System and method for determining the 3D position of aircraft, independently onboard and on the ground, for any operation within a “gate-to-gate” concept

• US 6,529,820 B2
• Filed: 04/10/2001
• Issued: 03/04/2003
• Est. Priority Date: 04/10/2001
• Status: Expired due to Fees

• Current Assignee: Ion Tomescu
• Original Assignee: Ion Tomescu
• Inventors: Tomescu, Ion
• Primary Examiner(s): Zanelli, Michael J.
• Application Number:
  US09/832,234
• Publication Number:
  US 20020147542A1
• Time in Patent Office: 693 Days
• Field of Search: 701/120, 701/16, 701/17, 342/36, 342/450, 342/451, 342/463, 340/961
• US Class Current: 701/120
• CPC Class Codes: G01S 13/91 for traffic control G01S13/93 takes precedence
• CPC Class Codes: G01S 5/0063 of measured values, i.e. measurement on base station and position calculation on mobile
• CPC Class Codes: G01S 5/0081 Transmission between base stations
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: G08G 5/0043 Traffic management of multiple aircrafts from the ground G08G5/003 takes precedence; data processing specially designed for resource management, e.g. scheduling or allocating time, human or machine resources G06Q10/06
• CPC Class Codes: G08G 5/0082 for monitoring traffic from a ground station radar or analogous systems specially adapted for traffic control G01S13/91

Abstract

A system and method for determining simultaneously and independently onboard of each aircraft and on the ground at ATC centers utilizing substantially identical surveillance modules for determining the 3D position of all aircraft in an ATC area utilizing a UTC clock to further synchronize all of the surveillance modules on the aircraft and at ground stations. Five ground stations including a master and four slaves communicate with each other and all aircraft in the ATC areas. The same precise 3D position of all aircraft operating in that ATC airspace is simultaneously computed by all the aircraft in that ATC area utilizing the measured distance between the aircraft and ground stations in that area providing full automated support for landing, take-off and taxi operation of the aircraft to a Gate or from a Gate, by using a ground infrastructure of radio communication stations which are operating worldwide within a 16 MHZ frequency spectrum from the existing DME 962-1213 MHZ spectrum. During functioning of the system, any mobile equipped with a dedicated receiver could determine its 2D position on the ground within an airport area or within any ATC area, such mobile being a truck, a car, a boat, a train, a mobile phone, or any other mobile operating in that ATC area and tuned on the frequency of operation of that ATC area.

Claims

1. A surveillance system for air traffic control in selected ATC areas comprising:

first means for independently and simultaneously determining the 3D location in flight and on the ground of all active aircraft in the selected aircraft ATC area; and

second means onboard each aircraft for indicating the determined 3D locations of all said active aircraft;

said first means comprises a plurality of ground stations corresponding to each said selected area, each said ground station including a first surveillance module for determining the 3D position of all associated aircraft in said selected area.

2. The system of claim 1 wherein the first surveillance module in each of the ground stations are identical and further including a second surveillance module in each of the aircraft identical to the ground station first surveillance module, each first and second modules including calculating means for calculating the 3D position of all said aircraft based on a measured distance between each aircraft and each ground station.

3. The system of claim 2 wherein the first and second surveillance modules each include 3D position calculating means for calculating the distance between each aircraft and each ground station.

4. The system of claim 3 including means for synchronizing each calculating means of each module with each other.

5. The system of claim 2 including a minimum of four ground stations including a ground master station with the remaining stations forming slave stations, each ground station and aircraft having a unique ID code, each ground station and aircraft including transmitter/receiver means for communicating with each other a plurality of information signals, each information signal from a ground station including the ground station ID code and each aircraft information signal including an aircraft ID code, said calculating means for calculating the distances based on the transmission delays of said information signals to and from the aircraft and ground stations, a portion of each said information signals including said calculated distances.

