Terrain referenced navigation electromagnetic-gravitational correlation

• US 5,272,639 A
• Filed: 01/14/1992
• Issued: 12/21/1993
• Est. Priority Date: 01/14/1992
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: McGuffin, John T.
• Primary Examiner(s): Chin, Gary
• Application Number:
  US07/821,397
• Time in Patent Office: 707 Days
• Field of Search: 364/443, 364/449, 364/453, 364/454, 364/457, 364/460, 364/571.01, 342/63, 342/64, 342/65, 342/450, 342/451, 342/457, 244/3.2
• US Class Current: 701/207
• CPC Class Codes: G01C 21/005 with correlation of navigation data from several sources, e.g. map or contour matching G01C21/30 takes precedence

Abstract

A terrain reference navigation system for an aircraft, surface vessel or subsurface vessel utilizing three sets of geo-physical correlation data. A kalman filter is used to correlate terrain data, electromagnetic data and gravimetric data with the output of a digital map of terrain, electromagnetic field and gravity. An optical disk stores the digitized data for sections of the globe. A Best of 3 selection process decides based on the errors in the kalman filter whether to accept the prediction of the terrain system, electromagnetic system or gravity system. An inertial navigation system uses the results of the Best of 3 selection to update aircraft, surface vessel or sub-surface vessel position and velocity and provide a more accurate positional estimate.

Claims

1. A terrain referenced navigation system for use in an aircraft comprising:

(a) a means for determining a current terrain elevation from the aircraft having a current terrain elevation output;

(b) a means for determining a current electromagnetic field from the aircraft having a current electromagnetic field output;

(c) a means for detecting a current gravity field from the aircraft having a current gravity field output;

(d) a means for inertial navigation having a latitude/longitude positional output, a selected position update input and a selected velocity update input;

(e) a means for storing a digital terrain elevation map having a terrain latitude/longitude input connected to the latitude/longitude positional output and having a digital terrain elevation residual output and a digital terrain elevation output wherein the means for storing a digital terrain elevation map provides the digital terrain elevation residual output and digital terrain elevation output in response to the terrain latitude/longitude input;

(f) a means for computing the difference between elevations connected to the current terrain elevation output and the digital terrain elevation output, wherein the means for computing the difference between elevations also includes a terrain error output;

(g) a means for storing a digital electromagnetic field map having a electromagnetic latitude/longitude input connected to the latitude/longitude positional output and a digital electromagnetic field residual output and a digital electromagnetic field output wherein the means for storing a digital electromagnetic field provides the digital electromagnetic residual output and digital electromagnetic field output in response to the electromagnetic latitude/longitude input;

(h) a means for subtracting a digital electromagnetic field connected to the digital electromagnetic field output and the current electromagnetic field output and wherein the means for subtracting a digital electromagnet field also includes a electromagnetic error output;

(i) a means for storing a gravity field map having a gravity latitude/longitude input connected to the latitude/longitude positional output and having a gravity field residual output and a gravity field output wherein the means for storing a gravity field map provides the gravity field residual output and gravity field output in response to the gravity latitude/longitude input;

(j) a means for subtracting a gravity field connected to the gravity field output and the current gravity field output and wherein the means for subtracting a gravity field also includes a gravity error output;

(k) a means for terrain correlation connected to the digital terrain elevation residual output and the terrain error output and wherein the means for terrain correlation provides a terrain velocity update and a terrain position update;

(l) a means for electromagnetic correlation connected to the digital electromagnetic elevation residual output and the electromagnetic error output and wherein the means for electromagnetic correlation provides a electromagnetic velocity update and a electromagnetic position update;

(m) a means for gravity correlation connected to the digital gravity elevation residual output and the gravity error output and wherein the means for gravity correlation provides a gravity velocity update and a gravity position update;

(n) a means for selecting between the terrain velocity update, the electromagnetic velocity update and the gravity velocity update to provide a selected velocity update wherein the selected velocity update is connected to the selected velocity update input; and

(o) a means for selecting between the terrain position update, the electromagnetic position update and the gravity position update to provide a selected position update wherein the selected position update is connected to the selected position update input.

2. The terrain referenced navigation system of claim 1 wherein the means for terrain correlation is a kalman filter.

3. The terrain referenced navigation system of claim 1 wherein the means for electromagnetic correlation is a kalman filter.

4. The terrain referenced navigation system of claim 1 wherein the means for gravity correlation is a kalman filter.

5. The terrain referenced navigation system of claim 1 wherein the means for selecting between the terrain velocity update, the electromagnetic velocity update and the gravity velocity update selects the update with the least error.

6. The terrain referenced navigation system of claim 1 wherein the means for selecting between the terrain position update, the electromagnetic position update and the gravity position update selects the update with the least error.

7. The terrain referenced navigation system of claim 1 wherein the means for determining a current terrain elevation from the aircraft further comprises a barometric altimeter and a radar altimeter wherein the current terrain elevation is calculated from the difference between the barometric altimeter and the radar altimeter.

8. The terrain referenced navigation system of claim 1 wherein the means for determining the current electro-magnetic field from the aircraft further comprises a magnetic flux valve.

9. The terrain referenced navigation system of claim 1 wherein the means for detecting a gravity field from the aircraft comprises a gravitometer.

10. The terrain referenced navigation system of claim 1 wherein the means for inertial navigation further comprises a laser gyro inertial navigation system.

11. The terrain referenced navigation system of claim 1 wherein the means for storing a digital terrain elevation map further comprises an optical disk.

12. The terrain referenced navigation system of claim 1 wherein the means for storing a digital electromagnetic field map further comprises an optical disk.