Remote Sensing Basics : Understanding core principle and Applications
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 as sensors mounted on satellites and aircrafts. The sensors help create the images of any location of the earth. There are two types of sensors viz. passive and active.
Passive sensors require natural energy and can detect energy falling on them. The passive sensors such as high definition cameras and electro-optic scanners record the sunlight reflected by objects in the form of a photograph/data which can be converted to an imagery. The sun's heat reflected by objects(i.e. reflective infrared radiation) and the temperature of hot objects(i.e. thermal infrared radiation) are recorded using infrared film and infrared scanners. Often low levels of very high frequency radio waves emitted by objects are detected by sensors referred a radiometers.
Different objects emit different wavelength and hence distinguised by different colors in the image as mentioned in the following table.
| Color | Earth resource |
|---|---|
| Black | Clear water |
| Blue | Turbid water |
| Cyan | Base soil and buildings |
| Green | dense forest |
| Orange | Grass |
| Red | Base soil/Builtup area |
| White | Buildings |
| Yellow | Shrubs and less dense forests |
Active sensors provide their own source of energy. These type of sensors emit radiation towards the target and detects the reflected radiation from the target.
Specifications of Satellite radiometer
Following are the silent features or technical specifications of a typical remote sensing satellite or radiometer.
• They are placed in a orbit at a distance of 800 to 900 Km
• Orbit period is usually about 90 to 100 minutes.
• Placed in sun-synchronous with inclination of 99o.
• Wavelength band 0.4 to 0.9 µm
• Swath: 180/70/40 Km
• Resolution:80/40/15 meters
• Repetivity:once in 20 days
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.