6. The system of claim 5 wherein all said information signals together form a surveillance cycle, the system including an ATM data base associated with an ATC and further comprising:

means in the master ground station surveillance module to generate a sequence of radio communication signals, for a list of aircraft provided by the ATM database through an ATC center flying in the air space of the ATC, to each slave ground station and to a selected aircraft;

the sequence comprising;

(a) a first interrogation signal S1 from the master station addressed to the selected aircraft containing the ID code of this signal S1, the ID code of selected aircraft and the ID code of master ground station;

(b) a receiving radio communication signal S2 from the selected aircraft, transmitted by that selected aircraft after a worldwide known T1 time delay from the moment of receiving the S1 signal, containing the ID code of this signal S2, the code of master ground station, the altitude and the ID code of selected aircraft;

(c) a second interrogation signal S3 generated from the master station after a worldwide known T1 time delay from the moment of receiving S2 signal, addressed to the same selected aircraft, containing the ID code of this signal S3, the code of the selected aircraft, the distance value to the selected aircraft, measured on the ground by the master station based on the time delay between the moment of transmission of signal S1 and the moment of receiving the signal S2 by taking out the known T1 value, and the ID code of master ground station M1;

(d) a receiving radio communication signal S4 generated by the selected aircraft, transmitted by that aircraft after the same T1 period of time from the moment of receiving S3 signal, containing the ID code S4 of this signal, the distance value to the master ground station, measured onboard based on the time delay between the moment of transmission of S2 signal and the moment of receiving S3 signal by taking out the known value T1, and the selected aircraft ID code;

(e) a third interrogation signal S5, generated from the master station after the same known T1 period of time from the moment of receiving the S4 signal, addressed to the first slave ground station, containing the ID code of this S5 signal, the code of a first slave station and the code of master station;

(f) a receiving radio communication signal S6 generated by the first selected slave ground station, transmitted by that slave station after the same known T1 period of time from the moment of receiving S5 signal, containing the ID code of this S6 signal, the distance value between this first slave station and the same selected aircraft, measured on ground by this slave station, the ID code of the aircraft received through alert channel and distance to that aircraft measured by this first slave station and the ID code of the first slave station;

(g) a fourth interrogation signal S7, generated from the master station after the same known T1 period of time from the moment of receiving the S6 signal, addressed to a second slave ground station, containing the ID code S7 of this signal, the code of the second slave station and the ID code of master station;

(h) a receiving radio communication signal S8 from the second selected slave ground station, transmitted by that slave station after the same known T1 period of time from the moment of receiving S7 signal, containing the ID code of this S8 signal, the distance value between this second slave station and the same selected aircraft, measured on the ground by this slave station, the ID code of the aircraft received through an alert channel and the distance to that aircraft measured by this slave station, and the ID code of second slave station;

(i) a fifth interrogation signal S9, generated from the master station after the same known T1 period of time from the moment of receiving the S8 signal, addressed to the third slave ground station, containing the ID code of this S9 signal, the ID code of the third slave station and the ID code of master station;

(j) a receiving radio communication signal S10 from the third selected slave ground station, transmitted by that slave station after the same known T1 period of time from the moment of receiving the S9 signal, containing the ID code of this S10 signal, the distance value between this slave station and the same selected aircraft, measured on ground by this slave station, the ID code of the aircraft received through alert channel and distance to that aircraft measured by this slave station, and the ID code of third slave station;

(k) a sixth interrogation signal S11, generated from the master station after the same known T1 period of time from the moment of receiving the S10 signal, addressed to the fourth slave ground station, containing the ID code of this signal S11, the ID code of the fourth slave station and the code of master station;

(l) a receiving radio communication signal S12 from the fourth selected slave ground station, transmitted by that slave station after the same known T1 period of time from the moment of receiving S11 signal, containing the S12 ID code of this the distance value between this slave station and the same selected aircraft, measured on ground by this slave station, the ID code of the aircraft received through the alert channel and the distance to that aircraft measured by this slave station, and the ID code of the fourth slave station; and

(m) a UTC clock synchronization radio signal S0 from the master station addressed to all aircraft in flight or on the ground in that ATC airspace and to all slave ground stations, the signal S0 containing the ID code of this signal S0, the UTC clock value at the moment CV of the beginning of transmission of the S0 signal, and the master ground station ID code.

7. The system of claim 6 wherein each slave station surveillance module has a receiver associated therewith to identify each of a plurality of received radio signals S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S0 and to respond to a transmission from the master station, after a known generated T1 period of time, with a dedicated signal S6 by a first slave station, with a dedicated signal S8 by a second slave station, with a dedicated signal S10 by a third slave station and with a dedicated signal S12 by a fourth slave station, each signal containing the ID code of such signal, the ID code of the selected aircraft, the distance value between that slave station and selected aircraft, measured on ground by that slave station, and the ID code of that slave station.

