Integrity monitoring of differential satellite positioning system signals

• US 5,436,632 A
• Filed: 06/02/1994
• Issued: 07/25/1995
• Est. Priority Date: 06/02/1994
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Sheynblat, Len
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US08/252,681
• Time in Patent Office: 418 Days
• Field of Search: 342/357, 455/12.1
• US Class Current: 342/357.64
• CPC Class Codes: G01S 19/071 DGPS corrections
• CPC Class Codes: G01S 19/08 providing integrity information, e.g. health of satellites or quality of ephemeris data
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]

Abstract

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)_RS and PRC(t;i;j)_SIM and pseudorange rate correction values PRRC(t;i;j)_RS and PRRC(t;i;j)_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)_RS -PRC(t;i;j)_SIM and DRRE(t;i;j)=PRRC(t;i;j)_RS -PRRC(t;i;j)_SIM are computed from these correction values. If |DPRE(t;i;j)|≦DPRE(i;j)_thr and |DPRRE(i;j)|≦DPRRE(i;j)_thr, where DPRE(i;j)_thr and DPRRE(i;j)_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.

Claims

1. A method of determining the integrity of DSATPS signals formed at a reference SATPS station and used for correcting at least one of a set of K location parameters and a set of K velocity parameters of a mobile SATPS station (K=1, 2, 3, 4), the method comprising the steps of:

providing an S ATPS reference station, numbered i, whose location coordinates are accurately known, and a plurality of selected SATPS satellites, numbered j=j1, j2, . . . , jM (M≧

K);

providing an SATPS signal integrity monitoring station, whose location coordinates are accurately known, spaced apart from the reference station by a distance of no more than about 1 km;

allowing the reference station and the signal monitoring station to receive SATPS signals;

determining the correction values PRC(t;

i;

j)_RS and PRRC(t;

i;

j)_RS for the pseudorange and pseudorange rate signals PR(t;

i;

j)_RS and PRR(t;

i;

j)_RS, respectively, as a function of time t associated with SATPS signals that are received by the reference station number i from satellite number j for j=j1, j2, . . . , jM;

determining the pseudorange error values PRRE(t;

i;

j)_SIM and the pseudorange rate error values PRRRE(t;

i;

j)_SIM as a function of time t associated with SATPS signals that are received by the signal integrity monitoring station number i from satellite number j for j=j1, j2, . . . , jM;

forming the difference values DPRE(t;

i;

j)_SIM =PRC(t;

i;

j)_RS -PRC(t;

i;

j)_SIM and DRRE(t;

i;

j)_SIM =PRRC(t;

i;

j)_RS -PRRC(t;

i;

j)_SIM ;

comparing the magnitudes |DPRE(t;

i;

j)_SIM | of the pseudorange residuals with selected threshold values DPRE(i;

j)_thr ;

comparing the magnitudes |DRRE(t;

i;

j)_SIM | of the pseudorange rate residuals with selected threshold values DPRRE(i;

j)_thr ;

when at least one of the relations |DPRE(t;

i;

j)_SIM |≦

DPRE(i;

j)_thr and |DRRE(t;

i;

j)_SIM |≦

DRRE(i;

j)_thr is not valid for a satellite j, transmitting a signal indicating that the SATPS signals received from the satellite j cannot be used to help correct at least one of a set of K location parameters and a set of K velocity parameters for a mobile SATPS station using DSATPS signals from the reference station; and

when the relations |DPRE(t;

i;

j)_SIM |≦

DPRE(i;

j)_thr and |DRRE(t;

i;

j)_SIM |≦

DRRE(i;

j)_thr are both valid for at least satellite j, transmitting a signal indicating that the SATPS signals received from the satellite j can be used to help correct at least one of a set of K location parameters and a set of K velocity parameters for a mobile SATPS station using DSATPS signals from the reference station.

2. The method of claim 1, further comprising the step of determining said pseudorange rate values PRR(t;

i;

j) by the relation

space="preserve" listing-type="equation">PRR(t;

i;

j)=[Φ

(t;

i;

j)-Φ

(t-Δ

t;

i;

j)]/Δ

t,

where Φ

(t;

i;

j) is the carrier phase signal at said reference station number i at time t from said SATPS satellite number j.

3. The method of claim 1, further comprising the step of determining said pseudorange rate values PRR(t;

i;

j) by the steps of;

approximating the variable y(t)=Φ

(t;

i;

j) in a time interval t_n-1 ≦

t≦

t_n+1 by the relations

space="preserve" listing-type="equation">y(t)=y.sub.n +a.sub.n (t-t.sub.n)+b.sub.n (t-t.sub.n).sup.2,

using known values of y at three selected consecutive times t=t_n-1 ;

t=t_n and t=t_n+1 ; and

defining the pseudorange rate value PRR(t;

i;

j) for said reference station i at the time t=t_n from SATPS satellite j by the relation

space="preserve" listing-type="equation">PRR(t.sub.n ;

i;

j)=y(t.sub.n)=a.sub.n ={(t.sub.n -t.sub.n-1).sup.2 [y(t.sub.n+1)-y(t.sub.n)]+(t.sub.n+1 -t.sub.n).sup.2 [y(t.sub.n-1)-y(t.sub.n)]}/(t.sub.n+1 -t.sub.n)(t.sub.n+1 -t.sub.n-1)(t.sub.n+1 t.sub.n-1).

