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

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:

AmbiguitySolver

Constructor Summary

Constructors

Constructor and Description
LambdaMethod()

Method Summary

Modifier and Type	Method and Description
protected void	discreteSearch() Find the best solutions to the Integer Least Square problem.
protected void	inverseDecomposition() Inverse the decomposition.
protected void	ltdlDecomposition() Perform Lᵀ.D.L = Q decomposition of the covariance matrix.
protected void	reduction() Perform LAMBDA reduction.

Methods inherited from class org.orekit.estimation.measurements.gnss.AbstractLambdaMethod

addSolution, getDecorrelatedReference, getDiagReference, getLowReference, getMaxSolution, getSolutionsSize, integerGaussTransformation, lIndex, permutation, removeSolution, solveILS, zIndex

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LambdaMethod

public LambdaMethod()

Method Detail

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