8. The system of claim 6 wherein each aircraft second surveillance module includes a computer for computing, during the period of being a “

selected aircraft”

, onboard the selected aircraft the 3D position of that aircraft based on the distance values between that aircraft and each of the said ground stations, measured onboard of that aircraft and the same distance values measured on the ground by each of the ground stations and transmitted by radio communication signals S3, S6, S8, S10, S12 to all active aircraft in flight or on the ground within that ATC airspace and known 3D geographical coordinates of each of the ground stations, where the second onboard surveillance module is selected within a surveillance cycle formed by signals S1-S12 and S0 for computing onboard the 3D aircraft position based on the aircraft onboard measured distances and a third onboard surveillance module for computing onboard that aircraft the 3D position based on ground measured distances and for synchronizing both onboard surveillance module UTC clocks to a master ground station UTC clock, based on distance value to that master station, measured on the ground by that master station, and the S0 signal, and computing the same 3D position of that aircraft, outside of the “

selected aircraft”

surveillance cycle period, based on the distance value between that aircraft and the selected master ground station, by using the time delay between the moment of transmitting and the moment of receiving of the S0 signal from the selected master station, measured onboard by an aircraft UTC clock, and the distance values between that aircraft and each slave ground station from a group of selected ground stations, measured onboard of that aircraft, based on time delays measured between the receiving moments of signals S5, S6 for a first slave station and signals S7, S8, for a second slave station and signals S9, S10, for a third slave station and signals S11, S12, for a fourth slave station and knowing the same 3D geographical coordinates of each ground station selected by the corresponding onboard second surveillance module of the selected aircraft.

9. The system of claim 6 wherein each slave station surveillance module includes means for measuring in nanoseconds the time delay period between the moments of receiving of the signals S1 and S2 and between the moment of transmitting and the moment of receiving of the S6, S7 signals for the first slave station, signals S8, S9 for the second slave station, signals S10, S11 for the third slave station and signals S12, S0 for the fourth slave station.

10. The system of claim 6 wherein each aircraft second surveillance module identifies each of the receiving radio signals S1, S3, S5, S6, S7, S8, S9, S10, S11, S12, S0 transmitted by the ground stations and to measure the time delay between the moment of transmitting and the moment of receiving of the S2, S3 signals and between the moments of receiving of the signals S5, S6 and S7, S8 and S9, S10, and S11, S12.

11. The system of claim 6 wherein said transmitter/'"'"'receiver means includes means such that any receiver, at a fixed location or on a mobile location, identifies, on a selected frequency, radio communication signal pairs S5-S6, S7-S8, S9-S10, S11-S12 and signal S0 and includes means to measure in nanoseconds the time delay between the moments of receiving of the pairs of signals S5-S6 and S6-S7 and S7-S8 and S8-S9 and S9-S10 and S10-S11 and S11, S12 and S12, S0.

12. The system of claim 6 including clock means wherein each first surveillance module located on the ground at each ground station generates a clock signal of one nanosecond period using a DDS-Driven PLL oscillator and an oscillator of 50.255055 MHZ as a reference for the DDS oscillator to deliver an output of 10 MHZ+/−

0.011 HZ and a fixed multiplication factor of one hundred for the PLL oscillator to deliver an output signal of 1 GHZ+/−

1 Hz and to maintain at all times such output at a fixed value of 1 GHZ+/−

1 HZ by using as reference the difference between a local ground station UTC clock value and a UTC clock value provided by a GPS receiver installed at each ground station location.

13. The system of claim 6 including clock means wherein each second surveillance module located onboard of each aircraft generates a clock signal of one nanosecond period using a DDS-Driven PLL oscillator and an oscillator of 50.255055 MHZ as a reference for the DDS PLL oscillator to deliver an output of 10 MHZ+/−

0.011 HZ and a fixed multiplication factor of one hundred for the PLL oscillator to deliver an output signal of 1 GHZ+/−

1 Hz and to maintain at all times such output at a fixed value of 1 GHZ+/−

1 HZ by using as reference the master ground station UTC clock value received onboard within the signal S0 and the time delay of the S0 signal to travel the distance between the master ground station and the selected aircraft, as measured on ground.

