Intervisibility determination

• US 20050267652A1
• Filed: 02/23/2005
• Published: 12/01/2005
• Est. Priority Date: 05/28/2004
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Allstadt, Mark, Glickstein, Ira S., Stiles, Peter N., Blais, Marc, Vienneau, Ronald
• Granted Patent: US 7,280,897 B2
• Time in Patent Office: Days
• US Class Current: 701/9
• CPC Class Codes: G06F 16/29 Geographical information databases

Abstract

A system and method for efficient intervisibility determination. The intervisibility determination method of the present invention provides a multiple threat processing capability within a specified area of terrain using a common database. Computation is simplified through the method of processing data posts in the terrain elevation database. By taking integer steps and incrementing distance, x or y, and a predicted elevation value at each step, a small number of operations may be performed. Recomputing a change in elevation value may be reduced. An umbra database provides an enhanced look-up capability for displaying and updating the intervisibility display information. The systems and methods of the present invention may be suitable for use on a vehicle and in mission management activities.

Claims

1. A method for determining threat intervisibility for an aircraft comprising:

receiving a terrain elevation database comprising a plurality of data points, wherein each data point corresponds to a geographic location and adjacent geographic locations are uniformly spaced in each of a first direction and a second direction perpendicular to said first direction, and wherein each data point represents a terrain elevation of the corresponding geographic location;

creating an umbra database comprising umbra database cells, wherein each umbra database cell corresponds to a terrain elevation database data point;

receiving a threat location and a threat range capability for one or more threats within the area of terrain covered by the terrain elevation database;

determining a plurality of line of sight vectors to compute for each threat;

initializing cell coordinate variables X and Y to cell coordinates representing a threat location of a first threat;

initializing a distance variable and a step count variable;

calculating an initial umbra value, wherein the initial umbra value is calculated as an elevation at the threat location and stored in the umbra database at the umbra database cell corresponding to the geographic location of the first threat;

incrementing the cell coordinate variables X and Y to reference a next point on a first line of sight vector;

incrementing the distance variable by the distance taken in each step along the first line of sight vector;

incrementing the step count variable;

calculating a change in elevation value at a second step along a line of sight vector being processed and storing said change in elevation value, wherein the change in elevation value is calculated as the difference between a current terrain elevation value and the threat elevation, divided by the step count;

calculating a predicted umbra value by summing the change in elevation value with a preceding umbra value;

if the predicted umbra value is at or above the current terrain elevation value, then storing the predicted umbra value in the umbra database, otherwise, recomputing the change in elevation value by subtracting the initial elevation value from the current terrain elevation value and dividing the resulting difference by the step count and storing the current terrain elevation value in the umbra database at a corresponding location;

if the distance traversed along the line of sight vector is equal to or greater than the threat range capability of the threat being processed, then ending processing for the first line of sight vector and processing a second line of sight vector, otherwise, continuing processing of the first line of sight vector by repeating the steps of incrementing the cell coordinate variables X and Y, incrementing a distance variable, incrementing the step count variable, calculating a change in elevation value, calculating a predicted umbra value and computing the distance traversed along the first line of sight vector;

if there are no other line of sight vectors to process, then ending intervisibility processing for the first threat; and

proceeding to a second threat by repeating the steps of determining a number of line of sight vectors to compute, and for each line of sight vector repeating the steps of initializing cell coordinate variables X and Y, initializing the distance variable and the step count variable, calculating an initial umbra value, incrementing the cell coordinates X and Y, incrementing the distance variable, incrementing the step count variable, calculating the change in elevation value, and calculating the predicted umbra value for each next threat;

if there are no other threats to process, then ending intervisibility processing.

2. The method of claim 1, further comprising the step of displaying intervisibility data.

3. The method of claim 1, further comprising the step of coupling the umbra database to a mission management module to perform mission management activities.

4. The method of claim 1, further comprising the step of re-computing intervisibility when the altitude of the aircraft changes by a predetermined amount.

5. The method of claim 1, further comprising the step of re-computing intervisibility in response to a command from an operator of the aircraft.

6. The method of claim 2, further comprising the step of updating a display of intervisibility data in response to computing of intervisibility data.

7. The method of claim 1, further comprising the step of re-computing intervisibility in response to receipt of updated threat information.

8. The method of claim 1, further comprising the step of receiving an altitude of the aircraft for which intervisibility is being determined and computing intervisibility results based on a comparison of the altitude of the aircraft for which intervisibility is being determined and the umbra database.

9. The method of claim 8, further comprising the step of displaying an image corresponding to the intervisibility results for at least a portion of the umbra database cells in the umbra database.

10. The method of claim 1, wherein the step of receiving a threat location and a threat range capability further comprises receiving a threat location and a threat range capability from a pre-loaded threat information database.

11. The method of claim 1, wherein the step of receiving a threat location and a threat range capability further comprises receiving a threat location and a threat range capability from sensors.

