PhD Studentship – Reaching the diffraction-limit of acoustic imaging with autonomous underwater vehicles

Closing Date
1 June 2020

Project Description

Project team: Dr Alan Hunter (University of Bath), Dr Thomas Fickenscher (Helmut-Schmidt University) & Dr Holger Schmaljohann (Bundeswehr, Maritime Technology & Research)

Informal queries should be directed to Dr Alan Hunter ()

Seafloor remote-sensing is important for ensuring the safety of sea lanes, surveying for offshore construction, environmental conservation, and various other purposes. Seafloor imaging and mapping is normally performed using acoustics (i.e., sonar) instead of optics or microwaves due to the high attenuation of electromagnetic waves in seawater. As is the case with electromagnetic imaging systems (e.g., a camera), a larger sensor aperture provides higher resolution. However, the size of the autonomous underwater vehicles (AUVs) that typically carry and operate these payloads limits the size of the sonar sensor and, thus, the image resolution.

The modern technique of synthetic aperture sonar (SAS) gets around the physical limitation on aperture size by synthesising huge “virtual” apertures as the AUV moves through the water. The theoretical diffraction-limited resolution of this approach can be attained when the AUV travels in a circular path around the imaged region; this is known as circular SAS (CSAS). At typical operating frequencies, the theoretical image resolution is of the order of millimetres (compared to only centimetres for conventional systems). While this incredibly high image resolution is theoretically possible and has been demonstrated in controlled experiments, it is not yet a robust operational capability.

This PhD project aims to develop new algorithms that will enable AUVs to generate focused CSAS images of the seafloor with unprecedented diffraction-limited resolution in real-world environments and scenarios. The key challenge will be to estimate the AUV’s circular path accurately and to compensate for this within the imaging algorithms.

A representative application for this new capability is the identification of small objects on the seafloor in turbid waters with zero visibility, e.g., for the remediation of unexploded ordnance (shells, bombs, mines, etc.) that are legacies from past wars; this is a significant but unseen environmental issue worldwide. To this end, the project will be carried out in collaboration with Helmut-Schmidt University in Hamburg and the German Armed Forces (Bundeswehr). Our German collaborators will be providing the experimental capabilities, including AUV / SAS hardware and data. Therefore, while the PhD student will be based in Bath, they will be required to spend some extended periods of time in Hamburg, Germany.

Applicants should hold, or expect to receive, an undergraduate Masters first class degree or MSc distinction (or non-UK equivalent). English language entry requirements must be met at the time of application to be considered for funding, see

Formal applications should be made via the University of Bath’s online application form for a PhD in Mechanical Engineering. Please ensure that you state the full project title and lead supervisor name on the application form.

More information about applying for a PhD at Bath may be found here:

Expected start date: 28 September 2020

Funding Notes

A full studentship is available to UK/EU applicants only, and will include UK/EU tuition fees, a training support fee and a tax-free stipend (£15,285 p.a. 2020/21 rate) for up to 3.5 years. EU students are eligible to apply if they have been resident in the UK for 3 years prior to the funding commencing.