4. A method of determining the integrity of DSATPS signals formed at a reference SATPS station and used for monitoring at least one of a set of K location parameters and a set of K velocity parameters of a mobile S ATPS station (K=1, 2, 3, 4), the method comprising the steps of:

providing an SATPS reference station, numbered i, whose location coordinates are accurately known, and a plurality of selected SATPS satellites, numbered j=j1, j2, . . . , jM (M≧

K+1);

providing an SATPS signal integrity monitoring station, whose location coordinates are accurately known, spaced apart from the reference station by a distance of no more than about 1 km;

allowing the reference station and the signal monitoring station to receive SATPS signals;

determining the correction values PRC(t;

i;

j)_RS and PRRC(t;

i;

j)_RS for the pseudorange and pseudorange rate signals PR(t;

i;

j)_RS and PRR(t;

i;

j)_RS, respectively, as a function of time t associated with SATPS signals that are received by the reference station number i from satellite number j for j=j1, j2, . . . , jM;

determining the pseudorange error values PRRE(t;

i;

j)_SIM and the pseudorange rate error values PRRRE(t;

i;

j)_SIM as a function of time t associated with SATPS signals that are received by the signal integrity monitoring station number i from satellite number j for j=j1, j2, . . . , jM;

forming the difference values DPRE(t;

i;

j)_SIM =PRC(t;

i;

j)_RS -PRC(t;

i;

j)_SIM and DRRE(t;

i;

j)_SIM =PRRC(t;

i;

j)_RS -PRRC(t;

i;

j)_SIM ;

comparing the magnitudes |DPRE(t;

i;

j)_SIM | of the pseudorange residuals with selected threshold values DPRE(i;

j)_thr ;

comparing the magnitudes |DRRE(t;

i;

j)_SIM | of the pseudorange rate residuals with selected threshold values DPRRE(i;

j)_thr ;

when at least one of the relations |DPRE(t;

i;

j)_SIM |≦

DPRE(i;

j)_thr and |DRRE(t;

i;

j)_SIM |≦

DRRE(i;

j)_thr is not valid for a satellite j, transmitting a signal indicating that the SATPS signals received from the satellite j cannot be used for monitoring at least one of a set of K location parameters and a set of K velocity parameters for a mobile SATPS station using DSATPS signals from the reference station; and

when the relations |DPRE(t;

i;

j)_SIM |≦

DPRE(i;

j)_thr and |DRRE(t;

i;

j)_SIM |≦

DRRE(i;

j)_thr are both valid for at least satellite j, transmitting a signal indicating that the SATPS signals received from the satellite j cart be used to help monitor at least one of a set of K location parameters and a set of K velocity parameters for a mobile SATPS station using DSATPS signals from the reference station.

5. The method of claim 4, further comprising the step of determining said pseudorange rate values PRR(t;

i;

j) by the relation

space="preserve" listing-type="equation">PRR(t;

i;

j)=[Φ

(t;

i;

j)-Φ

(t-Δ

t;

i;

j)]/Δ

t,

where Φ

(t;

i;

j) is the carrier phase signal at said reference station number i at time t from said SATPS satellite number j.

6. The method of claim 4, further comprising the step of determining said pseudorange rate values PRR(t;

i;

j) by the steps of;

approximating the variable y(t)=Φ

(t;

i;

j) in a time interval t_n-1 ≦

t≦

t_n+1 by the relations

space="preserve" listing-type="equation">y(t)=y.sub.n +a.sub.n (t-t.sub.n)+b.sub.n (t-t.sub.n).sup.2,

using known values of y at three selected consecutive times t=t_n-1, t=t_n and t=t_n+1 ; and

defining the pseudorange rate value PRR(t;

i;

j) for said reference station i at the time t=t_n from SATPS satellite j by the relation

space="preserve" listing-type="equation">PRR(t.sub.n ;

i;

j)=y(t.sub.n)=a.sub.n ={(t.sub.n -t.sub.n-1).sup.2 [y(t.sub.n+1)-y(t.sub.n)]+(t.sub.n+1 -t.sub.n).sup.2 [y(t.sub.n-1)-y(t.sub.n)[}/(t.sub.n+1 -t.sub.n)(t.sub.n+1 -t.sub.n-1)(t.sub.n+1 t.sub.n-1).

