Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2000-01-24
2001-02-13
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S207000, C701S213000, C701S214000, C340S988000, C342S357490, C342S357490, C342S357490
Reexamination Certificate
active
06188958
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention departs from a satellite navigation method according to the preamble of claim
1
.
The invention in particular is used in navigation in connection with GPS-satellites (Global Positioning System). For the navigation within a three-dimensional space a (satellite)-receiver, the geographic position of which shall be evaluated, always requires four different satellite communications (SV) at the same time. In navigation the ranges between the receiving antenna (receiver antenna) of the receiver to three different satellites, the positions of which are known and which can be received at this time are measured. The simultaneous reception of the signals of a fourth satellite is required for time synchronisation of the receiver to the system time of the satellites. Herewith the position of the receiving antenna within the three-dimensional space is determined.
BACKGROUND OF THE INVENTION
Since GPS-satellites transmit coded signals, range-measuring by a receiver may be implemented in different ways, namely:
By evaluating the received code signals (code measuring) or
By evaluating the carrier phases (carrier phase measuring).
Correlated errors may occur in these measurements between the receivers, which e.g. are due to satellite clock errors and changes in the troposphere and the ionosphere. Those errors are determined as corrections (correction values) for the mobile station. In a differential mode (DGPS) of GPS a range correction can be evaluated in a reference station from a comparison between a pseudo range for the reference station (range evaluated by satellite navigation between the reference station and a receiveable satellite) and a known geometrical range between the reference station and the received satellite. The pseudo range measurements of the mobile station are corrected by means of range corrections which are transmitted by the reference station by means of (data)-radio relay. Non-correlated errors may also appear between receivers, e.g. due to effects of multi-path propagation of the signals between the receivers. Those errors should be suppressed as much as possible since they cannot be reduced by the differential correction. For reducing the effects of non-correlated errors the measured value of the carrier phase is used, the measurement noise and multi-path propagation of which is within the mm and cm wavelength range. However, an ambiguity of the number of wavelengths from carrier phase measurement in a detrimental manner results since the measuring of the carrier phase in a phase-locked loop (PLL)-measuring device does not change in a displacement by a random integer number of the phase cycles. A known technique, the so-called “carrier-smoothed code” combines the code-values with the carrier phase values and suppresses herewith measurement noise and effects of multi-path propagation during code measurement. Herewith by means of the code phase measurement the Doppler shift or the range change from the satellite to the receiver, respectively, between two points of time is determined, and the phase ambiguities by means of a code measurement with the smoothed phase are approximately evaluated. The time constant of the filter of the present technique with the carrier-smoothed code is limited by the ionosphere error since this error has a counter-current behavior during code and phase measurement. In the differential operational mode with the carrier-smoothed code a large filter time constant may reduce the non-correlated errors between the reference and the mobile station. However, a large filter constant in a disadvantageous manner also distorts the ionospheric error in the differential correction which per se is correctable so that the ionospheric error may not completely be corrected at the mobile station. With such a method, which is known as the DGPS-navigation method, a determination of the position of the receiver with an accuracy of approximately ±2 m to ±3 m (95%) may be attained. This accuracy in the case of some applications, e.g. in approach of landing of a commercial aircraft, is not sufficient, in particular in the case where this approach of landing is to be made under socalled CATIIIb conditions, i.e. at a visual range of zero.
SUMMARY OF THE INVENTION
It is the object of the invention to devise a method according to this species, with which a reliable and accurate navigation is possible, in particular during the approach of landing of an aircraft.
This object is achieved according to the features as indicated within the characterizing portion of claim
1
. Advantageous embodiments and/or developments may be taken from the further claims.
The first advantage of the invention consists in that an accurate and quick determination of the position becomes possible so that in particular a complete landing of a commercial aircraft may be performed completely automatic. During the approach of landing, it is possible in a reliable manner to accurately determine the position and velocity also under possible influences of long-wave multi-path propagations so that higher accuracies than under the mentioned CAT IIIb-conditions are attainable.
A second advantage consists in that the method for the reference station is nearly independent from the type of the (mobile) receiver and the included evaluation of the received GPS-satellite signals.
Further advantages result from the following description.
REFERENCES:
patent: 4891655 (1990-01-01), Joguet et al.
patent: 5311194 (1994-05-01), Brown
patent: 5471217 (1995-11-01), Hatch et al.
Gu Xiaogang
Leiprecht Ansgar
Beaulieu Yonel
Cuchlinski Jr. William A.
Honeywell International , Inc.
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