- The term 'remote sensing' literally means observation and gathering data from a distance.
- But in more specific terms it refers to the recording and analysis of electromagnetic radiation in the visible, infra-red, ultraviolet and microwave wavelength reflected, scattered or radiated from various objects on Earth.
- In present day satellites-based remote sensing, 'multi-spectral imaging' is used that is simultaneous imaging of the Earth's surface in more than one color, or wavelength, both visible and invisible, to bring out a lot of latent information unavailable in ordinary photographs.
- Unlike ordinary cameras which use photographic film to record images, multi-spectral cameras carried on board Remote-Sensing Satellites use solid-state electronic destroy known as Charge-Coupled Devices or CCDs to receive the images.
- Remote sensing satellite's orbit is called a polar orbit because it passes over both the polar regions of the earth in a north-south direction.
- It is called sun-synchronous because the orbit also keeps step with the Sun in that it passes over a specific location on the sun lit side of the Earth when the Sun is at the same height above the eastern horizon.
- This helps in image interpretation because with the same Sun-angle, the shadows cast by different features are then only a function of their heights.
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