KR19990014949A - System for determining the position of the movable object - Google Patents

Abstract

In order to reduce the transfer capacity requirement for correction data in a differential GPS system, while in particular improving the interpretation of any correction data suffering from transmission interference and ensuring fast correction as much as possible, continuous error reading 7 is performed by a reference GPS receiver ( From a fixed stream of GPS signals 12, 22, 32, 42 received from 50 and known position coordinates 6. In accordance with the present invention, an evaluation system 60 is provided to recalculate a correction reading that ends at the last full time at a particular time point. The correction reading 8 calculated by the evaluation system is transmitted by at least one radio transmitter 80 in the radio data signal RDS included in the program signal. Attached to the moving object 5 whose position coordinates are determined by the moving GPS receiver 120 is connected to the RDS decoder 100 for receiving and decoding the received RDS signal incorporating the processed correction readout 8. Computer 110 extracts the correction read 7 from the radio receiver 90 and the decoded RDS and updates it to the current time. The computer reconstructs the standard correction signal 7 in accordance with the RTCM standard. The reconstructed standard correction data is finally supplied to the GPS receiver which corrects the reading in accordance with the received reconstruction correction reading 7.

Description

System for determining the position of the movable object

Regarding the positioning and navigation of moving objects, a method based on satellites which can be used under the Global Positioning System (GPS system) is disclosed, in which the so-called GPS satellites are orbitals with high precision on, for example, a frequency of 1.575 kHz. Release time in addition to data. The orbit of a GPS satellite extends its position continuously in relation to a fixed position on earth. The GPS receiver calculates the distance for each GPS satellite by measuring the time the signal travels from the satellite to the receiver. Since the GPS satellite position is known, the spatial coordinates of the receiver position on earth and the internal clock error of the GPS receiver are calculated by four GPS satellites. However, this achieves an accuracy of approximately ± 100 meters. Since this precision is not suitable for many applications, it is known to determine an error value from a reference GPS receiver whose position coordinates are known precisely and to transmit the error value in the form of correction data (Washington, USA 20005). 3 January 1994, version 2.1 Chapter 4 RTCM Initiative Standard for Differential GPS Services. GPS measurement data determined by the mobile GPS receiver is corrected with the aid of the received correction data. The data format of modified data as defined in the RTCM standard is shown in Documents 4-3 and 4-8 above.

For each individual GPS satellite, the scale factor, an indication taking into account the error range (UDRE = user differential range error), the associated satellite identification table (satellite ID), the so-called pseudo range correction value (PRC = pseudo range correction), and the test signal (ferry) Each message consists of a parity), an expected rate value of PRC data (PRC = rate range correction) change, and an indication of the orbital data with which the correction value is related (data result). Each message is combined directly with each other to form a string, which is separated into a series of 30-bit words, despite the limitations of each message. Each message string is preceded by a header consisting of two words, 30 bits long, to indicate the beginning of each string. The first 30 bit word of the header consists of a contiguous sequence (full text), an identifier in the form of a message later (message form), an identifier of the transmission station (station ID) and a check word (parity). The second 30-bit word of the header contains time information (modified z counts), sequence number, identifier (frame length) which takes into account the total length of the subsequent message, an indication (station health condition) and check word (which takes into account the conditions of the transmitting station) Periphery).

For real time transmission of correction data, DE 41 36 136 C1 initiates using the broadcast station's current transmitter network, which correction data is inserted into a 37 bit free group of each periodic transmission radio data (RDS) signal, and The group is transmitted inaudible within the radio program signal. Since the data format of the radio data system does not match the data format of the GPS correction data, the header and subsequent messages of each string are divided into 37 bits each allocated to the free RDS group in successive RDS signal cycles. Partial contents of the RDS group are completely arbitrary and cannot be identified as above. The data format of the GPS correction data can be reconstructed from this part and evaluated if all RDS groups to which the header and successive messages of each string are assigned are received continuously without confusion. For example, in the case of VHF reception confusion, combining only a single RDS group leads to the loss of the entire string information, which means that the modified values of all messages related to the string are lost for all relevant GPS satellites. In addition, the modification message period for all GPS satellites, i.e. strings, takes several seconds because of the limited capacity of the RDS system, even if each cycle (cycle period 1 second) is occupied by three RDS groups; This decreases gradually until the correction value computed simultaneously for all GPS satellites is transmitted through the string. This aging problem is more prominent when less free capacity is used in the RDS system for correction value transfer, if necessary, because other services require the RDS system capacity.