14. The system of claim 6 wherein each first surveillance module located at each ground station generates a distance measurement signal of one pulse/foot using a DDS-Driven PLL oscillator and an oscillator operating at 50.255055 MHZ as a reference for the DDS PLL oscillator to deliver an output of 10.16 MHZ+/−

0.011 HZ and a fixed multiplication factor of one hundred for the PLL oscillator to deliver an output signal of 1016 MHZ and to adjust such frequency to keep the rate of one pulse/foot by using as an absolute reference the known geographical distances between the master ground station and each of the slave ground stations during the distance measurement procedure performed by the master station and each slave station using the time delay between the moment of transmitting and the moment of receiving of the signal pairs S5, S6 and S7, S8 and S9, S10 and S11, S12 for the master station and signals S6, S7 for the first slave station and signals S8, S9 for the second slave station and signals S10, S11 for the third slave station and signals S12, S0 for the fourth slave station and by taking out from each of the above time delay the value of universal calculation time period T1 for each surveillance module.

15. The system of claim 6 wherein the second surveillance module onboard each aircraft includes means for generating a distance measurement signal of one pulse/foot using a DDS-Driven PLL oscillator and an oscillator of 50.255055 MHZ as a reference for the DDS oscillator to deliver an output of 10.16 MHZ+/−

0.011 HZ and a fixed multiplication factor of one hundred for the PLL oscillator to deliver an output signal of 1016 MHZ and to adjust such frequency to keep the rate of one pulse/foot using as an absolute reference the distance between the aircraft and master ground station, measured by the master ground station and transmitted to the aircraft within the S3 signal and between the aircraft and each slave ground station, measured by that slave station and transmitted to the aircraft within the S6 signal for the first slave station, within the signal S8 for the second slave station, within the S10 signal for the third slave station and within the signal S12 for the fourth slave station and compare these distance values with the same values measured onboard the aircraft.

16. The system of claim 5 including an ATM system for selecting any of said slave stations as a master station.

17. The system of claim 2 including a plurality of ATC areas each having a master station and associated ground stations, at least one computer at each ATC center location to compute the 3D position of a selected aircraft by using the distances values between each ground station and the selected aircraft for each said ATC center, measured on the ground by each ground station and transmitted to that ATC center, and the same known 3D geographical coordinates of each of ground station and an associated validation procedure using the altitude of the selected aircraft transmitted within a first S2 signal and the distance value between the selected aircraft and the master ground station, measured onboard, transmitted within a second signal S4.

18. The system of claim 2 wherein the ground stations include a master station for generating an S0 signal manifesting the 3D position of each aircraft and associated slave stations, each station having a UTC clock, and including a TWR area in the ATC area, the aircraft each including a third aircraft surveillance module and a switching arrangement associated with each aircraft surveillance module for manually selecting a GROUND mode of operation when the aircraft is on ground, the switching arrangement including means arranged for manually selecting a TWR frequency used for an ATC surveillance and 3D positioning entering means to manually enter the 3D position of the aircraft to determine the distance to that master ground station within that TWR area and means for synchronizing an onboard UTC clock with the master station UTC clock after receiving the S0 signal from that master station, including display means for displaying the GROUND mode when the onboard 3D computed position is identical with the manually entered 3D position, the switching means for maintaining this mode of operation until the TWR system automatically selects this aircraft during a surveillance cycle when the aircraft receives an initial interrogation signal from the master station and the first surveillance module is switched automatically into a NAV mode of operation and the second surveillance module maintains its GROUND mode of operation for as long as the aircraft is on the ground in the active mode and in a FLIGHT mode after take-off.

19. The system of claim 2 including a TWR area, a runway including said ground stations comprising a master station and four slave stations forming a runway system, each aircraft including said second surveillance module and a third aircraft surveillance module, each aircraft second and third surveillance modules having a LANDING mode, and an arrangement associated with each aircraft surveillance module to select the LANDING mode of operation when the aircraft is in flight within the TWR area and is preparing for landing at the runway associated therewith, the TWR system including means arranged to automatically electronically transfer the aircraft to that runway system, based on the 3D position of that aircraft as computed on the ground by that TWR system, whereby the respective aircraft becomes a “

selected aircraft”

for that runway system and wherein the aircraft includes means for switching the onboard surveillance modules automatically into a LANDING mode, and each module is arranged to receive one or more signals manifesting the distance to that master station, located at one side of that runway medially between the ends of that runway, and manifesting the distance to the slave stations of that runway system wherein a first two slave stations are located at a first end of that runway and a second two slave stations are located on the other opposite second end of that runway, said surveillance modules for computing onboard the aircraft the distance values to that master station and to each of the four slave station allocated to that runway system and for determining onboard the aircraft deviation signals manifesting the deviation of the aircraft path to the center axial length direction of that runway and manifesting the required glide slope of that aircraft to the runway, said modules for maintaining the LANDING mode of operation as long as the aircraft is on the runway surface and includes means to change the mode of operation to NAV mode, for the first onboard surveillance module and to the GROUND mode of operation for the second module, the means for switching including means arranged for immediately after the aircraft leaves the runway surface to transfer the GROUND mode automatically back to that TWR system based on the 3D position of that aircraft computed on the ground by that runway system.

