High-precision near-land aircraft navigation system

• US 6,018,698 A
• Filed: 06/23/1997
• Issued: 01/25/2000
• Est. Priority Date: 05/31/1994
• Status: Expired due to Term

• Current Assignee: Winged Systems Corporation
• Original Assignee: Winged Systems Corporation
• Inventors: Nicosia, Joseph M., Loss, Keith R., Taylor, Gordon A.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): PIPALA, EDWARD J
• Application Number:
  US08/880,362
• Time in Patent Office: 946 Days
• Field of Search: 701/16, 701/213, 701/219, 701/220, 701/214, 342/26, 342/33, 342/63, 342/64, 342/118
• US Class Current: 701/214
• CPC Class Codes: G01C 21/1652 with ranging devices, e.g. LIDAR or RADAR
• CPC Class Codes: G01C 23/005 Flight directors indicating arrangements specially adapted for rotary gyroscopes G01C19/32
• CPC Class Codes: G01S 13/286 frequency shift keyed
• CPC Class Codes: G01S 13/86 Combinations of radar systems with non-radar systems, e.g. sonar, direction finder
• CPC Class Codes: G01S 13/90 using synthetic aperture techniques , e.g. synthetic aperture radar [SAR] techniques
• CPC Class Codes: G01S 13/913 for landing purposes
• CPC Class Codes: G01S 13/953 mounted on aircraft
• CPC Class Codes: G01S 19/15 Aircraft landing systems
• CPC Class Codes: G01S 19/52 Determining velocity
• CPC Class Codes: G01S 7/412 based on a comparison between measured values and known or stored values
• CPC Class Codes: G05D 1/0676 specially adapted for landing
• CPC Class Codes: G08G 5/0021 located in the aircraft
• CPC Class Codes: G08G 5/0065 for taking-off
• CPC Class Codes: G08G 5/0086 for monitoring terrain radar or analogous systems specially adapted for terrain avoidance G01S13/935
• CPC Class Codes: G08G 5/0091 for monitoring atmospheric conditions radar or analogous systems specially adapted for meteorological use G01S13/95; meteorology G01W
• CPC Class Codes: G08G 5/025 Navigation or guidance aids radar or analogous systems specially adapted for landing purposes G01S13/913
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

An aircraft including an approach and landing system, including a navigation unit for providing navigation information, a weather radar unit for providing radar information, a processor which receives navigation information from the navigation unit and information from the weather radar unit, the processor unit providing an output representing information concerning the aircraft in accordance with the provided navigation information and radar information, a memory for storing information representing a scene, the processor unit correlating the stored scene information with the output representing information concerning the aircraft to provide a mapped scene, a display unit for displaying the output of said processor and the mapped scene, and a steppable frequency oscillator for providing a signal which is stepped in frequency to the weather radar unit, thereby providing an increased range resolution.

Claims

1. A method of aircraft navigation using radar, comprising:

storing information of cultural or natural features in an area of the ground along and to the sides of a flight path;

using said radar during flight to obtain information of said features along and to the sides of said flight path;

comparing said stored information with said information obtained by radar to determine successive different match points representing different ground locations;

determining the range and range rate of each of said match points;

determining the aircraft'"'"'s location and velocity based on repetitive range and range rate measurements of said match points; and

supplementing the accuracy of said aircraft location and velocity determination with information from at least one of an additional navigation unit.

2. The method according to claim 1, wherein said additional navigation unit information is based upon integration of inertial measurements.

3. The method according to claim 1, wherein said additional navigation unit information represents locations between said match points and is combined with said aircraft location and velocity determination using Kalman statistical filtering.

4. The method according to claim 1, wherein a phase changing effect created by motion of said navigation unit is reduced, said method comprising:

defining subsets of a frequency hopped radar signal and a center frequency for each subset,

bouncing said radar signal off of an object and receiving a reflected version of said signal to determine a phase change in said signal;

receiving reflected versions of said subsets, and

subtracting phase effects from the samples that correspond to the center frequency of said subset.

5. The method of claim 1 wherein phase compensation is provided for said radar, said method comprising:

storing a pseudo-random frequency order;

changing a transmission frequency of a radar signal based on said pseudo-random frequency order;

using said pseudo-random frequency order to sample a received radar signal which is a reflected version of said transmitted radar signal, thereby generating samples of said received radar signal; and

reordering said samples in an order of increasing frequency.

6. The method according to claim 5, further comprising:

summing a group of said samples; and

performing an Inverse Digital Fourier Transform on said samples to develop a range value.

7. The method according to claim 5, further comprising:

tagging said received samples with information of their order of reception and order of frequency;

identifying a coarse range of interest based on a particular area of the ground;

selecting the received samples which correspond to said particular area;

defining signal subsets of said transmitted signal;

determining the Doppler frequencies for said selected samples and center frequencies for the subsets corresponding to said particular area;

arranging said received samples in frequency order within said subsets;

calculating the phase rotation due to transmit frequencies and receive times for the received samples, and subtracting said phase rotations from the corresponding samples according to the time order and wavelength of said sample, to thereby reduce effects of motion of the navigation unit on the interpretation of the received radar signals.

8. A method of aircraft navigation using radar, comprising:

storing information of cultural or natural features in an area of the ground along and to the sides of a flight path;

using said radar during flight to obtain information of said features along and to the sides of said flight path;

comparing said stored information with said information obtained by radar to determine match points representing different ground locations;

determining the range and range rate of said match points; and

using said range and range rate in the navigation or state vector measurements of said aircraft.

9. A method according to claim 8 wherein a phase changing effect created by motion of said navigation unit is reduced, said method comprising:

defining subsets of a frequency hopped radar signal and a center frequency for each subset,

bouncing said radar signal off of an object and receiving a reflected version of said signal to determine a phase change in said signal;

receiving reflected versions of said subsets, and

subtracting phase effects from the samples that correspond to the center frequency of said subset.

10. The method of claim 8 wherein phase compensation is provided for said radar, said method comprising:

storing a pseudo-random frequency order;

changing a transmission frequency of a radar signal based on said pseudo-random frequency order;

using said pseudo-random frequency order to sample a received radar signal which is a reflected version of said transmitted radar signal, thereby generating samples of said received radar signal; and

reordering said samples in an order of increasing frequency.

11. The method according to claim 10, further comprising:

summing a group of said samples; and

performing an Inverse Digital Fourier Transform on said samples to develop a range value.

12. The method according to claim 10, further comprising:

tagging said received samples with information of their order of reception and order of frequency;

identifying a coarse range of interest based on a particular area of the ground;

selecting the received samples which correspond to said particular area;

defining signal subsets of said transmitted signal;

determining the Doppler frequencies for said selected samples and center frequencies for the subsets corresponding to said particular area;

arranging said received samples in frequency order within said subsets;

calculating the phase rotation due to transmit frequencies and receive times for the received samples, and subtracting said phase rotations from the corresponding samples according to the time order and wavelength of said sample, to thereby reduce effects of motion of the navigation unit on the interpretation of the received radar signals.