Apparatus and method for determining aircraft position and velocity

• US 4,671,650 A
• Filed: 06/14/1984
• Issued: 06/09/1987
• Est. Priority Date: 09/20/1982
• Status: Expired due to Fees

• Current Assignee: Crane Company
• Original Assignee: Crane Company
• Inventors: Longyear, Douglas M. Jr., Hirzel, Edgar A.
• Primary Examiner(s): Buczinski, Stephen C.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/620,505
• Time in Patent Office: 1,090 Days
• Field of Search: 356/28, 356/27, 356/4, 358/105, 382/10, 364/424, 364/433, 324/160, 324/175
• US Class Current: 356/28
• CPC Class Codes: G01P 3/806 in devices of the type to be classified in G01P3/68

Abstract

An apparatus and method for determining aircraft position and velocity is disclosed. The system includes two CCD sensors which take overlapping front and back radiant energy images of front and back overlapping areas of the earth'"'"'s surface. A signal processing unit digitizers and deblurs the data that comprise each image. The overlapping first and second front images are then processed to determine the longitudinal and lateral relative image position shifts that produce the maximum degree of correlation between them. The signal processing unit then compares the first and second back overlapping images to find the longitudinal and lateral relative image position shifts necessary to maximize the degree of correlation between those two images. Various correlation techniques, including classical correlation, differencing correlation, zero-mean correction, normalization, windowing, and parallel processing are disclosed for determining the relative image position shift signals between the two overlapping images. The front longitudinal relative image position shift signal, the front lateral relative image position shift signal, the back longitudinal relative image position shift signal and the back lateral relative image position shift signal are then corrected by an altitude factor to respectively produce a front longitudinal ground distance signal, a front lateral ground distance signal, a back longitudinal ground distance signal, and a back lateral ground distance signal. These ground distance signals can be divided by the time delay between forming the first and second images to produce longitudinal and lateral ground velocity signals. The longitudinal and lateral ground distance signals can also be processed to produce other navigational measurements, such as the yaw, rotation, roll and ground track of the aircraft. The ground distance data and navigational measurements may be error checked against independent data and output to various displays.

Claims

1. An apparatus for determining the ground velocity of an aircraft comprising:

means for detecting a first two-dimensional radiant energy image of a first area of the earth'"'"'s surface, and following a time delay, a second two-dimensional radiant energy image of a second area of the earth'"'"'s surface which overlaps the first area;

means for producing an altitude signal;

means for processing the first and second overlapping images and the altitude signal to produce a longitudinal ground distance signal and a lateral ground distance signal; and

the process means generating a longitudinal ground velocity signal and a lateral ground velocity signal based on the longitudinal and lateral ground distance signals, respectively, and the time delay.

2. The apparatus of claim 1 wherein the processing means includes:

means for selecting a window in the first image;

means for comparing the window with the second image to generate a longitudinal position shift signal and a lateral position shift signal;

means for multiplying the longitudinal position shift signal and the lateral position shift signal by the altitude signal to generate the longitudinal ground distance signal and the lateral ground distance signal, respectively; and

means for dividing the longitudinal ground distance signal and the lateral ground distance signal by the time delay to generate the longitudinal ground velocity signal and the lateral ground velocity signal, respectively.

3. The apparatus of claim 1 wherein the processing means includes:

means for selecting a first window in the first image;

means for selecting a second window in the secind image;

means for comparing the first window with the second window to generate a longitudinal position shift signal and a lateral position shift signal;

means for multiplying the longitudinal position shift signal and the lateral position shift signal by the altitude signal to generate the longitudinal ground distance signal and the lateral ground distance signal, respectively; and

means for dividing the longitudinal ground distance signal and lateral ground distance signal by the time delay to generate the longitudinal ground velocity signal and the lateral ground velocity signal, respectively.