12. The method of claim 1, wherein the step of receiving a threat location and a threat range capability further comprises extracting a threat location and a threat range capability from a communications message received by the aircraft.

13. A computer program product for determining threat intervisibility, comprising:

software instructions for enabling the computer to perform predetermined operations; and

a computer readable medium bearing the software instructions;

the predetermined operations including the steps of;

receiving a terrain elevation database comprising a plurality of data points, wherein each data point corresponds to a geographic location, wherein adjacent geographic locations are uniformly spaced in each of a first direction and a second direction perpendicular to said first direction, and wherein each data point represents a terrain elevation of the geographic location corresponding to the data point;

creating an umbra database comprising umbra database cells, wherein each umbra database cell corresponds to a terrain elevation database data point;

receiving a threat location and a threat range capability for a threat within the area of terrain covered by the terrain elevation database;

determining a line of sight vector to compute for the threat;

initializing cell coordinate variables X and Y to cell coordinates representing the threat location;

initializing a distance variable and a step count variable;

calculating an initial umbra value, wherein the initial umbra value is calculated as the elevation of the ground at the threat location and stored in the umbra database in the umbra database cell corresponding to the threat location;

incrementing the cell coordinate variables X and Y to reference a next cell on the line of sight vector;

incrementing the distance variable by the distance taken in each cell step along the line of sight vector;

incrementing the step count variable;

calculating a change in elevation value at a second step along the line of sight vector being processed and storing said change in elevation value, wherein the change in elevation value is calculated as the difference between a current terrain elevation value and the threat elevation, divided by the step count;

calculating a predicted umbra value by summing the change in elevation value with a preceding umbra value;

if the predicted umbra value is at or above the current terrain elevation value, then storing the predicted umbra value in the umbra database, otherwise, recomputing the change in elevation factor by subtracting the initial elevation value from the current terrain elevation value and dividing the resulting difference by the step count and storing the current terrain elevation value in the umbra database;

if the distance variable value is equal to or greater than the threat range capability of the threat being processed, ending processing for the line of sight vector, otherwise, continuing processing of the line of sight vector by repeating the steps of incrementing the cell coordinate variables X and Y, incrementing the distance variable, incrementing the step count variable, calculating a change in elevation value, calculating a predicted umbra value.

if the line of sight vector processing is complete and the threat processing is complete, then ending intervisibility processing.

14. A computer system adapted to calculate intervisibility comprising:

a processor, and

a memory including software instructions that cause the computer system to perform the steps of;

receiving a terrain elevation database comprising a plurality of data points, wherein each data point corresponds to a geographic location, wherein adjacent geographic locations are uniformly spaced in each of a first direction and a second direction perpendicular to said first direction, and wherein each data point represents a terrain elevation of the geographic location corresponding to the data point;

creating an umbra database comprising umbra database cells, wherein each umbra database cell corresponds to a terrain elevation database data point;

receiving a threat location and a threat range capability for a threat within the area of terrain covered by the terrain elevation database;

determining a line of sight vector to compute for the threat;

initializing cell coordinate variables X and Y to cell coordinates representing the threat location;

initializing a distance variable and a step count variable;

calculating an initial umbra value, wherein the initial umbra value is calculated as the elevation of the ground at the threat location and stored in the umbra database in the umbra database cell corresponding to the threat location;

incrementing the cell coordinate variables X and Y to reference a next cell on the line of sight vector;

incrementing the distance variable by the distance taken in each cell step along the line of sight vector;

incrementing the step count variable;

calculating a change in elevation value at a second step along the line of sight vector being processed and storing said change in elevation value, wherein the change in elevation value is calculated as the difference between a current terrain elevation value and the threat elevation, divided by the step count;

calculating a predicted umbra value by summing the change in elevation value with a preceding umbra value;

if the predicted umbra value is at or above the current terrain elevation value, then storing the predicted umbra value in the umbra database, otherwise, recomputing the change in elevation factor by subtracting the initial elevation value from the current terrain elevation value and dividing the resulting difference by the step count and storing the current terrain elevation value in the umbra database;

if the distance variable value is equal to or greater than the threat range capability of the threat being processed, ending processing for the line of sight vector, otherwise, continuing processing of the line of sight vector by repeating the steps of incrementing the cell coordinate variables X and Y, incrementing the distance variable, incrementing the step count variable, calculating a change in elevation value, calculating a predicted umbra value.

if the line of sight vector processing is complete and the threat processing is complete, then ending intervisibility processing.

15. The computer system of claim 14, further comprising a display coupled to the processor for displaying at least a portion of intervisibility data in response to operator input.

16. The computer system of claim 14, further comprising a communications link.

17. The computer system of claim 16, wherein the communications link receives threat information.

18. The computer system of claim 16, wherein the communications link transmits threat information.

19. The computer system of claim 15, wherein the computer system is a portable computer.

20. The computer system of claim 15, wherein the computer system is on board an aircraft.