Situation dependent lateral terrain maps for avionics displays

• US 20040059473A1
• Filed: 09/23/2002
• Published: 03/25/2004
• Est. Priority Date: 09/23/2002
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: He, Gang
• Granted Patent: US 6,782,312 B2
• Time in Patent Office: Days
• US Class Current: 701/4
• CPC Class Codes: B64D 45/04 Landing aids; Safety measures to prevent collision with earth's surface
• 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

Abstract

In a lateral terrain map for avionics displays, a terrain relief contrast adjustment parameter, based on a statistical terrain roughness measure, is used to compute optimal terrain presentation for current display conditions. The contrast adjustment parameter allows situation dependent map presentation to enhance, for example, caution and warning situations, or de-emphasize the terrain map features for balanced presentation along with foreground symbology, while reducing computational resource requirements.

Claims

1. A method for adapting an aircraft terrain display in response to situational parameters comprising:

computing a parameter to characterize terrain roughness for an area of terrain to be displayed;

computing a contrast multiplier as a function of the terrain roughness;

multiplying the contrast multiplier by a situation parameter that varies depending upon the flight mode of the aircraft;

computing a lighting component for each terrain data point;

multiplying the lighting component for each data point to obtain a set of terrain data to be displayed; and

displaying the terrain data on the display.

2. A method as set forth in claim 1 wherein the terrain is displayed in color representing the altitude of each data point.

3. A method as set forth in claim 2 wherein the color of the terrain displayed is modified as a function of the lighting component.

4. A method as set forth in claim 1 wherein terrain roughness is calculated by computing an average elevation of the data points in the area of terrain to be displayed, computing the standard deviation of the average elevation of the data points, and computing a roughness index as a function of the standard deviation and the average elevation.

5. A method as set forth in claim 1 wherein terrain roughness is calculated by using a Fast Fourier Transform.

6. A method as set forth in claim 1 wherein the lighting component for each data point is computed by;

computing a normal vector for a set of polygons surrounding a data point;

computing the average of the set of normal vectors;

multiplying the elevation of the data point by the contrast multiplier; and

computing the lighting component of a data point as a function of the normalized vector and a normalized lighting vector.

7. A method as set forth in claim 6 wherein the lighting component is the inner product of the normalized vector and a normalized lighting vector.

10. In a display for displaying terrain features in conjunction with non-terrain features, wherein features may be enhanced or de-emphasized as a function of a situation external to the display, the method comprising:

retrieving a set of data points representing the location and elevation of terrain in an area of terrain to be displayed;

computing the color of each data point as a function of the elevation of the terrain at the data point;

calculating the desired contrast of each data point as a function of the situation;

modifying the color of each data point as a function of the desired contrast; and

displaying the modified color of each data point on the display.

11. A method as set forth in claim 10 wherein the display is an avionics display for an aircraft and the terrain is represented as a terrain map.

12. A method as set forth in claim 11 wherein the display also displays graphical flight planning information.

13. A method as set forth in claim 12 wherein the color of each data point signifies the elevation of the terrain above or below the altitude of the aircraft.

14. A method as set forth in claim 13 wherein if the aircraft is at an altitude equal to or lower than the elevation of the immediate terrain, the terrain map is enhanced and the graphical flight planning data is de-emphasized.