Airborne thermography and ground geophysical investigation for detecting

Airborne thermography and ground geophysical investigation for detecting shallow ground disturbance Dr. K. B. Mc. Manus, University of Durham Dr. D. N. M. Donoghue, University of Durham Dr. S. H. Marsh, British Geological Survey Dr. C. Brooke, Leicestershire County Council

Physical Context Soil Marks variation in mineralogy and moisture properties Crop Marks variation in vegetation health Differential Crop Marks constraint on root depth and moisture availability

How do materials respond to solar heating? vegetation Temperature bare soil water Time 00: 00 12: 00 24: 00

Physical and Apparent Thermal Inertia • Physical Thermal Inertia (TI) – Response to temperature change – Physical TI = √(density*thermal conductivity*heat capacity) • Apparent Thermal Inertia (ATI) – ATI = (1 -albedo) / (Temperature max - Temperature min) – Thermal image pair solar noon and pre-dawn Temperature vegetation bare soil water 00: 00 12: 00 24: 00 Time

Comparison of visible, near-infrared and thermal Natural Colour Composite VISR: VISG: VISB False Colour Composite NIR: VISG Day TIR Night TIR

TIR -v- Geophysical Properties (1) Buried archaeology at Bosworth, Leics. Apparent Thermal Inertia Magnetometry

Characteristics of thermal response of soil

TIR -v- Geophysical Properties (2) Topographic feature on Baildon Moor, W. Yorks. Thermal profile Electromagnetic profile

TIR -v- Geophysical Properties (3) Vegetation feature on Baildon Moor, W. Yorks. Thermal profile Resistivity profile

TIR –v- Soil properties FEATURE C Thermal and Geophysical Anomaly FEATURE B Thermal Anomaly

Conclusions • Thermal imaging during the day or night can enhance detection of anomalous materials compared to visible and near-infrared imaging • Contrast between thermal images also enhances anomaly detection with sensitivity to bulk variations • Comparison of thermal images with physical soil parameters suggest – Thermal response beneath vegetation sensitive to diurnal variations shallower than 0. 50 m (thermal profiling) – Good correlation with topographic features due to differential solar heating – Good correlation with moisture properties (resistivity and soil samples)