The present invention relates to a system according to the preamble of claim 1 and a receiving apparatus according to the preamble of claim 6. Systems and receiving devices of this type are disclosed in DE 41 36 136 C1.

1 is a schematic diagram of a known position determination system according to so-called differential GPS.

2 is a block diagram of a transmitter-type component of a system in accordance with the present invention.

3 is a block diagram of a receiver end component of a system in accordance with the present invention.

4 is a diagram of the data format of a continuous transmit RDS signal cycle with fully modified data for a GPS satellite.

5 is a schematic diagram of the data format of a sometimes transmitted RDS signal cycle with time information (modified Z counts) derived from a received GPS signal.

6 is a schematic diagram of the data format of an RDS signal cycle with data identification information (IOD) derived from a received GPS signal.

In comparison, it is an object of the present invention to provide a system of the above-mentioned type in which the demand for transmission capacity is reduced, the ability to interpret correction data is significantly improved in the case of transmission confusion and the flow of transmitted correction data is improved. To improve. In addition, a receiving device is formed to fulfill these purposes on the receiver end.

This object is achieved according to the features of claims 1 and 6 of the invention.

Preferred embodiments and modifications of the system according to the invention and the receiving device according to the invention appear in the dependent claims 2 to 5 and 7 and 8 respectively.

The invention is explained by way of example with reference to the drawings.

As shown in FIG. 1, the illustrated positioning system is based on so-called GPS satellites 1-4 orbiting around the earth in a manner that continuously changes position relative to a fixed point on earth. Only four GPS satellites shown represent the minimum number; In practice, there are a greater number of GPSs that orbit around the earth with precision mesh nets.

The GPS receiver 120 (FIG. 3) installed on the moving object 5 on the earth's surface 8 can determine spatial coordinates based on the received GPS signals 11, 21, 31 and 41, but with partial system characteristics and The accuracy of the approximate ± 100 meters is due to an error source caused in part by environmental disturbances. In order to improve measurement accuracy, so-called differential GPS is provided at a fixedly installed reference GPS receiving and processing unit 50 position 6 where the position coordinates are known precisely. From the GPS signals 12, 22, 32 and 42 received by the unit and the known position coordinates, the reference GPS receiving and processing unit 50 continuously outputs error values for which the correction data 7 is formed in a standardized data format. The data is transmitted to the GPS receiver 120 on the moving object 5 in real time. The unit 50 includes, for example, one or more GPS receivers as well as downstream computers. In such a computer the reference station software can in particular supply correction data 7. Alternatively, the unit 50 may be configured as one GPS receiver in which the generation of the correction data 7 takes place via an integral component. Based on the correction data 7 received by the mobile GPS receiver 120, the measured instantaneous position coordinates can be corrected with a precision of up to ± 1 meter. These values are effective only in any surroundings around the reference GPS receiving and processing unit 50.

In order to ensure wide area transmission of the correction data 7, the system according to the invention provides that the correction data 7 is transmitted in a radio program signal. For this purpose, the coordinates are determined (measured values) from the GPS signals 12 to 42 received by the reference GPS receiving and processing unit 50 via the satellite receiving antenna 51 as shown in FIG. 2; However, these coordinates are distorted due to various effects. By comparing with the position coordinates of the receiving antenna 51 exactly known, the reference GPS receiving and processing unit 50 produces standardized correction data 7. These correction data 7 are processed by the downstream computer 60 and supplied to the RDS coder 70 of the radio station 80 (FM or AM station). The RDS coder 70 inserts the processed correction data 8 into an RDS data stream conforming to the format of the manner described in detail below. The radio station 80 emits an RDS signal 9 added to a large area within the radio program signal via the transmitter mast 81 of the station.

