Trimble Navigation Limited

Trumble Navigation Limited

Len Sheynblat

James M Janky

John F Schipper

Peter V Loomis

Allan M Pelley

The partial decoding algorithm for decoding the partially damaged differential satellite positioning system (SATPS) messages is disclosed. The algorithm is based on the modified parity test. The information included in the decoded messages can be used for the high level differential SATPS testing.

Optimum utilization of pseudorange and range rate corrections by SATPS

Methods for determining integrity of pseudorange and pseudorange rate signals received from a plurality of M Satellite Positioning System satellites (including GPS and GLONASS), numbered j=j1, j2, . . . , jM, at a reference SATPS station (RS), using pseudorange or pseudorange rate signals received from the same satellites at a nearby signal integrity monitoring (SIM) station. Pseudorange correction values or, alternatively, pseudorange rate correction values, for SATPS signals received at an RS station and at the corresponding SIM station are computed, and difference values between the RS and SIM values are computed for each satellite. If the magnitude of each difference is less than a selected threshold difference, pseudorange corrections or pseudorange rate corrections for that reference station can be used by a nearby mobile station to differentially correct the mobile station location fix coordinates or velocity fix coordinates. If N acceptable pairs of difference values are found for the pseudorange or pseudorange rate corrections, for particular satellites: clock bias or frequency offset can be corrected if N.gtoreq.1; accuracy of the clock bias or frequency offset coordinate can be monitored if N.gtoreq.2; and location fix coordinates or velocity fix coordinates can be corrected if N.gtoreq.3. If magnitudes of differences between measured and known location coordinates or velocity coordinates for the SIM station are less than threshold differences, pseudorange corrections or pseudorange rate corrections for that reference station can be used by a nearby mobile station to differentially correct the mobile station location fix coordinates or velocity fix coordinates.

Integrity monitoring of location and velocity coordinates from

Method and apparatus for reducing the contributions of ionospheric propagation time delay error, multipath signal error and receiver noise error from signals received in a Satellite Positioning System (SATPS) from one or more SATPS satellites by formation and appropriate filtering of differences of signals DD that are differences of SATPS signals received by the SATPS receiver/processor. A difference signal DD of code-phase-derived, ionosphere-free signals and carrier-phase-derived, ionosphere-free signals is formed, and this difference signal is passed through a first statistical processing filter with an associated time constant .tau.1 in the approximate range 50-500 sec, to produce smoothed or filtered first difference signal with the estimated receiver noise error reduced or removed. The difference signal DD is passed through second and third statistical processing filters having associated time constants .tau.2=5-20 sec and .tau.3=50-500 sec, and the difference of the output signals of the second and third statistical processing filters is formed and subtracted from the filtered first difference signal to form a new difference signal that is primarily due to multipath error. This new difference signal is subtracted from thge pseudorange measaurement values to produce a signal with reduced multipath error.

Compensating for multipath errors, ionospheric time delay and noise

Methods for authentication or validation of the location of a putative source (ps) of a message, using time varying location determination (LD) signals that are received from J sources (J&gt;1) of LD signals G(t;j;ps) that are spaced apart from the putative source. The putative source forms an augmented data signal that includes the original message, one or more segments g�t.sub.k(m),t.sub.k(m+1) ; j; ps!={G(t.sub.r ;j;ps).vertline.t.sub.k(m) .ltoreq.t.sub.r .ltoreq.t.sub.k(m+1) } of the LD signals for a selected time interval, a putative source asserted location L(t'.sub.k(m) ;ps) for a time t'.sub.k(m) in the selected time interval, and other identifying parameters. The augmented data signal is received by a central station that analyzes the LD signal segments and determines whether the asserted location L(t'.sub.k(m) ;ps) is likely to be the true message source location. Part or all of the augmented data signal can be encrypted for transmission. One application is validation of use of licensed software on a computer whose location may be mobile. Another application is validation of votes cast from a plurality of remote voting sites.

Authentication of a message source

The partial decoding algorithm for decoding the partially damaged differential SATPS messages and the decoding device is disclosed. The algorithm is based on the modified parity test. The information contained in the decoded messages is used for the high level differential SATPS testing.

A method for compensating for temporary loss of differential GPS correction signals for a satellite, numbered j, during an IODE changeover interval. Differences .DELTA.e.sub.i (t;j;n+1,n)=e.sub.i (t;j;n+1)-e.sub.i (t;j;n) (i=1, . . . , I) are formed for I ephemeris parameters used to describe the ephemeris for the satellite (j) during IODE intervals number n+1 and n. These differences are approximated for a DGPS blank-out time interval, given by t(j;n+1).sub.IODE .DELTA.t.sub.rev,mob .ltoreq.t&lt;t(j;n+1).sub.IODE +.DELTA.t.sub.ch +.DELTA.t.sub.rev,ref, during which a GPS reference station continues to broadcast DGPS correction information based on the old ephemeris data that was valid during the preceding IODE time interval, given by t(j;n).sub.IODE .ltoreq.t&lt;t(j;n+1).sub.IODE. These ephemeris differences are used by a mobile station that receives DGPS correction information from the GPS reference station to produce corrected GPS information for a blank-out time interval. Ephemeris parameter differences can be replaced by differences of satellite-station ranges .DELTA.R(t;j;n+1,n)=R(t;j;n+1)-R(t;j;n) in an alternative approach.

