REVIEW 3 major objections 5 minor 31 references
Invariant Extended Kalman Filtering with Partial Orientation Measurement Integration: Theoretical Derivations and Application to Autonomous Surface Vessels
T0 review · 3 major / 5 minor · reviewed 2026-08-07 · deepseek-v4-flash
Pith's one-line read An invariant EKF on SE2(3) can absorb roll, pitch, and yaw measurements as full-orientation updates by projecting the belief into a planar frame and giving unobserved components infinite covariance.
desk verdict A useful, clearly written extension of InEKF to partial orientation measurements, but the paper's central convergence claim rests on an unproven linearization step and a favorable baseline comparison. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing object is the planar-frame projection $P(R)$, which maps a full rotation to its X-then-Y roll–pitch component by extracting yaw as $\psi = \operatorname{atan2}(R_{1,0}, R_{0,0})$, constructing $R_z(\psi)$, and left-multiplying its transpose into the belief. Together with the group homomorphism $h: SE2(3) \to SO(3)$ and the analytic infinite-covariance limit for the unobserved rotation component, this lets a partial measurement reuse the full-orientation innovation $V^l = \log(z^{-1}\hat{z})^\vee$ with $H = I$. The validity of this machinery rests on the semi-planar assumption that roll and pitch stay moderate, so that the non-commutativity of small rotations does not spoil the linearization.
What would settle it
Run the filter on simulated trajectories whose roll or pitch excursions exceed the validated envelope—for example, wave-driven angles of ±10 or ±30 degrees—and compare the estimation error against ground truth; if the innovation becomes biased or the filter diverges where a full-orientation InEKF does not, the $H = I$ linearization of the RollPitchProjection is the cause. A direct calculation of the neglected second-order rotation terms as a function of roll and pitch magnitude would settle the claim without additional experiments.
Extended reading notes
Core claim
The central discovery, stated on the paper's own terms, is a measurement-integration pattern for left-invariant filters. A function $P(R)$ called the RollPitchProjection extracts the yaw of the current rotation belief, builds the planar frame $R_z(\psi)$, and rotates the belief into that frame, leaving a residual rotation that can be handled as a full SO(3) measurement with $H = [\,I_{3\times3}\;\;0_{3\times6}\,]$. Because the yaw component of a roll/pitch measurement would otherwise incorrectly reinforce the filter's current yaw belief, that component is assigned infinite variance and the innovation covariance is evaluated analytically using a matrix-inversion identity, keeping the update well conditioned. The same construction is applied to yaw-only heading measurements by building the planar frame from the estimated heading. The paper reports that the resulting partial-orientation InEKF outperforms an InEKF using lower-frequency full orientation measurements, and that it retains superior convergence speed and reliability compared with a multiplicative EKF under high initial uncertainty.
Load-bearing premise
The load-bearing premise is the semi-planar assumption: roll and pitch stay within moderate limits (validated at about ±5 degrees, claimed up to about ±30 degrees without full validation), so that projecting the rotation into a planar frame and linearizing with $H = I$ remains accurate despite the non-commutativity of rotations.
Editorial extensions
If this is right
- High-frequency roll and pitch from a horizon camera can be used at their native rate rather than being downsampled and stitched into a synthetic full orientation measurement.
- A pure yaw or heading measurement can be fused without a magnetometer and without constraining roll and pitch, because the unmeasured components receive infinite covariance.
- The filter keeps the InEKF's convergence behavior under large initial state errors, which the paper identifies as its practical advantage over a multiplicative EKF.
- The framework applies to any semi-planar vehicle—surface vessels, aircraft in level flight, or wheeled robots on mild terrain—not only to the specific boat simulated here.
- The reported simulation results support using the horizon as the primary orientation reference in open-ocean autonomy, where fixed landmarks are absent.
Reading between the lines
- The planar-frame projection pattern likely generalizes to other partial measurements whose unobserved directions form a subgroup of the state group, such as single-axis position updates on SE(3), by zeroing the unobserved directions and taking the same infinite-covariance limit.
- A natural stress test is to drive roll or pitch excursions beyond the validated ±5 degree envelope; the paper's suggestion that the method may work up to ±30 degrees is explicitly not fully validated.
- Because the camera-height estimate shifts the horizon pixel location by under a pixel over a 1–3 m height range, the pitch measurement may be sensitive to calibration error; a real-world dataset would be needed to confirm the simulation findings.
