Using Time Domain Reflectometry (TDR) to         Monitor the Geophysical Properties of               Archaeological Residu...
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesThe Problem  • DART is focused on improving the d...
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesThe ProblemKEY QUESTION: Can prior knowledge of g...
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesEM radiation and Permittivity Basics• EM transmis...
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesPermittivity SOIL TYPE                           ...
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesTDR Operating Principals
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesDesign and InstallationRequirements• Needs to tak...
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesDesign and Installation
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesDesign and Installation: clay sites
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesDesign and Installation: simpler sites
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesDesign and Installation
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesWaveform Interpretation• Identifying start and en...
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesOther Challenges Since Installation• Loggers beha...
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesExample data: Permittivity
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesExample data: Conductivity
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesExample data: Temperature
Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesThe future?• Complete geotechnical analysis on so...
Progress UpdateAcknowledgments                   The Rest of the DART Project • Dave Stott , Dr. Anthony Beck and Dr. Anth...
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Caa2012 dan boddice

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Dan Boddice: Using Time Domain Reflectometry (TDR) to Monitor the Geophysical Properties of Archaeological Residues

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  1. 1. Using Time Domain Reflectometry (TDR) to Monitor the Geophysical Properties of Archaeological Residues Dan Boddice, Laura Pring, Dr. Nicole Metje, Dr. David ChapmanSchool of Civil EngineeringCollege of Engineering and Physical Sciences
  2. 2. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesThe Problem • DART is focused on improving the detection of archaeological sites through both aerial remote sensing and geophysical techniques • Many of these use Electromagnetic (EM) radiation and require a contrast in EM properties • Ground penetrating radar (GPR) • Airborne multi and hyper-spectral sensors • Low frequency EM slingrams (e.g. EM38) • Other techniques use electrical properties • Electrical resistance surveying 1. EVIDENCE FOR SOIL CONTRASTS IS ANECDOTAL 2. POOR DETECTION RATES ON CERTAIN SOILS
  3. 3. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesThe ProblemKEY QUESTION: Can prior knowledge of geotechnical and climatic factors improve our understanding of the geophysical contrast factors between archaeological residues and the surrounding soil matrix • To map the soil and archaeological residues geophysical properties and identify the contrasts between them through a long term monitoring strategy. • Find ways to use the geotechnical properties of the soil, and weather data to predict sensor response and inform sensor choice. • Develop an appropriate methodology for similar or follow-on projects studying other geologies and archaeological feature types
  4. 4. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesEM radiation and Permittivity Basics• EM transmission is governed by complex permittivity which varies according to changing ground conditions• Real permittivity is the ability to store and release energy through charge separation • Can occur due to separation of charges in atom, movement of ions or rotation of molecules in line with applied field • Governs the speed of EM radiation propagation as produces displacement electrical field • Difference in layers will determine size of reflection• Imaginary Permittivity causes loss of signal energy • Relaxation mechanisms – lag in polarisation with applied field • Conductivity - causes the energy to attenuate as a function of distance
  5. 5. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesPermittivity SOIL TYPE DIELECTRIC PERMITTIVITY Air 1 Water 80-81 Dry Sand 3-5 Dry Silt 3-30 Asphalt 3-5 Limestone 4-8 Granite 4-6 Shale 5-15 Clay 5-40 Organic rich surface soil 12 Saturated sand 20-30 Adapted from Conyers 2004
  6. 6. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesTDR Operating Principals
  7. 7. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesDesign and InstallationRequirements• Needs to take hourly readings of permittivity, conductivity and temperature• Needs probes both in and out of archaeological feature and at different depths• Needs constant power supply• Needs some kind of communication
  8. 8. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesDesign and Installation
  9. 9. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesDesign and Installation: clay sites
  10. 10. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesDesign and Installation: simpler sites
  11. 11. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesDesign and Installation
  12. 12. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesWaveform Interpretation• Identifying start and end reflection points takes time• 16 permittivity per hour• c.11520 per station per month• Currently 6 stations –too many to do this manually!• Conductivity data is simpler• Quantity is the same as for permittivitySOLUTION: Script needed
  13. 13. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesOther Challenges Since Installation• Loggers behaving erratically • Skipped readings and scans • Unexplained stopping • Solved by slowing the scan rate and switching CF card brand• Animal Damage • Weather Station cables eaten http://free-extras.com/images/elmer_fudd-5189.htm • Probes re-excavated• Telemetry system will reduce future loss of data
  14. 14. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesExample data: Permittivity
  15. 15. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesExample data: Conductivity
  16. 16. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesExample data: Temperature
  17. 17. Using TDR to Monitor the Geophysical Properties of ArchaeologicalResiduesThe future?• Complete geotechnical analysis on soils from the lab to categorise them• Create a link between permittivity, moisture content and bulk density using the TDR on prepared samples in the lab• Analyse frequency dependence of soils in different states in the lab• Continue to analyse data flow using statistical tests and time delay correlation
  18. 18. Progress UpdateAcknowledgments The Rest of the DART Project • Dave Stott , Dr. Anthony Beck and Dr. Anthony Cohn (University of Leeds) • Rob Fry and Dr. Chris Gaffney (University of Bradford) • Dr. Keith Wilkinson (University of Winchester) • The other stakeholders and academic consultants Also • Giulio Curioni and Andrew Foo (Mapping the Underworld)
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