4. An apparatus for determining the ground velocity of an aircraft comprising:

means for forming a first two-dimensional radiant energy image of a first area of the earth'"'"'s surface, and after a time delay, a second two-dimensional radiant energy image of a second area of the earth'"'"'s surface which overlaps the first area;

means for digitizing the first image and the second image into a plurality of discrete values;

means for selecting a first window from the first image;

means for selecting a second window from the second image, wherein the second window is bigger than the first window;

means for correlating the first window and the second window to produce a longitudinal position shift signal and a lateral position shift signal;

means for producing an altitude correction signal;

means for multiplying the longitudinal position shift signal and the lateral position shift signal by the altitude correction signal to produce a longitudinal ground distance signal and lateral ground distance signal; and

means for dividing the longitudinal ground distance signal and the lateral ground distance signal by the time delay to produce a longitudinal ground velocity signal and a lateral ground velocity signal.

5. An apparatus for providing ground position data for navigation of an aircraft comprising:

front means for detecting a first front two-dimensional radiant energy image of a first front area of the earth'"'"'s surface, and following a time delay, a second front two-dimensional radiant energy image of a second front area of the earth'"'"'s surface, which overlaps the first front area;

back means for detecting a first back two-dimensional radiant energy image of a first back area of the earth'"'"'s surface, and following the time delay, a second back two-dimensional radiant energy image of a second back area of the earth'"'"'s surface which overlaps the first back area;

the front and back detecting means cooperating such that the first front and first back images are detected concurrently and the second front and second back images are detected concurrently;

means for producing an altitude signal; and

means for processing the first and second front overlapping images and the altitude signal to produce a front longitudinal ground distance signal and a front lateral ground distance signal, and the first and second back images and the altitude signal to generate a back longitudinal ground distance signal and a back lateral ground distance signal.

6. The apparatus of claim 5 wherein the processing means includes:

means for selecting a first window in the first front image and a second window in the first back image;

means for comparing the first window with the second front image to produce a front longitudinal position shift signal and a front lateral position shift signal, and the second window with the second back image to produce a back longitudinal position shift signal and a back lateral position shift signal; and

means for multiplying the front lateral position shift signal, the front longitudinal position shift signal, the back longitudinal position shift signal and the back lateral position shift signal by the altitude signal to respectively produce the front longitudinal ground distance signal, the front lateral ground distance signal, the back longitudinal ground distance signal and the back lateral ground distance signal.

7. The apparatus of claim 5 wherein the processing means includes:

means for selecting a first front window in the first front image, a second front window in the second front image, a first back window in the first back image and a second back window in the second back image;

means for comparing the first front window with the second front window to produce a front longitudinal position shift signal and a front lateral position shift signal, and the first back window with the second back window to produce a back longitudinal position shift signal and a back lateral position shift signal; and

means for multiplying the front longitudinal position shift signal, the front lateral position shift signal, the back longitudinal position shift signal and the back lateral position shift signal by the altitude signal to respectively produce the front longitudinal ground distance signal, the front lateral ground distance signal, the back longitudinal ground distance signal and the back lateral ground distance signal.

8. An apparatus for providing positional data for navigation of an aircraft comprising:

front means for forming a first front two-dimensional radiant energy image of a first front area of the earth'"'"'s surface, and following a time delay, a second front two-dimensional radiant energy image of a second front area of the earth'"'"'s surface which overlaps the first front area;

back means for forming a first back two-dimensional radiant energy image of a first back area of the earth'"'"'s surface, and following the time delay, a second back two-dimensional radiant energy image of a second back area of the earth'"'"'s surface which overlaps the first back area;

the front and back forming means cooperating such that the first front and first back images are formed concurrently and the second front and second back images are formed concurrently;

means for digitizing the first front image, the second front image, the first back image and the second back image into a plurality of discrete values;

first means for selecting a first front window and a first back window from the first front and first back images, respectively;

second means for selecting a second front window and a second back window from the second front and second back images, respectively;

means for correlating the first front window with the second front window to generate a front longitudinal position shift signal and a front lateral position shift signal, and the first back window with the second back window to generate a back longitudinal position shift signal and a back lateral position shift signal;

means for generating an altitude signal; and

means for correcting the front longitudinal position shift signal, the front lateral position shift signal, the back longitudinal position shift signal, and the back lateral position shift signal by the altitude signal to respectively generate a front longitudinal ground distance signal, a front lateral ground distance signal, a back longitudinal ground distance signal and a back lateral distance signal.