- If the same pattern extends to other Lie groups with a planar subgroup, it could become a general recipe for 'partial invariant measurements' beyond orientation, such as partial velocity or partial position observations.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes a Left-Invariant Extended Kalman Filter (InEKF) on SE2(3) for autonomous surface vessels that fuses partial orientation measurements: roll and pitch from a monocular horizon camera and yaw from dual-antenna GPS. The authors define a planar-frame projection P(R) that strips yaw from a full rotation, treat the resulting roll/pitch measurement as a full SO(3) update whose yaw component is given infinite covariance, and derive an analytical infinite-covariance update via the Woodbury identity. They compare the filter in the VRX simulation against an InEKF using lower-rate full orientation updates and against a multiplicative EKF, reporting comparable steady-state accuracy and faster convergence of the InEKF under large initial errors.
Significance. If the theoretical derivation were sound, the paper would fill a genuine gap: integrating partial orientation measurements into the invariant filtering framework is practically relevant for open-ocean ASVs, and the proposed framework is clearly motivated. The paper also provides a modular pipeline (horizon line detection, roll/pitch extraction) and a simulation-based comparison with two baselines, which is a good empirical starting point. However, the two load-bearing theoretical steps—the Jacobian of the nonlinear projection P(R) and the infinite-covariance matrix identity—are not established; one is asserted and the other is mathematically incorrect as stated. The empirical results cannot compensate for these gaps because the convergence experiment is exactly the regime where the unmodeled cross-coupling is largest. With corrected derivations, the approach may well be salvaged, but as it stands the paper's central claims are not supported by the presented analysis.
major comments (3)
- [Section III.C.1] The claim that the RollPitchProjection P(R) has the same measurement Jacobian H=[I3 0] as a full orientation measurement is not derived and is not correct in general. Since P is not a group homomorphism, the left-invariant error structure of Section III.A does not carry over. For R_hat = R_t exp(ξ^) and Rp = Rz(ψ_t)^T R_t, the innovation satisfies z^{-1}ẑ = exp(-ξ^) · Rp^{-1} Rz(δψ) Rp (with δψ the yaw error), so the conjugated yaw error contaminates the roll/pitch components at order ||(φ,θ)||·|δψ|. Under the conditions of Fig. 4 and Table II (60° initial orientation error, ±5° true roll/pitch, 2° measurement noise), this contamination exceeds the measurement noise and introduces a bias in the updates that are claimed to provide fast convergence. The manuscript's own caveat that 'a more thorough analysis is needed' highlights the gap, yet the abstract and conclusion claim unqualified preservation of the InEKF's convergence properties. Please provide the true Jacobian of P(R) (including the yaw-error coupling) and quantify the resulting bias, or restrict the claims to the validated small-roll/pitch regime and report bias and convergence results there.
- [Section III.C.3, Eq. (14)] The Woodbury identity is misstated. For non-commuting matrices A and B, (A+B)^{-1} is not A^{-1}-A^{-1}(AB^{-1}+I)^{-1}; the standard identity is (A+UBV)^{-1}=A^{-1}-A^{-1}U(B^{-1}+VA^{-1}U)^{-1}VA^{-1}. As a result, the limiting expression for S^{-1} in Eq. (14) does not follow. For example, with R = Rx(π/2) and Σ̃ = I, Eq. (14) gives S^{-1}=diag(1/2,0,1/2), whereas the correct limit is diag(1/2,1,0). Because this formula is the mechanism that discards the yaw information in the roll/pitch update, the error is load-bearing; please re-derive S^{-1} using the standard identity (e.g., by writing S = (Σ̃+R^T M_φθ R) + L (R^T e3)(R^T e3)^T and taking the limit) or state that the implementation uses a finite, large covariance instead of the analytical formula.
- [Section V.C and Conclusion] The convergence claim attributed to the partial-orientation framework is not clearly supported by the experiments. In the with-horizon condition (6 Hz roll/pitch), the text states that the InEKF is only 'slightly faster' than the MEKF; the dramatic MEKF divergence that motivates the conclusion occurs in the second condition, where the proposed roll/pitch horizon measurements are removed and the filters use only heading and GPS updates. Thus the conclusion that 'our integration of partial orientation measurements, such as roll and pitch, or yaw alone, preserves the InEKF's superior convergence properties' conflates the baseline InEKF behavior with the effect of the proposed roll/pitch measurement model. Please report separate convergence statistics for the with-horizon condition (e.g., time to reach a threshold error, divergence counts, or a convergence-rate curve) and either substantiate or qualify the claim about the specific benefit of the proposed projection-based updates.
minor comments (5)
- [Section V.B / Fig. 3] The text in Section V.B says 'A series of 50 Monte Carlo simulations' while the caption of Fig. 3 says 'across 100 Monte Carlo simulations'; please reconcile the number.
