Communications: directive radio wave systems and devices (e.g. – Directive – Including a satellite
Patent
1997-09-25
2000-01-25
Issing, Gregory C.
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a satellite
701215, G01S 502
Patent
active
060183136
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention relates to a system according to the preamble of claim 1 and to a receiving arrangement according to the preamble of claim 6. A system and a receiving arrangement of this type were disclosed in DE 41 36 136 C1.
For the position finding and navigation of travelling objects, a satellite-based method which was introduced under the name "Global Positioning System (GPS System)".sup.1 is known, wherein so-called GPS satellites emit the time in addition to their orbital data with great precision, for example, on the 1.575 GHz frequency. The orbit of the GPS satellites extends such that their position changes continuously relative to a stationary point on the earth. A GPS receiver calculates the distance to the individual GPS satellites by measuring the time which the signal takes to travel from the satellite to the receiver. Since the positions of the GPS satellites are known, the space coordinates of the receiver location on the earth and the errors of the internal clock of the GPS receiver can be calculated by means of four GPS satellites. However, this only accomplishes a precision of approx. .+-.100 meters. Since this precision is not sufficient for many applications, it is known (RTCM Recommended Standards for Differential GPS Service", Version 2.1, Chapter 4, of Jan. 3, 1994, published by Radio Technical Commission for Maritime Services, 655 Fifteenth Street, NW, Suite 300, Washington, D.C. 20005 U.S.A).sup.2 to determine error values from a reference GPS receiver whose location coordinates are known precisely and to transmit them in the form of correction data. The GPS measurement data determined by a mobile GPS receiver are corrected with the assistance of the received correction data. The data format of the correction data defined in the RTCM Standard ensues from the above-mentioned passage in the literature, pages 4-3 and 4-8 as follows: appears in English in the original German text. Recommended Standards . . . " to " . . . Chapter 4" and "Radio Technical Commission . . . " to " . . . U.S.A)" appear in English in the original German text.
For each individual GPS satellite, there is a separate "message" comprised of a scale factor, an indication regarding the error range (UDRE=User Differential Range Error), an identification of the satellite concerned (satellite ID), so-called pseudo range correction values (PRC=Pseudo Range Correction), a check signal (parity), values for the expected rate of change of the PRC data (RRC=Rate Range Correction), and an indication specifying the orbital data to which the correction values are related (issue of data). The individual "messages" are joined directly to one another to form a string, with the string being divided into a sequence of words of 30 bit length regardless of the boundaries of the individual "messages". Each string of "messages" is preceded by a header comprised of two words of 30 bit length so as to mark the beginning of each string. The first 30 bit word of the header is comprised of a run-in sequence (preamble), followed by an identification of the type of the subsequent messages (message type), an identification of the transmitting station (station ID) and a check word (parity). The second 30 bit word of the header is comprised of a time information (modified Z-count), a sequence number, an indication regarding the total length of the subsequent "messages" (length of frame), an indication regarding the condition of the transmitting station (station health) and a check word (parity).
For the real-time transmission of the correction data, DE 41 36 136 C1 discloses to use the existing transmitter network of the broadcast corporations, with the correction data being inserted into free groups of 37 bit each of the cyclically transmitted radio data (RDS) signal, which groups are being transmitted inaudibly within the radio program signals. Since the data format of the radio data system does not match the above-described data format of the GPS correction data, the header and the subsequent "messages" of each string are divided
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Engelmayer Wolfgang
Lindstrot Walter
Raven Paul
Sandmann Stefan
Schoemakers Guenter
Issing Gregory C.
Spencer George H.
Tilmar Konle
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