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EP-4741882-A1 - ANTENNA PHASE CENTER AND SNR CALIBRATION FOR DUAL AND MULTI-ANTENNA GNSS RECEIVERS

EP4741882A1EP 4741882 A1EP4741882 A1EP 4741882A1EP-4741882-A1

Abstract

Described herein are a system and method for compensating for antenna phase center and SNR variation in dual- and multi-antenna GNSS receivers. Satellite signals are received at a GNSS receiver having a plurality of antennas including a first antenna and a second antenna. GNSS measurements are collected based on the received wireless signals using the first and second antennas. A horizontal orientation of the plurality of antennas with respect to a transmitting satellite is estimated. One or both of an antenna phase center correction and an SNR correction are obtained from one or more calibration tables based on the horizontal orientation. A geospatial position of the GNSS receiver is estimated using the GNSS measurements and one or both of the antenna phase center correction and the SNR correction.

Inventors

  • CLARE, Adam
  • WEISENBURGER, SHAWN
  • BEST, Gregory

Assignees

  • Trimble Inc

Dates

Publication Date
20260513
Application Date
20241223

Claims (15)

  1. A method comprising: receiving wireless signals from a satellite at a global navigation satellite system (GNSS) receiver having a plurality of antennas including a first antenna and a second antenna; collecting, based on the received wireless signals, first GNSS measurements using the first antenna and second GNSS measurements using the second antenna; estimating a horizontal orientation of the plurality of antennas with respect to the satellite; obtaining one or both of an antenna phase center (APC) correction and a signal-to-noise ratio (SNR) correction from one or more calibration tables based on the horizontal orientation; and estimating a geospatial position of the GNSS receiver using the first GNSS measurements, the second GNSS measurements, and one or both of the APC correction and the SNR correction.
  2. The method of claim 1, wherein the horizontal orientation of the plurality of antennas includes or is estimated based a heading of the plurality of antennas.
  3. The method of claim 1 or 2, further comprising: estimating a vertical orientation of the plurality of antennas with respect to the satellite, wherein one or both of the APC correction and the SNR correction are obtained from the one or more calibration tables further based on the vertical orientation.
  4. The method of claim 3, wherein the horizontal orientation and the vertical orientation are estimated using the first GNSS measurements and the second GNSS measurements.
  5. The method of claim 4, wherein the horizontal orientation and the vertical orientation are estimated further using one or both of a previous APC correction and a previous SNR correction obtained previously from the one or more calibration tables based on a previous horizontal orientation and a previous vertical orientation.
  6. The method of claim 3, further comprising: collecting an orientation measurement using an orientation sensor of the GNSS receiver, wherein the horizontal orientation and the vertical orientation are estimated using the orientation measurement.
  7. The method of any one of claims 1-6, further comprising: storing the one or more calibration tables at a memory of the GNSS receiver, wherein obtaining one or both of the APC correction and the SNR correction includes retrieving one or both of the APC correction and the SNR correction from the memory.
  8. A non-transitory computer-readable medium comprising instructions that, when executed by one or more processors, cause the one or more processors to perform operations comprising: collecting, based on wireless signals received from a satellite at a global navigation satellite system (GNSS) receiver having a plurality of antennas including a first antenna and a second antenna, first GNSS measurements using the first antenna and second GNSS measurements using the second antenna; estimating a horizontal orientation of the plurality of antennas with respect to the satellite; obtaining one or both of an antenna phase center (APC) correction and a signal-to-noise ratio (SNR) correction from one or more calibration tables based on the horizontal orientation; and estimating a geospatial position of the GNSS receiver using the first GNSS measurements, the second GNSS measurements, and one or both of the APC correction and the SNR correction.
  9. The non-transitory computer-readable medium of claim 8, wherein the horizontal orientation of the plurality of antennas includes or is estimated based a heading of the plurality of antennas.
  10. The non-transitory computer-readable medium of claim 8, wherein the operations further comprise: estimating a vertical orientation of the plurality of antennas with respect to the satellite, wherein one or both of the APC correction and the SNR correction are obtained from the one or more calibration tables further based on the vertical orientation.
  11. The non-transitory computer-readable medium of claim 10, wherein the horizontal orientation and the vertical orientation are estimated using the first GNSS measurements and the second GNSS measurements.
  12. The non-transitory computer-readable medium of claim 11, wherein the horizontal orientation and the vertical orientation are estimated further using one or both of a previous APC correction and a previous SNR correction obtained previously from the one or more calibration tables based on a previous horizontal orientation and a previous vertical orientation.
  13. The non-transitory computer-readable medium of claim 10, wherein the operations further comprise: collecting an orientation measurement using an orientation sensor of the GNSS receiver, wherein the horizontal orientation and the vertical orientation are estimated using the orientation measurement.
  14. The non-transitory computer-readable medium of claim 8, wherein the operations further comprise: storing the one or more calibration tables at a memory of the GNSS receiver, wherein obtaining one or both of the APC correction and the SNR correction includes retrieving one or both of the APC correction and the SNR correction from the memory.
  15. A system comprising: one or more processors; and the computer-readable medium of any one of claims 8-14.