- [Section IV.4] The camera declination angle is denoted by the same symbol ψ used throughout Section III for yaw, which is confusing; please use a different symbol (e.g., β) for the camera declination.
- [Section II.C] There are two typos in the related-work paragraph on the underwater InEKF: 'Woodsbury identity' should be 'Woodbury identity' and 'meanigful' should be 'meaningful'.
- [Section III.C.1] The sentence 'By left multiplying RW p by Rp R' appears incomplete or mislabeled; the intended rotation composition (e.g., R_b^p = Ry(θ)Rx(φ) applied to Rz(ψ)) should be written explicitly to avoid ambiguity.
- [Fig. 3] The figure caption says 'The boxplots illustrate the distribution of errors across 100 Monte Carlo simulations,' but the vertical axis and the text in Section V.B describe 'Trajectory Mean Abs. Error,' which mixes per-trajectory and per-timestep quantities; please clarify what each boxplot entry represents.
Circularity Check
No significant circularity: the partial-orientation update rests on an explicitly bounded approximation and a fully re-derived matrix identity; only a non-load-bearing self-citation and a confounded comparison remain.
full rationale
The derivation chain is self-contained. The paper's core step — treating roll/pitch and yaw measurements as full SO(3) innovations with H = [I3x3 0] — rests on the explicitly stated 'semi-planar' approximation (Section III.C.1): when roll and pitch are small, the Lie-algebra error components approximately decouple into roll/pitch/yaw. The authors concede this is unproven ('While a more thorough analysis is needed to formally characterize this limitation, our system has demonstrated strong empirical performance in experiments with roll and pitch variations up to ±5 degrees'), which makes it a bounded, acknowledged correctness risk rather than a circularity: the H = I assertion is not derived by assuming the conclusion, and it is checked against ground truth and an external baseline (MEKF) in simulation. The infinite-covariance technique is cited to the authors' own prior work [20], a self-citation, but the paper re-derives the complete S^{-1} expression in Eq. (14) using Woodbury's matrix identity, which is parameter-free external mathematics; thus [20] is not load-bearing. The empirical headline claim ('high-frequency partial orientation measurements outperform... an InEKF relying on lower-frequency full orientation measurements,' Section V.B) does confound update rate with measurement type — the 'full orientation' comparator is constructed by discarding the 30 Hz roll/pitch and keeping only 1 Hz, so the comparison outcome is partly forced by experimental design; however, no parameter is fitted and the claim is an experimental observation rather than a theory-derived prediction, so it does not constitute an equation-level circularity. No step in Sections III.C.1–III.C.3 equates an input to an output by construction; the yaw-ambiguity handling via P(R) = Rz(ψ)^T R is not a homomorphism, and the paper never derives results that require it to be one.
Assumptions & free parameters
assumptions (4)
- ad hoc to paper Semi-planar operation: roll and pitch remain within moderate limits (around plus or minus 5 degrees validated, up to plus or minus 30 degrees claimed).
- standard math Group homomorphism h: SE2(3) to SO(3) exists and has Jacobian [I 0].
- domain assumption The horizon provides absolute roll and pitch relative to the geodetic frame.
- standard math Woodbury identity and the infinite-covariance limit are valid for the innovation covariance inversion.
Cite this review
Pith. "Pith review of Invariant Extended Kalman Filtering with Partial Orientation Measurement Integration: Theoretical Derivations and Application to Autonomous Surface Vessels." pith.science (2026). https://pith.science/paper/A2TLDVM7
@misc{pith2026250610850,
author = {Pith},
title = {Pith review of: Invariant Extended Kalman Filtering with Partial Orientation Measurement Integration: Theoretical Derivations and Application to Autonomous Surface Vessels},
year = {2026},
howpublished = {\url{https://pith.science/paper/A2TLDVM7}},
note = {Machine review of arXiv:2506.10850}
}
read the original abstract
Autonomous surface vessels (ASVs) are increasingly vital for marine science, offering robust platforms for underwater mapping and inspection. Accurate state estimation, particularly of vehicle pose, is paramount for precise seafloor mapping, as even small surface deviations can have significant consequences when sensing the seafloor below. To address this challenge, we propose an Invariant Extended Kalman Filter (InEKF) framework designed to integrate partial orientation measurements. While conventional estimation often relies on relative position measurements to fixed landmarks, open ocean ASVs primarily observe a receding horizon. We leverage forward-facing monocular cameras to estimate roll and pitch with respect to this horizon, which provides yaw-ambiguous partial orientation information. To effectively utilize these measurements within the InEKF, we introduce a novel framework for incorporating such partial orientation data. This approach contrasts with traditional InEKF implementations that assume full orientation measurements and is particularly relevant for vehicles operating in a \say{semi-planar} environment, where the attitude is characterized by a dominant yaw rotation with limited roll and pitch variations. This paper details the developed InEKF framework; its integration with horizon-based roll/pitch observations and dual-antenna GPS heading measurements for ASV state estimation; and provides a comparative analysis against the InEKF using full orientation and a Multiplicative EKF (MEKF). Our results demonstrate the efficacy and robustness of the proposed partial orientation measurements for accurate ASV state estimation in open ocean environments.