Iode changeover coverage for GPS signals

Gap coverage for GPS signals

Method and apparatus for reducing the contributions of receiver noise signal error and multipath signal error from signals received in a Satellite Positioning System (SATPS) from one or more SATPS satellites by formation and appropriate filtering of differences of signals DD that are differences of SATPS signals received by the SATPS receiver/processor. A difference signal DD of code-phase-derived delta range signals and carrier-phase-derived delta range signals is formed, and this difference signal is passed through a first statistical processing filter with an associated time constant .tau.1 in the approximate range 50-[500] 100 sec, to produce smoothed or filtered signal with the estimated receiver noise error reduced or removed. The difference signal DD is passed through second and third statistical processing filters having associated time constants .tau.2=5-20 sec and .tau.3=50-[500] 1000 sec, and the difference of the output signals of the second and third statistical processing filters is formed and subtracted from DD to form a new difference signal. This new difference signal is passed through a fourth statistical processing filter with an associated time constant .tau.4=50-[500] 1000 sec, to produce a smoothed or filtered signal with the estimated multipath signal error and estimated receiver noise error reduced or removed.

Compensation for multipath errors and ionospheric delays in differential

Method and apparatus for reducing the contributions of receiver noise signal error and multipath signal error from signals received in a Satellite Positioning System (SATPS) from one or more SATPS satellites by formation and appropriate filtering of differences of signals DD that are differences of SATPS signals received by the SATPS receiver/processor. A difference signal DD of code-phase-derived delta range signals and carder-phase-derived delta range signals is formed, and this difference signal is passed through a first statistical processing filter with an associated time constant .tau.1 in the approximate range 50-500 sec, to produce smoothed or filtered signal with the estimated receiver noise error reduced or removed. The difference signal DD is passed through second and third statistical processing filters having associated time constants .tau.2=5-20 sec and .tau.3=50-500 sec, and the difference of the output signals of the second and third statistical processing filters is formed and subtracted from DD to form a new difference signal. This new difference signal is passed through a fourth statistical processing filter with an associated time constant .tau.4=50-500 sec, to produce a smoothed or filtered signal with the estimated multipath signal error and estimated receiver noise error reduced or removed.

Removal of signal errors for differential satellite positioning systems

Methods for determining the integrity of pseudorange and pseudorange rate signals received from a plurality of M Satellite Positioning System satellites (SATPS, including GPS and GLONASS), numbered j=j1, j2, . . . , jM, at a reference SATPS station (RS), using pseudorange and pseudorange rate signals received from the same satellites at a signal integrity monitoring (SIM) station located near the reference station. Pseudorange correction values PRC(t;i;j).sub.RS and PRC(t;i;j).sub.SIM and pseudorange rate correction values PRRC(t;i;j).sub.RS and PRRC(t;i;j).sub.SIM for the signals received at the reference station (RS, number i) and at the SIM station are computed, and difference values DPRE(t;i;j)=PRC(t;i;j).sub.RS -PRC(t;i;j).sub.SIM and DRRE(t;i;j)=PRRC(t;i;j).sub.RS -PRRC(t;i;j).sub.SIM are computed from these correction values. If .vertline.DPRE(t;i;j).vertline..ltoreq.DPRE(i;j).sub.thr and .vertline.DPRRE(i;j).vertline..ltoreq.DPRRE(i;j).sub.thr, where DPRE(i;j).sub.thr and DPRRE(i;j).sub.thr are selected threshold values for a satellite (j), the pseudorange corrections and/or pseudorange rate corrections for that reference station are acceptable and can be used by a mobile station located near that reference station to differentially improve the accuracy of the location coordinates and/or the velocity coordinates for that mobile station. If at least one acceptable pair of difference values DPRE(t;i;j) and DPRRE(t;i;j) is found, for a particular satellite j, clock bias and frequency offset can be corrected using the SATPS signal received from that satellite at the SIM station. If at least two pairs of difference values DPRE(t;i;j) and DPRRE(t;i;j) are acceptable, for satellites j1 and j2, the accuracy of the clock bias and frequency offset parameters can be monitored using the SATPS signals received from that pair of satellites. If at least three pairs of difference values DPRE(t;i;j) and DPRRE(t;i;j) are acceptable (for three distinct satellites), the location coordinates and/or velocity coordinates can be corrected using the signals received from those satellites, if a precise SIM station clock is provided; otherwise, at least four acceptable pairs of difference values are required.

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Belmont, CA, United States of America

Len Sheynblat