Description

BACKGROUND OF THE INVENTION Global navigation satellite systems (GNSS) are systems that use satellites in Earth orbit to provide geospatial positioning of receiving devices. Typically, wireless signals transmitted from such satellites can be used by GNSS receivers to determine their position, velocity, and time. Examples of currently operational GNSSs include the United States' Global Positioning System (GPS), Russia's Global Navigation Satellite System (GLONASS), China's BeiDou Satellite Navigation System, the European Union's (EU) Galileo, Japan's Quasi-Zenith Satellite System (QZSS), and the Indian Regional Navigation Satellite System (IRNSS). Today, GNSS receivers are used in a wide range of applications, including navigation (e.g., for automobiles, planes, boats, persons, animals, freight, military precision-guided munitions, etc.), surveying, mapping, and time referencing. The accuracy of GNSS receivers has improved drastically over the past few decades due to several technological improvements. One such improvement is the use of differential measurement techniques, in which GNSS signals received by a fixed receiver are used to generate correction data that is communicated to a mobile receiver. Typically, a roving receiver (or simply "rover") receives the correction data from a reference source or base station that already knows its exact location, in addition to receiving signals from GNSS satellites. To generate the correction data, the base station first tracks all the satellites in view and measures their pseudoranges. Next, the base station computes its position and compares the computed position to its known position to generate a list of corrections needed to make the measured pseudorange values accurate for all visible satellites. The correction data is then communicated to the rover, which applies these corrections to its computed pseudoranges to produce a more accurate position. This technique may be referred to as differential GNSS. Another improvement to GNSS accuracy came through the use of real-time kinematic (RTK) measurement techniques, in which the rover determines its position relative to a base station by comparing the phases of carrier waves received at the rover with those measured at the base station. Multiple satellite signals transmitted by GNSS satellites are used to measure these carrier phases. Once the rover receives a set of carrier phases from the base station, it compares them with its own set of carrier phases. This comparison allows the rover to calculate a vector between itself and the base station. With the known coordinates of the base station, which can be communicated to the rover by the base station, the rover can compute its precise location within a specific coordinate frame. The carrier signal used in RTK has a shorter wavelength than the width of a PRN code, enabling more accurate distance measurement. RTK enables fast and centimeter-level positioning anywhere within a large area. Another positioning technology that provides centimeter-level positioning without the need for a local base station relies on a network of reference stations strategically located around the world. These reference stations continuously collect precise GNSS data and monitor satellite signals. The data collected by the reference stations is sent to a centralized processing center. In the processing center, advanced algorithms and models are employed to compute highly accurate corrections for satellite orbits, clock errors, and atmospheric conditions. The computed correction data is communicated to the rover via satellites (which act as relay stations) or via cellular or IP networks. The rover receives these correction signals and uses them to enhance its position calculation in real-time by accounting for systematic errors and distortions present in the GNSS signals. SUMMARY OF THE INVENTION A summary of the various embodiments of the invention is provided below as a list of examples. As used below, any reference to a series of examples is to be understood as a reference to each of those examples disjunctively (e.g., "Examples 1-4" is to be understood as "Examples 1, 2, 3, or 4"). Example 1 is a method comprising: receiving wireless signals from a satellite at a global navigation satellite system (GNSS) receiver having a plurality of antennas including a first antenna and a second antenna; collecting, based on the received wireless signals, first GNSS measurements using the first antenna and second GNSS measurements using the second antenna; estimating a horizontal orientation of the plurality of antennas with respect to the satellite; obtaining one or both of an antenna phase center (APC) correction and a signal-to-noise ratio (SNR) correction from one or more calibration tables based on the horizontal orientation; and estimating a geospatial position of the GNSS receiver using the first GNSS measurements, the second GNSS measurements, and one or both of the APC correction and the SN