Differential GPS ground station system

• US 5,610,616 A
• Filed: 05/06/1996
• Issued: 03/11/1997
• Est. Priority Date: 08/23/1994
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Vallot, Lawrence C., Brenner, Mats A.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US08/643,495
• Time in Patent Office: 309 Days
• Field of Search: 342/357, 342/352, 364/424.06, 340/979
• US Class Current: 342/357.44
• CPC Class Codes: G01S 19/071 DGPS corrections

Abstract

A differential satellite positioning system is configured to include a plurality of satellite positioning system receivers in spatial proximity of one another for determining independent pseudo range values which are processed in accordance with a selected averaging scheme for determining highly reliable satellite differential corrections.

Claims

1. A DGPS for use with a plurality of satellites each transmitting information including satellite position (R) and the time of transmission;

a plurality of receivers whose positions (G) are known, the receivers operable to produce pseudo range values (P) indicative of the distance between receiver and satellite based on the transit time of the signal from satellite to the receiver;

range calculation means operable to produce calculated range values (Racal) from the difference between G and R;

differential correction means receiving the Racal and P values to produce differential correction values (C);

averaging means connected to receive the differential correction values and to produce average differential correction values (Cave); and

integrity monitoring means connected to receive only C and Cave and to produce a fault signal if the difference therebetween exceeds a threshold value.

2. A differential satellite positioning system ground station operative for determining a satellite-specific pseudo range error associated with each received satellite information signal transmitted from selected ones of a plurality of satellites, where "n" represents a specific one of said plurality of satellites, said differential satellite positioning system ground station comprising:

a plurality of GPS receivers, where "K" represents the total number of said plurality GPS receivers and where "k" represents a specific one of said "K" GPS receivers and wherein each one of said plurality of GPS receivers,

(i) is independent of each other,

(ii) is operative for receiving a satellite information signal from each of selected ones said plurality of satellites,

(iii) has a known geocentric position, identified as G^k, and

(iv) is in spatial proximity to a spatial location of special interest,

(v) is operative for deriving from satellite data associated with each received satellite information signal at least a geocentric satellite position, identified as R(t_m)ⁿ, at a receiver-specific measurement time, identified as t_m, of the specific satellite, "n", transmitting the satellite information signal, and

(vi) is operative for deriving from satellite data associated with each received satellite information signal at least a satellite-receiver-specific pseudo range value identified as P(t_m)^k,n where k and n represent said specific GPS receiver and satellite, respectively, and t_m corresponds to said receiver-specific measurement time, and where said satellite-receiver-specific pseudo range value is an estimate of the true range value between a specific GPS receiver, "k", and a specific satellite, "n", derived from said satellite information signal and related to the corresponding satellite signal travel time from the specific satellite to the specific GPS receiver; and

a differential correction processor including,

means for determining receiver-satellite-specific calculated range values, identified as r(t_m)_calc^k,n, where each receiver-satellite-specific calculated range value is the difference between (i) corresponding "k" and "n" ones of said geocentric receiver position G^k of a specific GPS receiver, "k" and (ii) said satellite position R(t_m)ⁿ of a specific satellite, "n" at a corresponding receiver-specific measurement time, t_m,

means for calculating corresponding receiver-satellite-specific difference values, identified as C(t_m)^k,n, each being the difference between (i) corresponding "k" and "n" ones of said receiver-satellite-specific calculated image values, r(t_m)_calc^k,n, and (ii) said satellite-receiver-specific pseudo range values, P(t_m)^k,n,

means for deriving said satellite-specific pseudo range error associated with said satellite information signal transmitted from each of said selected plurality of satellites as an average of said receiver-satellite-specific difference values, C(t_m)^k,n derived by selected ones of said "K" GPS receivers for each of said selected ones of said satellite information signals; and

integrity monitoring means comparing the difference between the receiver-satellite specific difference values with the average of said receiver satellite-specific difference values and producing a fault signal if the difference is greater than a predetermined threshold value.

3. The differential satellite positioning system ground station of claim 2 further comprising an integrity monitoring system including:

means for computing first receiver-satellite specific discriminate values as the difference between corresponding ones of said satellite-specific pseudo range error values and said receiver-satellite specific difference values; and

means for computing second receiver-satellite specific discriminate values as the difference between corresponding ones of said first receiver-satellite specific discriminate values and said detection threshold.

