Abstract:
A TCAS view image format with horizontal trend for a traffic situation awareness display in a craft, having the craft represented by a center symbol, having traffic represented by position symbols that indicate by shape the horizontal heading of a craft, having the shape of the represented vehicle and varying size to represent level of traffic threat or closeness in altitude differential, having symbols that indicate altitude and trend of altitude, and having symbols that in shape and color redundantly indicate the level of traffic threat.

Description:
This invention was developed under U.S. Government contract DTFA01-85-C-0005. 
    
    
     FIELD OF THE INVENTION 
     The present invention pertains to air traffic displays and particularly to display formats for an air traffic alert and collision avoidance system (TCAS). More particularly, the invention pertains to TCAS display formats having three-dimensional perspective color graphics. 
     BACKGROUND OF THE INVENTION 
     The function of the TCAS display is to present air traffic information, declare threats, and provide advisories on potential air traffic conflicts before the closest point of approach. The TCAS display of the related art uses two-dimensional graphics to convey traffic information in the own aircraft&#39;s protected volume of airspace. However, since two-dimensional graphics can only depict information on two (X- and Y-axes) of the three dimensions required to completely represent spacial traffic relationships for TCAS (X-, Y- and Z-axes), numerics are used to portray relative altitude on the Z-axis. This two-dimensional plan view display of TCAS traffic information (supplemented with numeric data tags for the third-dimension, altitude) does not provide a direct visual display of dynamic spacial relationships existing between air traffic in the natural three-dimensional space. Interpretation of such a display requires considerable time and mental effort, in that it requires pilots to mentally construct a three-dimensional image of the traffic situation by combining graphically displayed azimuth and range information with numerically-presented altitude information. 
     The related art TCAS display, therefore, is limited to function as an aid to direct visual acquisition of target aircraft, rather than as a correct, veridical, and easily interpretable complete &#34;picture&#34; of the current traffic situation. Pilots simply use the presented information as a cue for visual search to locate potential threats by direct visualization of aircraft outside the cockpit. Furthermore, since the traffic information is dynamic and continuously updated, direct visualization will require pilots to continuously alternate their attention from reading the numerics on the head-down TCAS display to the head-up search for aircraft outside the cockpit. Thus, using the related art TCAS display, pilots often find it time-consuming and confusing to visually acquire and process dynamic changes in the air traffic situation under moderate or high cockpit work load situations. 
     Attempts of the related art to solve the problems of indirect visualization of conventional displays have focused on basic symbology refinement for the two-dimensional TCAS display format. Efforts have been made to reduce confusion and misinterpretation by modifying the symbols. For example, all the numeric codes were intially displayed above the aircraft symbol with a &#34;plus&#34; or &#34;minus&#34; sign to indicate relative elevation. The most current baseline TCAS display presents the numerics either above or below the symbol for conceptual compatibility. No effort has been made to explore other innovative approaches or to empirically validate current design concepts. However, research on display formats for other applications reveals potential benefits of an innovative three-dimensional perspective format. Ground-based perspective traffic display formats have bee studied in the related art to demonstrate the advantages of utilizing respective graphics for portraying complex spacial situations. Conditionally, respective displays for naval battle field management systems have been previously studied to examine the feasibility and the advantages of three-dimensional graphic presentations. Such studies have shown significant advantages of three-dimensional formats over two-dimensional formats. 
     SUMMARY OF THE INVENTION 
     The present invention relates to formats for the display of data in an airborne environment to assist the pilot in being more cognizant of the conditions in his/her airspace, thereby enhancing his/her situational awareness. This format is specifically designed for the TCAS, in which aircraft information in a protected three-dimensional volume of air space surrounding an aircraft is presented with respect to that aircraft. The present invention implements three-dimensional perspective graphics in color to display easily and directly interpretable dynamic spacial relationships for the TCAS system. This format is equally applicable to military situation awareness formats where the pilot needs to quickly and accurately recognize what traffic and targets are in the surrounding airspace. 
     The invention uses three-dimensional perspective graphics rather than a two-dimensional format supplemented with numeric data tags. The advantages of the present invention are: the realistic and intuitive portrayal of traffic information in three-dimensional perspective that results in the correct perception of the three-dimensional air space; appropriate use of color, shape and size coding that is compatible with the pilot&#39;s expectations; and the integration of displayed situational information to facilitate rapid interpretation by the pilot. The primary objectives of this new display format are: to enhance the speed and accuracy of the pilot&#39;s understanding of the egocentric traffic situation; to minimize complex cognitive processing and pilot mental workload; and to allow the pilot to review and plan evasive maneuvers earlier and more effectively in order to avoid potential air traffic conflicts. Therefore, the function of the TCAS display is greatly extended and is no longer limited to providing cues for visual acquisition of traffic outside the aircraft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 reveals the TCAS format of the present invention, wherein the threat level is indicated by the size of the traffic alert symbol. 
