Geophysical Mapping: Method Details
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Method Name: Ground infrared thermography
Method Type:   Thermic Methods
Assigned Problems:
+ Cavity detection Civil Engineering
+ Quality / Thickness of concrete Buildings and Structures
+ Quality of roads/ airfields Buildings and Structures
+ Temperature Groundwater
   '+' = Technique applicable
Principle:   Determination of ground temperature using infrared surface temperature measurements (thermal / infrared radiation; remote sensing) or temperature testing probes (resistance thermometer; requires contact with object)
Keywords:   Thermal imaging; infrared measurements; thermal and infrared radiation; temperature distribution
Prerequisites:  
  • Existence of thermal contrast
  • Infrared radiation measurements should be conducted during night (preferentially shortly before sunrise)
  • Thermal influences by cars (measuring car, if device is truck-mounted) and other heat sources
  • Measurements within shallow depths may need corrections for daily temperature variations (ground testing probes)
  • The field of view of radiation-measurement devices is limited
  • Weather / climate conditions: images may be difficult to interpret if recorded over snow-covered areas, wet ground, frost or during rain or high wind
Resolution:   Radiation measurements (infrared thermography): Thermal resolution: usually 0,03 K; spatial / geometrical resolution: usually 1,5 mrad
Resistance thermometers: Thermal resolution: 0,03 K
The typical depth of investigation: Surface (infrared radiation measurements) or first few m (ground temperature testing probes).
Expected Results:  
  • Measured parameter: Infrared thermography measures the intensity of the emitted electromagnetic radiation of a body; Resistance thermometer measures the electric resistance that is directly related to temperature (in K or C)
  • Data analysis: The measured signal may then 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, etc.), weather conditions, camera position (for processing / interpretation)
  • Related add-on information: depending on problem set ( e.g., geological information)
  • Independent additional information: georadar
Operating Expense:  
  • Crew size: 1 key person; 1 - 2 assistants
  • Acquisition speed: several measurements per hour
  • 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, present personnel)
Products:  
  • Map / images (or profiles) of temperature distribution
  • Interpretation
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