NAVIGATIONAL SYSTEM

• US 3,721,985 A
• Filed: 06/22/1970
• Issued: 03/20/1973
• Est. Priority Date: 06/22/1970
• Status: Expired due to Term

• Current Assignee: Thomas E. Perfitt
• Original Assignee: Thomas E. Perfitt
• Inventors: Perfitt, Thomas E.
• Primary Examiner(s): Borchelt, Benjamin A.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US05/048,409
• Time in Patent Office: 1,002 Days
• Field of Search: 343/103,105,5LS,112C 235/150.271,150.272
• US Class Current: 342/388
• CPC Class Codes: G01S 1/02 using radio waves G01S19/00 takes precedence

Abstract

Loran navigational signals are received at a destination and at dirigible craft traveling towards that destination. The time differences between signals received at the destination are calculated. Upon receipt of a signal from a master station, these time differences at the destination are signaled to the craft by a data link or slave signal. The craft also receives the signal from the master station. The relative positions of the destination and the craft are determined in accordance with Loran navigation techniques. This position information is then utilized, along with the time difference information transmitted to the craft simultaneously with the master signal by the data link or slave signal, and the slant range between the craft and the destination is then computed. Altitude of the craft is then computed, as by triangulation. The slant range rate is determined by measuring the Doppler shift in the frequency of the data link or slave signal.

Claims

1. A method of navigating a dirigible craft at an altitude above ground level to a destination at ground level, comprising the steps:

receiving signals at said destination from a predetermined number of sending stations at ground level having known locations, and simultaneously emitting a slave signal from said destination upon receipt of at least one such signal;

receiving said station signals at said dirigible craft;

receiving said slave signal at said craft;

using the received signals to determine the position of said destination with respect to at least one of saiD stations;

using the received signals to determine the coordinate position of said craft with respect to at least one of said stations; and

determining the slant range of said craft from said destination, based on the relative coordinate positions of said craft and said destination and based on the times at which certain of said signals are received at said craft.

2. The method of claim 1 in which information as to the relative position of said destination is determined at said destination and is then transmitted to said craft.

3. The method of claim 2 in which said slave signal carries to said craft information as to the respective position of said destination.

4. The method of claim 1 in which navigational information is received at said destination and transmitted from said destination to said craft, and the determination of the relative position of said destination is performed at said craft.

5. The method of claim 4 in which said slave signal carries to said craft said information received at said destination.

6. A method of navigating a dirigible craft to a destination, comprising the steps:

receiving signals at said destination from a predetermined number of sending stations having known locations, and simultaneously emitting a slave signal from said destination upon receipt of at least one such signal;

receiving said station signals at said dirigible craft;

receiving said slave signal at said craft;

using the received signals to determine the position of said destination with respect to at least one of said stations;

using the received signals to determine the position of said craft with respect to at least one of said stations;

determining the slant range of said craft from said destination, based on the relative positions of said craft and said destination and based on the times at which certain of said signals are received at said craft;

using the said determination of position for said destination and said craft to determine the surface distance between said respective positions; and

using said surface distance and said slant range to determine the altitude of said craft.

7. The method of claim 6 in which said slave signal carries to said craft information as to the respective position of said destination.

8. The method of claim 7 in which said steps of determining the surface distance between said craft and said destination and determining the altitude of said craft are performed at said craft.

9. A method of navigating a dirigible craft to a destination, comprising the steps:

receiving signals at said destination from a predetermined number of sending stations having known locations, and simultaneously emitting a slave signal from said destination upon receipt of at least one such signal;

receiving said station signals at said dirigible craft;

receiving said slave signal at said craft;

using the received signals to determine the position of said destination with respect to at least one of said stations;

using the received signals to determine the position of said craft with respect to at least one of said stations;

determining the slant range of said craft from said destination, based on the relative positions of said craft and said destination and based on the times at which certain of said signals are received at said craft;

measuring the Doppler shift in the frequency of said slave signal received at said craft; and

using the measurement of said Doppler shift to determine the rate of change of said slant range.

