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US-12618983-B2 - Methods and systems for excess path length corrections for GNSS receivers

US12618983B2US 12618983 B2US12618983 B2US 12618983B2US-12618983-B2

Abstract

Methods and systems for estimating and using excess path length (EPL) corrections in GNSS receivers are described. A method can estimate the EPLs using a selection of line of sight and non line of sight pseudorange measurements, and these EPLs can be used to correct non selected non-line of sight pseudoranges. In one embodiment, a cloud based system can receive data from a crowd source set of EPL corrections (e.g., from GNSS receivers in an urban canyon environment) and then can develop a crowd sourced set of EPL corrections and then provide to GNSS receivers (some of which may part of the crowd of GNSS receivers) the crowd sourced set of EPL corrections. The EPL corrections can be used to improve position solutions in, for example, an urban canyon.

Inventors

  • Lionel Garin

Assignees

  • ONENAV, INC.

Dates

Publication Date
20260505
Application Date
20230206

Claims (9)

  1. 1 . A method of operating a global navigation satellite system (GNSS) system, the method comprising: receiving a set of estimated excess path lengths (EPLs) from one or more GNSS receivers, each of the estimated EPLs associated with an approximate location of the one or more GNSS receivers and a GNSS satellite's (SV's) position in a representation of sky above the approximate location at the approximate location at a time when pseudoranges were collected to determine the approximate location; receiving the approximate location for each estimated EPL; receiving or determining the GNSS SV's position in the representation of sky at the time and the approximate location; selecting a bin based on the SV's position in the representation and the approximate location; assigning one or more of the estimated EPLs to the selected bin; determining, for the selected bin, an adjusted EPL value based on a set of estimated EPLs assigned to the selected bin.
  2. 2 . The method as in claim 1 , wherein the method is performed in a cloud based system that communicates with systems containing the one or more GNSS receivers and wherein the position of a GNSS SV is specified in a coordinate system that is one of: (a) azimuth and elevation; (b) a cartesian coordinate system; (c) a polar coordinate system; (d) a spherical coordinate system; or other coordinate systems that specify position relative to the approximate location.
  3. 3 . The method as in claim 2 , wherein the cloud based system further receives estimated EPL uncertainty for each EPL in the set of estimated EPLs.
  4. 4 . The method as in claim 2 , wherein the elevation and azimuth for each SV is determined from SV ephemeris data for each SV.
  5. 5 . The method as in claim 4 , wherein the assigning is based on a match between an estimated EPL's associated SV elevation and azimuth and a bin's elevation and azimuth and approximate location.
  6. 6 . The method as in claim 5 , wherein the method further comprises: storing the adjusted EPL value in a database that is indexed by several precise grid locations and SV elevation and SV azimuth.
  7. 7 . The method as in claim 6 , wherein the adjusted EPL is computed as a weighted sum of the set of estimated EPLs assigned to the selected bin.
  8. 8 . The method as in claim 1 , wherein the method further comprises: transmitting the adjusted EPL to another GNSS receiver for use in the another GNSS receiver to correct non-line of sight (NLOS) pseudoranges using the adjusted EPL.
  9. 9 . The method as in claim 1 , wherein the method further comprises: transmitting the adjusted EPL to one of the one or more GNSS receivers for use in the one of the one or more GNSS receivers to correct non-line of sight (NLOS) pseudoranges using the adjusted EPL.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefits of the following US provisional patent applications: application No. 63/415,245, filed Oct. 11, 2022 and application No. 63/365,710, filed Jun. 2, 2022, and both of these provisional patent applications were filed by applicant oneNav, Inc and are hereby incorporated herein by reference. BACKGROUND This disclosure relates to the field of systems that determine a position of a radio receiver, and in particular this disclosure relates to global navigation satellite system (GNSS) receivers, such as a GNSS receiver that can determine the position of the GNSS receiver from signals received from GNSS satellites (GNSS SVs). Over the last few decades, the global navigation satellite systems have revolutionized our daily lives by providing the positioning and navigation services that play an important role in a variety of applications, spanning from transportation, agriculture, marine, and unmanned vehicles. As an example, the Uber Technologies, Inc., which is one of the pioneers in the smartphone-based transportation services and ride-hailing applications, is estimated to have over 93 million monthly active users worldwide. GNSS receivers first reached the commercial domain in the early 1980s. By considerably rapid advancement in the technology, the GNSS receivers have been revolutionized through different generations. The first generation of truly mobile receivers were L1 C/A code only. The second generation started in approximately 2010, when the GLONASS GNSS system became modernized and reliable. The third generation of the GNSS receivers added support for the Galileo system launched by the European Union in 2011. The evolution to the fourth generation took some time as it added a new capability, i.e., to support for single sideband L5 receivers, where the Beidou constellation of SVs, the Galileo constellation of SVs, and the US GPS constellation of SVs all have modernized signals. It is known that multipath effects on GNSS signals can cause large errors in position calculations in GNSS receivers. Multipath effects often occur in urban canyons where the same transmitted signal from a GNSS SV is reflected multiple times off surfaces of the buildings surrounding a street where a GNSS is located; diffraction effects can also occur causing a significantly polluted signal at the receiver. For example, the GNSS receiver in this case can receive both a line of sight (LOS) signal and multiple non-line of sight (NLOS) signals from the same SV. This can distort the pseudorange measurements made in the GNSS receiver, often to the point that the GNSS receiver measures a pseudorange that has significant error, resulting in a position solution that can be in error by more than 100 meters (100 m). This inaccuracy can result in situations in which a driver of a taxi service (e.g., Uber) is directed to the wrong side of the street by the GNSS receiver of the potential passenger who is waiting for the taxi service. This problem has been studied in the GNSS field, and many solutions have been proposed. One solution uses a classifier to classify signals as either LOS or NLOS; in this solution, the goal is to ignore or reject the NLOS signal and use only the LOS signal, if available, in the pseudorange measurement. This solution has been achieved with different approaches, including the use of machine learning (e.g., a neural network used to classify the signals). If the LOS signal is not available, then the signal is ignored (so no pseudorange measurement of the signal is provided as an output from the GNSS receiver). Another solution is described in U.S. Pat. No. 9,562,770 (inventor: Lionel J. Garin); in this approach, a signal visibility database, that contains information about the size (e.g., height, width and length) of signal obstacles (e.g., buildings in an urban canyon), is used to determine expected line of sight signals and expected NLOS signals at locations along a pathway (e.g., street in the urban canyon). This approach can use ray tracing algorithms with a 3D building map and the exact location of the SVs (at any given time) to provide location information without attempting to measure pseudoranges at the GNSS receiver. SUMMARY OF THE DESCRIPTION The methods and systems described herein can provide EPL corrections that can correct pseudorange measurements in a GNSS receiver, and these corrected pseudorange measurements can then be used in a position solution algorithm to produce a position of the GNSS receiver. In one embodiment, a method of operating a GNSS receiver can include the following operations: receiving GNSS signals from a set of GNSS satellites (SVs); determining a set of pseudoranges from the received GNSS signals; classifying each of the pseudoranges in the set of pseudoranges as one of a line of sight (LOS) pseudorange or a non-line of sight (NLOS) pseudorange; computing an initial position of the GNSS receiver using one of: (a)