The radio receiver 90 (FIG. 3) installed in the moving object 5 is tuned to the carrier frequency of the radio station 80 and processed together with the radio program signal of the radio station 80 via the receiver antenna 91 of the receiver. The RDS signal 9 added by the correction data 8 is received. In the downstream (RDS) decoder 100, the RDS signal 9 is supplied to a computer 110 which is separated from the radio program signal, decoded and processed correction data 8 separated from the RDS signal and normalized from the computer. The correction data 7 are reconstructed. From the computer 110, the reconstructed, standardized correction data 7 is supplied and measured to the GPS receiver 120 of the moving object 5 which receives the GPS signals 11 to 41 via the satellite receiving antenna 119. Receive coordinates The derived measured coordinate values are corrected in the GPS receiver 120 with the aid of the reconstructed coordinate correction data 7. The GPS receiver 120 supplies the modified coordinate value 121 to the output device 130.

According to the initially cited standard, the correction data 7 (for GPS satellites 1,2,3,4, respectively) generated in the reference GPS receiving and processing unit 50 are useful pseudo range correction values for the calculation moment ( PRC data as identified below). In addition, the correction data formed in the reference GPS receiving and processing unit includes a value for the rate of change of the PRC data. In the following context, these rate of change values are identified as PRC data. From the PRC data, the actual PRC value is inferred from the actual moment that comes after the calculation moment of the PRC data, and the precision of the estimated actual PRC value is a precise range function in which the rate of change first picked up as the PRC data coincides with the rate of actual change.

For the transmission of the correction data 7, the present invention provides that a radio data system (RDS) for FM or AM radio is used, wherein the RDS data stream is modulated with a secondary carrier of, for example, 57 kHz, It is inserted into the program signal base of the FM or AM radio station to prevent listening. The data format of the RDS data stream consists of a sequence of periodically transmitted data blocks with RDS cycles, as shown in FIG. 4, and longer data separated from each other by shorter check words 10a, 20a, 30a, 40a. Blocks 10, 20, 30, and 40. In each case, the four data blocks 10. 20, 30, 40 form an RDS group with 37 bits of free data capacity. In the example shown in FIG. 4, the longer data blocks 10 and 20 comprise a program identification code (PI) and a program type code (PTY) according to the European RDS standard (CENELEC) EN 50067. The free data capacity of the RDS group is used to integrate the correction data for the GPS satellites, and the PRC data is used to identify each GPS satellite's identification (satellite number), time flag (time switch), scale factor and IOD flag (IOD switch). It is inserted into the block 40 together.

In order to reduce the group data capacity of the RDS signal cycle, i.e. the data volume of each satellite's PRC data and RRC data for 37 bits, the standardized data format of the GPS correction value (the standard for the differential GPS service discussed earlier) is a header. And does not transmit a check word (ferity). The check word (ferity) of the RTCM standard is easily omitted because the RDS data format each contains a format characteristic check word in a shorter data block due to two long data blocks. However, the abandonment of the header includes abandonment of successive transmissions of information (modified Z counts) taking into account the calculation moments of the correction values for all GPS satellites. In order to assign a correction value with respect to time in spite of this abandonment, the present invention recalculates the PRC data in the computer 60 (FIG. 2) in the last few minutes with the aid of the RRC data. This is illustrated by the following example:

At moment 12:01:11, the Z count has a value 71 (60 seconds plus 11 seconds after moment 12:00:00), the PRC value is estimated to be +10.32 m, and the RRC value is +0.98 m / s Is estimated.

At a rate of change (RRC value) of +0.98 m / s, the inverse calculation (Z count with value 60) for moment 12:01:00 is a PRC value of -0.46 m (+10.32 m minus 0.98 m / sx 11s). Cause.

