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A system determines three-dimensional attitude of a moving platform using signals from two closely spaced Global Positioning System (GPS) antennas. The system includes three rate gyroscopes and three accelerometers rigidly mounted in a fixed relationship to the platform to aid in determining the att

A system determines three-dimensional attitude of a moving platform using signals from two closely spaced Global Positioning System (GPS) antennas. The system includes three rate gyroscopes and three accelerometers rigidly mounted in a fixed relationship to the platform to aid in determining the attitude. The system applies signals from a first of the two GPS antennas to sufficient channels of a GPS receiver to support navigation. The system applies signals from a second of the two GPS antennas to the remaining receive channels, which are configured to support interferometry. The system optimally selects the navigation and interferometry channels to provide an interferometric heading solution. The system resolves the ambiguity normally associated with the interferometric heading solution by having the closely spaced GPS antennas and using interferometry to refine a coarse heading estimate from a GPS plus Inertial Measurement Unit (IMU) transfer alignment solution. The system achieves close sub-meter spacing of the two GPS antennas by merging many temporal interferometric measurements that result from an attitude memory provided by the IMU time-history solution.

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1. A motion characterization system, comprising:two antennas, mounted to a rigid body, to receive navigation signals;a collection of motion sensing devices, including rate gyroscopes providing poorer than ten degrees per hour accuracy, mounted on the rigid body to provide electrical signals providin