4. The differential satellite positioning system ground station of claim 2 further including means for removing receiver-specific clock bias from each of said receiver-satellite-specific difference values, and said satellite-specific pseudo range error values are computed as an average of those receiver-satellite-specific difference values with clock bias removed.

5. The differential satellite positioning system ground station of claim 3 further including means for synchronizing each of said receiver-satellite-specific difference values to a common synchronization time, and said satellite-specific pseudo range error values are computed as an average of those synchronized receiver-satellite-specific difference values synchronized to said common synchronization time.

6. The differential satellite positioning system ground station of claim 3 further including

means for removing receiver-specific clock bias from each of said receiver-satellite-specific difference values;

and

means for synchronizing each of said receiver-satellite-specific difference values to a common synchronization time, and said satellite-specific pseudo range error values are computed as an average of those synchronized receiver-satellite-specific difference values synchronized to said common synchronization time with clock bias removed.

7. The differential satellite positioning system ground station of claim 2 wherein said plurality of GPS receivers are sufficiently separated from each other to avoid receiving an identical multipath satellite information signal from the same satellite as received by another one of said plurality of GPS receivers.

8. A differential satellite positioning system ground station operative for determining a satellite-specific pseudo range error associated with each received satellite information signal transmitted from at least first and second satellites each transmitting a signal indicative of its position, said differential satellite positioning system ground station comprising:

a first receiver for receiving the signal from the first and second satellites and to calculate first and second true ranges, one for each of the distances between the first receiver and the first and second satellites, respectively, and to calculate first and second pseudo ranges, one for each of the distances between the first receiver and the first and second satellites, respectively, said first receiver calculating a first error signal representing the difference between the first true range and the first pseudo range, and a second error signal representing the differences between the second true range and the second pseudo range;

a second receiver located proximate the first receiver to receive the signals from the first and second satellites, and to calculate third and fourth true ranges, one for each of the distances between the second receiver and the first and second satellites, respectively, and to calculate third and fourth pseudo ranges, one for each of the distances between the second receiver and the first and second satellites, respectively, said second receiver calculating a third error signal representing the difference between the third true range and the third pseudo range, and a fourth error signal representing the differences between the fourth true range and the fourth pseudo range;

means for computing a first average being the average of said first and third error signals and for computing a second average being the average of the second and fourth error signals and integrity monitoring means comparing the differences between the first and third error signals and the average of said first and third error signals and comparing the difference between the second and fourth error signals and the average of the second and fourth error signals and producing a fault signal if the differences exceed a predetermined threshold value.

9. The differential satellite positioning system ground station of claim 8 further comprising means for communicating said first and second averages to a remote user.

10. A differential satellite positioning system ground station operative for determining a satellite-specific pseudo range error associated with each received satellite signal transmitted from a plurality of satellites, the ground station comprising:

a plurality of GPS receivers operative for receiving selected satellite signals and deriving from the satellite data associated with each of said received satellite signals at least I) a satellite-receiver-specific pseudo range value at a corresponding receiver-specific measurement time, were said satellite-receiver-specific pseudo range value is an estimate of the true range value between a corresponding one of said plurality of receivers and one of said plurality of satellites derived from said satellite signal and related to the corresponding satellite signal travel time from the specific satellite of said plurality of satellites to the specific receiver of said plurality of receivers, and ii) the corresponding satellite-receiver-specific position of said one satellite at said satellite-receiver-specific measurement time; and

a differential correction processor including,

means for determining a receiver-satellite-specific calculated range for each receiver and each of said selected satellites, where said calculated range is the range between corresponding ones of the geocentric position of each of said plurality of receivers and the satellite-receiver-specific geocentric position of each of said satellites,

means for calculating a receiver-satellite-specific difference between corresponding ones of said receiver-satellite-specific calculated ranges and said satellite-receiver-specific pseudo range values, and

means for deriving said satellite-specific pseudo range error associated with said satellite signal transmitted from each of said selected plurality of satellites as a function of a plurality of said satellite-receiver-specific pseudo range values from said plurality of GPS receivers and associated with a specific one satellite,

means comparing the satellite-specific pseudo range error with the average of all of the satellite-specific pseudo range errors to produce individual receiver-satellite specific deviations; and

integrity monitoring means comprising means for comparing the satellite-specific deviations with a predetermined threshold value and producing a fault signal whenever a satellite-specific deviation exceeds the predetermined threshold value.