underwater archaeology school 2011, session 5, paulo presentation
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Paulo Younse
Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA, USA
Underwater Field School
Session 5
August 9, 2011
Overview Linear surveying of Port Sanitja for
artifacts is currently done using rope swim lines
Swim lines contain inherent challenges stemming from maintaining formations, diver limitations, and environmental obstacles
Linear surveying using a team of autonomous underwater vehicles can improve effectiveness of linear surveying in Port Sanitja
Port Sanitja, Menorca
Ceramics Shipwrecks
Anchors Net Rings
Linear Survey with Swim Line
Ground line Rope
(A. Bowens, 2009)
- Dive formation (diver position, heading, speed)- Communication (tugs)- Position fix (measurements, flags)
Challenges using a Swim Line Observed difficulties in Port Sanitja from field school Snagging of line due to rugged terrain interfering with
search
Nonlinear search patterns due to fixed rope positions and elevation gradients along swim line
Difficulty holding heading if ground line not used
Difficulty maintaining tension in long swim lines
Communication to allow smooth advancement of line
Limited search capability due to diving limitations (no decompression time, air supply, time and resource availability, variations between divers)
Robot capable of navigating underwater with a human operator Range in size from portable to torpedo-sized Deployed/recovered from ships, submarines, or by personnel Can perform surveys and collect data, then transmit or upload to a user Capable of travel to depths of 3000+ m Operational time limited by batteries
Sensors- Sonar- Cameras- MagnetometersNavigation
- GPS- Compass- IMU- DVL
Propulsion - Propeller
Computer
HullBatteries
Communication- Radio- Acoustic
Autonomous Underwater Vehicle (AUV)
AUV (University of California San Diego Scripps Institution of Oceanography)
Remus 100 (Kongsberg Maritime AS)
Examples of AUVs
Solar Powered Autonomous Underwater Vehicle (Sauv II) (Autonomous Undersea Systems Institute)
Long-term Mine Reconnaissance System (LMRS) (The Boeing Company)
Examples of AUVs
Planning Phase
AUV Field Campaign
What, Where EnvironmentMethod, Instruments
Logistics, Prep, Schedule, Team
AUV Field Campaign Operation Phase
Start
Finish
Path Planning Upload Program to AUV Deployment
AUV Field Campaign Analysis Phase
Data Download from AUV Post-processing Scientific Analysis
Linear Survey With Teamed AUVs
AUV SpacingSurface Height
Scan Overlap
Communication
Virtual Swim Line
Technology Requirements Communication
Acoustic Radio
Navigation Inertial measurement unit (IMU) Visual odometry Doppler velocity log Compass Depth sensor GPS (surface) Reference buoy or node
Instrumentation Cameras Sonar Sub-bottom profilers Magnetometers
Power sources Batteries Recharging techniques
Advantages of Linear Surveying with Teamed AUVs Teamed AUVs advantages over traditional dive team
Autonomy Greater bottom time per survey at depth Communication effectiveness same regardless of number of
AUVs Freedom from rope Ability to use various instrumentation Performance consistency throughout survey
Teamed AUVs advantages over single AUV Increased surface coverage per survey Increased path accuracy from multiple sensor feedback Redundancy
Linear Surveying of Port Sanitja with AUVs Survey scenario
Deployment of AUVs from cove in the morning
Preprogrammed linear survey of Port throughout day
Autonomous return to cove when complete for pickup and download of data
Recharge AUVs overnight and repeat operation for subsequent survey the following morning
Analysis of data by archaeologists
Challenges Current, sea grass, sand coverage Boat and diver traffic Adaption of instrumentation to
local artifacts
Summary Current linear surveying of Port Sanitja is done using a
swim line of divers
Swim lines possess inherent difficulties and limitations
A team of autonomous underwater vehicles (AUVs) can improve surveying performance and efficiency
AUVs can potentially be configured and deployed to perform linear surveys in Port Sanitja
References A. Bowens, Underwater Archaeology: The NASA Guide
to Principles and Practice, 2nd ed., Nautical Archaeological Society, 2009.
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