RFRemote Sensing Basics: Principles and Applications
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Remote sensing is a technique used to gather information about objects or areas from a distance, typically using satellites or aircraft. By capturing data in the form of images or signals, remote sensing helps in monitoring environmental changes, mapping landscapes, and conducting research.
This article explores the fundamental principles of remote sensing, how it works, and its wide range of applications.
Remote sensing is a technique for studying the land, ocean, and atmosphere using instruments called sensors mounted on satellites and aircraft. The sensors help create images of any location on Earth.
Types of Sensors
There are two main types of sensors: passive and active.
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Passive sensors rely on natural energy sources and detect energy that falls upon them. Examples include high-definition cameras and electro-optic scanners. These sensors record sunlight reflected by objects, forming a photograph or data that can be converted into imagery. They also record the sun’s heat reflected by objects (reflective infrared radiation) and the temperature of hot objects (thermal infrared radiation) using infrared film and scanners. Radiometers are another type of passive sensor that detects low levels of very high-frequency radio waves emitted by objects.
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Active sensors, on the other hand, provide their own source of energy. These sensors emit radiation towards the target and detect the reflected radiation.
Color and Earth Resources
Different objects emit or reflect different wavelengths of energy. This allows us to distinguish them by different colors in the resulting imagery.
| Color | Earth Resource |
|---|---|
| Black | Clear water |
| Blue | Turbid water |
| Cyan | Bare soil and buildings |
| Green | Dense forest |
| Orange | Grass |
| Red | Bare soil/Built-up area |
| White | Buildings |
| Yellow | Shrubs and less dense forests |
Specifications of Satellite Radiometers
Here are some typical specifications for remote sensing satellites or radiometers:
- Orbit Altitude: 800 to 900 km
- Orbit Period: 90 to 100 minutes
- Orbit Type: Sun-synchronous with an inclination of approximately 99 degrees.
- Wavelength Band: 0.4 to 0.9 µm
- Swath Width: 180/70/40 Km (varies depending on the sensor)
- Resolution: 80/40/15 meters (varies depending on the sensor)
- Revisit Time: Approximately once every 20 days
Applications
Remote sensing finds application in diverse fields, including:
- Agriculture monitoring
- Deforestation and forest degradation assessment
- Urban planning
- Disaster management
- Weather forcasting
- Climate change studies
Conclusion
Understanding the basics of remote sensing and its underlying principles is essential for leveraging this technology in various fields, such as agriculture, forestry, and urban planning. As remote sensing continues to evolve, it offers valuable insights for making informed decisions and addressing global challenges, making it a key tool for scientific and practical applications.
