Western Atlas International, Inc.

Massachusetts Institute of Technology

Trueposition, Inc.

Western Geophysical Co.

Aero Service Div, Western Geophysical

Charles C Counselman, Iii

Louis A Stilp

Donald H Steinbrecher

Timothy D Hall

Instantaneous radio positioning method and system. Signals from a plurality of spatially distributed transmitters are received at a known reference position and at an unknown position to be determined. A composite of the radio signals, simultaneously including a component signed from each of the transmitters, is digitized and then processed to measure phases that is then digitized. Ambiguity is resolved by finding the location in parameter space of the maximum of an ambiguity function related to sets of phase-measurement data. Position is determined at a point in time without keeping track of phase history.

Instantaneous radiopositioning using signals of opportunity

A wireless location system receives signals transmitted by wireless telephones at a plurality of signal collection sites. To improve the accuracy of the location information, the system synthesizes greater bandwidth, and thus greater time resolution, than would otherwise be available. The location system commands an MTSO to make the wireless transmitter to be located change frequency channels, and a doubly-differenced carrier phase of the transmitted signal, or the time difference of arrival, is observed at each of many frequencies spanning the widest possible bandwidth. The phase-measurement data from these many frequencies are combined to resolve the inherent integer-wavelength ambiguity. To begin the process of ambiguity resolution, single-frequency channel, doubly-differenced, group delay measurements are used to resolve the ambiguity in the doubly-differenced phase difference between the most closely spaced frequency channels. The invention may be utilized to obtain a bandwidth greater than the typical 20 KHz bandwidth of the signals to be cross-correlated (in either the time or frequency domains) in a cellular telephone location application, With such bandwidth synthesis, up to the 12.5 MHz bandwidth allocated by the FCC to each cellular system operator may be exploited for location purposes.

Bandwidth synthesis for wireless location system

This invention provides a method and apparatus for determining position from code modulated, suppressed carrier signals received from satellites, in which a digital composite of the signals received from a plurality of satellites is formed at a first point, the digital composite is processed to measure the carrier phase of the signal from each of the plurality of satellites to derive computer data, and said computer data are combined with data derived from measurements of signals received from the same plurality of satellites at another point, to determine position data.

System for determining position from pseudorandomly modulated radio

Method and system for determining position from suppressed carrier signals transmitted by satellites in which a digital representation of the satellite signals is sampled and distributed for simultaneous measurement in synchronous parallel circuits. The phases of suppressed carriers implicit in the signals are combined in a time series of measurements with phase data from a second receiver to determine position.

System for determining position from suppressed carrier radio waves

The invention is a system for determining position by measuring phases of suppressed carrier-waves implicit in radio signals received from earth-orbiting satellites which include receiving the signals from a plurality of satellites simultaneously by means of an omnidirectional antenna, separating the received signals into first and second portions representing different radio-frequency bands and correlating the first portion with the second portion to obtain data representing the phases of the carrier-waves for a plurality of the satellites simultaneously.

A method and a system are disclosed for measuring the baseline vector b between a pair of survey marks on the ground by radio interferometry using radio signals broadcast from the earth orbiting satellites of the NAVSTAR Global Positioning System (GPS), the radio signals broadcast by the satellites being double-sideband modulated with their carriers suppressed. An antenna is positioned at each survey mark. The signals received by one antenna during a predetermined time span are separated into upper and lower sideband components. These separate components are filtered, converted to digital form, and then multiplied together. Their product is analyzed digitally by means of correlation with quadrature outputs of a local oscillator to determine the power, and the phase relative to that local oscillator, of the carrier wave that is implicit in the double-sideband signal being received from each satellite. Differences in Doppler shift are utilized to distinguish the carriers of different satellites. The signals received at the same time by the other antenna are processed in the same manner. Thus, the powers and carrier phases of the signals from a plurality of satellites are measured simultaneously and numerical data representing the measurement results are obtained at each survey mark. The measurements are performed in real time at each mark without reference to signals that are received at any other place and without knowledge of any of the coded signals that modulate the GPS carriers. The data from the measurements performed simultaneously but independently at the two survey marks, once per second for a predetermined time span, are then processed together to determine the baseline vector that extends from one mark to the other. Two methods of processing are disclosed in either method, an 'ambiguity function' is computed which is a function of the measurement data and of a trivial value of the baseline vector. The vector space of b is systematically searched to find the unique value of b that maximizes the computed function. This value of b is taken to be the desired determination of b. By using signals from a plurality of five satellites and a time span of about 5000 seconds, a baseline vector determination can be obtained by the method of the present invention with an accuracy of about 5 millimeters in each coordinate for a baseline length of about 100 meters.

