Methods and systems for detecting forward obstacles

• US 6,885,334 B1
• Filed: 07/07/2004
• Issued: 04/26/2005
• Est. Priority Date: 04/06/2004
• Status: Expired due to Fees

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Becker, Robert C., Hager, James R., Almsted, Larry D.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US10/885,860
• Time in Patent Office: 293 Days
• Field of Search: 342 62- 65, 342120-122, 342/195
• US Class Current: 342/62
• CPC Class Codes: G01S 13/288 phase modulated
• CPC Class Codes: G01S 13/426 Scanning radar, e.g. 3D radar G01S13/66 takes precedence
• CPC Class Codes: G01S 13/882 for altimeters measuring height using barometric means G01C5/06
• CPC Class Codes: G01S 13/935 for terrain-avoidance

Abstract

Methods and apparatus for detecting obstacles in the flight path of an air vehicle are described. The air vehicle utilizes a radar altimeter incorporating a forward looking antenna and an electronic digital elevation map to provide precision terrain aided navigation. The method comprises determining a position of the air vehicle on the digital elevation map, selecting an area of the digital elevation map in the flight path of the air vehicle, based at least in part on the determined air vehicle position, and scanning the terrain representing the selected map area with the forward looking antenna. The method also comprises combining the digital elevation map data for the selected map area with radar return data for the scanned, selected area and displaying the combined data to provide a representation of the terrain and obstacles in the forward flight path of the air vehicle.

Claims

1. A method for detecting obstacles in the forward flight path of an air vehicle, the air vehicle utilizing a radar altimeter and an electronic digital elevation map for precision terrain aided navigation, the radar altimeter incorporating a forward looking antenna, said method comprising:

determining a position of the air vehicle on the digital elevation map;

selecting an area of the digital elevation map in the flight path of the air vehicle, based at least in part on the determined air vehicle position;

scanning the terrain representing the selected map area with the forward looking antenna;

combining the digital elevation map data for the selected area with radar return data for the scanned, selected area; and

displaying the combined data to provide a representation of the terrain and obstacles in the forward flight path of the air vehicle.

2. A method according to claim 1 wherein said retrieving data and said scanning terrain are dependent on a vehicle speed.

3. A method according to claim 2 wherein the selected area of the digital elevation map and the scanned terrain are determined to provide a pilot with a sufficient warning time to avoid any obstacles scanned or present on the DEM.

4. A method according to claim 1 wherein scanning the terrain representing the selected map area with the forward looking antenna comprises scanning a field of view of about ±

20 degrees in azimuth by about ±

10 degrees in elevation.

5. A method according to claim 1 wherein scanning the terrain representing the selected map area with the forward looking antenna comprises scanning in a raster motion with a beam of about 2 degrees in width.

6. A method according to claim 1 wherein scanning the terrain representing the selected map area with the forward looking antenna comprises:

scanning with the forward looking antenna in a raster motion; and

performing radar altimeter functions during turnaround portions of the raster motion.

7. A method according to claim 1 wherein combining the digital elevation map data for the selected area with radar return data for the scanned, selected area comprises providing a range, a heading, and an elevation of obstacles forward of the vehicle in body coordinates.

8. A radar altimeter, comprising:

a precision terrain aided navigation (PTAN) processor configured to process interferometric radar altimeter data;

a terrain correlation processor configured to correlate data from said PTAN processor to a present vehicle location on a digital elevation map (DEM);

a forward map scanning processor configured to receive an altitude from said PTAN processor and determine a position on the DEM to scan which is forward of the vehicle;

a forward looking processor configured to receive data relating to a scan of the terrain corresponding to the position on the DEM that said forward map scanning processor is configured to scan; and

a display processor configured to process and reconcile data from said forward map scanning processor and said forward looking processor.

9. A radar altimeter according to claim 8 further comprising a forward looking antenna, said forward looking antenna configured to scan in a raster motion and further configured to provide data relating to the scan to said forward looking processor.

10. A radar altimeter according to claim 9 wherein the raster motion is about ±

20 degrees in azimuth and about ±

10 degrees in elevation.

11. A radar altimeter according to claim 9 configured to receive interferometric radar altimeter data during turnaround portions of the raster motion.

12. A radar altimeter according to claim 8 wherein the position on the DEM that said forward map scanning processor is configured to scan is dependent on a velocity of the vehicle.

13. A method according to claim 12 wherein said forward map scanning processor and said forward looking processor are configured to respectively select an area of the digital elevation map and scan a section of terrain such that a pilot has a sufficient warning time to avoid any forward obstacles scanned or present on the DEM.

14. A radar altimeter according to claim 8 further comprising a navigation processor, said navigation processor configured to receive data from said terrain correlation processor relating to a present vehicle location on the DEM and location information from an inertial navigation unit (INU), and further configured to output a combined PTAN/INU navigation position.

15. A radar altimeter according to claim 8 wherein said forward map scanning processor is configured to receive velocity and heading from an inertial navigation unit.

16. A radar altimeter according to claim 8 wherein said forward looking processor is configured to provide a range, a heading, and an elevation of obstacles forward of the vehicle in body coordinates.

17. A processing unit for a radar altimeter, said processing unit configured to:

receive and process interferometric radar altimeter data;

correlate processed interferometric radar altimeter data to a present vehicle location on a digital elevation map (DEM);

determine a terrain position to scan which is forward of the vehicle based at least in part on a position generated from the correlated interferometric radar altimeter data;

receive data relating to a scan of the terrain corresponding to the correlated interferometric radar altimeter data; and

combine the data relating to the scan of the terrain with data from the DEM.

18. A processing unit according to claim 17 wherein said unit is further configured to receive data relating to a raster motion scan of a forward looking antenna.

19. A processing unit according to claim 18 wherein said unit is further configured to receive the interferometric radar altimeter data during turnaround portions of the raster motion scan.

20. A processing unit according to claim 17 wherein said unit is configured to utilize a velocity of the vehicle when determining a position of the terrain to be scanned.

21. A processing unit according to claim 17 wherein said unit is further configured to utilize data relating to a present vehicle location on the DEM and location information from an inertial navigation unit (INU) to determine a combined precision terrain aided navigation (PTAN)/INU navigation position.

22. A processing unit according to claim 17 configured to receive velocity and heading from an inertial navigation unit.

23. A processing unit according to claim 17 configured to provide a range, a heading, and an elevation of obstacles forward of the vehicle in body coordinates.