Oct 1, 2021· 1. Introduction. Throughout the years, and depending on the field of application, the thermal infrared (TIR) spectral range has received different definitions, ranging from 1.1 µm upwards (Billings and Morris 1951) to 3–35 μm (Prakash 2000), and even to 3–1000 μm (Kuenzer and Dech 2013).The most widely accepted range for TIR …