Package org.orekit.estimation.measurements.gnss

Class ModifiedLambdaMethod

java.lang.Object

org.orekit.estimation.measurements.gnss.AbstractLambdaMethod

org.orekit.estimation.measurements.gnss.ModifiedLambdaMethod

All Implemented Interfaces:

IntegerLeastSquareSolver

public class ModifiedLambdaMethod
extends AbstractLambdaMethod

Decorrelation/reduction engine for Modified LAMBDA method.

This class implements Modified Least Square Ambiguity Decorrelation Adjustment (MLAMBDA) method, as described in 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:

10.2

Author:

David Soulard

See Also:

• AmbiguitySolver

Constructor Summary

Constructors

Constructor	Description
ModifiedLambdaMethod()	Empty constructor.

Method Summary

Modifier and Type	Method	Description
protected void	discreteSearch()	Find the best solutions to the Integer Least Square problem.
protected void	inverseDecomposition()	Inverse the decomposition.
protected void	ltdlDecomposition()	Compute the LᵀDL factorization with symmetric pivoting decomposition of Q (symmetric definite positive matrix) with a minimum symmetric pivoting: Q = ZᵀLᵀDLZ.
protected void	reduction()	Perform MLAMBDA reduction.
protected double	sign(double a)	Return the symbol of parameter a.

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

addSolution, getDecorrelatedReference, getDiagReference, getLowReference, getMaxDistance, getMaxSolution, getSize, getSolutionsSize, getZInverseTransformationReference, integerGaussTransformation, lIndex, permutation, recoverAmbiguities, removeSolution, setComparator, solveILS, zIndex

Methods inherited from class java.lang.Object

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

Constructor Details

ModifiedLambdaMethod

public ModifiedLambdaMethod()

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()

Compute the LᵀDL factorization with symmetric pivoting decomposition of Q (symmetric definite positive matrix) with a minimum symmetric pivoting: Q = ZᵀLᵀDLZ.

Specified by:

ltdlDecomposition in class AbstractLambdaMethod

reduction

protected void reduction()

Perform MLAMBDA 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

sign

protected double sign(double a)

Return the symbol of parameter a.

Parameters:

a - the double for which we want the want the symbol

Returns:

-1.0 if a is lower than or equal to 0 or 1.0 if a is greater than 0