The word “Quantitative” is added to indicate that something is measured in the thermal imaging process. The measured variable is most often temperature or temperature difference (often referred to as “Delta T”).
The special information pages at About Temperature & Moisture Sensors provides one of the easiest-to-read introductions to the topic plus links to many further resources including organizations that train people to become “Thermographers”.
The latter are the specialists that make thermal images.
There’s listings here on the cameras suppliers, thermal imaging service companies, training groups and the organizations that the professionals belong to and use as communications resources to interchange details about their art and science.
Also, realize, please, that Thermal Imaging Cameras are first infrared imagers and second temperature measurement devices. So, there is considerable overlap in the training of imager operators and use of such devices.