System and method for providing accurate position location information to military forces in a disadvantaged signal environment
View Patent ↗A system for determining a location in a disadvantaged signal environment includes three aerial vehicles hovering at high altitude and spaced apart to form a triangle, and a mother aerial vehicle positioned a distance away and at a lower altitude. The mother aerial vehicle acquires and transmits coarse geolocation information, using a pulse compression, high-power X Band radar and directional antenna, to each of the three aerial vehicles to direct them to coarse geo-positions above designated respective ground locations. One of the three aerial vehicles has a synthetic aperture radar for producing a terrain strip-map that is mensurated against a map database to provide fine position adjustments for each of the three aerial vehicles, which are also also configured to transmit a respective signal coded with its latitude, longitude, and altitude, for a computing device to perform time difference of arrival measurements of the signals to determine its location.
1. A system for determining a location in a disadvantaged signal environment, said system comprising:
a plurality of aerial vehicles at a first altitude and spaced apart;
a mother aerial vehicle, said mother aerial vehicle positioned a distance away from said plurality of aerial vehicles at a second altitude; said mother aerial vehicle configured to acquire and transmit coarse geolocation information to each of said plurality of aerial vehicles to direct each of said plurality of aerial vehicles to coarse positions above respective ground location;
wherein said plurality of aerial vehicles comprise a master aerial vehicle, and one or more secondary aerial vehicles each synchronized with said master aerial vehicle;
wherein said master aerial vehicle comprises a synthetic aperture radar configured to produce a terrain strip-map; and wherein said master aerial vehicle is further configured to mensurate said strip-map against a map database to provide fine position adjustments for each of said plurality of aerial vehicles;
wherein each of said plurality of aerial vehicles comprises a receiver, and a transmitter configured to transmit a respective coded signal; and
a computing device configured to perform time difference of arrival measurements of said respective signals to determine a location of said computing device.
2. The system according to claim 1 , wherein said master aerial vehicle comprises a stable rubidium reference oscillator configured to provide frequency and timing data for said secondary aerial vehicles to be synchronized with said master aerial vehicle.
3. The system according to claim 2 , wherein said stable rubidium reference oscillator is configured to operate in the range of 425 MHz to 2.4 GHz.
4. The system according to claim 1 , wherein each said coded signal comprises a respective latitude, longitude, and altitude and modulated with non-random, non-repeating patterns.
5. The system according to claim 4 , wherein each said coded signal is transmitted over an ISM band frequency.
6. The system according to claim 5 , wherein each said respective coded signal is refreshed at a rate or 5 Hz.
7. The system according to claim 1 , wherein each of said plurality of aerial vehicles are configured to hover above said respective ground location.
8. The system according to claim 1 , wherein said master aerial vehicle is configured to mensurate said strip-map against a level two digital terrain elevation map dataset to provide fine position adjustments for each of said plurality of aerial vehicles for a respective positional accuracy of within thirty meters.
9. The system according to claim 1 , wherein said master aerial vehicle is configured to mensurate said strip-map against a google earth map to provide fine position adjustments for each of said plurality of aerial vehicles for a respective positional accuracy being within three meters.
10. The system according to claim 1 , wherein said mother aerial vehicle is configured to transmit the coarse geolocation information to each of said plurality of aerial vehicles via an X-Band link.
11. The system according to claim 1 , wherein said mother aerial vehicle comprises a pulse compression, high-power X Band radar configured to transmit the coarse geolocation information to each of said plurality of aerial vehicles.
12. The system according to claim 11 , wherein said X band radar is configured to transmit coarse geolocation information to each of said plurality of aerial vehicles with a directional antenna.
13. The system according to claim 12 , wherein said directional antenna is configured to use a beam width of approximately one degree with sidelobe levels of less than 40 dB.
14. The system according to claim 13 , wherein said directional antenna is configured to use frequency hopped spread spectrum waveforms to increase jam resistance.
15. The system according to claim 14 , wherein said X band radar comprises a bearing accuracy of 0.2 degrees rms and an rms range measurement accuracy of less than two hundred feet.
16. The system according to claim 1 , wherein said X band radar is configured to coarsely locating the UAV's in 3D space within a spherical error probable of 1000 feet when said distance is 50 nautical miles or less.
17. The system according to claim 1 , wherein said plurality of aerial vehicles comprises three aerial vehicles spaced apart to form a triangular shape.
18. The system according to claim 17 , wherein said plurality of aerial vehicles are spaced between five miles and ten miles apart.
19. The system according to claim 18 , wherein said plurality of aerial vehicles are spaced apart to form an equilateral triangle.
20. The system according to claim 1 , wherein said first altitude is higher than said second altitude.
21. The system according to claim 1 , wherein said first altitude is selected to be above adverse weather, and above a range capability of anti-aircraft artillery gunfire.
22. The according to claim 1 , wherein each of said secondary aerial vehicles comprise a synthetic aperture radar configured to produce said terrain strip-map and to mensurate said terrain strip-map against said map database to independently provide fine position adjustments.