james williams msc dissertation v1 121202 - ths.org.uk · visualisation, with the exception of the...
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Swathe ServicesSwathe Services
our results speak for themselvesour results speak for themselvesour results speak for themselvesour results speak for themselves
Swathe Services offers:Swathe Services offers:
Equipment SalesEquipment Sales
Equipment RentalEquipment Rental
Who we are
Equipment RentalEquipment Rental
Experience Hydrographic SurveyorsExperience Hydrographic Surveyors
TurnTurn--key survey supportkey survey support
High Resolution Geophysical SurveyingHigh Resolution Geophysical Surveying
Swathe Bathymetry Performance for Mapping Swathe Bathymetry Performance for Mapping
Underwater Archaeological SitesUnderwater Archaeological Sites
Dissertation Title
bby James Williamsy James Williams
Thesis Submitted to Plymouth University in partial fulfilment of the Thesis Submitted to Plymouth University in partial fulfilment of the
requirementsrequirements for the degree offor the degree of
MScMSc HydrographyHydrography
(In collaboration with The SHIPS Project)(In collaboration with The SHIPS Project)
The objective of the dissertation was to determine which type of The objective of the dissertation was to determine which type of
acoustic swathe technology provides the best bathymetry acoustic swathe technology provides the best bathymetry
performance for mapping underwater archaeological sites.performance for mapping underwater archaeological sites.
It aimed to achieve this by:It aimed to achieve this by:
Aims & Objectives
considering the theoretical performance of two commercially considering the theoretical performance of two commercially
available systems; one for each type of technology,available systems; one for each type of technology,
comparing field acquired data against theoretical comparing field acquired data against theoretical
performance,performance,
comparing results against data previously acquired through comparing results against data previously acquired through
diver techniques.diver techniques.
1. Introduction to swathe bathymetry systems
used
2. Survey vessel setup and equipment used
3. Overview of survey location
Content
3. Overview of survey location
4. Presentation of results
5. Conclusion
Types of Swathe SystemsTypes of Swathe Systems
Multi-beam systems are called:
• Multi-beam
• Multi-beam Echo Sounder (MBES)
• Beam FormersDifferent type of
Types of System
• Beam Formers
Swath(e)? systems are called:
• Phase Measuring Bathymetric Sonar
• Phase Differencing Bathymetric Sonar
• Interferometric Multi-beam
• Bathymetric Side-Scan
• Vernier Interferometer
• Wide Swathe Sonar
Different type of
technology
Points to remember
• Multi-beam manufacturers often quote a system as a 1x0.5 degree but this is only representative at NADIR.
The foot print size can be
MBES
The foot print size can be calculated at any give angle by considering the:
• angular resolution of the system
• frequency of the sonar
• operational water depth
• swathe sector angle
• number of beams
TransducerThe returning acoustics wave reaches each piezoelectric
element only a fraction of a second apart.
Interferometry
Sea Bed
Piezoelectric Elements
Returning Acoustic Wave
ASP
Images of structures around the base of Plymouth Breakwater Fort
(SONIC 2024 @400 kHz + POS MV + CNAV)GeoSwath Plus SONIC 2024
ASP
Images of structures around the base of Plymouth Breakwater Fort
(SONIC 2024 @400 kHz + POS MV + CNAV)GeoSwath Plus x1 line GeoSwath Plus x3 Lines
Blocks & Tavy
Images of two hollow concrete blocks near the Plymouth Breakwater Fort
(SONIC 2024 @400 kHz + POS MV + CNAV)
Blocks
Images of two hollow concrete blocks near the Plymouth Breakwater Fort
(SONIC 2024 @400 kHz + POS MV + CNAV)
Images of the CSWIP structure near the Plymouth Breakwater Fort (SONIC
2024 @400 kHz + POS MV + CNAV)
CSWIP
Images of the CSWIP structure near the Plymouth Breakwater Fort (SONIC
2024 @400 kHz + POS MV + CNAV)
CSWIP
Glaucus & Task
Images of an old dive chamber and hollow tube
tripod near the base of the Plymouth Breakwater
Fort (SONIC 2024 @400 kHz + POS MV + CNAV)
1. The data density of the GS+ is far greater than the SONIC system, however the spread of data around the statistical mean reduces its imagery capability.
2. The SONIC system proved much better at imaging the structures around the Breakwater Fort.
3. Most of the SONIC rendered images added an extra dimension to the visualisation, with the exception of the CSWIP which lost detail in the
Main Conclusions
visualisation, with the exception of the CSWIP which lost detail in the DTM production due to the presence of more than one vertical data point at the same horizontal position.
4. The GeoSwath produced improved imaging capability when additional lines were run over the same structure.
5. The SONIC obtained 100% coverage at a 10cm cell resolution whereas the GS+ exhibited many data gaps mainly at NADIR.
6. Both systems proved capable of mapping the entire Breakwater Fort site proving their effectiveness for wide area underwater archaeological mapping to put objects on the seabed in context.
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