Patents by Inventor Liwen L. Dai

Liwen L. Dai has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20120176271
    Abstract: A system and method for providing improved correction information to navigation receivers includes receiving, from a plurality of reference stations at known locations, a plurality of satellite navigation measurements of signals from a plurality of global navigation satellites. A state of the plurality of global navigation satellites is computed based on the received satellite navigation measurements. Baselines, each corresponding to a pair of the reference stations, are identified. For each identified baseline, computing floating and integer values for a double-differenced integer ambiguity. Double-differenced integer ambiguities that satisfy a set of predefined conditions are identified, and the computed state of the plurality of global navigation satellites is adjusted in accordance with an integer value constraint applied to each double-differenced integer ambiguity that satisfies the set of predefined conditions.
    Type: Application
    Filed: November 17, 2011
    Publication date: July 12, 2012
    Inventors: Liwen L. Dai, Ronald R. Hatch, Yujie Zhang, Min Wang
  • Publication number: 20120029810
    Abstract: In a system and method for navigating a moving object according to signals from satellite, a moving object receives satellite navigation signals from a number of satellites. The moving object also receives moving base data from a moving base. The received moving base data includes satellite measurement data of the moving base. At the moving object a relative position vector of the moving object relative to the moving base is determined, based on the received moving base data and the received satellite navigation signals. The moving object sends a signal reporting information corresponding to the relative position vector.
    Type: Application
    Filed: May 25, 2011
    Publication date: February 2, 2012
    Inventors: Liwen L. Dai, Yunfeng Shao
  • Publication number: 20110316735
    Abstract: A method for mitigating atmospheric errors in code and carrier phase measurements based on signals received from a plurality of satellites in a global navigation satellite system is disclosed. A residual tropospheric delay and a plurality of residual ionospheric delays are modeled as states in a Kalman filter. The state update functions of the Kalman filter include at least one baseline distance dependant factor, wherein the baseline distance is the distance between a reference receiver and a mobile receiver. A plurality of ambiguity values are modeled as states in the Kalman filter. The state update function of the Kalman filter for the ambiguity states includes a dynamic noise factor. An estimated position of mobile receiver is updated in accordance with the residual tropospheric delay, the plurality of residual ionospheric delays and/or the plurality of ambiguity values.
    Type: Application
    Filed: September 6, 2011
    Publication date: December 29, 2011
    Inventors: Liwen L. Dai, Daniel J. Eslinger, Richard T. Sharpe, Ronald R. Hatch
  • Patent number: 8035552
    Abstract: A method for mitigating atmospheric errors in code and carrier phase measurements based on signals received from a plurality of satellites in a global navigation satellite system is disclosed. A residual tropospheric delay and a plurality of residual ionospheric delays are modeled as states in a Kalman filter. The state update functions of the Kalman filter include at least one baseline distance dependant factor, wherein the baseline distance is the distance between a reference receiver and a mobile receiver. A plurality of ambiguity values are modeled as states in the Kalman filter. The state update function of the Kalman filter for the ambiguity states includes a dynamic noise factor. An estimated position of mobile receiver is updated in accordance with the residual tropospheric delay, the plurality of residual ionospheric delays and/or the plurality of ambiguity values.
    Type: Grant
    Filed: May 12, 2008
    Date of Patent: October 11, 2011
    Assignee: Navcom Technology, Inc.
    Inventors: Liwen L. Dai, Daniel J. Eslinger, Richard T. Sharpe, Ronald R. Hatch
  • Patent number: 7961141
    Abstract: In a method of mitigating errors in satellite navigation measurements at a satellite navigation receiver, respective single-frequency signals are received from respective satellites in a plurality of satellites in a satellite navigation system. Pseudorange and carrier-phase measurements corresponding to respective received single-frequency signals are calculated. These calculations include filtering the pseudorange and carrier-phase measurements in a Kalman filter having a state vector comprising a plurality of states, including a position state, a receiver clock state, and a plurality of bias states. Each bias state corresponds to a respective satellite in the plurality of satellites. The filtering includes updating the state vector. An estimated position of the satellite navigation receiver is updated in accordance with an update to the state vector.
    Type: Grant
    Filed: December 9, 2008
    Date of Patent: June 14, 2011
    Assignee: Navcom Technology, Inc.
    Inventors: Liwen L. Dai, Chaochao Wang, Daniel J. Eslinger, John Perry Genta
  • Patent number: 7961143
    Abstract: A method for performing integer ambiguity resolution in a global navigation satellite system is disclosed. A set of ambiguities, which are associated with carrier phase measurements of at least some of the signals received from the satellites in an identified set of satellites, are identified. Integer ambiguities are estimated and a best candidate set and a second best candidate set of integer ambiguity values are determined. Upon determining that the best set of integer ambiguity values fail to meet a discrimination test, each ambiguity for which integer ambiguity values in the best candidate set and second best candidate set fail to meet predefined criteria are removed from the set of ambiguities to produce a reduced set of ambiguities. The integer ambiguities in the reduced set of ambiguities are then resolved and an output is generated in accordance with the resolved integer ambiguities.
    Type: Grant
    Filed: May 12, 2008
    Date of Patent: June 14, 2011
    Assignee: Navcom Technology, Inc.
