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A system for generating and utilizing a look-up mechanism consisting of one or more phase difference error maps, tables and/or mathematical models calculates the respective maps, tables and/or models by placing a short baseline or ultra-short baseline antenna array in a known location and known orie

A system for generating and utilizing a look-up mechanism consisting of one or more phase difference error maps, tables and/or mathematical models calculates the respective maps, tables and/or models by placing a short baseline or ultra-short baseline antenna array in a known location and known orientation, determining angles of incidence of incoming GNSS satellite signals with respect the antenna array and calculating expected carrier phase differences between respective pairs of antennas, calculating measured carrier phase differences between the respective pairs of antennas, and determining carrier phase difference errors using the expected and measured carrier phase differences. The carrier phase difference errors are then recorded in the look-up mechanism, with the maps and, as appropriate, look-up tables for the respective pairs of antennas being indexed by angles of incidence. Thereafter, the system utilizes the look-up mechanism when determining the unknown orientation of the antenna structure. For respective pairs of antennas, the system enters the look-up mechanism based on angles of incidence determined from a calculated orientation, and uses the retrieved values in the calculation of a corrected orientation, to compensate for phase distortion.

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1. A method of determining antenna orientation, comprising: A. providing two or more GNSS signal antennas at known separations from neighboring antennas and at an unknown orientation;B. tracking common GNSS carrier signals simultaneously at the antennas;C. making carrier phase measurements of GNSS s

