Method and apparatus for precision attitude determination and kinematic positioning

Claim 3

A method as defined in claim 1, and further comprising the steps of: making redundant carrier phase measurements based on the reception of a carrier signal from other additional satellites; and eliminating other false solutions from the set of potential solutions, based on a comparison of the additional redundant carrier phase measurements with the initial set of potential solutions.

Claim 4

A method as defined in claim 1, and further comprising the steps of: comparing items in the set of potential solu­tions with solutions obtained in a prior time interval, to provide another basis for eliminating false solu­tions.

Claim 5

A method as defined in claim 1, wherein: the step of deriving an initial set of poten­tial solutions includes locating points of intersection of planar carrier wavefronts defining possible loca­tions of the secondary antenna within the region of uncertainty; and the step of eliminating false solutions in­cludes, locating a set of planar carrier wavefronts from the additional satellite such that the wavefronts also define possible locations of the secondary antenna within the region of uncertainty, selecting, for each of the initial set of potential solutions, a planar carrier wavefront from the additional satellite such that the selected wavefront is the one closest to the potential solution, and disregarding each potential solution for which the closest wavefront from the additional satellite is spaced from the potential solution by more than a selected threshold.

Claim 6

A method as defined in claim 1, wherein: the initial set of potential solutions is initially stored in a local tangent coordinate system, x, y, z, where z is a vertical axis; and the method further comprises, after the step of making redundant carrier phase measurements, the additional step of rotating the coordinate system of the set of potential solutions, to point the z axis toward the additional satellite and thereby facilitate the step of eliminating false solutions.

Claim 7

A method as defined in claim 4, wherein: the initial set of potential solutions is initially stored in a local tangent coordinate system, x, y, z, where z is a vertical axis; and the method further comprises, after the step of making redundant carrier phase measurements, the additional step of rotating the coordinate system of the set of potential solutions, to point the z axis toward the additional satellite and thereby facilitate the step of eliminating false solutions.

Claim 8

A method as defined in claim 6, wherein the step of selecting a planar carrier wavefront from the additional satellite is performed by comparing the z-axis component of each potential solution with pos­ssible positions of wavefronts in the region of uncer­tainty.

Claim 9

A method as defined in claim 1, wherein: the secondary antenna is held at a fixed dis­tance from the reference antenna; the method further comprises the step of deter­mining from the relative position of the secondary an­tenna the angular attitude of a line between the two antennas, with respect to a selected set of coordinate axes; and the minimum number or satellites N is two.

Claim 10

A method as defined in claim 8, wherein: the method further comprises the steps of making carrier phase measurements and deriving poten­tial solutions for a third antenna located at a fixed distance from each of the secondary and reference an­tennas, and the further step of determining the angular position of the third antenna with respect to an axis of rotation through the reference and secondary an­tennas; and and wherein the two satellites also function as redundant satellites by providing additional carrier phase information to the third antenna.

Claim 11

A method as defined in claim 1, wherein: the secondary antenna is freely movable with respect to the reference antenna; and the method further comprises the initial step of determining the approximate initial relative posi­tion of the secondary antenna.

Claim 12

A method as defined in claim 10, wherein: the step of determining the approximate posi­tion includes making measurements of pseudorandom codes received from the satellites, and computing the approxi­mate position from the code measurements.

Claim 15

A method as defined in claim 12, wherein: the carrier phase measurements are first-dif­ference measurements made measuring the phase differ­ence between signals arriving simultaneously at the two antennas from a single satellite source.

Claim 16

A method as defined in claim 13, and fur­ther comprising the steps of: making redundant carrier phase measurements based on the reception of a carrier signal from other additional satellites; and eliminating other false solutions from the set of potential solutions, based on a comparison of the additional redundant carrier phase measurements with the initial set of potential solutions.

Claim 17

A method as defined in claim 13, and fur­ther comprising the steps of: comparing items in the set of potential solu­tions with solutions obtained in a prior time interval, to provide another basis for eliminating false solu­tions.

Claim 18

A method as defined in claim 13, wherein: the step of deriving an initial set of poten­tial solutions includes locating points of intersection of planar carrier wavefronts defining possible loca­tions of the secondary antenna within the region of uncertainty; and the step of eliminating false solutions in­cludes locating a set of planar carrier wavefronts from the additional satellite such that the wavefronts also define possible locations of the secondary antenna within the region of uncertainty, selecting, for each of the initial set of potential solutions, a planar carrier wavefront from the additional satellite such that the selected wavefront is the one closest to the potential solution, and disregarding each potential solution for which the closest wavefront from the additional satellite is spaced from the potential solution by more than a selected threshold.

