(1) In the broadest sense, the measurement or acquisition of information about some property of an object or phenomenon, by a recording device that is not in physical or intimate contact with the object or phenomenon under study.
(2) Instruments that record characteristics of objects at a distance, sometimes forming an image by gathering, focusing, and recording reflected light from the Sun, or reflected radio waves emitted by the spacecraft.
[Source: Glossary of the Landsat Missions, 06/16/2017]
The scanning of the Earth by satellite or high-flying aircraft in order to obtain information about it. ‘Remote sensing technology is deemed to include photo interpretation, photogrammetry, aerial photography, image processing, and other related technologies in the field of survey, planning, and management of natural resources, and other areas of application where the technology is considered to be appropriate’ (Indian J. Remote Sensing).