System for simultaneously deriving position information from a plurality

A method and a system are disclosed for measuring the baseline vector b between a pair of survey marks on the ground by radio interferometry using radio signals broadcast from the earth orbiting satellites of the NAVSTAR Global Positioning System (GPS), the radio signals broadcast by the satellites being double-sideband modulated with their carriers suppressed. The signals received by one antenna during a predetermined time span are separated into upper and lower sideband components. These separate components are filtered, converted to digital form, and then multiplied together. Differences in Doppler shift are utilized to distinguish the carriers of different satellites. Thus, the powers and carrier phases of the signals from a plurality of satellites are measured simultaneously and numerical data representing the measurement results are obtained at each survey mark. The measurements are performed in real time at each mark without reference to signals that are received at any other place and without knowledge of any of the coded signals that modulate the GPS carriers.

Techniques are disclosed for determining orbital data of space borne vehicles including earth satellites such as those of the NAVSTAR Global Positioning System. Each of a set of such satellites transmits signals which include carrier waves which may be suppressed, or only implicity present. The signals are received from the observable satellites concurrently by means of an antenna at each of at least three ground stations forming a network of baselines. The stations are arrayed such that the ratio of the maximum to the minimum baseline length is much greater than one. From the signals received at a station pair forming each baseline a time series of doubly-differenced phase measurement data is formed which is biased by an integer number of cycles of phase. The data series for different satellite and station pairs are processed together to determine the orbits of the satellites and the doubly-differenced phase biases. Unique determination of the integer values of at least some of the biases is facilitated by the above noted spatial arrangement of the stations such that the ratio of the maximum to the minimum baseline length is much greater than one. This integer bias determination enhances the accuracy of the related orbit determination. Unique determination of the integer values of at least some of the doubly-differenced carrier phase biases may also be facilitated by the use of a plurality of carrier frequencies with the ratio of the maximum to the minimum frequency being much greater than one.

Techniques for determining orbital data

Method and apparatus are disclosed for accurately determining position from GPS satellites and received on a ship using C/A code group delay observable TAU, 308 f.sub.o implicit carrier phase observable PHI, L1 band implicit f.sub.o carrier residual phase observable PSI.sub.L1, and L2 band implicit f.sub.o carrier residual phase observable PSI.sub.L2. A precise measurement of the group-phase delay range to each satellite is made based upon the L1 center frequency carrier phase. A correction for ionospheric effects is determined by simultaneous observation of the group delays of the wide bandwidth P code modulations in both the L1 and L2 bands. These group delays are determined by measuring the phases of carrier waves implicit in the spread-spectrum signals received in both bands. These carriers are reconstructed from both the L1 and L2 band signals from each satellite without using knowledge of the P code. The unknown biases in the L1 center frequency carrier phase range measurements are determined from simultaneous, pseudorange measurements, with time averaging. The instantaneous position of the ship may then be determined from the ranges so determined, with both the bias and the ion-spheric effects having been eliminated.

Method and system for determining position on a moving platform, such as

A method and a system are disclosed for measuring the baseline vector b between a pair of survey marks on the ground by radio interferometry using radio signals broadcast from the earth orbiting satellites of the NAVSTAR Global Positioning System (GPS), the radio signals broadcast by the satellites being double-sideband modulated with their carriers suppressed. An antenna is positioned at each survey mark. The signals received by one antenna during a predetermined time span are separated into upper and lower sideband components. These separate components are filtered, converted to digital form, and then multiplied together. Their product is analyzed digitally by means of correlation with quadrature outputs of a local oscillator to determine the power, and the phase relative to that local oscillator, of the carrier wave that is implicit in the double-sideband signal being received from each satellite. Differences in Doppler shift are utilized to distinguish the carriers of different satellites. The signals received at the same time by the other antenna are processed in the same manner. Thus, the powers and carrier phases of the signals from a plurality of satellites are measured simultaneously and numerical data representing the measurement results are obtained at each survey mark. The measurements are performed in real time at each mark without reference to signals that are received at any other place and without knowledge of any of the coded signals that modulate the GPS carriers. The data from the measurements performed simultaneously but independently at the two survey marks, once per second for a predetermined time span, are then processed together to determine the baseline vector that extends from one mark to the other. Two methods of processing are disclosed. In either method, an 'ambiguity function', is computed which is a function of the measurement data and of a trial value b of the baseline vector. The vector space of b is systematically searched to find the unique value of b that maximizes the computed function. This value of b is taken to be the desired determination of b. By using signals from a plurality of five satellites and a time span of about 5000 seconds, a baseline vector determination can be obtained by the method of the present invention with an accuracy of about 5 millimeters in each coordinate for a baseline length of about 100 meters.