1. A method of determining antenna orientation, comprising: A. providing two or more GNSS signal antennas at known separations from neighboring antennas and at an unknown orientation;B. tracking common GNSS carrier signals simultaneously at the antennas;C. making carrier phase measurements of GNSS satellite signals at the antennas and differencing the carrier phase measurements from all or selected pairs of antennas to form raw carrier phase differences;D. using the raw carrier phase differences to compute an approximate orientation of the antennas;E. determining angles of incidence of incoming GNSS satellite signals with respect to the computed approximate orientation of the antennas;F. using the angles of incidence to index into and obtain phase difference error correction values associated with respective pairs of antennas from an associated lookup mechanism consisting of one or more associated phase error correction maps, lookup tables and models;G. adjusting the raw carrier phase differences using the phase error correction values obtained from the lookup mechanism;H. computing a corrected orientation of the antennas using the adjusted phase differences;I. determining whether the difference between the calculated orientation of the antennas and the corrected orientation of the antennas is larger than a pre-determined threshold, and if the difference is larger, using the corrected orientation as the calculated orientation and determining angles of incidence of incoming GNSS satellite signals with respect to the calculated orientation of the antennas and repeating steps (F) through (I) until the difference is no longer larger than the threshold. 2. The method of determining antenna orientation of claim 1 further comprising: collecting raw carrier phase difference data over a period of time;batch processing the data; andsolving for the orientation of the antennas. 3. The method of determining antenna orientation of claim 1 further comprising: collecting sets of raw carrier phase difference data once a period of time;computing orientation with each set of raw carrier phase difference data to determine a direction of a moving vehicle. 4. A system for determining antenna orientation comprising: (A) two or more GNSS signal antennas affixed to a rigid frame at known small distances of separation, the antennas and the rigid frame at an unknown orientation;(B) a look-up mechanism indexed to provide phase difference error values based on angles of incidence of the GNSS satellite signals at the antennas; and(C) a receiver coupled to the antennas and adapted to track common GNSS carrier signals from each of the antennas and measure carrier phase angles of said GNSS signals received at the antennas, the receiver being further adapted to calculate an approximate antenna orientation based on raw carrier phase differences at the antennas and calculate angles of incidence of GNSS satellite signals based on the calculated orientation, the receiver further adapted to the look-up mechanism based on the calculated angles of incidence to retrieve phase difference error correction values and utilizing the retrieved values to correct the calculated approximate orientation to compensate for phase distortion. 5. The system of claim 4 wherein the look-up mechanism is constructed as one or more look-up tables. 6. The system of claim 4 wherein the look-up mechanism is constructed as one or more mathematical models. 7. The system for claim 4 wherein the look-up mechanism is constructed as one or more phase maps. 8. The system of claim 4 wherein the receiver further resolves integer carrier cycle ambiguities before calculating the carrier phase differences. 9. The system of claim 8 wherein the receiver calculates the carrier phase differences by subtracting the measured carrier phase angles. 10. The system of claim 4 wherein the antennas are located within one wavelength of the carrier signals from neighboring antennas;the receiver compensates for cycle rollover for selected signal angles of arrival before calculating the carrier phase differences by subtracting the associated carrier phase angles, andfor the signals at other angles of arrival calculates the carrier phase differences by subtracting the measured carrier phase angles. 11. The method of claim 1 wherein the phase difference error map or look up table for a GNSS satellite system, are calculated by: i. providing at a known position and orientation an antenna structure having at least a first antenna and a second antenna positioned a known distance apart;ii. computing angles of arrival of GNSS satellite carrier signals with respect to vectors that extend between phase centers of one or more pairs of the antennas;iii. computing expected phase differences based on the computed angles of arrival;iv. determining a measured carrier phase difference from carrier phase measurements at the antennas;v. differencing the expected carrier phase difference from the measured phase difference to produce carrier phase difference error values; andvi. recording the phase difference error values and corresponding angles of arrival. 12. The method of claim 11 further comprising: repeating (i) through (vi) with different angles of arrival; andgenerating a lookup mechanism from the recorded phase difference error values and angles of arrival. 13. The method of claim 12 wherein the lookup mechanism for a given pair of antennas is generated by sorting the phase difference error data into table grid cell elements based on the angles of arrival. 14. The method of claim 12 wherein the lookup mechanism is one or more mathematical models. 15. The method of claim 12 wherein the lookup mechanism further includes one or more lookup figures of merit that are based on the dispersions of phase difference error values at common angles of incidence. 16. The method of claim 11 further comprising repeating (i) through (vi) at different times of day, allowing the GNSS satellites to move to different locations in the sky. 17. The method of claim 11 further comprising repeating (i) through (vi) while moving the antenna structure to various orientations. 18. The method of claim 15 wherein the figures of merit are one of averages and means. 19. The method of claim 15 wherein the figures of merit de-weight the values associated with larger dispersions. 20. The method of claim 11 wherein the lookup mechanism is a phase map and the map grid sizes are proportional to gradients of the phase difference errors, with smaller grid sizes used for higher gradients. 21. The method of claim 20 wherein the grid sizes are based also on accuracy requirements, with smaller grid sizes utilized for greater accuracy requirements. 22. The method of claim 1 further including incorporating into the table line biases calculated using phase difference values for respective pairs of antennas across multiple satellites. 23. The system of claim 4 wherein the receiver further calculates line biases associated with the GNSS antennas and corrects the calculated orientation to compensate for the phase distortion associated with the line biases. 24. The system of claim 23 wherein the receiver calculates the line biases periodically. 25. The method of claim 1 further including double differencing the measured phase differences to eliminate line biases associated with the multiple antennas. 26. The method of claim 1 wherein the antennas are provided on a rigid frame and receive multipath signals reflected from the frame, andthe obtained phase difference error correction values are associated also with the multipath signals received by respective pairs of antennas. 27. The method of claim 1 further including correcting the calculated orientation to compensate for phase distortion associated with line biases. 28. The system of claim 4 wherein the receiver is further adapted to repeatedly determine if the calculated orientation and the corrected orientation differ by more than a predetermined threshold and if so utilize the corrected orientation as the calculated orientation and calculate angles of incidence based on the calculated orientation, re-enter the look-up mechanism based on the calculated angles of incidence and retrieve phase difference error correction values and utilize the values to correct the calculated orientation.