20. The system of claim 2 including a TWR area, a runway including said ground stations comprising a master station and four slave stations forming a runway system, each aircraft including said second surveillance module and a third aircraft surveillance module, the surveillance modules each having NAV, GROUND and TAKE OFF modes of operation, including an arrangement associated with each aircraft surveillance module to select the TAKE-OFF mode when the aircraft is on the ground within a TWR area and selected in an ATM database associated with that area and wherein a first surveillance module is in the NAV mode and the second module is in the GROUND mode, the TWR system including means for automatically electronically transferring the surveillance modules of the aircraft about to take off to that runway system, based on the 3D position of that aircraft computed on the ground by that TWR system, and the runway system including means for selecting the respective aircraft as a “

selected aircraft”

for that runway system, the runway system including means for automatically switching the first and second onboard surveillance modules to the TAKE-OFF mode, the onboard surveillance modules for computing the onboard deviation signal to the middle of that runway, based on the distance values, measured onboard, to each slave station of that runway system, and for computing the distances to a first end of that runway at which are located a first two slave station portion of that runway system and to a second end of the same runway opposite the first end at which are located a second two slave station portion of the runway system, including means such that the aircraft keeps this mode of operation until the runway system electronically automatically transfers this aircraft back to the TWR system based on the 3D position of this aircraft computed on the ground by that runway system.

21. The system of claim 1 wherein the selected area is an ACC area.

22. The system of claim 1 wherein the selected area is a TWR area.

23. The system of claim 1 wherein the selected area is a runway.

24. The system of claim 23 wherein each aircraft has a second surveillance module, the runway has a length L and a width W and first and second touch-down lines, including a master ground station at the center of said length on a first side of the runway, a first slave station on the first side at the first touch down line, a second slave station on the first side at the second touch down line, a third slave station on the second side at the first touch down line, and fourth slave station on the second side at the second touch down line, each station and aircraft including the respective first and second surveillance modules for determining the 2D position of an aircraft on the runway and including means for communicating with the aircraft second surveillance module.

30. A method to compute onboard of an aircraft during the landing or take-off operation the value of runway direction deviation of the aircraft during said landing or take-off for a runway equipped with the system of claim 6 where the slave ground stations are located on each corner of that runway and the master ground station is located on one side of that runway at the half distance between the ends of that runway and where the direction deviation of an aircraft relative to that runway center length direction axis is computed as a difference between the sum of the distance values between the aircraft and two first slave stations located on one side of that runway and the sum of the same distance values between the aircraft and two second slave stations located on the other side of that runway.

25. A method to determine on the ground the distance value between any ground slave station and a selected aircraft using the time delay measured by that slave station between the receiving moments of S1 and S2 signals generated respectively by a ground station surveillance module and by a selected aircraft surveillance module and by receiving a first distance value between a master ground station and the selected aircraft, computed on the ground by that master station, within a S3 signal transmitted by that master station, said first distance value being computed by summing two components from which the first component is computed as a result of multiplication between the speed of light, in feet/ns, and the difference between the measured time delay between the S1 and S2 signals and the value of a T1 known time delay and the second component being computed as a difference between two distance values where the first distance value is the known distance value between the master station and the selected aircraft and the second distance value is the known geographical distance between the master station and that slave station.

26. A method to determine onboard of any active aircraft the distance value between that aircraft and each slave station of a plurality of stations and a master station on the ground using the time delay measured onboard of that aircraft between the receiving moments of S5, S6 signals corresponding to a first slave station, signals S7, S8 corresponding to a second slave station, signals S9, S10 corresponding to a third slave station and signals S11, S12 corresponding to a fourth slave station where the distance value is computed as the sum of two components, where the first component is a result of multiplication between the speed of light, in feet/ns, and the difference between the measured time delay and known value of a given T1 time delay and the second component is the computed difference between the distance value between the master ground station associated with the slave stations and the aircraft, measured onboard the aircraft, by using the time delay between the S2 and S3 signals generated by the master station during a “

selected aircraft”

status or as a time delay between the moment of transmitting and the moment of receiving of a surveillance signal S0 manifesting the 3D position of the aircraft, measured onboard the aircraft using a clock, or the same distance measured on the ground by the master station and transmitted to the aircraft within an S3 signal and the known geographical distance value between the master station and that slave station.