The calculated back PRC data is transmitted with the RRC as processed correction data 8. The receiver end computer 110 extrapolates the back PRC data calculated with the aid of the computer internal Z counter for the relevant RRC data and the instantaneous actual values. This is illustrated by the following example.

At a rate of change (RRC value) of +0.98 m / s, the extrapolation for moment 12:01:12 (Z count with value 72) is +11.30 m (-O.46m plus O.98m / sx 12s). Cause PRC values).

To ensure that the computer 110 always recognizes that the PRC value received and calculated sufficiently finely will be effective, the above-described time flag (0 = even minute; 1 = odd minute) is added to block 40. Is sent to. In addition, the computer internal Z counts are occasionally synchronized by time information (modified Z counts), for example 1-2 times per minute, the time information being in accordance with FIG. 5 instead of preemption blocks 30 and 40 according to FIG. 4. Is sometimes emitted along with the station identification (station ID). In addition, Identification Marking (IOD) (Data Identification) sends all data and identification markings at different frequencies to the computer 110, which is necessary for the computer to reconstruct a standardized RTCM correction signal from the partial information arriving at the RDS data stream. To blocks 30 and 40 from time to time. The computer 110 derives a parity check word of the RTCM modified signal that matches the standard from the partial information received in accordance with the parity rules for embedding the signal and relating to the signal according to the standard.

In order to reduce the correction data per satellite for 37 bits, it is possible for 9 satellites to transmit all of the satellite's correction data in a single RDS group (37 bit capacity), decreasing from 680 bits to 333 bits (9x37), and RDS A playable assignment is achieved, in which the format is explicit in the RTCM data format. Therefore, in the case of transmission confusion, the loss of the RDS group no longer means that the correction data for all nine satellites is lost, as in the above state of the art, but the correction data for one satellite associated with the confused RDS group is lost. it means.

In this way, the system according to the invention can achieve significantly improved perks for transmission disruption.

In order to improve the flow of transmitted correction data, the PRC and RRC data associated with the remaining satellites are updated in the computer 110 after inserting all PRC and RRC data into the RDS group. In this way, the average lifespan of the modified data is reduced by more than half compared to the state of the art, where the modified data must be calculated for all satellites at a common moment and without updateability due to partial insertion into the RDS data stream. Must be sent.

An additional option for improving the flow of data is to insert PRC data, where the rate of change (RRC) is equal to or equal to an RDS data stream with a lower priority than the rapidly changing PRC data. It remains almost the same. Faster replay of poorly predicted RRC values by more updated RRC values further increases position correction prediction. In order to improve the above priority control for satellite selection, at least two predictions are calculated for each satellite, for example for a period of 20 seconds. One prediction is based on the actual PRC and RRC values, and the other prediction is based on the PRC and RRC values already sent. Some deviations in the predictions indicate errors that may be of different magnitude for each satellite so that this magnitude of error is used as a reference for prioritized decisions.

Claims (8)