7. A method of determining the integrity of DSATPS signals formed at a reference SATPS station and used for correcting the clock bias and frequency offset parameters of a mobile SATPS station, the method comprising the steps of:

providing an SATPS reference station, numbered i, whose location coordinates are accurately known, and a plurality of selected SATPS satellites, numbered j=j1, j2, . . . , jM (M≧

1);

providing an SATPS signal integrity monitoring station, whose location coordinates are accurately known, spaced apart from the reference station by a distance of no more than about 1 km;

allowing the reference station and the signal monitoring station to receive SATPS signals;

determining the pseudorange correction values PRC(t;

i;

j)_RS and the pseudorange rate correction values PRRC(t;

i;

j)_RS as a function of time t associated with SATPS signals that are received by the reference station number i from satellite number j for j=j1, j2, . . . , jM;

determining the pseudorange error values PRRE(t;

i;

j)_SIM and the pseudorange rate error values PRRRE(t;

i;

j)_SIM as a function of time t associated with SATPS signals that are received by the signal integrity monitoring station number i from satellite number j for j=j1, j2, . . . , jM;

forming the differences DPRE(t;

i;

j)_SIM =PRC(t;

i;

j)_RS -PRC(t;

i;

j)_SIM and DPRRE(t;

i;

j)_SIM =PRRC(t;

i;

j)_RS -PRRC(t;

i;

j)_SIM ;

comparing the magnitudes |DPRE(t;

i;

j)_SIM | of the pseudorange residuals with selected threshold values DPRE(i;

j)_thr ;

comparing the magnitudes |DPRRE(t;

i;

j)_SIM | of the pseudorange rate residuals with selected threshold values DPRRE(i;

j)_thr ;

when the pairs of relations |DPRE(t;

i;

j)_SIM |≦

DPRE(i;

j)_thr and |DPRRE(t;

i;

j)_SIM |≦

DPRRE(i;

j)_thr are valid for no more than one of the satellites j, transmitting a signal indicating that the SATPS signals received from the satellite j cannot be used for correcting the clock bias and frequency offset parameters of a mobile SATPS station using DSATPS signals from the reference station; and

when the pairs of relations |DPRE(t;

i;

j)_SIM |≦

DPRE(i;

j)_thr and |DPRRE(t;

i;

j)_SIM |≦

DPRRE(i;

j)_thr are valid for at least two of the satellites j, transmitting a signal indicating that the SATPS signals received from the satellite j can be used for correcting the clock bias and frequency offset parameters of a mobile SATPS station using DSATPS signals from the reference station.

8. The method of claim 7, further comprising the step of determining said pseudorange rate values PRR(t;

i;

j) by the relation

space="preserve" listing-type="equation">PRR(t;

i;

j)=[Φ

(t;

i;

j)-Φ

(t-Δ

t;

i;

j)]/Δ

t,

where Φ

(t;

i;

j) is the carrier phase signal at said reference station number i at time t from said SATPS satellite number j.

9. The method of claim 7, further comprising the step of determining said pseudorange rate values PRR(t;

i;

j) by the steps of;

approximating the variable y(t)=Φ

(t;

i;

j) in a time interval t_n-1 ≦

t≦

t_n+1 by the relations

space="preserve" listing-type="equation">y(t)=y.sub.n +a.sub.n (t-t.sub.n)+b.sub.n (t-t.sub.n).sup.2,

using known values of y at three selected consecutive times t=t_n-1, t=t_n and t=t_n+1 ; and

defining the pseudorange rate value PRR(t;

i;

j) for said reference station i at the time t=t_n from SATPS satellite j by the relation

space="preserve" listing-type="equation">PRR(t.sub.n ;

i;

j)=y(t.sub.n)=a.sub.n ={(t.sub.n -t.sub.n-1).sup.2 [y(t.sub.n+1)-y(t.sub.n)]+(t.sub.n+1 -t.sub.n).sup.2 [y(t.sub.n-1)-y(t.sub.n)]}/(t.sub.n+1 -t.sub.n)(t.sub.n+1 -t.sub.n-1)(t.sub.n+1 -t.sub.n-1).

10. A method of determining the integrity of DSATPS signals formed at a reference SATPS station and used for monitoring the clock bias and frequency offset parameters of a mobile SATPS station, the method comprising the steps of:

providing an SATPS reference station, numbered i, whose location coordinates are accurately known, and a plurality of selected SATPS satellites, numbered j=j1, j2, . . . , jM (M≧

