relative to the ground, i.e., AGL altitude, is provided to the integrated terrain situational awareness display presentation circuit of the invention by signals from a radio altimeter  316  which is commonly a low powered radar that measures vertical distance between the aircraft and the ground. Radio altimeters are an essential part of many avionics systems and are widely used over mountainous regions to indicate terrain clearance. Also known are laser altimeters in which a laser beam modulated by radio frequencies is directed downward and reflected from the terrain. The reflection is gathered by a telescope system, sensed with a photomultiplier, and phase compared with the original signal. Optionally, GPS altitude data is used. In another known system, an altitude estimate above the ground is based upon an algorithm that combines data from one or more of GPS, inertial sensors, and ADHRS. 
   A Flight Management System (FMS)  318  coupled to the data bus  302  has stored therein information about the intended course during the current flight, including information about the positions of waypoints along the aircraft&#39;s flight path. Waypoints may either be three dimensional or four dimensional (including time). Also, an attitude direction indicator  320  provides pitch and roll information for the aircraft, and a horizontal situation indicator  322  provides a compass heading of the aircraft to processor  310 . 
   These signals available on data bus  302  are applied to processor  310  for enabling the integrated display presentation (illustrated in  FIGS. 5–8 ) according to the different ones of attitude, heading, and the terrain situational awareness information presentation operations performed by integrated display presentation system  300  and displayed as integrated display  140  or a like display. 
   A memory device  324  coupled to the processor  310  stores a digital terrain database  326  as a function of position, such as latitude and longitude position data. The source of the digital terrain database  326  is, for example, a public United States Geographic Survey (USGS) having a resolution on the order of 3 arc-seconds or 90 meters, and includes topographical relief information. The terrain database may include not only the locations of natural terrain obstacles such as mountains or other high ground areas, but also man-made obstacles such as radio towers, buildings, enemy or friendly tank positions, and the like. The terrain database may also include the boundaries of restricted airspace, e.g., airspace around military installations, restricted elevations for particular airspace, airport locations, bodies of water and the like. Alternatively, the display generated using a Jeppesen supplied database of terrain and, optionally, includes topographical relief information. A location search logic device  328  is coupled between memory device  324  and processor  310  for accessing terrain database  326  during operation. Other suitable terrain databases are also known, such as the Enhanced Ground Proximity Warning System (EGPWS). 
   Using the data supplied by the different instrument information signals available on data bus  302 , processor  310  operates one or more algorithms for generating the plurality of display control signals. The display control signals are output to display generator  304  which interprets the display control signals to generate the terrain situation awareness symbology (e.g., display  140 ) presented on display  306 . 
   Integrated display presentation system  300  as embodied in  FIG. 9  includes a plurality of machine instructions stored in the onboard memory  304 , which are retrieved and operated by a processor  310  to generate the simulated field of view (FOV) of the terrain on display  140  (as shown in  FIG. 5 ) or another similar display. Processor  310  also receives pitch and roll data signals from attitude direction indicator  320  from data bus  302  to provide current information about the attitude of the aircraft. Further, processor  310  also receives heading data signals from horizontal situation indicator  322  from data bus  302  to provide current information about the magnetic heading of the aircraft. 
   An additional plurality of machine instructions stored in the onboard memory  308  are retrieved and operated by processor  310  to retrieve real-time spatial position information available on data bus  302 , such as a position defined by latitude and longitude values. As a function of the real time aircraft position information, processor  310  uses location search logic circuit  328  to retrieve terrain information from the database of terrain information  326  stored in memory device  324 . The terrain information retrieved from database  326  includes at least data relevant to the terrain to the extent of the selected range within a wide-angle FOV of display  140 . In other words, processor  310  retrieves terrain information projected along the current real-time heading of the host aircraft within the vertical, lateral and range extents of the displayed FOV. 
   In one embodiment, processor  310  operates machine instructions for determining tactical and strategic terrain awareness as a function of the terrain information relevant to the real-time spatial position, attitude, heading, optional track and acceleration, altitude above ground, and the pre-selected strategic threshold altitude, below which the terrain is categorized as strategic. The strategic terrain information awareness is coded according to a monochromatic scale that is graduated as a function of terrain elevation to develop a three-dimensional representation of the terrain relief. In other embodiments, alternative color coding schemes are utilized. 
   In one embodiment, tactical terrain above the pre-selected strategic threshold altitude is categorized as a function of the potential hazards presented. The tactical terrain divided into “warning,” “caution,” and “all clear” bands as a function of the terrain elevation relative to the aircraft&#39;s current altitude above ground. As discussed herein, the tactical terrain information is color coded relative to the aircraft&#39;s current altitude above ground based upon the pre-selected “warning,” “caution,” and “all clear” relative elevation thresholds. Each elevation band being coded on a graduated scale as a function of terrain elevation to develop a three-dimensional representation of the terrain relief, as discussed herein. 
   Optionally, processor  310  operates additional machine instructions for generating display control signals that are applied to display generator  304  to generate a plurality of display control signals that result in the updated terrain situational awareness information, as well as attitude and heading, being displayed on display  140  in real-time. 
   Processor  310  further operates the machine instructions to update the strategic and tactical terrain awareness information, including the coding thereof, in real-time using the real-time spatial position and heading signals received from the data bus  302  to retrieve terrain information relevant to the aircraft&#39;s current spatial position, heading and altitude. Processor  310  then generates display control signals that are applied to display generator  304  to generate a plurality of display control signals that result in the updated terrain situational awareness information being displayed on display  140  in real-time. 
   Integrated display presentation system  300  as embodied in  FIG. 9  includes a plurality of machine instructions stored in onboard memory  308 , which are retrieved and operated by a processor  310  to generate the terrain awareness information, attitude and heading on display  140  using conformal symbology, whereby outside relationships are replicated on display  140  inside the aircraft. In one embodiment, simulated terrain information is alternatively rendered on display  140  using true one-to-one mapping or a compressed mapping that maximizes the amount of information presented on display  140 . Integrated display presentation system  300  thus presents terrain information using symbology that substantially mimics the form of the terrain as it appears. In addition, integrated display presentation system  300  allows a user to zoom in on or zoom out on the terrain displayed. In other words, terrain information is presented in a format consistent with an above view of the actual terrain. The conformal symbology permits the pilot to utilize pre-attentive referencing rather than making conscious decisions, thereby reducing pilot workload. The conformal symbology comment not only refers to terrain as described above, but also to obstacles, a desired path, waypoints, airports, and other objects that might be displayed by integrated display presentation system  300 . 
   The integration of information from three separate displays as illustrated in  FIGS. 2–4 , into a single display (e.g., combined ADI, HSI, and navigational display  140  shown in  FIG. 5 ) reduces pilot workload by providing a mental map that is consistent with the operator&#39;s movement through space. Therefore, by creating convergence for the information previously contained in the three separate displays, specifically, integrating attitude information with strategic and tactical terrain awareness on one display, there is less need for mental rotation and translation on the part of the pilot. The above described integration into a single display reduces pilot workload, facilitates situational assessment, and reduces pilot error, increasing safety for flights into terrains. 
   While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.