ABSTRACT
Remote sensing is the process of collecting data about objects or landscape features without coming into direct physical contact with them. Most remote sensing is performed from orbital or suborbital platforms using instruments designed to measure electromagnetic radiation reflected or emitted from the earth’s surface. The most common form of remote sensing is human vision. Photography is also a common and easily understandable form of capturing remotely sensed data. The placement of a camera onto an airplane vastly improves the usability of the data for scientific applications, and for our purposes, also introduces the concept of platform. The human eye is carried within the platform of the body. The location and orientation of the sensor, the eye itself, is determined by its position within the body platform and the direction or orientation is controlled by the movement of the head and body as a whole. It is important to recognize the inherent difference between sensor and platform. The human eye is an example of a passive sensor. It is unable to create its own energy source. A camera without a flash is a passive sensor. In a dark room no information can be recorded on the film. However, add a flash to the camera, and even in an entirely dark room, the flash creates enough light for the film to record some information. The camera with flash is an active sensor. Most earth observation satellites are passive sensors, with radar being the notable active exception.