Claim 19

A method as defined in claim 13, wherein: the initial set of potential solutions is initially stored in a local tangent coordinate system, x, y, z, where z is a vertical axis; and the method further comprises, after the step of making redundant carrier phase measurements, the additional step of rotating the coordinate system of the set of potential solutions, to point the z axis toward the additional satellite and thereby facilitate the step of eliminating false solutions.

Claim 20

A method as defined in claim 16, wherein: the initial set of potential solutions is initially stored in a local tangent coordinate system, x, y, z, where z is a vertical axis; and the method further comprises, after the step of making redundant carrier phase measurements, the additional step of rotating the coordinate system of the set of potential solutions, to point the z axis toward the additional satellite and thereby facilitate the step of eliminating false solutions.

Claim 21

A method as defined in claim 18, wherein the step of selecting a planar carrier wavefront from the additional satellite is performed by comparing the z-axis component of each potential solution with possible positions of wavefronts in the region of uncertainty.

Claim 22

A method as defined in claim 13, wherein: the method further comprises the steps of making carrier phase measurements and deriving poten­tial solutions for a third antenna located at a fixed distance from each of the secondary and reference antennas, and the further step of determining the angular position of the third antenna with respect to an axis of rotation through the reference and secondary antennas; and and wherein the first two satellites also func­tion as redundant satellites by providing additional carrier phase information to the third antenna.

Claim 23

Apparatus for determining the relative position of a secondary receiving antenna with respect to a reference receiving antenna in a satellite-based positioning system, the apparatus comprising: means for making carrier phase measurements based on the reception of a carrier signal from each of a plurality N of satellites, where N is the minimum number of satellites needed to compute the relative position of the secondary antenna; means for deriving from the carrier phase measurements an initial set of potential solutions for the relative position, wherein the initial set of poten­tial solutions all fall within a region of uncertainty defined by a sphere having a radius equal to the maxi­mum distance between the two antennas, and wherein mul­tiple potential solutions arise because of whole-cycle ambiguity of the carrier signal; means for making redundant carrier phase measurements based on the reception of a carrier signal from an additional (N+1)the satellite; and means for eliminating false solutions from the initial set of potential solutions, based on a compari­son of the redundant carrier phase measurements with the initial set of potential solutions, to reduce num­ber of potential solutions to close to one, whereby the number of potential solutions is not reduced by use of the redundant carrier phase measurements.

Claim 24

Apparatus for determining the relative position of a secondary receiving antenna with respect to a reference receiving antenna in a satellite-based positioning system, the apparatus comprising: means for making carrier phase measurements based on the reception of a carrier signal from each of a plurality N of satellites, where N is the minimum number of satellites needed to compute the relative position of the secondary antenna; means for deriving from the carrier phase measurements an initial set of potential solutions for the relative position, wherein the initial set of poten­tial solutions all fall within a region of uncertainty defined by a sphere having a radius equal to the maxi­mum distance between the two antennas, and wherein mul­tiple potential solutions arise because of whole-cycle ambiguity of the carrier signal; means for making redundant carrier phase measurements based on the reception of a carrier signal from an additional (N+1)the satellite; and means for eliminating false solutions from the initial set of potential solutions, based on a compari­son of the redundant carrier phase measurements with the initial set of potential solutions, to reduce num­ber of potential solutions to close to one, whereby the number of potential solutions is not reduced by use of the redundant carrier phase measurements.

Claim 25

Apparatus as defined in claim 21, and further comprising: means for making redundant carrier phase measurements based on the reception of a carrier signal from other additional satellites; and means for eliminating other false solutions from the set of potential solutions, based on a com­parison of the additional redundant carrier phase measurements with the initial set of potential solu­tions.

Claim 26

Apparatus as defined in claim 21, and further comprising: means for comparing items in the set of poten­tial solutions with solutions obtained in a prior time interval, to provide another basis for eliminating false solutions.

Claim 27

Apparatus as defined in claim 21, wherein: the means for deriving an initial set of poten­tial solutions includes means for locating points of intersection of planar carrier wavefronts defining possible locations of the secondary antenna within the region of uncertainty; and the means for eliminating false solutions includes means for locating a set of planar carrier wave fronts from the additional satellite such that the wave fronts also define possible locations of the secondary antenna within the region of uncertainty, means for selecting, for each of the initial set of potential solutions, a planar carrier wavefront from the additional satellite such that the selected wave­front is the one closest to the potential solution, and means for disregarding each potential solution for which the closest wavefront from the additional satel­lite is spaced from the potential solution by more than a selected threshold.