1. A motion characterization system, comprising:two antennas, mounted to a rigid body, to receive navigation signals;a collection of motion sensing devices, including rate gyroscopes providing poorer than ten degrees per hour accuracy, mounted on the rigid body to provide electrical signals providing motion information; anda processor electrically coupled to process electrical signals from the antennas and the motion sensing devices to provide an attitude measurement of the rigid body under arbitrary motion conditions. 2. The measurement system as claimed in claim 1, wherein the antennas are separated by less than three wavelengths of a signal received from an external signaling source. 3. The measurement system as claimed in claim 2, wherein the external signaling source is a plurality of GPS satellites. 4. The measurement system as claimed in claim 3, wherein the antennas are separated by about 150 millimeters (mm). 5. The measurement system as claimed in claim 1, wherein the motion sensing devices include at least one MEMS device. 6. The measurement system as claimed in claim 5, wherein the processor processing the motion sensing devices provides an acceleration signal. 7. The measurement system as claimed in claim 1, wherein the arbitrary motion conditions include general moving motions, constant velocity motions, and stationary motions. 8. The measurement system as claimed in claim 1, wherein the attitude measurement is accurate to within about 1 degree. 9. The measurement system as claimed in claim 1, wherein one antenna is used supports navigation processing and the other antenna supports interferometry processing. 10. The measurement system as claimed in claim 1, wherein alignment error between the antenna baseline and the motion sensing devices is estimated by software. 11. The measurement system as claimed in claim 1, wherein the processor includes a twelve-channel GPS receiver. 12. The measurement system as claimed in claim 11, wherein after an initialization process, unused channels in the GPS receiver (i) receive data by one of the antennas supporting interferometry, and (ii) track GPS satellites most nearly orthogonal to the antenna baseline. 13. A method for determining attitude of a rigid body, comprising:receiving navigation signals at the rigid body;measuring motion of the rigid body, including rate with poorer than ten degrees per hour accuracy, and providing corresponding motion signals; andprocessing the navigation signals and motion signals to provide an attitude measurement of the rigid body under arbitrary motion conditions. 14. The method as claimed in claim 13, wherein the navigation signals are GPS signals. 15. The method as claimed in claim 13, wherein the arbitrary motion conditions include general moving motions, constant velocity motions, and stationary motions. 16. A motion characterization system, comprising:platform means;means for receiving navigation signals at said platform means;means for sensing motion of said platform means and for providing associated motion signals, including rate of said platform means with an accuracy of poorer than ten degrees per hour; andmeans for processing the navigation signals and the motion signals to provide an attitude measurement of said platform means under arbitrary motion conditions. 17. A mobile system, comprising:a platform;a motion characterization system including:(i) a first navigation antenna and second navigation antenna coupled to the platform to receive navigation carrier signals, (ii) a plurality of motion sensing devices coupled to the platform to provide motion signals representative of motion of the platform, and (iii) a processor (a) coupled to the antennas to make range and carrier phase measurements of the navigation carrier signals at a plurality of epochs defining the navigation carrier signals and to segment the range and carrier phase measurements for the navigation carrier signals into a navigation set and an interferometry set, th e sets having at least one navigation carrier signal for a plurality of navigation epochs and supporting interferometry calculations and (b) coupled to the motion sensing devices to receive the motion signals and to convert the motion signals into measurements of platform motion for a plurality of epochs defined for the motion signals, the processor determining a navigation solution including position and attitude of the platform from the range and carrier phase measurements for the navigation carrier signals and from measurements of platform motion developed from the motion signals; anda subsystem in communication with the motion characterization system responsive to the navigation solution. 18. The mobile system as claimed in claim 17, wherein the motion sensing devices include rate gyroscopes providing poorer than ten degrees per hour accuracy. 19. The mobile system as claimed in claim 17, wherein the first and second navigation antennas are separated by less than three wavelengths of the navigation carrier signal. 20. The mobile system as claimed in claim 17, wherein the navigation carrier signals are provided by a plurality of GPS satellites. 21. The mobile system as claimed in claim 17, wherein the motion sensing devices include at least one MEMS device. 22. The mobile system as claimed in claim 17, wherein the platform motion includes general moving motions, constant velocity motions, and stationary motions. 23. The mobile system as claimed in claim 17, wherein the attitude measurements are accurate to within about 1 degree. 24. The mobile system as claimed in claim 17, wherein the first navigation antenna supports navigation processing and the other antenna supports interferometry processing. 25. The mobile system as claimed in claim 17, wherein software executed by the processor corrects for alignment error between a baseline defined by the first and second navigation antennas and a coordinate system defined by the motion sensing devices. 26. The mobile system as claimed in claim 17, wherein the processor includes a twelve-channel GPS receiver. 27. The mobile system as claimed in claim 26, wherein, after an initialization process, unused channels in the GPS receiver (i) receive data from the second navigation antenna, acting as an interferometry antenna, and (ii) track GPS satellites most nearly orthogonal to a baseline defined by the first and second navigation antennas. 28. The mobile system as claimed in claim 17, wherein the processor allocates, in an optimized manner, a plurality of navigation signals to the navigation set or the interferometry set using navigation and interferometry performance estimates. 29. The mobile system as claimed in claim 17, wherein the processor improves the accuracy of the range, carrier phase, and interferometry processing for the navigation carrier signals by providing estimates of acceleration along a line-of-sight from the platform to each of a plurality of navigation signal sources. 30. The mobile system as claimed in claim 17, wherein the processor synchronizes the measurements of platform motion, provided by the motion sensing devices, using time estimates developed from the navigation carrier signals. 31. The mobile system as claimed in claim 17, wherein the subsystem includes a directive antenna directing an associated antenna beam via mechanical means. 32. The mobile system as claimed in claim 17, wherein the subsystem includes a directive antenna directing an associated antenna beam via electronic means. 33. The mobile system as claimed in claim 17, wherein the subsystem includes a directive antenna mechanically coupled to the platform and electrically coupled to the motion characterization system to direct an associated antenna beam in response to the navigation solution. 34. The mobile system as claimed in claim 17, wherein the subsystem includes a vehicle safety system. 35. A method for determining attitude of a stationary or moving platform, comprising:receiving navigat ion carrier signals;making range and carrier phase measurements of the navigation carrier signals at a plurality of navigation system epochs defining the navigation carrier signals;segmenting the range and carrier phase measurements for the navigation carrier signals into a navigation set and an interferometry set, the sets (i) having at least one navigation carrier signal for a plurality of the navigation system epochs and (ii) supporting interferometry calculations;receiving motion signals representing motion of the platform;converting the motion signals into measurements of platform motion for a plurality of epochs defined for the motion signals; anddetermining a navigation solution including position and attitude of the platform from the range and carrier phase measurements for the navigation carrier signals and from the measurements of platform motion developed from the motion signals. 36. The method according to claim 35, further including allocating, in an optimizing manner, a plurality of navigation carrier signals to the navigation set or the interferometry set using navigation and interferometry performance estimates. 37. The method according to claim 35, further including improving the accuracy of the range, carrier phase, and interferometry processing for the navigation carrier signals by providing estimates of the acceleration along the line-of-sight from the platform to each of a plurality of navigation system signal sources. 38. The method according to claim 35, further including synchronizing the measurements of vehicle motion, provided by the motion sensing devices, using the time estimates developed from the navigation carrier signals. 39. The method according to claim 35, wherein the navigation carrier signals are received by two navigation system antennas that are mounted to the platform and the motion signals are provided by motion sensing devices also mounted to the platform. 40. The method according to claim 35, wherein the navigation set is associated with one of the two navigation system antennas and the interferometry set is associated with the other of the two navigation system antennas. 41. The method according to claim 35, to further include providing the navigation solution for use by a subsystem associated with the platform. 42. The method according to claim 35, wherein the subsystem is a safety system, stability control system, pointing system, geodetic position control system, attitude control system, or mapping projection system. 43. The method according to claim 35, wherein the navigation carrier signals are provided by a plurality of GPS satellites. 44. An apparatus for determining attitude of a platform under arbitrary motion conditions, comprising:means for receiving navigation carrier signals;means for making range and carrier phase measurements of the navigation carrier signals at a plurality of epochs defining the navigation carrier signals;means for segmenting the range and carrier phase measurements for the navigation carrier signals into a navigation set and an interferometry set, the sets (i) having at least one navigation carrier signal for a plurality of navigation system epochs and (ii) supporting interferometry calculations;means for converting the motion signals into measurement of platform motion for a plurality of navigation system epochs defined for the motion signals; andmeans for determining a navigation solution including position and attitude of the platform from the range and carrier phase measurements of platform motion developed from the motion signals.