2);

providing an SATPS signal integrity monitoring station, whose location coordinates are accurately known, spaced apart from the reference station by a distance of no more than about 1 km;

allowing the reference station and the signal monitoring station to receive SATPS signals;

determining the pseudorange correction values PRC(t;

i;

j)_RS and the pseudorange rate correction values PRRC(t;

i;

j)_RS as a function of time t associated with SATPS signals that are received by the reference station number i from satellite number j for j=j1, j2, . . . , jM;

determining the pseudorange error values PRRE(t;

i;

j)_SIM and the pseudorange rate error values PRRRE(t;

i;

j)_SIM as a function of time t associated with SATPS signals that are received by the signal integrity monitoring station number i from satellite number j for j=j1, j2, . . . , jM;

forming the differences DPRE(t;

i;

j)_SIM =PRC(t;

i;

j)_RS -PRC(t;

i;

j)_SIM and DPRRE(t;

i;

j)_SIM =PRRC(t;

i;

j)_RS -PRRC(t;

i;

j)_SIM ;

comparing the magnitudes |DPRE(t;

i;

j)_SIM | of the pseudorange residuals with selected threshold values DPRE(i;

j)_thr ;

comparing the magnitudes |DPRRE(t;

i;

j)_SIM | of the pseudorange rate residuals with selected threshold values DPRRE(i;

j)_thr ;

when the pairs of relations |DPRE(t;

i;

j)_SIM |≦

DPRE(i;

j)_thr and |DPRRE(t;

i;

j)_SIM |≦

DPRRE(i;

j)_thr are valid for no more than one of the satellites j, transmitting a signal indicating that the SATPS signals received from the satellite j cannot be used for monitoring the clock bias and frequency offset parameters of a mobile SATPS station using DSATPS signals from the reference station; and

when the pairs of relations |DPRE(t;

i;

j)_SIM |≦

DPRE(i;

j)_thr and |DPRRE(t;

i;

j)_SIM |≦

DPRRE(i;

j)_thr are valid for at least two of the satellites j, transmitting a signal indicating that the SATPS signals received from the satellite j can, be used for monitoring the clock bias and frequency offset parameters of a mobile SATPS station using DSATPS signals from the reference station.

11. The method of claim 10, further comprising the step of determining said pseudorange rate values PRR(t;

i;

j) by the relation

space="preserve" listing-type="equation">PRR(t;

i;

j)=[Φ

(t;

i;

j)-Φ

(t-Δ

t;

i;

j)]/Δ

t,

where Φ

(t;

i;

j) is the carrier phase signal at said reference station number i at time t from said SATPS satellite number j.

12. The method of claim 10, further comprising the step of determining said pseudorange rate values PRR(t;

i;

j) by the steps of;

approximating the variable y(t)=Φ

(t;

i;

j) in a time interval t_n-1 ≦

t≦

t_n+1 by the relations

space="preserve" listing-type="equation">y(t)=y.sub.n +a.sub.n (t-t.sub.n)+b.sub.n (t-t.sub.n).sup.2,

using known values of y at three selected consecutive times t=t_n-1, t=t_n and t=t_n+1 ; and

defining the pseudorange rate value PRR(t;

i;

j) for said reference station i at the time t=t_n from SATPS satellite j by the relation

space="preserve" listing-type="equation">PRR(t.sub.n ;

i;

j)=y(t.sub.n)=a.sub.n ={(t.sub.n -t.sub.n-1).sup.2 [y(t.sub.n+1)-y(t.sub.n)]+(t.sub.n+1 -t.sub.n).sup.2 [y(t.sub.n-1)-y(t.sub.n)]}/(t.sub.n+1 -t.sub.n)(t.sub.n+1 -t.sub.n-1)(t.sub.n+1 -t.sub.n-1).

13. A method of determining the integrity of DSATPS signals formed at a reference station and used for monitoring a set of K location parameters for a mobile SATPS station (K=1, 2, 3), the method comprising the steps of:

providing an SATPS reference station, numbered i, whose location coordinates are accurately known, and a ;

plurality of selected SATPS satellites, numbered j=j1, j2, . . . , jM (M≧

K+1);

providing an SATPS signal integrity monitoring station, whose location coordinates are accurately known, spaced apart from the reference station by a distance of no more than about 1 km;

allowing the reference station and the signal monitoring station to receive SATPS signals and to determine their respective locations using the received SATPS signals;

determining correction values PRC(t;

i;

j)_RS as a function of time t for pseudorange signals PR(t;

i;

j)_RS received by the reference station number i from satellite number j for j=j1, j2, . . . , jM;

determining correction values PRC(t;

i;

j)_SIM as a function of time t associated with the pseudorange signals PR(t;

i;

j)_SIM received by the signal integrity monitoring station number i from satellite number j for j=j1, j2, . . . , jM;

forming the differences DPRE(t;

i;

j)_SIM =PRC(t;

i;

j)_RS -PRC(t;

i;

j)_SIM ;

forming a (K+1)×

M Jorgensen matrix H(t) that transforms pseudorange values received at an SATPS station from the M SATPS satellites into K location coordinates and clock bias for the SATPS station;

forming an M×

1 column matrix y whose entry at the position k=1, 2, . . . , M is the value DPRE(t;

i;

jk);

forming an M×

M first statistical covariance matrix R=Expectation [w w^tr ], where w is an M×

1 column matrix whose entry in the kth position (k=1, 2, . . . , M) is noise values associated with the pseudorange signal from satellite j=jk;

forming an M×

M second statistical covariance matrix

space="preserve" listing-type="equation">S=I-R.sup.-1/2 H(H.sup.tr R.sup.-1 H).sup.-1 H.sup.tr R.sup.-1/2;

