Electrical Resistance Imaging Looking beneath the surface… Or Finding where the bodies are buried...
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Transcript of Electrical Resistance Imaging Looking beneath the surface… Or Finding where the bodies are buried...
Electrical Resistance ImagingLooking beneath the surface…
OrFinding where the bodies are buried without a backhoe…
AndLooking for buried ice on the side of
a mountain…
Dr. Greg Gaston, Department of Geography, University of North Alabama
Dr. George Makowski, Department of History, University of North Alabama
Changing lives. Creating futures.
Looking beneath the surface…Or
Finding where the bodies are buried without a backhoe…
AndLooking for buried ice on the side of
a mountain…
Dr. George Makowski, Department of History, University of North Alabama
Remote Sensing?
• Subsurface targets
• Simple technology with high order data processing
Significance?
• Big target technology searching for small targets
• Potentially a significant tool in exploring the impacts of climate change
• Identification of historical and recent archeological sites without damage
• High resolution images
• Flexibility
Why Electrical Resistance (ER) Imaging?
• Non-invasive • Widely used tool in archeological investigations• ER tools are more capable of recording data
where sub-surface water is present (Ground Penetrating RADAR [GPR] has difficulty penetrating saturated ground conditions)
• Relatively low cost• Buried ice has very high electrical resistance
The physical principles…
Penetration is a function of the length of the electrode line and the distance between electrodes. Functionally, depth is 10-20% of the total length of the electrode array and the minimum target discrimination is ½ the electrode spacing.
Testing the ER system
Known Steam Tunnel
Steam Tunnel to adjoining building
Compaction and moisture near sidewalk
Case Study 1
Sweetwater PlantationER Data collected 15 December ‘06Additional Field Mapping 16 Feb. ‘07
Historical Applications:
Cemetery Site
(Approximately 450 feet from the house)
Survey Lines
Survey Line 3Data line 5 Schlumberger electrode firing pattern
Survey Line 4Data line 7 Schlumberger electrode firing pattern
Case Study 2: Coffee Plantation
Coffee Cemetery Line 8
LaGrange Mountain Cemetery
• Experimental Data Collection
• Field Methods Class 6 March 2007
Results:
• Initial results at the Sweetwater Plantation site are encouraging.
• Results from the Coffee Plantation site are not as expected.
• The interpretation of ER images can change with different environmental conditions.
• The ‘Art’ rather than the ‘Science’ of image interpretation and analysis
Next steps in the research program:
• Test ER imaging at additional sites with known and suspected burial sites.
• We will retest Coffee cemetery with drier conditions.
Changes in glacial ice and ice marginal features of the
Cascades
Research sponsored by a grant from the College of Arts and Sciences at the University of North Alabama.
Thanks also to the UNA Department of Physics and Earth Science for the loan of the Electrical Resistance Imaging equipment.
Why glacial features in the Cascades?
• Glaciers exist at comparatively low elevationsIt is possible to measure moraine
features at 6000-7000 feet• Changes in ice and ice marginal features are
fairly well documented including a long record of aerial photography
• A wide variety of glacial features have (relatively) easy accessibility
• Previous Research Experience
The Pacific Northwest
The angle of repose of dry earth materials is generally 25-40 degrees.
35 degrees is the accepted ‘normal’ angle of repose
A steeper angle implies some sort of cohesion between particles.
1990
2006
http://glaciers.pdx.edu/gdb/maps/oregon_website/or_glaciers.html
1901
Carver Lake…
An example of a glacial lake created by ice cored moraines.
Site 2: Known Glacial Ice
Site 1:
Suspected Ice Cored Moraine
Conclusions • The steeper angle of repose in many of the moraines of
the Cascades is caused by an ‘ice core’.• Electrical resistance imaging equipment was useful in
confirming the presence of ice in the moraine.• Interpretation of the levels of resistance suggest
discontinuous ice lenses rather than a solid mass of ice.• Lakes in the Cascades dammed by moraines with
similar slope are likely to fail as ice in the Cascades continues to melt.
• Mountains are taller and gravity appears to have dramatically increased over the last 16 years!