     FIG. 2 reveals a TCAS format of the present invention, wherein the altitude differential is indicated by the size of the traffic alert symbol. 
     FIG. 3 is a 2.5 dimensional perspective format of the invention. 
     FIG. 4 is a block diagram of the processing and generation system for the perspective format. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention is a view presentation for a TCAS system which integrates color coding and symbols which rotate to provide horizontal trend and threat levels to the pilot. This view can be observed from various perspective viewpoints which can vary from direct overhead normal plan view (look-down view) to a direct forward view, or to a viewpoint about halfway between the two. The present display format enhances the pilot&#39;s understanding and monitoring of dynamic spacial relationships between his or her own aircraft and other aircraft within the proximal airspace and to improve his or her ability to detect and avoid potential traffic and collisions. The function of the TCAS display is to present traffic information, declare threats, and provide resolution advisories before the closest point of approach. FIG. 1 depicts the present invention which is a direct look-down view of the TCAS plan view presentation with horizontal trend data. The TCAS plan view of FIG. 1 utilizes an aircraft symbol 12, for instance, which resembles a passenger jet aircraft and indicates the aircraft directional trend. A numerical readout 14 indicates relative altitude and directional arrow 16 indicates the vertical trend of the aircraft resembled by symbol 12. On symbol 12 there is a traffic alert symbol 18 which is a yellow medium circle superimposed on symbol 12. Symbol 20 associated with altitude symbol 14 indicates that the aircraft represented by symbol 12 is at an altitude above the own aircraft which is represented by symbol 22 at the center of format 10. When symbol 20 is a &#34;-&#34;, that means that the associated symbol 12 represents an aircraft which is at an altitude below own aircraft 22. Since aircraft symbol 12 may rotate the position of the altitude tags, 14, 16 and 20 are situated such that the tag centroid is directly behind the right wing tip of symbol 12. The centroid of the altitude tags 14, 16 and 20 thus rotates with aircraft symbol 12 although the numerics and associated symbols remain upright for easy reading. This approach allows the pilot to more easily correlate the aircraft observed and its corresponding symbol 12 with its associated altitude tags 14, 16 and 20. The particular format of FIG. 1 has aircraft symbols that enlarge as the threat level of the represented aircraft increases. Normal traffic is presented at a 0.75 size, the traffic having a traffic advisory is drawn at a 1.0 size, and the traffic having a resolution advisory is drawn at a 1.25 size, relative to a norm of a 1.0 dimension. Hence, the most prominent threat is clearly larger than the normal traffic. Threat status is also indicated by overlaying TCAS threat symbols on the traffic or airplane symbol 12. These items provide the pilot a triple redundant coding of threat, that is, color, size and overlaid threat symbol. A traffic symbol 24 having no threat symbol superimposed upon it, represents an aircraft that is above a certain altitude and is not a threat to own aircraft 22. Not having extra symbols, which would represent the absence of threat, superimposed on traffic symbols such as symbol 24, helps declutter display 10. Symbol 26, not having altitude tags, represents an aircraft whose altitude is unknown to the pilot of own aircraft 22. Typically, an aircraft represented by symbol 26 has no altitude transponders to provide own aircraft with altitude or vertical directional data. Symbol 28 is a symbol of 1.25 size indicating a resolution advisory of the aircraft that it represents. Superimposed on symbol 28 is symbol 30 which is a square which means a resolution advisory and has a color red which also indicates a resolution advisory of the aircraft represented by symbol 28. A normal proximate traffic symbol 24 represents an aircraft or traffic that is more than 1200 feet in altitude differential. Aircraft symbol 32 is at size 0.75 but has a normal proximate traffic symbol superimposed on it which represents that the aircraft is within 1200 feet of the present altitude of own aircraft 22. Symbol 34 is a diamond-shape representing normal proximate traffic at less than 1200 feet altitude differential and has a color of cyan also designating normal traffic of less than 1200 feet altitude differential from own aircraft 22. The twelve symbols 36 represent azimuth about own aircraft symbol 22 and constitute a two nautical mile range indicator from own aircraft 22. 
