Module3: Thermal Infrared Image Interpretation

Roads: The roads in the picture look very bright. The warmer objects tend to appear brighter than the cooler objects in the aerial images. The roads being asphalt paved absorb more heat and remain warmer in the night compared to other objects which are cooler because there is no heat source (Sun) at that hour. It is dawn image (taken at 6:45 am) just around the sun rise time and hence cooler temperature. Roads are still warm that time because of its absorption characteristics mentioned above and hence appear bright.

Natural and man-made vegetation: The vegetation appears to be of different tones which depend highly on the moisture content of the soil and the leaves of the trees. Moisture in the moist soil keeps them cooler than the drier soil and hence some darker patterns whereas the moisture in the leaves retains heat for longer duration and being warmer it has lighter tone at some places. One can see the variations in the shades in vegetation.

Sidewalks & Patio: They appear of lighter tone. The main reason could be the material of which they are made. The material seems to absorb heat and hence remain warmer and therefore appears of the lighter tone.

Storage Sheds in backyards: They appear darker in the aerial image since at night/dawn there is no heat source and hence cooler temperature. Also, the material of which they are made does not seems to retain heat and hence are cold. Therefore they look darker.

Automobiles: Most of the automobiles (cars) appear dark in the image since there is no heat source (sun) at night and at dawn, the temperature just starts to warm up because of the sunrise but not yet heated up. Hence the cars are cold and appear darker. Although in some cars you can see hot spots which could be due to the heated engine (car may be running and just parked) so the front engine is heated and appears brighter even at the dawn/night.

Bright spots on many of the roofs: There are bright spots of many roofs explaining that there is higher radiant temperature over there than the surroundings. There is probably a heat source, it could be a heating system’s vent, a chimney, which is keeping the temperature warmer out there and looks brighter in the aerial image.