System for determining the location of mobile objects

• US 6,018,313 A
• Filed: 09/25/1997
• Issued: 01/25/2000
• Est. Priority Date: 09/01/1995
• Status: Expired due to Fees

• Current Assignee: BRAU Verwaltungsgesellschaft Mit Beschrankter Haftung
• Original Assignee: Tilmar Konle
• Inventors: Lindstrot, Walter, Sandmann, Stefan, Raven, Paul, Engelmayer, Wolfgang, Schoemakers, Guenter
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US08/913,935
• Time in Patent Office: 852 Days
• Field of Search: 342/357, 701/213, 701/214, 701/215
• US Class Current: 342/357.24
• CPC Class Codes: G01S 19/071 DGPS corrections
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 5/009 Transmission of differential positioning data to mobile

Abstract

To reduce the transfer capacity requirements for correction data in a differential GPS system, while notably improving the interpretability of any correction data having suffered transmission interference and ensuring that such correction be as up to date as possible, continuous error readings (7) are calculated from a steady stream of GPS signals (12, 22, 32, 42) received from a reference GPS receiver (50) and from the known co-ordinates of its location (6). According to the invention, an evaluation system (60) is provided which, at a specific point in time recalculates the correction readings rounded off to the last full minute. The correction reading (8), calculated by the evaluation system, is then transmitted by at least one radio transmitter (80) in a radio data signal (RDS) included in its program signal. Attached to the mobile object (5), whose situation co-ordinates are determined by a mobile GPS receiver (120), is a radio receiver (90) to which are connected an RDS decoder (100) for receiving and decoding the received RDS signals incorporating the processed correction readings (8) and a computer (110) which extracts the correction readings (7) from the decoded RDS and updates them to the present time. The computer also reconstructs a standard correction signal (7) complying with the RTCM standard. The reconstructed, standard correction data are finally fed to the GPS receiver which then corrects its reading according to the reconstructed correction readings (7) received.

Claims

1. A system for determining the position of mobile objects (5) with the assistance of position-finding and navigation satellites (GPS satellites 1, 2, 3, 4) which continuously change their position relative to a stationary point on the earth and emit GPS signals (11, 21, 31, 41) that permit a GPS receiver (120) installed on the mobile object (5) to determine its instantaneous position coordinates, the system comprising

at least one GPS receiving and processing unit (50) operating as a reference whose precise position coordinates are known, with the unit determining continuous error values from the continuously received GPS signals (12, 22, 32, 42) and from the known position coordinates of its location (6) and generating correction data (7) therefrom, with the correction data (7) comprising

pseudo range correction values (PRC data) valid for the moment of their calculation, and

values (RRC data) for the instantaneous rate of change of the RRC data;

at least one radio station (80) with RDS coder (70) which emits the generated correction data (7) as data of a radio data system signal (RDS signal) which are inserted into its program signal;

a radio receiver (90) present on the mobile object (5) and having an RDS decoder (100) for receiving and decoding the RDS signal that is provided with the correction data (7), and

a computer (110) for separating the correction data (7) from the decoded RDS signal and for feeding the correction data (7) into the GPS receiver (120) mounted on the mobile object (5), with the receiver correcting its measurement results according to the separated correction values (7),

characterized in that

a) downstream of the GPS receiving and processing unit (50) an evaluating device (60) is arranged which

calculates back the PRC data, which were calculated at a specific moment, with the assistance of the associated rate of change values (RRC data) to the moment of the last full minute, and,

for each GPS satellite, inserts into a single RDS group of an RDS signal cycle the calculated-back PRC data together with the associated RRC data and an identification of the satellite concerned, but while abandoning a header provided in a standard format for GPS correction signals;

b) in a computer (110) arranged downstream of the RDS decoder (100) of the radio receiver (90), the calculated-back PRC data are extrapolated to the actual time for each GPS satellite with the assistance of the associated rate of change values (RRC data) and computer-internally generated time information (internal Z count), and

c) the non-transmitted header is reconstructed with check words and continuous time information in the computer (110) and, together with the extrapolated PRC data for each GPS satellite and the associated RRC data, is put together to form the standardized format of the correction data (7).

2. A system according to claim 1, characterized in that, after every insertion of the processed correction data (8) for a GPS satellite into an RDS signal cycle, the PRC data and RRC data are updated for all satellites.

3. A system according to claim 1, characterized in that the evaluating device (60) occasionally inserts a time information derived from the received GPS signals into a group of an RDS signal cycle, which time information is used by the computer (110) to synchronize the internally generated time information (internal Z count).

4. A system according to claim 1, characterized in that the evaluating device (60) occasionally inserts a data identification information (IOD) derived from the received GPS signals into a group of an RDS signal cycle, which data identification information is used by the computer (110) to reconstruct the standardized correction data (7).

5. A system according to claim 1, characterized in that the evaluating device (60) continuously determines for each GPS satellite the exact extent to which the rate of change last transmitted as RRC data corresponds with the actual rate of change value, and that the evaluating device (60) inserts the correction data for satellites with inferior matching of the actual rate of change on a priority basis compared to correction data for satellites with better matching of the rate of change into the RDS signal cycle for the purpose of a priority control.

6. A receiving arrangement for determining the position of mobile objects (5) with the assistance of position-finding and navigation satellites (GPS satellites) which continuously change their position relative to a stationary point on the earth and emit GPS signals that permit a GPS receiver (120) installed on the mobile object (5) to determine its instantaneous position and altitude coordinates, wherein the receiving arrangement is designed to receive correction data--comprised of pseudo range correction values (PRC data), valid for the moment of their calculation, as well as of values (RRC data) for the rate of change of the PRC data--wherein the correction data are emitted as data of a radio data system signal (RDS signal) inserted into a radio program signal, the receiving arrangement comprising

an arrangement (90, 100) to continuously receive and decode the RDS signal provided with the correction data, and

a computer (110) to separate the correction data from the decoded RDS signal and to feed the correction data into the GPS receiver (120) installed on the mobile object (5), which GPS receiver corrects its measurement results according to the separated correction data,

characterized in that, for the evaluation of processed correction data (8), wherein the PRC data calculated at a specific moment are calculated back to the moment of the last full minute with the assistance of the associated rate of change values (RRC data), the computer (110) is designed such that

a) the calculated-back PRC data are extrapolated to the actual time for each GPS satellite with the assistance of the associated rate of change values (RRC data) and computer-internally generated time information (internal Z count), and

b) a non-transmitted header provided in a standardized format for correction data is reconstructed with check words and continuous time information and, together with the extrapolated PRC data for each GPS satellite and the associated RRC data, is put together to form the standardized format of the correction data.

7. A receiving arrangement according to claim 6, characterized in that a time information, which is inserted occasionally into a group of an RDS signal cycle and derived from the received GPS signals, is used by the computer (110) to synchronize the internally generated time information (internal Z count).

8. A receiving arrangement according to claim 6, characterized in that a data identification information (IOD), which is inserted occasionally into a group of an RDS signal cycle and derived from the received GPS signals, is used by the computer (110) to reconstruct the correction data (7) conforming to standard.