Remote Sensing

Remote sensing is the science and the art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not contact with the object, area or phenomenon under investigation.(Lillesand and Kiefer, 1994) It is a tool for resource survey and inventory which provides a primary source of up to date geographic data.

Devices which can collect information about an object from a distance, without touching it, except perhaps with energy emitted from the sensor. ‘Near’ remote sensors are ‘close’ to the object, e.g., infrared heat detectors for home insulation, ordinary photographs. We will consider ‘far’ remote sensors (from aircraft and spacecraft) that study areas of the earth’s surface, since land evaluation is always concerned with such areas.

Key point: The products of remote sensing are usually not direct samples of the phenomena of interest, so must be calibrated against reality in order to be useful. This process is called interpretation or ground truthing and may be manual or automated.

Reading this computer screen is Remote Sensing!!! Your eye is the sensor!!! Other common remote sensing systems include a 35 mm camera, radars, and fathometers. Radars can determine the position, course, and speed of aircraft and ships. Shipboard fathometers determine the distance from the ocean surface to the bottom (the depth).

Today aerial photo-interpretation remains the principle source of detail geographic information because of the detail level scale or observation. The limiting factors of aerial photographs include high cost, reliability, the time need to interpret large area and transferring the interpret information to the base map for georeferencing.

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