What is Remote Sensing?
Remote sensing is that the science of accumulating facts about the thing , area or phenomenon without doing any physical contact with the thing .
Mortals with their noses, eyes, and ears are always smelling, sensing and hearing objects from their surroundings. In order that they even have the quality of RS.
In order to review the areas, object or phenomenon on the surface of the world, which is usually called target, RS is that the most well liked technique.
Conventionally, RS detects the feature of the Earth’s surface by analysing and interpreting the multispectral electromagnetic radiations emitted or reflected by the surface of the world .
For analysing these different wavelengths, scanners are used, which situated at various platforms like aircrafts, satellites, etc.
Aerial photographs within the visible range of the electromagnetic wavelength was the first sort of remote sensing.
With the improvement of technology, the gathering of infornaation is expanded to other wavelengths like near infrared, thermal infrared and microwave.
This multispectral data collection makes RS a really dependable and reliable system in collection of data .
The capacity of RS has expanded to an excellent extent with the assistance of various satellites during the previous couple of years.
The study of varied phenomena, with the assistance of satellite-based information that changes continuously over the time in remote areas on the surface , is understood as natural resources management.
Nowadays, it’s a crucial a part of remote sensing.
Principle of Remote Sensing
The detection and discrimination of the targets or to gather the knowledge about the surface features of the world basically refers to the recording and analysis of electromagnetic energy that’s reflected or emitted by the target Object.
The amount of reflected energy is different for various objects depending upon their physical, chemical and structural properties which is understood as spectral signature.
The analysis of multispcctral bands of electromagnetic energy for collecting information requires knowledge of optics, photography and spectroscopy with computer interfacing.
This integrated approach of research and recommendation about the target on the Earth’s surface is tenned RS system.
Components of RS
Remote sensing is that the preferred and usual method of knowledge collection over the globe.
The basic mechanisms or techniques are more or less same and, therefore, the various components which make this technique successful also are an equivalent .
It’s understood that there are four fundamental components of RS. They’re as follows:
l . A target,
2. An energy source,
3. A transmission path through atmosphere, and
4. A sensor.
The target is nothing but an object on the Earth’s surface, to be studied with none physical contact. There should be a source which illuminates or provides electromagnetic waves to the target.
The amount and kind of this electromagnetic radiation or energy radiated and emitted back from the target object depends upon the spectral signature of the thing .
The radiating energy passing through the atmosphere is collected during a sensor located at a distant place from the thing .
The collected data by the sensor within the type of electromagnetic energy is then transmitted to a station located on the Earth’s surface, where it’s processed digitally.
The processed data is then interpreted with the assistance of computer software to predict the particular features of the target of interest.
Weather forecasting may be a very a preferred example of remote sensing. Here, the target is that the Earth’s surface.
The source of energy comes from the sun. The incoming source of electromagnetic energy falls over the surface of the world and warmth energy (infrared radiation) is radiated back to the sensor located within the satellite or the other platform located distant from the Earth’s surface.
The energy travels through the atmosphere both at the time of emission and reflection. After collecting the infrared by the sensor, it returns back to the collecting station located over the Earth’s surface.
The data are analysed here with the assistance of spectrophotometer and computer-supported software . The analysed data then gives the status of the temperature at the various parts of the earth [Fig. A.14].
Process of Remote Sensing
The process of remote sensing for acquiring information about the target, or maybe the Earth’s surface, comprises seven elements.
The interaction between the incident radiation and reflected radiation of energy with the atmosphere is extremely important.
The complete process is described within the (Fig. A. 14.) subsequent are the seven important elements of RS:
1. Energy Source or Illumination
The most important elements of RS may be a source of energy from where electromagnetic energy is incident upon the target. Sun is that the the excellent example of energy source.
2. Interaction of Radiation with Atmosphere
The energy travels from the energy source to the target and from the target to the sensor. For all the incidents, the electromagnetic energy take place in close contact with the atmosphere.
The interaction among the energy and hence the atmosphere passing through is additionally a component of the RS system.
3. Interaction with the Target
After producing from the energy source, the electromagnetic wave passes within the atmosphere and interacts with the target. This interaction is that the function of spectral signature of the thing .
4. Recording of Energy by the Sensor
The incident radiation is partially absorbed, scattered, reflected and emitted by the thing .
This reflected or emitted radiation is transmitted to the sensor, located at a remote place from the thing , for its record.
5. Transmission, Reflection and Processing
The data within the sensor is collected generally in electronic form. it’s then processed and transmitted to the gathering station on the Earth’s surface, where it’s received and processed digitally.
6. Interpretation and Analysis
The collected data in digital form is processed with the assistance of highly sophisticated instruments electronically and final interpretation is completed by computer software.
The last and final element of remote sensing is it’s application after acquiring information related to the target.
Types of Remote Sensing
The remote sensing work will be classified supported techniques adopted to predict the features of the thing with none physical contact with it.
1. Based on Energy Source
(a) Passive RS
RS work where system has no energy source of its own is termed passive RS.
During this system, RS work generally depends on an external energy source just like the sun.
(b) Active RS
An active RS system, has its own energy source for illumination. RS data is obtainable any time, day or night, for all the sensors.
2. Based on electromagnetic spectrum
(a) Optical RS
The highly corrupted instrument emits laser beams upon the target and gets return the reflected radiation for interpreting the types of the thing for the visible, near infrared, middle and short-wave infrared
portion of the electromagnetic spectrum starting from 300 nm to 3000 nm. this sort of labor is completed by LIDER (Light Detection and Ranging), an comprising transmitter and receiver.
(b) Thermal RS
Thermal RS deals With the wavelengths of radiation within the thermal infrared region, starting from 3000 nm to 5000 nm and 8000 nm to 14000 nm.
(c) Microwave RS
This sort of RS uses the wavelength starting from 1 nm to 1 m of the electromagnetic spectrum.
Most microwave sensors are active sensors. Radar may be a good cxample of a microwave sensor.
In this system, microwave is transmitted from the source to the thing . The sensor collects the reflected radiation to provide the gap of the thing from the station within a fraction of a second.
We have covered in this post the definition, types, principal, and components of Remote sensing.