At the UMass Amherst campus we regularly use UAS to conduct surveys of key infrastructure; whether it be to monitor and document stages of new construction on campus or to survey and inspect existing infrastructure. One of our more recent additions to our array of capabilities is the capacity to develop thermal orthomosaics from long-wave infrared (LWIR) imagery. This can help us map heat sources and thermodynamic processes of buried infrastructure, or look at heat loss in structures.
Fig. 1 – Example LWIR Thermal Image: In this LWIR thermal image temperature is represented in a linear white-hot grayscale; that is to say that black in the image represents the lowest apparent temperature (-12.5 degrees Celsius as indicated in the scale on the right of the image) and white represents the highest apparent temperature (5.5 degrees Celsius as indicated in the scale on the right of the image), and temperatures inside this range are represented with varying shades of gray that are assigned in a linear fashion. The temperatures are only “apparent” because other factors besides temperature can effect the emitted radiation that the camera detects, such as the varying emissivities of materials in the image field of view. This image is tuned to an emissivity of 0.98. The point “Sp1” in this image is shown to have an apparent temperature of -0.8 degrees Celsius. The mostly vertical white streak in this image is actually sewage line buried under the ground, but the heat from it reach the surface and the emitted thermal radiation is visible by a LWIR camera.
