摘要:
Multiple geographically fixed reference stations, with precisely known locations, that each receive GPS signals send information to a central processing facility that generates a three dimension topographical gradient map or model of the differences between the known locations and the locations as calculated from the received GPS signals. GPS signals received by mobile users are communicated to the central processing facility whereupon the central processing facility, using the model, generates precise corrected locations of the mobile users which is sent back to the mobile users. The mobile users can use and display the locally generated position from the locally received GPS signals or the corrected position from the central processing facility.
摘要:
A receiver for position-determining ranging signals transmitted by earth-orbiting satellites uses a set of accumulators, each of which accumulates signal samples corresponding with a position along the rising edges of incoming PRN pulses. An MMT processor calculates the rising edges of the direct path component of the received signal, selects the accumulator whose content correspond to a reference value related to the pulse height of the direct path component and compares the timing of the samples in that accumulator with the timing of the reference value on a reference pulse.
摘要:
A GNSS receiver utilizes an antenna structure that two or more antennas that are spaced apart from their neighboring antennas by less than 1 wavelength of a GNSS satellite carrier signal of interest. The receiver calculates the orientation of the antennas directly from differences in the carrier phase angles measured at the two antennas, without resolving integer carrier cycle ambiguity.
摘要:
A system for enhancing location estimates by movable rovers including one or more base stations that engage in two way time transfer (TWTT) with the rovers. Each TWTT operation between a given base station and a given rover provides range measurements and clock differences between the base station and rover. The range measurements are based on the travel time of return TWTT signals and the clock differences are based on a phase offset of a code in the return TWTT signal and/or timing information included in the return TWTT signals.
摘要:
A GNSS receiver reduces the time to first fix by utilizing the properties of existing radiated signals of opportunity, such as AM or FM radio signals, television signals and so forth, to reduce the uncertainties associated with oscillator frequency and phase , and further utilizing an Almanac and battery backed-up date and time to determine the satellites in view and reduce the uncertainties associated with Doppler. The receiver may use multiple signals of opportunity to determine the city or local area in which the receiver is located based on the set of frequencies of the signals, and also to reduce search uncertainties for oscillator frequency by estimating an offset based on the differences between the frequencies of the respective signals of opportunity at the receiver and the nominal broadcast frequencies of the signals.
摘要:
A system to determine position, frequency and clock offsets over a network utilizing signals of opportunity transmitted by one or more transmitters with known locations, the system includes a base receiver with a clock and a known position that determines ranges to the transmitters, takes a series of samples of the signals of opportunity and time tags the series with times of receipt, calculated times of transmission based on the calculated ranges, or both. The base receiver transmits the time tagged series and, as appropriate, computed ranges to the remote receivers. A given remote receiver saves and time tags samples of the signals of opportunity, correlates the time-tagged series with the saved samples, and calculates a time offset as a time difference of the times of receipt at the remote receiver and either the time of receipt at the base receiver or the time of transmission calculated at the base receiver. The remote receiver calculates position based on the time offsets, and as appropriate, the ranges provided by the base receiver. The elevations of the remote receivers may be calculated as part of the position calculations, determined iteratively based on constraining the Z coordinate to an average elevation, or determined from differences in air pressure sensor readings at the base and remoter receivers.
摘要:
A system to distribute accurate time and/or frequency over a network utilizing signals of opportunity transmitted by one or more local transmitters with known locations, the system includes a base receiver with a clock synchronized to a reference time scale such as GNSS or UTC time that saves a series of samples of the signals of opportunity and time tags the series with a calculated time of broadcast. A remote receiver saves samples of the signals of opportunity and correlates the series with the saved samples. The remote receiver calculates a time of transmission of saved samples that correspond to the series, determines a time offset as a difference in the time of broadcast calculated at the remote receiver and the time of broadcast calculated at the base receiver, and determines the time offset with respect to the base receiver. The base receiver further or instead phase locks to the signal opportunity and at predetermined intervals determines phase measurements of the integrated carrier frequency of the signal of opportunity and provides the phase information to the remote receiver. The remote receiver, which is also phase locked to the same signal of opportunity, uses the phase measurement information to frequency lock its clock to the base receiver clock by determining a frequency error based on the rate of change of phase measurements made at the base receiver and the remote receiver.
摘要:
A system for analyzing three-dimensional seismic data includes a plurality of digitizer units, each with a configuration of geophones, a data recording and control center, a base GPS receiver with an associated antenna with a substantially unrestricted view of the sky and at the respective digitizer units low-power slave GPS receivers that acquire and track GPS satellite signals using tracking assistance information provided by the base GPS receiver. The slave GPS receivers use the tracking assistance information to acquire and track GPS satellite signals from which the slave GPS receivers produce associated range information. The system batch processes the range information provided by the slave GPS receivers over an extended period of time to determine the precise positions of the respective slave GPS receivers. The system provides the position information to the slave GPS receivers, and the receivers locally produce associated timing signals that are based on the GPS codes. If a particular slave GPS receiver cannot, at a given time, track any GPS satellite signals, a nearby slave GPS receiver supplies timing information required for the geophone data gathering operations.
摘要:
An anti-jamming subsystem for a jamming signal originating along the horizon includes an anti-jamming antenna with a horizontal reception pattern constrained to receive signals originating along the horizon. The subsystem receives the signals from the anti-jamming antenna and a reference antenna, which has a half hemispherical reception pattern looking skyward. The subsystem utilizes associated phase information to phase shift the signals received by the anti jamming antenna and produce an anti-jamming signal, and combines the anti jamming signal with the signals received by the reference antenna to produce signals in which the interference from the jamming signal originating along the horizon is actively cancelled and the phase and timing information of signals received by the reference antenna from at least higher elevation satellites is preserved. The horizontal reception pattern of the anti-jamming antenna may be circular or directional toward a known jammer positioned along the horizon.
摘要:
A system for generating and utilizing a look-up mechanism consisting of one or more phase difference error maps, tables and/or mathematical models calculates the respective maps, tables and/or models by placing a short baseline or ultra-short baseline antenna array in a known location and known orientation, determining angles of incidence of incoming GNSS satellite signals with respect the antenna array and calculating expected carrier phase differences between respective pairs of antennas, calculating measured carrier phase differences between the respective pairs of antennas, and determining carrier phase difference errors using the expected and measured carrier phase differences. The carrier phase difference errors are then recorded in the look-up mechanism, with the maps and, as appropriate, look-up tables for the respective pairs of antennas being indexed by angles of incidence. Thereafter, the system utilizes the look-up mechanism when determining the unknown orientation of the antenna structure. For respective pairs of antennas, the system enters the look-up mechanism based on angles of incidence determined from a calculated orientation, and uses the retrieved values in the calculation of a corrected orientation, to compensate for phase distortion.