Measurements and models of the correlation of redundant spatial coherence measurements for the incoherently scattered field

Blanford, Thomas E.; Brown, Daniel C.; Meyer, Richard J.

doi:10.1121/1.5134441

Cited by 8 publications

(1 citation statement)

References 30 publications

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“…Methods that exploit the spatial correlation of overlapping measurements between consecutive pings for along-track micronavigation propose maximum likelihood estimators [261], analytical and numerical coherence models [262] and smoothing interpolation kernels [263,264] to improve the accuracy of the along-track, ping-to-ping translation estimate. Similarly, time delay estimation between signals recorded on overlapping along-track positions between pings provides an across-track micronavigation estimate.…”

Section: Micronavigationmentioning

confidence: 99%

An Overview of Advances in Signal Processing Techniques for Classical and Quantum Wideband Synthetic Apertures

Vouras¹,

Mishra²,

Artusio‐Glimpse³

et al. 2022

Preprint

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Rapid developments in synthetic aperture (SA) systems, which generate a larger aperture with greater angular resolution than is inherently possible from the physical dimensions of a single sensor alone, are leading to novel research avenues in several signal processing applications. The SAs may either use a mechanical positioner to move an antenna through space or deploy a distributed network of sensors. With the advent of new hardware technologies, the SAs tend to be denser nowadays. The recent opening of higher frequency bands has led to wide SA bandwidths. In general, new techniques and setups are required to harness the potential of wide SAs in space and bandwidth. Herein, we provide a brief overview of emerging signal processing trends in such spatially and spectrally wideband SA systems. This guide is intended to aid newcomers in navigating the most critical issues in SA analysis and further supports the development of new theories in the field. In particular, we cover the theoretical framework and practical underpinnings of wideband SA radar, channel sounding, sonar, radiometry, and optical applications. Apart from the classical SA applications, we also discuss the quantum electric-field-sensing probes in SAs that are currently undergoing active research but remain at nascent stages of development.

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Section: Micronavigationmentioning

confidence: 99%

An Overview of Advances in Signal Processing Techniques for Classical and Quantum Wideband Synthetic Apertures

Vouras¹,

Mishra²,

Artusio‐Glimpse³

et al. 2022

Preprint

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Synthetic Aperture Sonar Micronavigation with Variational Inference of a State-Space Model

Xenaki

Pailhas

Monti

2023

2023 IEEE International Conference on Acoustics, Speech, and Signal Processing Workshops (ICASSPW)

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Coherence-Induced Bias Reduction in Synthetic Aperture Sonar Along-Track Micronavigation

Thomas

Hunter

2022

IEEE J. Oceanic Eng.

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Sub-wavelength motion estimation is vital for the production of focused synthetic aperture sonar (SAS) imagery.The required precision is obtainable from the sonar data itself through a process termed micronavigation. Along-track micronavigation is achieved by a similar technique to that used in correlation velocity logs (CVLs), where sparse estimates of the spatial coherence function are interpolated to estimate the location of the peak coherence and hence estimate the inter-ping vehicle motion. However, along-track micronavigation estimates made using this technique are biased, which limits the utility of these measurements for long-term navigation of autonomous underwater vehicles (AUVs).Three sources of along-track motion estimation bias are considered in this paper. Firstly, imperfect temporal registration between the signals results in coherence estimates that are negatively biased as a function of the temporal offset. Secondly, the sparse estimates of the spatial coherence function are obtained by cross-correlation of complex baseband signals, a process which is known to result in positively biased coherence estimates, especially when the true coherence is low. Finally, mismatches between the underlying spatial coherence function and the interpolation kernel used to estimate the peak coherence location also result in along-track micronavigation bias.In this paper we describe and evaluate three methods for reducing along-track micronavigation bias. We introduce a temporal registration of the signals prior to coherence estimation, which reduces the impact of negative coherence bias due to temporal offsets. The remaining coherence estimation bias is reduced by combining multiple coherence estimates in a Bayesian coherence estimator. Additionally, an improved interpolation kernel is derived with a significantly improved fit compared to the current gold standard Gaussian interpolation kernel.The improvements in along-track micronavigation accuracy are demonstrated using two simulated datasets, which both allow comparison with ground truth. The first involves direct simulation of the spatial coherence from a given inter-ping geometry using the pulse-echo formulation of the van Cittert-Zernike theorem, while the second involves simulation of raw sonar echo data using a point scatterer model. Using these simulations, a reduction in along-track micronavigation bias of 48.5 -99.5% is demonstrated, with reductions in along-track micronavigation error standard deviation of up to 34%. This improvement expands the potential for SAS-equipped AUVs to reduce their long-term navigation drift, facilitating longer underwater transits, improved target localisation and reduced track misalignment in repeat-pass operations.

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Measurements and models of the correlation of redundant spatial coherence measurements for the incoherently scattered field

Cited by 8 publications

References 30 publications

An Overview of Advances in Signal Processing Techniques for Classical and Quantum Wideband Synthetic Apertures

An Overview of Advances in Signal Processing Techniques for Classical and Quantum Wideband Synthetic Apertures

Synthetic Aperture Sonar Micronavigation with Variational Inference of a State-Space Model

Coherence-Induced Bias Reduction in Synthetic Aperture Sonar Along-Track Micronavigation

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