Package org.orekit.estimation.measurements.gnss

Class LambdaMethod

java.lang.Object
org.orekit.estimation.measurements.gnss.AbstractLambdaMethod
org.orekit.estimation.measurements.gnss.LambdaMethod
All Implemented Interfaces:
IntegerLeastSquareSolver
Direct Known Subclasses:
IntegerBootstrapping
public class LambdaMethod extends AbstractLambdaMethod
Decorrelation/reduction engine for LAMBDA method.

This class implements PJG Teunissen Least Square Ambiguity Decorrelation Adjustment (LAMBDA) method, as described in both the 1996 paper The LAMBDA method for integer ambiguity estimation: implementation aspects by Paul de Jonge and Christian Tiberius and on the 2005 paper A modified LAMBDA method for integer least-squares estimation by X.-W Chang, X. Yang and T. Zhou, Journal of Geodesy 79(9):552-565, DOI: 10.1007/s00190-005-0004-x

It slightly departs on the original LAMBDA method as it does implement the following improvements proposed in the de Jonge and Tiberius 1996 paper that vastly speed up the search:

  • alternate search starting from the middle and expanding outwards
  • automatic shrinking of ellipsoid during the search
Since:
10.0
Author:
Luc Maisonobe
See Also:

  • Constructor Details

    • LambdaMethod

      public LambdaMethod()
      Empty constructor.

      This constructor is not strictly necessary, but it prevents spurious javadoc warnings with JDK 18 and later.

      Since:
      12.0

  • Method Details

    • ltdlDecomposition

      protected void ltdlDecomposition()
      Perform Lᵀ.D.L = Q decomposition of the covariance matrix.
      Specified by:
      ltdlDecomposition in class AbstractLambdaMethod

    • reduction

      protected void reduction()
      Perform LAMBDA reduction.
      Specified by:
      reduction in class AbstractLambdaMethod

    • discreteSearch

      protected void discreteSearch()
      Find the best solutions to the Integer Least Square problem.
      Specified by:
      discreteSearch in class AbstractLambdaMethod

    • inverseDecomposition

      protected void inverseDecomposition()
      Inverse the decomposition.

      This method transforms the Lᵀ.D.L = Q decomposition of covariance into the L⁻¹.D⁻¹.L⁻ᵀ = Q⁻¹ decomposition of the inverse of covariance.

      Specified by:
      inverseDecomposition in class AbstractLambdaMethod