GB2187616A

GB2187616A - Display methods and apparatus

Info

Publication number: GB2187616A
Application number: GB08704807A
Authority: GB
Inventors: Michael Lynn Busbridge; David John Puleston
Original assignee: GEC Avionics Ltd
Current assignee: Allard Way Holdings Ltd
Priority date: 1986-03-07
Filing date: 1987-03-02
Publication date: 1987-09-09
Anticipated expiration: 2007-03-02
Also published as: GB2187616B; GB8704807D0; GB8605713D0

Abstract

A display method and apparatus wherein a two-dimensional display constituting a perspective view of a three-dimensional surface comprises an array of discrete points appearing to model the surface. The invention finds particular application for providing an aircraft pilot with a display of ground terrain ahead of his aircraft using stored data representing the terrain. <IMAGE>

Description

SPECIFICATION Display methods and apparatus This invention relates to display methods and apparatus.

More particularly the invention relates to such methods and apparatus for using data representing a three-dimensional surface to produce a twodimensional display constituting a perspective view of the surface.

In the present specification the term perspective view includes a quasi-perspective view, e.g. an isometric view.

One particular application of such methods and apparatus is in an aircraft for providing a pilot with a real time display of the ground terrain ahead of the aircraft e.g. to assist navigation in poor visibility.

In known such methods and apparatus the display comprises a grid of lines appearing to conform to the surface. However such a representation of the surface is found by users to be aesthetically rather unsatisfactory, and it is an object of the present invention to provide a display of more satisfactory form in this respect.

According to a first aspect of the invention in a method of using data representing a threedimensional surface to produce a two-dimensional display constituting a perspective view of the surface, the data is used to produce a said display comprising an array of discrete elements which appears to model said surface.

According to a second aspect of the invention an apparatus for using data representing a threedimensional surface to produce a two-dimensional display constituting a perspective view of the surface comprises means for using said data to produce a said display comprising an array of discrete elements which appears to model said surface.

In one particular embodiment of such apparatus the apparatus comprises: storage means for storing said data; means for utilising said stored data to produce first signals representing the positions in a three-dimensional co-ordinate system of each point of an array of points in a selected region of said surface represented by said data; means utilising said first signals to produce second signals representing the positions of each of said points in a two-dimensional perspective view of said region; and means for utilising said second signals to provide said display.

It will be appreciated that when the surface is a non-transparent surface, the elements relating to hidden parts of the surface in the perspective view are preferably not displayed.

In a method and apparatus in accordance with the invention the display produced may also be arranged to provide emphasis of selected features of the display e.g. the edges of upstanding features in the perspective view which, if the surface is nontransparent, conceal more distance portions of said surface in the perspective view. Such emphasis is suitably in the form of continuous lines.

In a method or apparatus according to the invention said elements are suitably dots.

One method and apparatus in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings in which:~ Figure 1 is a schematic diagram of the apparatus; Figure 2 illustrates a display produced by the apparatus; and Figure 3 illustrates a corresponding display produced by known apparatus.

The apparatus is intended for use in an aircraft to provide the pilot or other observer in the aircraft with a real time display of the ground terrain ahead of the aircraft.

Referring to Figure 1, the apparatus includes a digital data store 1 in which is stored a representation of the earth's surface in the locality in which the aircraft is to fly. The representation is typically in the form of an array of values, each of which values represents the vertical height above a base plane of a respective point on the earth's surface, each point being vertically above a respective intersection point of a regular nominally rectangular grid of lines in the base plane.

The data stored in the store 1 thus comprises data of the kind contained in Digital Land Mass Survey~ Digital Terrain Elevation Data (DLMS DTED) data bases such as are available from the Defense Mapping Agency in the United States of America and the Mapping and Charting Establishment RE, Feltham in the United Kingdom.

The apparatus further includes a dot sampling pattern generator 3 which causes data to be passed from the store 1 to a 3D processing unit 5 and controls the unit 5 so as to enable the unit 5 to produce at its outputx, y and z signals in respect of each point, where x and y indicate the coordinates of the projection of the point on the base plane and z indicates the height of the point above the base plane.

The processing unit 5 also receives from a unit 7 an input representing the aircraft's position, heading and attitude so that the output signal of the unit 5 relates to the ground terrain ahead of the aircraft in its direction of flight correctly adjusted for pitch and roll.

