01 / Thermography
Start with what reaches the detector.
For a typical opaque target, the signal includes infrared emission from the surface and infrared energy reflected by that surface. The atmosphere between the target and camera also matters. Some materials transmit infrared in some wavelength bands; what is transparent to your eyes is not necessarily transparent to your thermal sensor.
A radiometric system uses the detected signal, calibration and entered parameters to estimate temperature. This is why an apparent temperature can differ from the temperature of the target. Before relying on a value, establish that the camera, scene and method are suitable for the question.
Sources: Infrared Training Center: Level I sUAS Thermography, ITC 107-RM [1.00], July 1, 2023 (private training reference) · Teledyne FLIR: What thermal imaging can and cannot see through
02 / Thermography
Emissivity and reflections belong in the same conversation.
Emissivity describes a surface’s emission relative to a reference emitter at the same temperature. It is a property of the surface under the relevant wavelength and viewing conditions, rather than a universal label for an object. Paint, oxidation and finish can change how a metal surface behaves. Adjacent surfaces should not be compared as if they necessarily share the same emissivity.
Low-emissivity surfaces can reflect a substantial part of the surroundings. A shiny fitting may appear unexpectedly cool because of a sky reflection or unexpectedly warm because of something nearby. A change of viewpoint can help examine a suspected reflection, when access and the flight plan permit. Choosing a convenient emissivity value does not remove the need to understand the target.
Sources: Infrared Training Center: Level I sUAS Thermography, ITC 107-RM [1.00], July 1, 2023 (private training reference) · Teledyne FLIR: How emissivity affects thermal imaging
03 / Thermography
Reflected apparent temperature is not the weather report.
The reflected-temperature parameter represents the apparent radiant contribution of the surroundings reflected toward the camera. It is different from the air temperature between the sensor and the target. Treating both inputs as the same outdoor forecast can introduce an error, particularly when the target is reflective.
For quantitative work, the operator needs an appropriate way to establish the relevant parameters and record the method. Distance, atmospheric temperature and humidity can also affect the result. If the scene does not support a defensible measurement, a carefully described qualitative observation may be the appropriate deliverable.
Sources: Infrared Training Center: Level I sUAS Thermography, ITC 107-RM [1.00], July 1, 2023 (private training reference) · Teledyne FLIR: Temperature measurement: focus, scale and parameters
04 / Thermography
A visible target is not automatically a measurable target.
A camera may detect a small warm feature without resolving enough of it for a reliable temperature estimate. Distance, detector resolution, lens and target size determine how much scene detail reaches the sensor. If the feature is too small, its signal can be mixed with the surrounding background.
Focus and motion also affect the useful record. Enlarging a picture with digital zoom does not collect additional detector samples. The appropriate measurement footprint is camera specific; a universal pixel count or distance is not a substitute for the manufacturer’s guidance and the field method. Plan safe proximity, viewing angle and image quality before promising a measurement.
Sources: Infrared Training Center: Level I sUAS Thermography, ITC 107-RM [1.00], July 1, 2023 (private training reference) · Teledyne FLIR: Understanding Distance:Size Ratio
05 / Thermography
Sensitivity, accuracy and resolution answer different questions.
Thermal sensitivity describes the ability to distinguish small signal differences under specified conditions. Temperature accuracy describes how close a reported value is expected to be under the manufacturer’s stated test conditions. Spatial resolution concerns how much detail the detector and optics can separate. A good figure in one category does not establish the others.
The Matrice 4T’s native thermal detector is 640 × 512 pixels. DJI lists its super-resolution output separately. More output pixels do not by themselves prove a finer independent measurement or better temperature accuracy. Use the current product documentation for specifications, then evaluate whether the capture and analysis meet the project need.
Sources: Infrared Training Center: Level I sUAS Thermography, ITC 107-RM [1.00], July 1, 2023 (private training reference) · DJI Enterprise: Matrice 4 series camera and measurement specifications
06 / Thermography
A measurement range and a display scale are different controls.
A camera’s measurement range or gain mode must suit the temperatures expected in the scene. The display scale decides how the captured values are spread across a palette. Narrowing that scale can make small differences look stronger without changing the underlying source data.
A red area is meaningful only with its legend, units and context. Two images using automatic scales may assign the same color to different values. An isotherm or threshold highlight is a display aid; crossing the chosen threshold is not, on its own, a defect classification. Preserve the scale and analysis settings when preparing a comparison.
Sources: Infrared Training Center: Level I sUAS Thermography, ITC 107-RM [1.00], July 1, 2023 (private training reference) · Teledyne FLIR: Achieving a good thermal image
07 / Thermography
Keep the original data beside the presentation.
A radiometric file retains measurement-related information supported by that camera and file format. A colorful screenshot may retain only the rendered view. Agree before capture whether the assignment needs original files, compatible analysis software, exported values or a visual presentation. Confirm the analysis path rather than assuming every JPEG can be remeasured.
A useful handoff records the camera, relevant settings, target, location, conditions and limits. Temperature differences can be valuable when the comparison is appropriate, but subtraction does not automatically cancel different materials, reflections or viewing conditions. The record should make clear what was observed, what was estimated and what still needs confirmation.
Sources: Infrared Training Center: Level I sUAS Thermography, ITC 107-RM [1.00], July 1, 2023 (private training reference) · Teledyne FLIR: Temperature measurement: focus, scale and parameters
VERIFY THE DETAILS / KEEP EXPLORING
Sources & further reading
Original explanation by Fly Maxwell. Technical and regulatory details are linked to the responsible organizations below. Product features, software plans and operating rules can change; check the current source when planning a project or a flight.
- Level I sUAS Thermography, ITC 107-RM [1.00], July 1, 2023Infrared Training Center · reviewed October 8, 2026
PDF pages 27–64 and 93–118. Owner-supplied course reference, reviewed privately. The copyrighted manual is not distributed on this website.
- What thermal imaging can and cannot see through Teledyne FLIR · reviewed October 8, 2026
- How emissivity affects thermal imaging Teledyne FLIR · reviewed October 8, 2026
- Temperature measurement: focus, scale and parameters Teledyne FLIR · reviewed October 8, 2026
- Understanding Distance:Size Ratio Teledyne FLIR · reviewed October 8, 2026
- Matrice 4 series camera and measurement specifications DJI Enterprise · reviewed October 8, 2026
- Achieving a good thermal image Teledyne FLIR · reviewed October 8, 2026
Manufacturer specifications describe the product under stated conditions. They are not a promise of project accuracy, flight duration, target detection or a particular outcome.