Geophysical Mapping: Method Details
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Method Name: Tunnel infrared thermography
Method Type:   Thermic Methods
Assigned Problems:
+ Cavity detection Civil Engineering
+ Fractures Groundwater
+ Porosity / Permeability Groundwater
+ Temperature Groundwater
0 Heat mining Natural Resources
   '+' = Technique applicable; '0' = Application possible/limited use
Principle:   Determination of surface temperature of tunnel walls using infrared surface temperature measurements (thermal / infrared radiation).
Keywords:   Thermal imaging; infrared measurements; thermal and infrared radiation; temperature distribution; surface temperature of tunnel walls
Prerequisites:  
  • Existence of thermal contrast
  • The field of view of radiation-measurement devices is limited.
  • Thermal influences by cars and other heat sources.
Resolution:   Radiation measurements (infrared thermography): Thermal resolution: usually 0,03 K; spatial/ geometrical resolution: usually 1,5 mrad
Typical depth of investigation: Surface
Expected Results:  
  • Measured parameter: Infrared thermography measures the intensity of the emitted electromagnetic radiation of a body
  • Data analysis: The measured signal may be converted to temperature (emission coefficient/ emissivity must be known)
  • Interpretation: Infrared thermography: Qualitative interpretation of relative thermal anomalies assuming that the measured signal (intensity of electromagnetic radiation) is correlated to the true temperature
Combination with other Methods:  
  • Required additional information: camera information / setup (valuable wavelength), environmental conditions
  • Related add-on information: optical scanning
  • Independent additional information: georadar
Operating Expense:  
  • Crew size: 1 key person; 1 - 2 assistants
  • Acquisition speed: 3 - 6 km / h
  • Processing: 1 - 2 days per measuring day
  • Equipment rental costs: intermediate
Parameters to specify:  
  • Instrument type
  • Measuring grid / continuous measurements (acquisition speed!)
  • Height of sensor / field of view
  • Resolution and accuracy
QC Documents:  
  • Field notes (e.g. all activities, effective time schedule, acquisition parameters)
Products:  
  • Map / image (or profiles) of temperature distribution
  • Interpretation
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