System and method for synthetic vision terrain display

• US 20030021491A1
• Filed: 07/03/2002
• Published: 01/30/2003
• Est. Priority Date: 07/06/2001
• Status: Active Grant

• Current Assignee: L-3 Communications Avionics Systems Incorporated (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Avionics Systems Incorporated (L3Harris Technologies, Inc.)
• Inventors: Brust, Clifford S.
• Granted Patent: US 7,123,260 B2
• Time in Patent Office: Days
• US Class Current: 382/294
• CPC Class Codes: G01C 23/00 Combined instruments indicating more than one navigational value, e.g. for aircraft; Combined measuring devices for measuring two or more variables of movement, e.g. distance, speed or acceleration
• CPC Class Codes: G02B 2027/0138 comprising image capture systems, e.g. camera
• CPC Class Codes: G02B 2027/014 comprising information/image processing systems
• CPC Class Codes: G02B 27/01 Head-up displays
• CPC Class Codes: G06T 15/10 Geometric effects
• CPC Class Codes: G06T 17/05 Geographic models

Abstract

A synthetic rendering of the terrain within a selected field of view is created from raw terrain elevation data, and the resolution of the rendering is proportioned to the altitude above ground level (altitude AGL) of the aircraft. All the data points are subdivided into tiles. Only data from tiles within a prescribed field of view are considered for processing; all others are ignored. Within the selected tiles, only some of the terrain elevation data points are passed to the graphics processor for rendering. At maximum resolution, when the aircraft is on the ground or at a low altitude, there are relatively fewer tiles within the field of view and the fraction of the data points from each tile within the field of view passed for rendering is relatively large. As the aircraft'"'"'s altitude AGL level increases, the field of view also increases in area increasing the number of tiles within the field of view. However, the number of data points forwarded for rendering by the graphics processor is kept approximately constant by selecting progressively fewer and fewer terrain elevation data points from each tile for rendering as altitude AGL increases. Only the data points that lie within tiles inside a prescribed field of view are forwarded to the graphics processor for rendering. Once the tiles have been selected, the terrain elevation data points are grouped in groups of a size that depends on altitude AGL, with more terrain data points in the grouped as attitude increases. Preferably the groups are triangle strips. Only the highest elevation from each group is passed to the graphics processor for rendering.

Claims

1. A method of rendering an image of terrain for display in a cockpit display, the method comprising forming a set of tiles from raw terrain data, each tile including information concerning the elevation of points on the ground;

selecting a subset of tiles to be processed to render the image, and sending the subset of tiles to a graphics processor to render an image based on the information in each tile.

2. The method of claim 1 wherein the step of selecting a subset of tiles includes the step of selecting the number of data points representing information concerning the elevation of points on the ground from each tile to be rendered, which number decreases with increasing aircraft altitude above ground level.

3. The method of claim 1 wherein the number of tiles in the selected subset of tiles increases as the aircraft'"'"'s altitude above ground level increases.

4. The method of claim 2 wherein the step of forming a set of tiles includes calculating the geometric center of each tile.

5. The method of claim 4 wherein the step of selecting a subset of tiles includes identifying tiles which have a geometric center within a preselected angle of view.

6. The method of claim 5 wherein the step of selecting a subset of tiles includes identifying tiles that have a geometric center within a preselected distance from the aircraft.

7. The method of claim 5 wherein the step of identifying tiles which have a geometric center within a preselected field of view includes the step of selecting tiles included within a selected angle measured with respect to the direction of motion of the aircraft and with respect to the altitude of the aircraft above ground level.

8. The method of claim 1 wherein each tile is associated with a specific area on the ground and includes elevation data with respect to the elevation of multiple locations within the specific area and further including the step of selecting elevation data with respect to some but not all of the multiple locations within the specific area.

9. The method of claim 8 wherein the step of selecting elevation data of some but not all of the multiple locations within the specific area includes forming a group of elevation data and selecting representative elevation data from the group.

10. The method of claim 9 wherein the step of selecting representative data includes arranging the data in a regular rectangular matrix, selecting the number (n) of data points to be representative data points, forming the group into an n sided polygon within the matrix, selecting a range of data points surrounding each vertex of the polygon such that every data point within the polygon is within the selected range of at least one vertex;

assigning to the data point at each vertex the highest value of any data point within the selected range of that vertex, and thereafter selecting the vertex data points as the representative data.

11. The method of claim 10 wherein the elevation data are grouped into triangle strips to form the groups and the step of selecting some but not all of the elevation data includes selecting the data points at the vertices of each triangle.

12. A program stored on a computer readable medium for performing the method of claim 1.

13. A system for rendering an image of terrain and displaying the image on a cockpit display including;

means for forming a set of tiles from raw terrain data, each tile including information concerning the elevation of points on the ground;

means for selecting a subset of tiles to be processed to render the image;

means for rendering an image based on the information in the subset of tiles; and

means for displaying the image.

14. A method of rendering an image of terrain for display in a cockpit display of an aircraft, characterized by selecting from a set of data points representing information concerning the elevation of points corresponding to the terrain being traversed by the aircraft, a subset of data points that are processed for display on the cockpit display, wherein the number of data points per unit area of terrain being displayed is decreased with increasing altitude over ground level while the area of terrain corresponding to the selected data points is increased with increasing altitude over ground level, and vice versa.

15. A system for performing the method of claim 14.