forming an M×

1 fault matrix f=S R^-1/2y and a scalar value D=∥

f∥

² =f^tr f;

comparing the value D with a selected threshold value D_thr ;

when D≦

D_thr, transmitting a signal indicating that the pseudorange correction values PRC(t;

i;

j) determined at the reference station can be used to correct a set of K location parameters for a mobile SATPS station that is located near the reference station;

when D>

D_thr, forming the sequence of values τ

_j =f_j² /S_jj (j=1, 2, . . . , M), where f_j is the jth entry in the fault matrix f and S_jj is the jth diagonal entry in the covariance matrix S;

forming the difference Δ

τ

_J1,J2 =τ

_J1 -τ

_J2, where τ

_J1 and τ

_J2 are the largest and second largest values of τ

_j, respectively;

forming the ratio R_J1,J2 =2 log_e (p_J1 /p_J2), where p_j is an estimate of the probability that the jth value in the sequence {τ

_j } attains the value τ

_j, and comparing the difference Δ

τ

_J1,J2 with the ratio R_J1,J2 ;

when Δ

τ

_J1,J2 >

R_J1,J2, transmitting a signal indicating that the SATPS signals from the satellite number J1 are faulty and should be deleted from the computations of pseudorange parameters; and

when Δ

τ

_J1,J2 ≦

R_J1,J2, transmitting a signal indicating that the pseudorange correction values PRC(t;

i;

j) determined at the reference station cannot be used to help correct location parameters for a mobile SATPS station that is receiving corrections from the reference station.

14. A method of determining the integrity of DSATPS signals formed at a reference station and used for monitoring a set of K velocity parameters for a mobile SATPS station (K=1, 2, 3), the method comprising the steps of:

providing an SATPS reference station, numbered i, whose location coordinates are accurately known, and a plurality of selected SATPS satellites, numbered j=j1, j2, . . . , jM (M≧

K+1);

providing an SATPS signal integrity monitoring station, whose location coordinates are accurately known, spaced apart from the reference station by a distance of no more than about 1 km;

allowing the reference station and the signal monitoring station to receive SATPS signals and to determine their respective locations using the received SATPS signals;

determining correction values PRRC(t;

i;

j)_RS as a function of time t for pseudorange rate signals PRR(t;

i;

j)_RS received by the reference station number i from satellite number j for j=j1, j2, . . . , jM;

determining correction values PRRC(t;

i;

j)_SIM as a function of time t associated with the pseudorange rate signals PRR(t;

i;

j)_SIM received by the signal integrity monitoring station number i from satellite number j for j=j1, j2, . . . , jM;

forming the differences DPRRE(t;

i;

j)_SIM =PRRC(t;

i;

j)_RS -PRRC(t;

i;

j)_SIM ;

forming a (K+1)×

M Jorgensen matrix H(t) that transforms pseudorange, rate values received at an SATPS station from the M SATPS satellites into K velocity coordinates and frequency offset for the SATPS station;

forming an M×

1 column matrix y whose entry at the position k=1, 2, M is the value DPRRE(t;

i;

jk);

forming an M×

M first statistical covariance matrix R=Expectation [w w^tr ], where w is an M×

1 column matrix whose entry in the kth position (k=1, 2, . . . , M) is noise values associated with the pseudorange rate signal from satellite j=jk;

forming an M×

M second statistical covariance matrix

space="preserve" listing-type="equation">S=I-R.sup.-1/2 H(H.sup.tr R.sup.-1 H).sup.-1 H.sup.tr R.sup.-1/2;

forming an M×

1 fault matrix f=S R^-1/2y and a scalar value D=∥

f∥

² =f_tr f;

comparing the value D with a selected threshold value D_thr ;

when D≦

D_thr, transmitting a signal indicating that the pseudorange rate correction values PRRC(t;

i;

j) determined at the reference station can be used to correct a set of K velocity parameters for a mobile SATPS station that is located near the reference station;

when D>

D_thr, forming the sequence of values τ

_j =f_j² /S_jj (j=1, 2, . . . , M), where f_j is the jth entry in the fault matrix f and S_jj is the jth diagonal entry in the covariance matrix S;

forming the difference Δ

τ

_J1,J2 =τ

_J1 -τ

_J2, where τ

_J1 and τ

_j2 are the largest and second largest values of τ

_j, respectively;

forming the ratio R_J1,J2 =2 log_e (p_J1 /p_J2), where p_j is an estimate of the probability that the jth value in the sequence {τ

_j } attains the value τ

_j, and comparing the difference Δ

τ

_J1,J2 with the ratio R_J1,J2 ;

when Δ

τ

_J1,J2 >

R_J1,J2, transmitting a signal indicating that the SATPS signals from the satellite number J1 are faulty and should be deleted from the computations of pseudorange rate parameters; and

when Δ

τ

_J1,J2 ≦

R_J1,J2, transmitting a signal indicating that the pseudorange rate correction values PRRC(t;

i;

j) determined at the reference station cannot be used to help correct velocity parameters for a mobile SATPS station that is receiving corrections from the reference station.

