A Closed-form Solution to the Wahba Problem for Pairwise Similar Quaternions

Fuente: arXiv
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Auteurs principaux: Radak, Hristina, Scheunert, Christian, Fitzek, Frank H. P.
Format: Preprint
Publié: 2025
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author Radak, Hristina
Scheunert, Christian
Fitzek, Frank H. P.
author_facet Radak, Hristina
Scheunert, Christian
Fitzek, Frank H. P.
contents We present a closed-form solution to Wahba's problem in the quaternion domain for the special case of two vector observations. Existing approaches, including Davenport's $q$-method, QUEST, Horn's method, and ESOQ algorithms, recover the optimal quaternion through the eigendecomposition of a $4\times4$ matrix or iterative numerical methods. Consequently, these methods do not reveal the analytic structure of the optimal quaternion. In this work, we derive an explicit analytical characterization of all quaternions that yield zero Wahba cost for the case $\ell=2$. Our approach builds on a connection between quaternion similarity, the singular Sylvester equation $aq=qb$, and quaternion square roots established in our previous work [1]. We provide (i) necessary and sufficient conditions under which the Wahba's cost function is zero and (ii) a closed-form parameterization of all such quaternions. This eliminates the need for eigenvalue computations and enables a direct algebraic understanding of the underlying geometry of Wahba's problem.
format Preprint
id arxiv_https___arxiv_org_abs_2512_07597
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A Closed-form Solution to the Wahba Problem for Pairwise Similar Quaternions
Radak, Hristina
Scheunert, Christian
Fitzek, Frank H. P.
Rings and Algebras
Numerical Analysis
We present a closed-form solution to Wahba's problem in the quaternion domain for the special case of two vector observations. Existing approaches, including Davenport's $q$-method, QUEST, Horn's method, and ESOQ algorithms, recover the optimal quaternion through the eigendecomposition of a $4\times4$ matrix or iterative numerical methods. Consequently, these methods do not reveal the analytic structure of the optimal quaternion. In this work, we derive an explicit analytical characterization of all quaternions that yield zero Wahba cost for the case $\ell=2$. Our approach builds on a connection between quaternion similarity, the singular Sylvester equation $aq=qb$, and quaternion square roots established in our previous work [1]. We provide (i) necessary and sufficient conditions under which the Wahba's cost function is zero and (ii) a closed-form parameterization of all such quaternions. This eliminates the need for eigenvalue computations and enables a direct algebraic understanding of the underlying geometry of Wahba's problem.
title A Closed-form Solution to the Wahba Problem for Pairwise Similar Quaternions
topic Rings and Algebras
Numerical Analysis
url https://arxiv.org/abs/2512.07597