Figures
Reference graph
Works this paper leans on
-
[1]
Relaxing the planar assumption: 3D state estimation for an autonomous surface vessel,
G. Hitz, F. Pomerleau, F. Colas, and R. Siegwart, “Relaxing the planar assumption: 3D state estimation for an autonomous surface vessel,” The International Journal of Robotics Research, vol. 34, no. 13, 2015
work page 2015
-
[2]
T. I. Fossen, Handbook of Marine Craft Hydrodynamics and Motion Control. Wiley, 2011
work page 2011
-
[3]
G. Hitz, F. Pomerlesau, F. Colas, and R. Siegwart, State estimation for shore monitoring using an autonomous surface vessel . Springer International Publishing, 2016
work page 2016
-
[4]
Kinematic motion models based vessel state estimation to support advanced ship predictors,
Y . Wang, L. P. Perera, and B.-M. Batalden, “Kinematic motion models based vessel state estimation to support advanced ship predictors,” Ocean Engineering, vol. 286, 2023
work page 2023
-
[5]
State estimation of autonomous surface vessel,
A. E. Kjeldal, “State estimation of autonomous surface vessel,” Ph.D. dissertation, Aalborg University, 2018. Presented at the 2025 IEEE ICRA Workshop on Field Robotics -180 -90 0 90 180MEKF Roll (deg) -90 -45 0 45 90 Pitch (deg) -180 -90 0 90 180 Yaw (deg) 190 200 210 220 230 X (m) -14 -7 0 7 14 Y (m) -85 -60 -35 -10 15 Z (m) -180 -90 0 90 180INEKF -90 -...
work page 2018
-
[6]
H. Wang, Y . Yin, and Q. Jing, “Comparative analysis of 3D lidar scan- matching methods for state estimation of autonomous surface vessel,” Journal of Marine Science and Engineering , vol. 11, no. 4, 2023
work page 2023
-
[7]
Estimation of berthing state of maritime autonomous surface ships based on 3D lidar,
B. Hu, X. Liu, J. Qianfeng, H. Lyu, and Y . Yin, “Estimation of berthing state of maritime autonomous surface ships based on 3D lidar,” Ocean Engineering, vol. 251, 2022
work page 2022
-
[8]
UA V position and attitude estimation using IMU, GNSS and camera,
C. V . Angelino, V . R. Baraniello, and L. Cicala, “UA V position and attitude estimation using IMU, GNSS and camera,” in International Conference on Information Fusion , 2012
work page 2012
Show all 31 references
-
[9]
Attitude determina- tion from single camera vector observations,
V . Sazdovski, P. M. G. Silson, and A. Tsourdos, “Attitude determina- tion from single camera vector observations,” in IEEE International Conference Intelligent Systems , 2010
2010
-
[10]
Using single-camera geometry to perform gyro-free navigation and attitude determination,
Z. Zhu, S. Bhattacharya, M. Uijt de Haag, and W. Pelgrum, “Using single-camera geometry to perform gyro-free navigation and attitude determination,” in IEEE/ION Position, Location and Navigation Sym- posium, 2010
2010
-
[11]
A survey on horizon detection algorithms for maritime video surveillance: advances and future techniques,
Y . Zardoua, A. Astito, and M. Boulaala, “A survey on horizon detection algorithms for maritime video surveillance: advances and future techniques,” The Visual Computer , vol. 39, 2021
2021
-
[12]
Real-time horizon locking on unmanned surface vehicles,
B. Kiefer and A. Zell, “Real-time horizon locking on unmanned surface vehicles,” in IEEE/RSJ International Conference on Intelligent Robots and Systems , 2024
2024
-
[13]
Marine vessel attitude estimation from coastline and horizon,
S. Singhal, Y . Ao, D. Maas, B. Arsenali, and S. Maran `o, “Marine vessel attitude estimation from coastline and horizon,” in IEEE/RSJ International Conference on Intelligent Robots and Systems , 2023
2023
-
[14]
Left-invariant extended kalman filter and attitude esti- mation,
S. Bonnabel, “Left-invariant extended kalman filter and attitude esti- mation,” in IEEE Conference on Decision and Control , 2008
2008
-
[15]
The invariant extended kalman filter as a stable observer,
A. Barrau and S. Bonnabel, “The invariant extended kalman filter as a stable observer,” IEEE Transactions on Automatic Control , vol. 62, no. 4, 2017
2017
-
[16]