27. A method to determine the 2D position of a receiver having a UTC clock with a fixed location on the ground or on a mobile location on the ground each forming a ground station including a master station and a plurality of slave stations, each station having a UTC clock and to synchronize the receiver clock with the master ground station UTC clock, by using two time delay values measured at that fixed location or mobile location between the receiving moments of a set of S5, S6 signals or a set of S7, S8 signals or a set of S9, S10 signals or a set of S11, S12 signals manifesting different data at ground stations for first time delay measurements and between the receiving moments of the S6, S7 signals or the S8, S9 signals or the S10, S11 signals or the S12, S0 signals for the second time delay measurements where the first time delay measured value dt1 n is given by dt1n=(LM1Mn−

A+Bn)/c+T1, where A is the distance value between that mobile or fixed ground station location and the master ground station, Bn is the distance value between that mobile or fixed ground station location and a selected slave ground station and LM1Mn is the known geographical distance between the master station and the selected slave station and c=0.98 feet/ns is the speed of light and T1 is a known time delay value and where the second time delay measured value dt2n is given by dt2n=(LM1Mn−

Bn+A)/c+T1, from which that mobile or fixed location station determines its 2D position by manually entering, for the first computation cycle after power up, its known 2D position from where the mobile or fixed location slave station computes its distance value to the master station and then synchronize its UTC clock with the master station UTC clock and validates its manually introduced 2D position by comparing the Bn computed value with the estimated values resulting from the manually introduced 2D position and known geographically coordinates of the slave stations and then determine that A value based on the time delay between the moment of transmitting an S0 signal by the master ground station and the moment of receiving S0 signal by the mobile or fixed location stations synchronized UTC clock and the value of the Bn distance by using the dedicated pair of signals from the ground stations allocated to that area and on which that mobile or fixed station receiver frequency is tuned and continuing to determine the 2D position of that mobile as long as is receiving the pair of signals.

28. A method to adjust any frequency deviation of a DDS-Driven PLL oscillator in a surveillance module in any ground station of a plurality of stations and in any active aircraft, the ground stations comprising a plurality of slave stations and a master station, the deviation being determined from the value of 1016 MHZ by comparing the known geographical distance value between the master ground station and each slave station with the measured distance value determined by each ground station as a measure of the time delay between the moment of transmitting and the moment of receiving of the sets of first signals S5, S6, signals S7, S8, signals S9, S10 and signals S11, S12 between the master ground station and the aircraft, and between the pairs of second signals S6, S7 for a first slave station, S8, S9 for a second slave station, signals S10, S11 for a third slave station and signals S12, S0 for a fourth slave station and the master station using the mean value of the difference between the known geographical distance value and the measured distance value computed by each ground station during a surveillance cycle determined by the surveillance module at each ground location and at each aircraft in communication with each other with certain of said signals and computing the appropriate frequency correction of that DDS-Driven PLL oscillator of that ground station and using the same correction procedure for each aircraft surveillance module DDS-Driven PLL oscillator using as the reference values for onboard correction the on ground measured distance values between each ground station and a selected aircraft and comparing these values with the same values measured onboard of the selected aircraft.

29. A method to adjust a frequency deviation from a fixed value of a DDS-Driven 1 GHz+/−

1 HZ oscillator of a precise oscillator at a fixed ground or mobile station and employing an oscillator at 50 MHZ and where the frequency deviation of such DDS-Driven PLL oscillator is automatically compensated for by maintaining the condition ((dt1n+dt2n)−

2*T1)*c=2*LM1Mn permanently fulfilled, where the measured value of dt1n, dt2n is directly affected by the DDS-Driven PLL oscillator frequency and consequently keeping this condition fulfilled, thus maintaining the frequency fixed to the 1 GHZ value for operating an aircraft surveillance system ground station UTC clock.