10. The method of claim 9 in which said slave signal carries to said craft information as to the respective position of said destination.

11. The method of claim 10 in which a calibrated oscillator is used in said measuring of Doppler shift.

12. A method of navigating a dirigible craft at an altitude above ground level to a destination at ground level by use of navigational signaling stations such as Loran stations at ground level, said method comprising:

receiving at said destinations, signals from said navigational stations;

determining data as to the arrival time of said signals at said destination and transmitting such data by a data link signal simultaneously with the receipt at said destination of a signal from a predetermined one of said stations;

receiving at said dirigible craft signals from said navigational stations, including said predetermined one of said stations;

receiving said data link signal at said craft;

determining the position of said destination with respect to said one station by use of said data received from said destination;

determining the relative coordinate position of said craft with respect to said one station by use of data as to the arrival time of said signals at said craft;

determining the slant range between said craft and said destination by use of the said determined relative positions of said craft and said destination and by use of the times at which said signal from said one station and said data link signal are received at said craft.

13. The method of claim 12 which includes:

using the said determination of position for said destination and said craft to determine the surface distance between said respective positions; and

using said surface distance and said slant range to determine the altitude of said craft.

14. The method of claim 12 which includes measuring the Doppler shift in the frequency of said data link signal received at said craft;

and using the measurement of said Doppler shift to determine the rate of change of said slant range.

15. The method of claim 12 which includes:

eliminating errors in said slant range determination by using a computer for calculating said relative positions of said craft and said destination and for calculating said slant range;

programming said computer with a non-linear filter program; and

feeding redundant range information into said non-linear filter in order to estimate and eliminate errors.

16. A navigational system for use by a dirigible craft at an altitude above ground level in navigating to a destination at ground level, comprising in combination:

means at said destination for receiving a master signal from a master signal-emitting station at a known ground level position;

means for emitting a slave signal from said destination simultaneously with receipt at said destination of said master signal;

means for receiving said master signal at said dirigible craft;

means for receiving said slave signal at said craft;

means for determining the relative position of said destination with respect to said position of master signal station;

means for determining the relative coordinate position of said craft with respect to said master signal station position; and

means for determining the slant range between said craft and said destination based on the relative coordinate positions of said craft and said destination and on the times at which said master and said slave signals are received at said craft.

17. The system of claim 16, wherein said means for determining said relative position of said destination is located at the latter;

and wherein said system includes means for transmitting data, including said relative position of said destination, from said destination to said craft.

18. The system of claim 17, in which said means for emitting said slave signal and said data-transmitting means comprise an integrated signaling means for transmission of said data as part of said slave signal.

19. The system of claim 16 which includes:

means at said craft for determining the Doppler shift in the frequency of said slave signal; and

computer means for determining the rate of change of said slant range based on said Doppler shift.

20. The system of claim 16 which includes means at said craft for determining the altitude of said craft based on said slant range and said relative positions of said destination and said craft.

21. A navigational system for use by a dirigible craft at an altitude above ground level, in navigating to a particular destination at ground level by use of existiNg navigational signal-emitting stations, said system comprising:

receiver means at said destination for receiving navigational signals from navigational signaling stations at known positions;

a data link transmitter means at said destination for sending data related to the times at which said signals are received by said receiver means;

means for causing said data transmission to occur simultaneously with the receipt of a signal from a predetermined one of said navigational signaling stations;

receiver means at said craft for receiving said navigational signals from said navigational signaling stations; and

computer means at said craft for determining relative coordinate positions of said destination and craft based on said transmitted data and on the arrival times of said navigational signals, and for determining the slant range between said craft and said destination based on said relative positions of said craft and said destination and on the arrival times of said predetermined one signal and said data transmission signal at said craft.

22. The system of claim 21 which includes:

means at said craft for determining the Doppler shift in the frequency of said slave signal; and

computer means for determining the rate of change of said slant range based on said Doppler shift.

23. The system of claim 21 which includes means at said craft for determining the altitude of said craft based on said slant range and said relative positions of said destination and said craft.