It emits GPS signals 11, 21, 31, 41 that continuously change their position in relation to a fixed position on the earth and allow the GPS receiver 120 installed on the moving object 5 to determine its instantaneous position coordinates. The system for determining the position of the moving object 5 with the aid of a positioning navigation and navigation satellites (GPS satellites 1, 2, 3, 4), The precise position coordinates operate as known reference portions, and determine successive error values from successively received GPS signals 12, 22, 32, 42 and the known position coordinates of the place 6 and from which correction data ( 7) at least one GPS receiving and processing unit (50) for generating said correction data (7), Valid pseudo range correction values (PRC data) for the calculated moment, and A value for the rate of instantaneous change of the RRC data (RRC data); At least one radio station 80 having an RDS coder 70 for emitting correction data 7 generated as data of a radio data system signal (RDS signal) embedded in a program signal; A radio receiver 90 having an RDS decoder 100 for receiving and decoding an RDS signal installed in the moving object 5 and provided with correction data 7; And A computer (110) for separating correction data (7) from the decoded RDS signal and for supplying the correction data (7) to a GPS receiver (120) installed on a moving object (5), the receiver having a separate correction In the positioning system of a movable object, correcting the measurement result according to the value (7), a) the evaluation device 60 is arranged after the GPS receiving and processing unit 50, With the help of the relative change value ratio (RRC data) for the moment of the last full time, the PRC data calculated at a particular moment is recalculated, For each GPS satellite, discard the header provided in the standard format for the GPS correction signal, insert the recalculated PRC data along with the associated RRC data and the identification of the associated satellite into a single RDS group of RDS signal cycles, b) In the computer 110 arranged next to the RDS decoder 100 of the radio receiver 90, the recalculated PRC data is associated with the associated change value ratio (RRC data) and computer generated time information (internal Z count). Extrapolated in real time for each GPS satellite, c) The untransmitted header is reconstructed at the computer 110 into a check word and continuous time information and forms a standardized format of the correction data 7 together with the PRC data extrapolated for each GPS satellite and associated RRC data. The system, characterized in that configured to. The system according to claim 1, wherein after inserting all the processed correction data (8) for the GPS satellites in the RDS signal cycle, the PRC data and the RRC data are updated for all satellites. 3. The evaluation apparatus 60 according to claim 1 or 2, wherein the evaluation device 60 is assigned to a group of RDS signal cycles, in which time information is used by the computer 110 to synchronize time information (internal Z count) generated internally. And sometimes inserting time information derived from a received GPS signal. 4. The evaluation device (60) according to any one of claims 1 to 3, wherein the evaluation device (60) is assigned to a group of RDS signal cycles, in which data identification information is used by the computer (110) to reconstruct the corrected data (7). And sometimes inserting data identification information (IOD) derived from a received GPS signal. 5. The apparatus according to any one of claims 1 to 4, wherein the evaluation device continuously determines, for each GPS satellite, a precise range in which the rate of change last transmitted as RRC data coincides with the rate of actual change value, and prior control. And inserting the correction data for the satellites that match the actual data change on the first reference compared to the correction data for the satellites that match the rate of change in the RDS signal cycle for the first time. Positioning and navigation satellites (GPS satellites) that emit a GPS signal that continuously changes its position in relation to a fixed point on the earth and allows the GPS receiver 120 installed on the moving object 5 to determine instantaneous position and altitude coordinates. In the receiving device for determining the position of the moving object 5 with the help of the receiving device, as well as the value for the rate of change of the PRC data (RRC data), as well as the pseudo range correction value (PRC data), the effective calculation moment Designed to receive the configured correction data, wherein the correction data is emitted as data of a radio data system signal (RDS signal) embedded in a radio program signal, Apparatus (90, 100) for continuously receiving and decoding RDS signals provided with correction data, and A computer for separating correction data from said decoded RDS signal and for supplying correction data to a GPS receiver 120 installed on a moving object (5), said GPS receiver correcting measurement results according to the separated correction data In the positioning receiving apparatus of the movable object, For the evaluation of the processed correction data 8, the PRC data calculated at a particular moment is recalculated to the last total time moment with the aid of the relevant ratio of change values (RRC data), and the computer 110 is designed, a) The recalculated PRC data is extrapolated in real time for each GPS satellite with the help of the associated rate of change value (RRC data) and computer generated time information (internal Z count), b) The non-transmission header provided in the standardized format for the modified data is reconstructed into the test words and the continuous time information and forms the standardized format of the modified data along with the extrapolated PRC data and associated RRC data for each GPS satellite. A receiving device, characterized in that configured to. 7. A method according to claim 6, characterized in that the time information sometimes inserted into the group of RDS signal cycles and derived from the received GPS signal is used by the computer 110 to synchronize internal generated time information (internal Z count). Receiving device. 8. The computer 110 according to claim 6 or 7, wherein data identification information (IOD), sometimes inserted into a group of RDS signal cycles and derived from a received GPS signal, is adapted to reconstruct relevant data 7 in accordance with the standard. A receiving device, characterized in that used by.