     FIG. 2 depicts a format wherein the size of aircraft symbol 42, 44 or 50 has a size related to altitude differential from own aircraft represented by symbol 22 rather than having a size related to a threat level as in FIG. 1. The changing size of aircraft symbols 42, 44, 48 and 50 provide relative motion cues to the pilot as the planes move away from or approach own aircraft 22. Such enhancement is useful to the pilot of own aircraft where direct visual contact is limited due to bad weather, for instance, or instrument flying is necessary. Symbol 46 is a relatively large symbol that represents proximate traffic of unknown altitude. A relatively small symbol 48 represents normal proximate traffic more than 1200 feet of relative altitude from own aircraft 22. The size of symbol 44 represents the relative altitude of the aircraft from own aircraft 22; however, the advisory of this aircraft is indicated by symbol 30 superimposed on symbol 44 wherein symbol 30 is a square signifying a resolution advisory and further has the color red likewise signifying a resolution advisory. Symbol 50 is of a relatively large size on format 40 in that it represents an aircraft at a low altitude difference (e.g., zero feet) from own aircraft 22. Symbol 34 superimposed on symbol 50 indicates normal proximate traffic at less than 1200 feet. Symbol 34 is a diamond which represents normal proximate traffic and is of the color cyan that also represents normal proximate traffic at less than 1200 feet relative altitude from own aircraft 22. Aircraft symbol 42 represents an aircraft that is about 1000 feet in relative altitude from own aircraft 22 which altitude is represented not only by symbol 14 but also by the size of symbol 42. Superimposed on symbol 42 is symbol 18 which is a medium circle that indicates a traffic alert and has the color yellow that likewise indicates a traffic alert. 
     FIG. 3 is a 2.5-dimension perspective view of the TCAS plan format 60. Format 60 is similar to plan view format 10 except that the observer of format 60 is looking at the scene from a point behind the scene at a particular elevation above the horizon rather than from directly above the scene. This is a preferred implementation. However, the pilot can switch perspectives for better perception of the horizontal or vertical positions of the traffic, respectively. In format 60, an aircraft symbol 62 sits on top an elevation post 64 which is proportional to the represented aircraft&#39;s relative altitude with respect to own aircraft represented by symbol 22. Elevation post 64 alternates between dashed and solid lines on a 500-foot basis, that is, a series of dashes represents 500 feet and a solid line represents 500 feet, and so on. The TCAS warning symbols, that is, filled-in square 30, filled-in circle 78, filled-in diamond 34 and open diamond 68, are located in reference plane 66 to indicate locations of represented aircraft, threat levels of aircraft, and threat azimuths of aircraft. The spoked reference plane 66 of FIG. 3 replaces the twelve symbols 36 in FIGS. 1 and 2, to enhance the perspective view and to increase the pilot&#39;s cognizance of his or her own altitude reference plane. The color codings, red, yellow and cyan, respectively, of filled-in square 30, filled-in circle and filled-in diamond, are like that of the standard TCAS format and present TCAS formats 10 and 40. Open diamond 68 represents no threat. Digital readout 14 indicates the relative altitude of the aircraft represented by symbol 62, with respect to own aircraft represented by symbol 22, in FIG. 3. Digital readout symbol 14 is placed just behind the right wing tip of symbol 62 representing the aircraft. Altitude vertical trend data of the aircraft is represented by the direction that filled triangles 70 is pointing, on the end of each of wing tip of symbol 62. No triangles on wing tips of aircraft symbol 72 indicate no vertical trend in altitude of represented aircraft. Format 60 may be decluttered by removing digital readout symbols 14 and 20 wherein the pilot relies wholly on the analog elevation post 64 height to determine relative altitude of the represented aircraft. Aircraft symbols 62 and 72 rotate to indicate horizontal trend in the same manner as aircraft symbols in the two-dimensional formats of FIGS. 1 and 2. A large aircraft symbol 74 (1.25 size) is red, extends from symbol 30 which is likewise red and represents resolution advisory traffic. A medium aircraft symbol 76 is yellow and extends from a solid yellow circle thereby representing a traffic alert with respect to the represented aircraft. A small aircraft symbol 23 would be cyan and extend from a cyan solid diamond thereby representing normal proximate traffic within 1200 feet of altitude to own aircraft 22. 
     The sizes of aircraft symbols 23, 62, 72 and 76, including other undesignated aircraft symbols, can be designated to indicate the level of threat of the respective represented aircraft on format 60 in FIG. 3. Another version is that sizes of the aircraft symbols represent closeness of the represented aircraft in terms of relative altitude, i.e., the closer the aircraft in altitude, the larger the symbol. The other version of aircraft symbols in format 60 may be implemented, in FIG. 3, wherein all aircraft symbols are of the same size and represent neither a level of threat discrimination nor nearness to own aircraft in terms of relative altitude. 
     Traffic information data are input to input interface 80 which passes the data in an appropriate data format to information processor 82 which processes the information for format and symbol generator 84 as shown in FIG. 4. The output of generator 84 goes to display 86 for presenting data to the observer in format 60. 
     Various sorts of processing devices may be utilized for generating the TCAS formats disclosed herein. In this particular embodiment, a Series 10000 personal supercomputer, from Apollo Computer Inc., of Chelmsford, Mass. 01824, is utilized with the ensuing programs listed below. The Apollo personal supercomputer may be used in actual operational use or as simulator for testing, or operational training. The TCAS format imagery from the computer may be displayed on a conventional CRT, color active matrix liquid crystal display or another kind of display device. The inputs of traffic information to the TCAS system may come from ground stations, own aircraft detection electronics, and/or other aircraft. 
     The following programs may be used to implement an above-described traffic information display format. ##SPC1##