A micro Lie theory for state estimation in robotics,
J. Sola, J. Deray, and D. Atchuthan, “A micro Lie theory for state estimation in robotics,” arXiv:1812.01537, 2018
2018 arXiv
-
[17]
Invariant extended kalman filter: theory and application to a velocity-aided attitude estimation problem,
S. Bonnable, P. Martin, and E. Sala ¨un, “Invariant extended kalman filter: theory and application to a velocity-aided attitude estimation problem,” in IEEE Conference on Decision and Control , 2009
2009
-
[18]
Contact- aided invariant extended kalman filtering for robot state estimation,
R. Hartley, M. Ghaffari, R. M. Eustice, and J. W. Grizzle, “Contact- aided invariant extended kalman filtering for robot state estimation,” The International Journal of Robotics Research , vol. 39, no. 4, 2020
2020
-
[19]
The geometry of navigation problems,
A. Barrau and S. Bonnabel, “The geometry of navigation problems,” IEEE Transactions on Automatic Control , vol. 68, no. 2, 2022
2022
-
[20]
Invariant extended kalman filtering for underwater navigation,
E. R. Potokar, K. Norman, and J. G. Mangelson, “Invariant extended kalman filtering for underwater navigation,” IEEE Robotics and Au- tomation Letters, vol. 6, 2021
2021
-
[21]
Woodbury, Inverting Modified Matrices, ser
M. Woodbury, Inverting Modified Matrices, ser. Memorandum Report / Statistical Research Group, Princeton. Princeton University, 1950
1950
-
[22]
An introduction to the in- variant extended kalman filter [lecture notes],
E. Potokar, R. Beard, and J. Mangelson, “An introduction to the in- variant extended kalman filter [lecture notes],” IEEE Control Systems, vol. 44, 2024
2024
-
[23]
Invariant extended kalman filter for measurements on Lie groups,
V . Kull, “Invariant extended kalman filter for measurements on Lie groups,” Master’s thesis, KTH Royal Institute of Technology, 2021
2021
-
[24]
B. C. Hall, Lie Groups, Lie Algebras, and Representations: An Elementary Introduction. Springer, 2015
2015
-
[25]
Quaternion to Euler angles conversion: a direct, general and computationally efficient method,
E. Bernardes and S. Viollet, “Quaternion to Euler angles conversion: a direct, general and computationally efficient method,” PLOS One , vol. 17, no. 11, 2022
2022
-
[26]
LSD: a line segment detector,
R. Grompone von Gioi, J. Jakubowicz, J.-M. Morel, and G. Randall, “LSD: a line segment detector,” Image Processing On Line , 2012
2012
-
[27]
Relative multiplicative extended kalman filter for observable GPS-denied navigation,
D. P. Koch, D. O. Wheeler, R. W. Beard, T. W. McLain, and K. M. Brink, “Relative multiplicative extended kalman filter for observable GPS-denied navigation,” The International Journal of Robotics Re- search, vol. 39, no. 9, 2020
2020
-
[28]
Generalized multiplicative extended kalman filter for aided attitude and heading reference system,
P. Martin and E. Sala ¨un, “Generalized multiplicative extended kalman filter for aided attitude and heading reference system,” in AIAA Guidance, Navigation and Controls Conference , 2010
2010
-
[29]
Toward maritime robotic simu- lation in gazebo,
B. Bingham, C. Aguero, M. McCarrin, J. Klamo, J. Malia, K. Allen, T. Lum, M. Rawson, and R. Waqar, “Toward maritime robotic simu- lation in gazebo,” in MTS/IEEE OCEANS Conference , 2019
2019
-
[30]
Design and use paradigms for gazebo, an open-source multi-robot simulator,
N. Koenig and A. Howard, “Design and use paradigms for gazebo, an open-source multi-robot simulator,” in IEEE/RSJ International Conference on Intelligent Robots and Systems , 2004
2004
-
[31]
asv wave sim: Autonomous surface vessel wave simulation [software],
R. Mainwaring, “asv wave sim: Autonomous surface vessel wave simulation [software],” 2023. [Online]. Available: https://github.com/srmainwaring/asv wave sim Presented at the 2025 IEEE ICRA Workshop on Field Robotics
2023
Reviewed August 7, 2026 · model on record in the stance chip above.
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