US5345241A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Self-contained method for correction of an inertial system over a body of water
Assignee: Northrop Grumman Guidance and Electronics Co Inc
•
Filing: 1992-12-07
•
Granted: 1994-09-06
•
Expires: 2012-12-07
Abstract
Abstract A method and apparatus for performing on-board corrections to the computed navigation variables of an inertial system on an aircraft while flying over a body of water. Onboard instruments, including a barometric altimeter and a radar altimeter, measure the vertical distance of the aircraft above an ellipsoidal model of the earth and above the body of water respectively. An on-board computer calculates the differences between such heights over a plurality of points along the path the aircraft travels over the water as indicated by its inertial navigation system. The differences are compared with a map of the undulation of the geoid encompassing the region to determine the deviation of the navigated course from the true course. Appropriate corrections to the aircraft's inertial system may then be made to reduce error.
Inventors
- 👤 James R. Huddle
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 03:32
CPC Classifications
G; G01; G01C; G01C21/00; G01C21/10; G01C21/12; G01C21/16; G01C21/183; G01C21/188; G01C21/005
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
188 words
An on-board method for the correction of the inertial system of an aircraft as it proceeds on a course over a region of a body of water comprising the steps of: a) continuously determining the location of a point horizontally along said course by means of said aircraft's inertial navigation system; and b) measuring the vertical distance of said aircraft, at said point, above an ellipsoidal model of a geoid that includes said region; and c) measuring the vertical distance of said aircraft, at said point, above the surface of said body of water; then d) computing the difference between the values measured in steps b and c to determine the measured undulation of said geoid at said point; then e) comparing said measured undulation of said geoid with the undulation of said geoid at said point as determined by gravitational surveys; then f) repeating steps a through e; then g) determining a position correction by correlating said measured undulation values with values pre-determined by said survey; and then h) adjusting at least one of the aircraft's inertial navigation system variable computations by means of said position correction.
Claim 2
Dependent Claim
188 words
An on-board method for the correction of the inertial system of an aircraft as it proceeds on a course over a region of a body of water comprising the steps of: a) continuously determining the location of a point horizontally along said course by means of said aircraft's inertial navigation system; and b) measuring the vertical distance of said aircraft, at said point, above an ellipsoidal model of a geoid that includes said region; and c) measuring the vertical distance of said aircraft, at said point, above the surface of said body of water; then d) computing the difference between the values measured in steps b and c to determine the measured undulation of said geoid at said point; then e) comparing said measured undulation of said geoid with the undulation of said geoid at said point as determined by gravitational surveys; then f) repeating steps a through e; then g) determining a position correction by correlating said measured undulation values with values pre-determined by said survey; and then h) adjusting at least one of the aircraft's inertial navigation system variable computations by means of said position correction.
Claim 3
Dependent Claim
32 words
A method as defined in claim 1 further including the step of measuring the vertical distance of said aircraft above said ellipsoidal model of the earth by means of a barometric altimeter.
Claim 4
Dependent Claim
30 words
A method as defined in claim 1 further including the step of measuring the vertical distance of said aircraft above said body of water by means of a radar altimeter.
Claim 5
Dependent Claim
26 words
A method as defined in claim 1 further including the step of correlating said measured and survey values of undulations by means of an on-board computer.
Claim 6
Dependent Claim
125 words
Apparatus for correcting at least one of the inertial system computed navigation variables of an aircraft while proceeding over a region of a body of water comprising, in combination: a) means for measuring the vertical distance of said aircraft above an ellipsoidal model of the earth; b) means for measuring the vertical distance of said aircraft above said body of water; c) means for computing the difference between said vertical distances; d) means for storing a map of the undulation of the geoid of said region; and e) means for comparing a plurality of said differences with said map of the undulation of the geoid of said region, correlating said differences with said map and adjusting at least one of said aircraft's navigation variable computations.
Claim 7
Dependent Claim
125 words
Apparatus for correcting at least one of the inertial system computed navigation variables of an aircraft while proceeding over a region of a body of water comprising, in combination: a) means for measuring the vertical distance of said aircraft above an ellipsoidal model of the earth; b) means for measuring the vertical distance of said aircraft above said body of water; c) means for computing the difference between said vertical distances; d) means for storing a map of the undulation of the geoid of said region; and e) means for comparing a plurality of said differences with said map of the undulation of the geoid of said region, correlating said differences with said map and adjusting at least one of said aircraft's navigation variable computations.
Claim 8
Dependent Claim
28 words
Apparatus as defined in claim 5 wherein said means for measuring the vertical distance of said aircraft above an ellipsoidal model of the earth is a barometric altimeter.
Claim 9
Dependent Claim
26 words
Apparatus as defined in claim 5 wherein said means for measuring the vertical distance of said aircraft above said body of water is a radar altimeter.
Claim 10
Dependent Claim
18 words
Apparatus as defined in claim 5 wherein said means for comparing, correlating and adjusting is an on-board computer.
References Cited (Backward Citations)
US4175285A
Cited
US5272639A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-09-05 | 1998-03-07 | 1998-09-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-09-05 | 2002-03-07 | 2002-09-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-09-05 | 2006-03-07 | 2006-09-06 | $7700.00 | Window Closed / Lapsed |