Remote sensing
Acquiring information about objects without physical contact.
Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring information about Earth and other planets, and it is used in numerous fields including geophysics, geography, land surveying, and most Earth science disciplines, as well as military, intelligence, commercial, economic, planning, and humanitarian applications.
- field
- Earth observation, geophysics, military intelligence
- known_for
- Acquiring information about Earth and other planets via satellite- or airborne-based sensor technologies
- methods
- Passive remote sensing (e.g., reflected sunlight) and active remote sensing (e.g., radar, lidar)
- applications
- Monitoring deforestation, glacial features, ocean depths, weather, national security, and natural resource management
Lore & Background
Remote sensing can be divided into two types of methods: passive and active. Passive sensors gather radiation that is emitted or reflected by the object or surrounding areas, with reflected sunlight being the most common source. Examples include film photography, infrared, charge-coupled devices, and radiometers. Active collection emits energy to scan objects and areas, then detects and measures the reflected or backscattered radiation; radar and lidar are examples where the time delay between emission and return is measured to establish location, speed, and direction.
Reader's Guide
Remote sensing makes it possible to collect data of dangerous or inaccessible areas, such as monitoring deforestation in the Amazon Basin, glacial features in Arctic and Antarctic regions, and depth sounding of coastal and ocean depths. It also replaces costly and slow data collection on the ground, ensuring areas or objects are not disturbed. Orbital platforms collect and transmit data from different parts of the electromagnetic spectrum, providing researchers with enough information to monitor trends such as El Niño and other natural phenomena. Applications include natural resource management, agricultural land usage and conservation, greenhouse gas monitoring, oil spill detection, and national security. The most common instruments are radiometers and photometers, which collect reflected and emitted radiation in a wide range of frequencies, including visible, infrared, microwave, gamma-ray, and rarely ultraviolet. Hyperspectral imaging produces image cubes where each pixel has full spectral information, used in mineralogy, biology, defence, and environmental measurements. Remote sensing also allows researchers to monitor desertification risk areas and assess biodiversity at different spatial scales.
Did You Know?
- Remote sensing can be split into active methods (e.g., radar, lidar) and passive methods (e.g., film photography, radiometers).
- Doppler radar is used by local law enforcement for monitoring speed limits and for enhanced meteorological collection.
- Landsat thematic mappers have been in use since the early 1970s, taking images in multiple wavelengths.
- Radiometers can detect artificial light emissions at night, providing data on population, GDP, and infrastructure damage.
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