Package org.orekit.estimation.measurements.gnss

Class AbstractLambdaMethod

java.lang.Object
org.orekit.estimation.measurements.gnss.AbstractLambdaMethod
All Implemented Interfaces:
IntegerLeastSquareSolver
Direct Known Subclasses:
LambdaMethod, ModifiedLambdaMethod
public abstract class AbstractLambdaMethod extends Object implements IntegerLeastSquareSolver
Base class for decorrelation/reduction engine for LAMBDA type methods.

This class is based on 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

Since:
10.0
Author:
Luc Maisonobe

  • Constructor Details

    • AbstractLambdaMethod

      protected AbstractLambdaMethod()
      Constructor.

      By default a IntegerLeastSquareComparator is used to compare integer least square solutions

  • Method Details

    • solveILS

      public IntegerLeastSquareSolution[] solveILS(int nbSol, double[] floatAmbiguities, int[] indirection, RealMatrix covariance)
      Find the best solutions to an Integer Least Square problem.
      Specified by:
      solveILS in interface IntegerLeastSquareSolver
      Parameters:
      nbSol - number of solutions to search for
      floatAmbiguities - float estimates of ambiguities
      indirection - indirection array to extract ambiguity covariances from global covariance matrix
      covariance - global covariance matrix (includes ambiguities among other parameters)
      Returns:
      at most nbSol solutions a to the Integer Least Square problem, in increasing squared distance order

    • setComparator

      public void setComparator(Comparator<IntegerLeastSquareSolution> newCompartor)
      Set a custom comparator for integer least square solutions comparison.

      Calling this method overrides any comparator that could have been set beforehand. It also overrides the default IntegerLeastSquareComparator.

      Parameters:
      newCompartor - new comparator to use
      Since:
      11.0

    • getDiagReference

      protected double[] getDiagReference()
      Get a reference to the diagonal matrix of the decomposition.

      BEWARE: the returned value is a reference to an internal array, it is only intended for subclasses use (hence the method is protected and not public).

      Returns:
      reference to the diagonal matrix of the decomposition

    • getLowReference

      protected double[] getLowReference()
      Get a reference to the lower triangular matrix of the decomposition.

      BEWARE: the returned value is a reference to an internal array, it is only intended for subclasses use (hence the method is protected and not public).

      Returns:
      reference to the lower triangular matrix of the decomposition

    • getDecorrelatedReference

      protected double[] getDecorrelatedReference()
      Get the reference decorrelated ambiguities.
      Returns:
      reference to the decorrelated ambiguities.

    • getMaxSolution

      protected int getMaxSolution()
      Get the maximum number of solutions seeked.
      Returns:
      the maximum number of solutions seeked

    • addSolution

      protected void addSolution(long[] fixed, double squaredNorm)
      Add a new solution.
      Parameters:
      fixed - solution array
      squaredNorm - squared distance to the corresponding float solution

    • removeSolution

      protected void removeSolution()
      Remove spurious solution.

    • getSolutionsSize

      protected int getSolutionsSize()
      Get the number of solutions found.
      Returns:
      the number of solutions found

    • getMaxDistance

      protected double getMaxDistance()
      Get the maximum of distance among the solutions found. getting last of solutions as they are sorted in SortesSet
      Returns:
      greatest distance of the solutions
      Since:
      10.2

    • getZInverseTransformationReference

      protected int[] getZInverseTransformationReference()
      Get a reference to the Z inverse transformation matrix.

      BEWARE: the returned value is a reference to an internal array, it is only intended for subclasses use (hence the method is protected and not public). BEWARE: for the MODIFIED LAMBDA METHOD, the returned matrix Z is such that Q = Z'L'DLZ where Q is the covariance matrix and ' refers to the transposition operation

      Returns:
      array of integer corresponding to Z matrix
      Since:
      10.2

    • getSize

      protected int getSize()
      Get the size of the problem. In the ILS problem, the integer returned is the size of the covariance matrix.
      Returns:
      the size of the ILS problem
      Since:
      10.2

    • ltdlDecomposition

      protected abstract void ltdlDecomposition()
      Perform Lᵀ.D.L = Q decomposition of the covariance matrix.

    • reduction

      protected abstract void reduction()
      Perform LAMBDA reduction.

    • discreteSearch

      protected abstract void discreteSearch()
      Find the best solutions to the Integer Least Square problem.

    • inverseDecomposition

      protected abstract 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.

    • integerGaussTransformation

      protected void integerGaussTransformation(int row, int col)
      Perform one integer Gauss transformation.

      This method corresponds to algorithm 2.1 in X.-W Chang, X. Yang and T. Zhou paper.

      Parameters:
      row - row index (counting from 0)
      col - column index (counting from 0)

    • permutation

      protected void permutation(int k0, double delta)
      Perform one symmetric permutation involving rows/columns k0 and k0+1.

      This method corresponds to algorithm 2.2 in X.-W Chang, X. Yang and T. Zhou paper.

      Parameters:
      k0 - diagonal index (counting from 0)
      delta - new value for diag[k0+1]

    • recoverAmbiguities

      protected IntegerLeastSquareSolution[] recoverAmbiguities()
      Recover ambiguities prior to the Z-transformation.
      Returns:
      recovered ambiguities

    • lIndex

      protected int lIndex(int row, int col)
      Get the index of an entry in the lower triangular matrix.
      Parameters:
      row - row index (counting from 0)
      col - column index (counting from 0)
      Returns:
      index in the single dimension array

    • zIndex

      protected int zIndex(int row, int col)
      Get the index of an entry in the Z transformation matrix.
      Parameters:
      row - row index (counting from 0)
      col - column index (counting from 0)
      Returns:
      index in the single dimension array