31. A method to compute onboard an aircraft, during a landing operation in which the aircraft exhibits a first touch down line as the aircraft approaches a runway and touches the ground, the value of a deviation signal of the approaching aircraft from the desired glide path of that runway by computing the difference between the perimeter value of a triangle formed by the runway length L2 between the first touch down line and a second touch down line at the opposite end of the runway and the middle line of that runway and the actual position of the aircraft and a perimeter triangle formed by the runway length L2, a distance between the aircraft and the second touch down line computed onboard of the aircraft based on measured values of distances to slave ground stations located on that runway end to which the aircraft intends to finish its landing and corresponding computed onboard required distance value to the first touch down line of that runway to keep the aircraft on that desired glide path corresponding to the real distance values measured at each of the slave stations located at that runway end to which the aircraft intends to finish its landing, the difference being used as a Glide Slope signal.

32. An air traffic control system comprising:

a plurality of ground stations each defining a corresponding unique first 3D position; and

means onboard each aircraft of a plurality of aircraft and at each station for communicating with each other and to determine a second 3D position of each aircraft and each ground station based on the first 3D positions.

33. The system of claim 32 wherein the means for determining the second 3D positions comprises a surveillance module onboard each aircraft and at each station, each surveillance module including pulse generating means for generating pulses utilized for said determining said second 3D positions.

34. The system of claim 33 wherein the surveillance modules on each said aircraft include distance measuring means comprising counting means for counting said pulses manifesting the transmission times of signals S communicated between each of the stations and each of said aircraft and for determining the distance between each said aircraft and each said station and for computing the 3D aircraft position from the determined distances.

35. The system of claim 34 wherein each said ground station has a unique ID code and each said aircraft has a unique ID code, each ground station and each said aircraft including respective first and second transmitter/receiver means for communicating with each other a plurality of said signals S uniquely identified to the respective transmitting station and to each respective aircraft by said ID codes, said distance measuring means for computing said distances from the delays in said signals in the transmission of the signals.

36. The system of claim 35 wherein each said module includes means for determining the distances further based on a fixed delay T1 caused by the determining of each said distance.

37. The system of claim 36 wherein each said means for determining the distance includes oscillator means for generating an output signal having a plurality of pulses, each pulse manifesting a given distance value and computing means for counting said pulses manifesting the time delay of the transmission of a signal S from each aircraft to a ground station and from each ground station to an aircraft for said determining said distance and for transmitting said signals S including said determined distance to each other.

38. The system of claim 32 wherein each ground station includes a GPS receiver for providing a 3D validation signal for each said ground station determined 3D position.

39. A method of determining the 3D position of all active aircraft in a given ATC area comprising independently computing on board each said aircraft the 3D position of all said aircraft in a given time period and selectively displaying the computed 3D positions;

said independently computing comprising transmitting signals between each said active aircraft and each of a plurality of ground stations, measuring the transmission time delay of certain of the signals and computing from the time delays the distances between each aircraft and said ground stations and between selected ground stations to each other.

40. The method of claim 39 wherein said ground stations comprise a master station and a plurality of slave stations, the transmission of signals including transmitting a first set of signals between the master station and a selected aircraft of the plurality of aircraft and then transmitting a second set of signals between the master station and each said slave station, a first set of said signals for use in said measuring step and a second set of said signals for transmitting the measured distances to and from the selected aircraft and the master station and a third set of signals for transmitting the measured distances to and from the master station and each said ground station to form a surveillance cycle.

41. The method of claim 40 including repeating the cycle by selecting each aircraft as a selected aircraft.

42. The method of claim 40 including receiving all said signals at each said aircraft simultaneously with the reception of the signals by the selected aircraft.

43. The method of claim 39 including the computing of the aircraft position of each said aircraft during take off and landing relative to predetermined positions on a runway.

44. The method of claim 43 wherein said computing the aircraft position of each said aircraft during said take off and landing includes determining the position of each said aircraft relative to touch down and take off positions of the runway relative to an end of the runway and with respect to the central length axis of the runway during said respective landing and take off.

45. The method of claim 39 wherein said measuring includes generating at each aircraft and at each ground station a plurality of pulses each pulse having a time duration manifesting a predetermined distance and then counting the pulses manifesting each said transmission delay times.

46. The method of claim 45 including synchronizing the generation of said pulses and adjusting the time duration of said pulses to a substantially common value.

47. A method of determining the 3D position of all active aircraft in a given ATC area comprising independently computing on board each said aircraft the 3D position of all said aircraft in a given time period and selectively displaying the computed 3D positions including computing the aircraft position of each said aircraft during take off and landing relative to predetermined positions on a runway.