    Inventors: Liwen L. Dai, Daniel J. Eslinger, Richard T. Sharpe, Ronald R. Hatch
  • Publication number: 20110090116
    Abstract: A system and method for compensating for faulty satellite navigation measurements. A plurality of measurements in a system is received for a measurement epoch. A Kalman filter is used to calculate a state of the system for the measurement epoch based on the plurality of measurements, wherein the state of the system for the measurement epoch is calculated using a first closed-form update equation. A faulty measurement is detected in the plurality of measurements for the measurement epoch and a revised state of the system for the measurement epoch that compensates for the faulty measurement is calculated, using the calculated state of the system for the measurement epoch as an input to the revised state calculation, and using a revised closed-form update equation comprising the first closed-form update equation modified with respect to the faulty measurement.
    Type: Application
    Filed: October 5, 2010
    Publication date: April 21, 2011
    Inventors: Ronald R. Hatch, Liwen L. Dai
  • Publication number: 20100141510
    Abstract: In a method of mitigating errors in satellite navigation measurements at a satellite navigation receiver, respective single-frequency signals are received from respective satellites in a plurality of satellites in a satellite navigation system. Pseudorange and carrier-phase measurements corresponding to respective received single-frequency signals are calculated. These calculations include filtering the pseudorange and carrier-phase measurements in a Kalman filter having a state vector comprising a plurality of states, including a position state, a receiver clock state, and a plurality of bias states. Each bias state corresponds to a respective satellite in the plurality of satellites. The filtering includes updating the state vector. An estimated position of the satellite navigation receiver is updated in accordance with an update to the state vector.
    Type: Application
    Filed: December 9, 2008
    Publication date: June 10, 2010
    Inventors: Liwen L. Dai, Chaochao Wang, Daniel J. Eslinger, John Perry Genta
  • Patent number: 7679555
    Abstract: A mobile satellite navigation receiver for calculating an offset between a local positioning system and a wide-area satellite positioning system is presented. The mobile satellite navigation receiver determines a first solution of a position of the mobile satellite navigation receiver relative to a first local positioning system, wherein the first local positioning system includes one or more reference receivers at known locations. The mobile satellite navigation receiver determines a second solution of the position of the satellite navigation receiver relative to a wide-area differential satellite positioning system. The mobile satellite navigation receiver then calculates an offset between the first solution and the second solution.
    Type: Grant
    Filed: December 22, 2008
    Date of Patent: March 16, 2010
    Assignee: Navcom Technology, Inc.
    Inventors: Liwen L. Dai, Chaochao Wang, Daniel J. Eslinger, Ronald R. Hatch, Richard T. Sharpe
  • Publication number: 20090135056
    Abstract: A method for mitigating atmospheric errors in code and carrier phase measurements based on signals received from a plurality of satellites in a global navigation satellite system is disclosed. A residual tropospheric delay and a plurality of residual ionospheric delays are modeled as states in a Kalman filter. The state update functions of the Kalman filter include at least one baseline distance dependant factor, wherein the baseline distance is the distance between a reference receiver and a mobile receiver. A plurality of ambiguity values are modeled as states in the Kalman filter. The state update function of the Kalman filter for the ambiguity states includes a dynamic noise factor. An estimated position of mobile receiver is updated in accordance with the residual tropospheric delay, the plurality of residual ionospheric delays and/or the plurality of ambiguity values.
    Type: Application
    Filed: May 12, 2008
    Publication date: May 28, 2009
    Inventors: Liwen L. Dai, Daniel J. Eslinger, Richard T. Sharpe, Ronald R. Hatch
  • Publication number: 20090102708
    Abstract: A mobile satellite navigation receiver for calculating an offset between a local positioning system and a wide-area satellite positioning system is presented. The mobile satellite navigation receiver determines a first solution of a position of the mobile satellite navigation receiver relative to a first local positioning system, wherein the first local positioning system includes one or more reference receivers at known locations. The mobile satellite navigation receiver determines a second solution of the position of the satellite navigation receiver relative to a wide-area differential satellite positioning system. The mobile satellite navigation receiver then calculates an offset between the first solution and the second solution.
    Type: Application
    Filed: December 22, 2008
    Publication date: April 23, 2009
    Inventors: Liwen L. Dai, Chaochao Wang, Daniel J. Eslinger, Ronald R. Hatch, Richard T. Sharpe
  • Publication number: 20080297408
    Abstract: A method for performing integer ambiguity resolution in a global navigation satellite system is disclosed. A set of ambiguities, which are associated with carrier phase measurements of at least some of the signals received from the satellites in an identified set of satellites, are identified. Integer ambiguities are estimated and a best candidate set and a second best candidate set of integer ambiguity values are determined. Upon determining that the best set of integer ambiguity values fail to meet a discrimination test, each ambiguity for which integer ambiguity values in the best candidate set and second best candidate set fail to meet predefined criteria are removed from the set of ambiguities to produce a reduced set of ambiguities. The integer ambiguities in the reduced set of ambiguities are then resolved and an output is generated in accordance with the resolved integer ambiguities.
    Type: Application
    Filed: May 12, 2008
    Publication date: December 4, 2008
    Inventors: Liwen L. Dai, Daniel J. Eslinger, Richard T. Sharpe, Ronald R. Hatch