15. A method of determining the integrity of DSATPS signals formed at a reference,, SATPS station and used for correcting at least one of a set of K location parameters and a set of K velocity parameters of a mobile SATPS station (K=1, 2, 3, 4), the method comprising the steps of:

providing an SATPS reference station, numbered i, whose location coordinates are accurately known, and a plurality of selected SATPS satellites, membered j=j1, j2, . . . , jM (M≧

K);

providing an SATPS signal integrity monitoring station, whose location coordinates and velocity coordinates (x(i)_SIM,known, y(i)_SIM,known, z(i)_SIM,known) and (v(i)_x,SIM,known, v(i)_y,SIM,known, v(i)_z,SIM,known) in a selected coordinate system are accurately known, spaced apart from the reference station by a distance of no more than about about 1 km;

allowing the reference station and the signal monitoring station to receive SATPS signals;

determining the location coordinates x(t;

i)_SIM, y(t;

i)_SIM, z(t;

i)_SIM and the velocity coordinates v(t;

i)_x,SIM, v(t;

i)_y,SIM, v(t;

i)_z,SIM of the SIM station from the SATPS signals received from the satellites;

forming the location difference values Δ

x(t;

i)_SIM =x(t;

i)_SIM -x(i)_SIM,known and Δ

y(t;

i)_SIM =y(t;

i)_SIM -y(i)_SIM,known and Δ

z(t;

i)_SIM =z(t;

i)_SIM -z(i)_SIM,known and the velocity difference values Δ

v(t;

i)_x,SIM =v(t;

i)_x,SIM -v(i)_x,SIM,known and Δ

v(t;

i)_y,SIM =v(t;

i)_y,SIM -v(i)_y,SIM,known and Δ

v(t;

i)_z,SIM =v(t;

i)_z,SIM -v(i)_z,SiM,known ;

comparing the magnitudes |Δ

x(t;

i)_SIM |, |Δ

y(t;

i)_SIM |, and |Δ

z(t;

i)_SIM | with respective selected threshold values Δ

x(i)_thr, Δ

y(i)_thr and Δ

z(i)_thr ;

comparing the magnitudes |Δ

v(t;

i)_x,SIM |, |Δ

v(t;

i)_y,SIM | and |Δ

v(t;

i)_z,SIM | with respective selected threshold values Δ

v(i)_x,thr, Δ

v(i)_y,thr and Δ

v(i)_z,thr ;

when at least one of the relations |Δ

x(t;

i)_SIM |≦

Δ

x(i)_thr, |Δ

y(t;

i)_SIM |≦

Δ

y(i)_thr, |Δ

z(t;

i)_SIM |≦

Δ

z(i)_thr, |Δ

v(t;

i)_x,SIM |≦

Δ

v(i)_x,thr, |Δ

v(t;

i)_y,SIM |≦

Δ

v(i)_y,thr and |Δ

v(t;

i)_z,SIM |≦

Δ

v(i)_z,thr, is not valid, transmitting a signal indicating that the SATPS signals received from the satellites j=j1,j2, . . . , jM cannot be used to help correct at least one of a set of K location coordinates and a set of K velocity coordinates for a mobile SATPS station using DSATPS signals from the reference station; and

when all the relations |Δ

x(t;

i)_SIM |≦

Δ

x(i)_thr, |Δ

y(t;

i)_SIM |≦

Δ

y(i)_thr, |Δ

z(t;

i)_SIM |≦

Δ

z(i)_thr, |Δ

v(t;

i)_x,SIM |≦

Δ

v(i)_x,thr, |Δ

v(t;

i)_y,SIM |≦

Δ

v(i)_y,thr and |Δ

v(t;

i)_z,SIM |≦

Δ

v(i)_z,thr, are valid, transmitting a signal indicating that the SATPS signals received from the satellites j=j1, j2, . . . , jM can be used to help correct at least one of a set of K location coordinates and a set of K velocity coordinates for a mobile SATPS station using DSATPS signals from the reference station.

