Remote Sensing Basics Page 3 of 4 The reflected energy from the earths surface can neither be seen nor photographed, but can be sensed with appropriate instruments, such as thermal devices, in particular radiometers. The sun has a much higher energy peak and is a level of energy to which our eyes and photographic film are sensitive to. Electromagnetic waves are radiated through space, and all forms travel at the speed of light, which is approximately 300,000 kilometres per second. When the energy interacts with an object the radiation is either: · REFLECTED off an object · ABSORBED by the object, or · TRANSMITTED through the object. Incident radiation is the total amount of radiation that comes in contact with the object, and is therefore equivalent to the: reflected radiation + absorbed radiation + transmitted radiation. All substances, whether they are natural or synthetic are capable of reflecting, absorbing and transmitting various fractions of electromagnetic energy. The proportions of these fractions vary for different features and enable us to distinguish various objects in an image. However remote sensing is primarily concerned with the radiation that is reflected, as this reflected radiation allows our eyes to see colours, allows infrared film to record vegetation and enables the production of radar images of the earths surface. Click HERE and attempt the electromagnetic spectrum activity. | 1 | 2 | 3 | 4 | Page 3 of 4