Position-fixing system
First Claim
1. A position-fixing system wherein a user station (N) determines its position from the ranges to and the positions of several reference stations (Sj) carried by satellites, the ranges being measured by one-way ranging, and wherein the signals used for position-fixing purposes are radio-frequency signals, characterized in that the reference stations (Sj) are controlled so that only one of the reference stations within sight of the user station is active at any given time, that the ranges from each of several ground stations (Bi) to each reference station (Sj) are measured by a two-way ranging method, wherein an interrogator station, the reference station or the ground station, transmits interrogation signals while a transponder station, the ground station or the reference station, transmits reply signals, and that the position of a reference station is defined by the intersection of spheres having their centers at the ground stations, the radii of the spheres being the ranges from the respective ground station to the respective reference station and further characterized in that the interrogation signals and the reply signals each consist of two parts (FIG. 2) the first of which is a synchronization preamble (SY), and the second of which indicates when the interrogation signal was transmitted (tj) from the interrogator station and received (ti) by the transponder station, respectively.
2 Assignments
0 Petitions
Accused Products
Abstract
Several satellites serving as reference stations (Sj) for a user revolve about the earth in different orbits. At least four reference stations must be within sight of a user station (N) at the same time. The user station measures the ranges to at least four reference stations by one-way ranging. From these ranges and the positions of the reference stations, which are transmitted as data words, the user station determines its position.
To determine the positions of the reference stations, the ranges from the respective reference station to at least three ground stations (Bi) are measured by two-way ranging. From these ranges and the known positions of the ground stations, the position of the reference station is obtained. The interrogation signals of all reference stations contain the same basic signal (Ks), which represents a pseudorandom code. The reply signals of the ground stations contain differently coded signals (KBi), so that the ground stations are identifiable with the aid of the codes assigned to them. If the interrogation and reply signals contain the times of transmission (tj) and arrival (ti), respectively, of the interrogation signal, and the signal transit times are measured, the clocks of the reference stations and of the ground stations can be synchronized.
70 Citations
8 Claims
- 1. A position-fixing system wherein a user station (N) determines its position from the ranges to and the positions of several reference stations (Sj) carried by satellites, the ranges being measured by one-way ranging, and wherein the signals used for position-fixing purposes are radio-frequency signals, characterized in that the reference stations (Sj) are controlled so that only one of the reference stations within sight of the user station is active at any given time, that the ranges from each of several ground stations (Bi) to each reference station (Sj) are measured by a two-way ranging method, wherein an interrogator station, the reference station or the ground station, transmits interrogation signals while a transponder station, the ground station or the reference station, transmits reply signals, and that the position of a reference station is defined by the intersection of spheres having their centers at the ground stations, the radii of the spheres being the ranges from the respective ground station to the respective reference station and further characterized in that the interrogation signals and the reply signals each consist of two parts (FIG. 2) the first of which is a synchronization preamble (SY), and the second of which indicates when the interrogation signal was transmitted (tj) from the interrogator station and received (ti) by the transponder station, respectively.
Specification