Abstract
The temporal change of thermal environment caused by weather conditions or by waste heat is one important index of environmental information. A temporal change of temperature is formally given by the difference between the thermal infrared images collected at the times t1 and t2. However, objects having different thermal infrared emissivities and temperatures are taken simultaneously into a pixel of remotely sensed multispectral and multitemporal images, and the proportions of different objects in the pixel change with time. Therefore, for two temporal thermal infrared images, one cannot distinguish between the true temporal change of the surface temperature and the apparent change of it caused by the temporal change of the proportions of the objects in the pixels.
The exterior product image processing by using the image information of the visible channels removes the apparent temporal change of surface temperature caused by the changes of the proportions on the two thermal infrared images. Consequently, the temperature change on the processed image gives the true temporal temperature difference pattern which is independent of the proportions of the various objects on the earth's surface.