16. A method of determining the integrity of DSATPS signals formed at a reference SATPS station and used for correcting the clock bias and frequency offset parameters of a mobile SATPS station, the method comprising the steps of:

providing an SATPS reference station, numbered i, whose location coordinates are accurately known, and a plurality of selected SATPS satellites, numbered j=j1, j2, . . . , jM (M≧

1);

providing an SATPS signal integrity monitoring station, whose location coordinates and velocity coordinates (x(i)_SIM,known, y(i)_SIM,known, z(i)_SIM,known) and (v(i)_x,SIM,known, v(i)_y,SIM,known, v(i)_z,SIM,known) in a selected coordinate system are accurately known, spaced apart from the reference station by a distance of no more than about about 1 km;

allowing the reference station and the signal monitoring station to receive SATPS signals;

determining the location coordinates x(t;

i)_SIM, y(t;

i)_SIM, z(t;

i)_SIM and the velocity coordinates v(t;

i)_x,SIM, v(t;

i)_y,SIM, v(t;

i)_z,SIM of the SIM station from the SATPS signals received from the satellites;

forming the location difference values Δ

x(t;

i)_SIM =x(t;

i)_SIM -x(i)_SIM,known and Δ

y(t;

i)_SIM =y(t;

i)_SIM -y(i)_SIM,known and Δ

z(t;

i)_SIM =z(t;

i)_SIM -z(i)_SIM,known and the velocity difference values Δ

v(t;

i)_x,SIM =v(t;

i)_x,SiM -v(i)_x,SIM,known and Δ

v(t;

i)_y,SIM =v(t;

i)_y,SIM =v(i)_y,SIM,known and Δ

v(t;

i)_z,SIM =v(t;

i)_z,SIM -v(i)_z,SIM,known ;

comparing the magnitudes |Δ

x(t;

i)_SIM |, |Δ

y(t;

i)_SIM |, and |Δ

z(t;

i)_SIM | with respective selected threshold values Δ

x(i)_thr, Δ

y(i)_thr and Δ

z(i)_thr ;

comparing the magnitudes |Δ

v(t;

i)_x,SIM |, |Δ

v(t;

i)_y,SIM | and |Δ

v(t;

i)_z,SIM | with respective selected threshold values Δ

v(i)_x,thr, Δ

v(i)_y,thr and Δ

v(i)_z,thr ;

when at least one of the relations |Δ

x(t;

i)_SIM |≦

Δ

x(i)_thr, |Δ

y(t;

i)_SIM |≦

Δ

y(i)_thr, |Δ

z(t;

i)_SIM |≦

Δ

z(i)_thr, |Δ

v(t;

i)_x,SIM |≦

Δ

v(i)_x,thr, |Δ

v(t;

i)_y,SIM |≦

Δ

v(i)_y,thr and |Δ

v(t;

i)_z,SIM |≦

Δ

v(i)_z,thr, is not valid, transmitting a signal indicating that the SATPS signals received from the satellites j=j1, j2, . . . , jM cannot be used to help correct the clock bias and frequency offset parameters for a mobile SATPS station using DSATPS signals from the reference station; and

when all the relations |Δ

x(t;

i)_SIM |≦

Δ

x(i)_thr, |Δ

y(t;

i)_SIM |≦

Δ

y(i)_thr, |Δ

z(t;

i)_SIM |≦

Δ

z(i)_thr, |Δ

v(t;

i)_x,SIM |≦

Δ

v(i)_x,thr, |Δ

v(t;

i)_y,SIM |≦

Δ

v(i)_y,thr and |Δ

v(t;

i)_z,SIM |≦

Δ

v(i)_z,thr, are valid, transmitting a signal indicating that the SATPS signals received from the satellites j=j1, j2, . . . , jM can be used to help correct the clock bias and frequency offset parameters for a mobile SATPS station using DSATPS signals from the reference station.

17. A method of determining the integrity of DSATPS signals formed at a reference SATPS station and used for correcting at least one of a set of K location parameters and a set of K velocity parameters of a mobile SATPS station (K=1, 2, 3, 4), the method comprising the steps of:

providing an SATPS reference station, numbered i, whose location coordinates are accurately known, and a plurality of selected SATPS satellites, numbered j=j1, j2, . . . , jM (M>

K);

providing an SATPS signal integrity monitoring station, whose two-dimensional location coordinates and velocity coordinates (x(i)_SIM,known, y(i)_SIM,known) and (v(i)_x,SIM,known, v(i)_y,SIM,known) in a selected coordinate system are accurately known, spaced apart from the reference station by a distance of no more than about about 1 km;

allowing the reference station and the signal monitoring station to receive SATPS signals;

determining the location coordinates x(t;

i)_SIM and y(t;

i)_SIM and the velocity coordinates v(t;

i)_x,SIM and v(t;

i)_y,SIM of the SIM station from the SATPS signals received from the satellites;

forming the location difference values Δ

x(t;

i)_SIM =x(t;

i)_SIM -x(i)_SIM,known and Δ

y(t;

i)_SIM =y(t;

i)_SIM -y(i)_SIM,known and the velocity difference values Δ

v(t;

i)_x,SIM =v(t;

i)_x,SIM -v(i)_x,SIM,known and Δ

v(t;

i)_y,SIM =v(t;

i)_y,SIM -v(i)_y,SIM,known ;

comparing the magnitude [(Δ

x(t;

i)_SIM)² +(Δ

y(t;

i)_SIM)² ]^1/2 with a selected threshold value Δ

d(i)₂,thr ;

comparing the magnitude [(Δ

v(t;

i)_x,SIM)² +(Δ

v(t;