The output of the processing unit 5 is passed to a perspective transformation unit 9 which uses a transformation algorith to convert the threedimensional coordinate input signals x, y, z to twodimensional coordinate signals, x', y' which indicate the position of each point represented in the output of the unit 5 in a two-dimensional perspective view from the position of the aircraft of the surface which the points represent.

The output of the transformation unit 9 is passed to a display unit 11, typically a raster scanning cathode ray tube display unit, via a feature emphasis and hidden feature removal unit 13.

The unit 13 suppresses all the x', y' signals relating to those points which lie in parts of the ground terrain ahead of the aircraft which will be hidden in the two-dimensional perspective view by virtue of the non-transparency of the surface.

The unit 13 further generates signals representing lines extending along the edges of upstanding features of the perspective view which conceal more distance portions of the perspective view i.e. socalled ridge lines.

The display unit 11 provides a display having a visible portion at each position represented by the x', y' signals at the output of the unit 13. The display thus comprises an array of discrete dots which appears to model the ground terrain ahead of the aircraft, as viewed from the perspective of the aircraft. In addition, the display has continuous lines extending along the ridge lines of the displayed perspective view.

It will be appreciated that if desired the unit 13 may be omitted.

An example of the display produced is shown in Figure 2. Figure 3 illustrates a display of the same terrain obtained with conventional display apparatus wherein the display produced comprises a grid of continuous lines conforming to the surface of the terrain.

In addition to providing a display more aesthetically satisfying than known methods and apparatus, a method and apparatus according to the invention has obvious computational speed advantages compared with known methods and apparatus, especially when utilising stored data of the DLMS DTED data base type. Furthermore, since only discrete dots, with the possible addition of ridge lines, are used to provide the required surface perspective view, additional visual data, such as flight and target symbology, added to the display can be more readily assimilated by the viewer.

Claims

1. A method of using data representing a threedimensional surface to provide a two-dimensional display constituting a perspective view of the surface wherein the data is used to produce a said display comprising an array of discrete elements which appears to model said surface.

2. A method according to Claim 1 comprising the steps of: deriving from said data first signals representing the positions in a three-dimensional coordinate system of each point in an array of points in a selected region of said surface; transforming said first signals to second signals representing the positions of said points in a two-dimensional perspective view of said region; and utilising said second signals to produce said display.

3. A method according to Claim 2 wherein those of the second signals representing the positions of points in said region which will be hidden from view in said perspective view if said surface is nontransparent are suppressed prior to said utilising step.

4. A method according to Claim 2 or Claim 3 including the further step of producing in said display continuous lines emphasising selected features of said perspective view.

5. A method according to Claim 4 wherein said lines extend along the edges of upstanding features in said perspective view which, if said surface is non-transparent, conceal more distance portions of said surface in said perspective view.

6. An apparatus for using data representing a three-dimensional surface to produce a twodimensional display constituting a perspective view of the surface comprising means for using said data to produce a said display comprising an array of discrete elements which appears to model said surface.

7. An apparatus according to Claim 6 comprising: storage means for storing said data; means for utilising said stored data to produce first signals representing the positions in a three-dimensional coordinate system of each point of an array of points in a selected region of said surface represented by said data; means utilising said first signals to produce second signals representing the positions of each of said points in a twodimensional perspective view of said region; and means for utilising said second signals to provide said display.

8. An apparatus according to Claim 7 including means for suppressing those of said second signals representing the positions of points in said region which will be hidden from view in said perspective view if said surface is non-transparent.

9. An apparatus according to Claim 7 or Claim 8 wherein said means utilising said first signals also produces second signals representing continuous lines to emphasise in said display selected features of said persective view.

1û. An apparatus according to Claim 9 wherein said lines extend along the edges of upstanding features in said perspective view which, if said surface is non-transparent, conceal more distance portions of said surface in said perspective view.

11. A method according to any one of Claims 1 to 5 or an apparatus according to any one of Claims 6 to 10 wherein said elements are dots.

12. A method according to any one of Claims 1 to 5 and 11 or an apparatus according to any one of Claims 6 to 11 wherein said surface is the ground terrain in a locality in which an aircraft is to fly.

13. A method or apparatus according to Claim 12 wherein said perspective view is a perspective view of said ground terrain ahead of the aircraft substentiallyfrom the position of the aircraft.

14. A method according to Claim 1 substantially as hereinbefore described with reference to Figure 1.

15. An apparatus according to Claim 6 substantially as hereinbefore described with reference to Figure 1.