Claim 28

Apparatus as defined in claim 21, wherein: the initial set of potential solutions is initially stored in a local tangent coordinate system, x, y, z, where z is a vertical axis; and the apparatus further comprises means for rotating the coordinate system of the set of potential solutions, to point the z axis toward the additional satellite and thereby facilitate elimination of false solutions.

Claim 29

Apparatus as defined in claim 24, wherein: the initial set of potential solutions is ini­tially stored in a local tangent coordinate system, x, y, z, where z is a vertical axis; and the apparatus further comprises means for rotating the coordinate system of the set of potential solutions, to point the z axis toward the additional satellite and thereby facilitate elimination of false solutions.

Claim 30

Apparatus as defined in claim 26, wherein the means for selecting a planar carrier wavefront from the additional satellite includes means for comparing the z-axis component of each potential solution with possible positions of wavefronts in the region of uncertainty.

Claim 31

Apparatus as defined in claim 21, wherein: the secondary antenna is held at a fixed dis­tance from the reference antenna; the apparatus further comprises means for de­termining from the relative position of the secondary antenna the angular attitude of a line between the two antennas, with respect to a selected set of coordinate axes; and the minimum number or satellites N is two.

Claim 32

A method as defined in claim 28, wherein: the apparatus further comprises means for making carrier phase measurements and deriving potential solutions for a third antenna located at a fixed distance from each of the secondary and reference antennas, and means for determining the angular position of the third antenna with respect to an axis of rotation through the reference and secondary antennas; and wherein the two satellites also function as redundant satellites by providing additional carrier phase information to the third antenna.

Claim 33

Apparatus as defined in claim 21, wherein: the secondary antenna is freely movable with respect to the reference antenna; and the apparatus further comprises means for determining the approximate initial relative position of the secondary antenna.

Claim 34

A method as defined in claim 30, wherein: the means for determining the approximate position includes means for making measurements of pseudorandom codes received from the satellites, and means for computing the approximate position from the code measurements.

Claim 35

Apparatus for determining the angular attitude of a line of fixed length between a reference receiving antenna and a secondary receiving antenna, from the relative position of the secondary receiving antenna with respect to the reference receiving antenna as determined in a satellite-based positioning. system, the apparatus comprising: means for making carrier phase measurements based on the reception of a carrier signal from each of two satellites, where two is the minimum number of satellites needed to compute the relative position of the secondary antenna; means for deriving from the carrier phase measurements an initial set of potential solutions for the relative position, wherein the initial set of potential solutions all fall within a region of uncer­tainty defined by the surface of a sphere having a radius equal to the fixed distance between the two antennas, and wherein multiple potential solutions arise because of whole-cycle ambiguity of the carrier signal; means for making redundant carrier phase measurements based on the reception of a carrier signal from a third satellite; and means for eliminating false solutions from the initial set of potential solutions, based on a compari­son of the redundant carrier phase measurements with the initial set of potential solutions, to reduce number of potential solutions to close to one, whereby the number of potential solutions is not reduced by use of the redundant carrier phase measurements.

Claim 36

Apparatus for determining the angular attitude of a line of fixed length between a reference receiving antenna and a secondary receiving antenna, from the relative position of the secondary receiving antenna with respect to the reference receiving antenna as determined in a satellite-based positioning. system, the apparatus comprising: means for making carrier phase measurements based on the reception of a carrier signal from each of two satellites, where two is the minimum number of satellites needed to compute the relative position of the secondary antenna; means for deriving from the carrier phase measurements an initial set of potential solutions for the relative position, wherein the initial set of potential solutions all fall within a region of uncer­tainty defined by the surface of a sphere having a radius equal to the fixed distance between the two antennas, and wherein multiple potential solutions arise because of whole-cycle ambiguity of the carrier signal; means for making redundant carrier phase measurements based on the reception of a carrier signal from a third satellite; and means for eliminating false solutions from the initial set of potential solutions, based on a compari­son of the redundant carrier phase measurements with the initial set of potential solutions, to reduce number of potential solutions to close to one, whereby the number of potential solutions is not reduced by use of the redundant carrier phase measurements.