Method and system for determining position from signals from satellites

System and method are disclosed for determining position related data from spread spectrum signals using reconstructed carrier receivers with continuous wave interference rejection. The spread spectrum signals are collected at a mark with a substantially omni-directional antenna and continuous wave interference is then rejected at or near a selected frequency. The spread spectrum signals are then reconstructed to provide a continuous wave component at that frequency form which the position data may be derived. The data is derived without interference because the potentially interfering signals, if present, have been rejected before the components were reconstructed.

Continuous wave interference rejection for reconstructed carrier

Method and apparatus are disclosed for accurately determining position from GPS satellites and received on a ship using observations of C/A code group delay, L1 band center frequency carrier phase, L1 band 5.115 MHz implicit carrier phase, and L2 band 5.115 MHz implicit carrier phase. A precise measurement of the range to each satellite is made based upon the L1 center frequency carrier phase. A correction for ionospheric effects is determined by simultaneous observation of the group delays of the wide bandwidth P code modulations in both the L1 and L2 bands. These group delays are determined by measuring the phases of carrier waves implicit in the spread-spectrum signals received in both bands. These carriers are reconstructed from both the L1 and L2 band signals from each satellite without using knowledge of the P code. The unknown biases in the L1 center frequency carrier phase range measurements are determined from simultaneous, pseudorange measurements, with time averaging. The instantaneous position of the antenna receiving these signals, and therefore the ship, may then be determined from the ranges so determined, with both the bias and the ionospheric effects having been eliminated. Additional antennas are positioned on the ship and a seismic streamer towed by the ship to reject false signals, compensate for blockage of signals by the ship's structure, and determine the position of sensors in the streamer.

Multi-antenna gas receiver for seismic survey vessels

A method and a system are disclosed for measuring the baseline vector b between a pair of survey marks on the ground by radio interferometry using radio signals broadcast from the earth orbiting satellites of the NAVSTAR Global Positioning System (GPS), the radio signals broadcast by the satellites being double-sideband modulated with their carriers suppressed. An antenna is positioned at each survey mark. The signals received by one antenna during a predetermined time span are separated into upper and lower sideband components. These separate components are filtered, converted to digital form, and then multiplied together. Their product is analyzed digitally by means of correlation with quadrature outputs of a local oscillator to determine the power, and the phase relative to that local oscillator, of the carrier wave that is implicit in the double-sideband signal being received from each satellite. Differences in Doppler shift are utilized to distinguish the carriers of different satellites. The signals received at the same time by the other antenna are processed in the same manner. Thus, the powers and carrier phases of the signals from a plurality of satellites are measured simultaneously and numerical data representing the measurement results are obtained at each survey mark. The measurements are performed in real time at each mark without reference to signals that are received at any other place and without knowledge of any of the coded signals that modulate the GPS carriers. The data from the measurements performed simultaneously but independently at the two survey marks.

Method and system for determining position using signals from satellites

A circularly polarized microwave radio antenna which is constructed so that its phase center can be very easily and very accurately positioned with respect to a marker point over which the antenna is placed is disclosed. The antenna includes a ground plane, antenna elements in a common plane parallel thereto and supported by a perpendicular center post, separate feed lines for each element and a combining network all positioned symmetrically about an axial bore in the center post so that the phase center of the antenna is on the axis of the center post at the intersection with the upper surface of the ground plane. A graduated rod may be positioned in the bore to align the antenna with the marker point. The antenna is especially useful in microwave radio interferometry systems for measuring relative position vectors between survey marks on the ground using radio frequency signals transmitted from earth orbiting satellites but may be used in any application where accurate positioning of an antenna's phase center relative to a reference point is desired or required. The antenna can be easily reproduced with substantially identical electrical and mechanical characteristics.

Growing community of inventors

Belmont, MA, United States of America

Charles C Counselman, Iii