i)_y,SIM)² ]^1/2 with a selected threshold value Δ

v(i)₂,thr ;

when at least one of the relations [(Δ

x(t;

i)_SIM)² +(Δ

y(t;

i)_SIM)² ]^1/2≦

Δ

d(i)₂,thr and [(Δ

v(t;

i)_x,SIM)² +(Δ

v(t;

i)_y,SIM)² ]^1/2<

Δ

v(i)₂,thr is not valid, transmitting a signal indicating that the SATPS signals received from the satellites j=j1, j2, . . . , jM cannot be used to help correct at least one of a set of K location coordinates and a set of K velocity coordinates for a mobile SATPS station using DSATPS signals from the reference station; and

when all the relations [(Δ

x(t;

i)_SIM)² +(Δ

y(t;

i)_SIM)² ]^1/2≦

Δ

d(i)₂,thr and [(Δ

v(t;

i)_x,SIM)² +(Δ

v(t;

i)_y,SIM)² ]^1/2≦

Δ

v(i)₂,thr is not valid, transmitting a signal indicating that the SATPS signals received from the satellites j=j1, j2, . . . , jM can be used to help correct at least one of a set of K location coordinates and a set of K velocity coordinates for a mobile SATPS station using DSATPS signals from the reference station.

18. A method of determining the integrity of DSATPS signals formed at a reference SATPS station and used for correcting at least one of a set of K location parameters and a set of K velocity parameters of a mobile SATPS station (K=1, 2, 3, 4), the method comprising the steps of:

providing an SATPS reference station, numbered i, whose location coordinates are accurately known, and a plurality of selected SATPS satellites, numbered j=j1, j2, . . . , jM (M≧

K);

providing an SATPS signal integrity monitoring station, whose location coordinates and velocity coordinates (x(i)_SIM,known, y(i)_SIM,known, z(i)_SIM,known,) and (v(i)_x,SIM,known, v(i)_y,SIM,known, v(i)_z,SIM,known,) in a selected coordinate system are accurately known, spaced apart from the reference station by a distance of no more than about about 1 km;

allowing the reference station and the signal monitoring station to receive SATPS signals;

determining the location coordinates x(t;

i)_SIM and y(t;

i)_SIM and z(t;

i)_SIM and the velocity coordinates v(t;

i)_x,SIM and v(t;

i)_y,SIM and v(t;

i)_z,SIM of the SIM station from the SATPS signals received from the satellites;

forming the location difference values Δ

x(t;

i)_SIM =x(t;

i)_SIM -x(i)_SiM,known, Δ

y(t;

i)_SIM =y(t;

i)_SIM -y(i)_SIM,known and Δ

z(t;

i)_SIM =z(t;

i)_SIM -z(i)_SiM,known and the velocity difference values Δ

v(t;

i)_x,SIM =v(t;

i)_x,SIM -v(i)_x,SIM,known and Δ

v(t;

i)_y,SIM =v(t;

i)_y,SIM -v(i)_y,SIM,known and Δ

v(t;

i)_z,SIM =v(t;

i)_z,SIM -v(i)_z,SIM,known ;

comparing the magnitude [(Δ

x(t;

i)_SIM)² +(Δ

y(t;

i)_SIM)² +(Δ

z(t;

i)_SIM)² ]^1/2 with a selected threshold value Δ

d(i)₃,thr ;

comparing the magnitude [(Δ

v(t;

i)_x,SIM)² +(Δ

v(t;

i)_y,SIM)² +(Δ

v(t;

i)_z,SIM)² ]^1/2 with a selected threshold value Δ

v(i)₃,thr;

when at least one of the relations [(Δ

x(t;

i)_SIM)² +(Δ

y(t;

i)_SIM)² +(Δ

z(t;

i)_SIM)² ]^1/2≦

Δ

d(i)₃,thr and [(Δ

v(t;

i)_x,SiM)² +(Δ

v(t;

i)_y,SIM)² +(Δ

v(t;

i)_z,SIM)² ]^1/2≦

Δ

v(i)₃,thr is not valid, transmitting a signal indicating that the SATPS signals received from the satellites j=j1, j2, . . . , jM cannot be used to help correct at least one of a set of K location coordinates and a set of K velocity coordinates for a mobile SATPS station using DSATPS signals from the reference station; and

when all the relations [(Δ

x(t;

i)_SIM)² +(Δ

y(t;

i)_SIM)² +(Δ

z(t;

i)_SIM)² ]^1/2≦

Δ

d(i)₃,thr and [(Δ

v(t;

i)_x,SIM)² +(Δ

v(t;

i)_y,SIM)² +(Δ

v(t;

i)_z,SIM)² ]^1/2≦

Δ

v(i)₃,thr are valid, transmitting a signal indicating that the SATPS signals received from the satellites j=j1, j2, . . . , jM can be used to help correct at least one of a set of K location coordinates and a set of K velocity coordinates for a mobile SATPS station using DSATPS signals from the reference station.