Airborne thermography and ground geophysical investigation for detecting

shallow ground disturbance

Dr. K.B. McManus, 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 Marksvariation in mineralogyand moisture properties

Crop Marksvariation in vegetation health

Differential Crop Marksconstraint on root depthand moisture availability

How do materials respond to solar heating?

12:00

Temperature

00:00 24:00

Time

bare soil

water

vegetation

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

12:00

Temperature

00:00 24:00Time

bare soil

water

vegetation

Comparison of visible, near-infrared and thermal

DayTIR

NightTIR

False ColourComposite

NIR:VISR:VISG

Natural ColourComposite

VISR:VISG:VISB

TIR -v- Geophysical Properties (1)Buried archaeology at Bosworth, Leics.

Apparent Thermal Inertia Magnetometry

Characteristics of thermal response of soil

0

5

10

15

20

25

0 360 720 1080 1440

Time (min)

Tem

pera

ture

(C

)

Surface

10cm

20cm

50cm

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 B

Thermal Anomaly

FEATURE C

Thermal and Geophysical

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 0.50m (thermal profiling)

– Good correlation with topographic features due to differential solar heating

– Good correlation with moisture properties (resistivity and soil samples)