Remote sensing is a process of obtaining information about an object area and phenomenon through the analysis of data obtained by a device without being in physical contact with them. It is a methodology to study the physical and chemical properties of the object from distance. In the field of surveying, remote sensing plays a vital role.
Remote sensing methods make use of reflected infrared bands and microwave portion of the electromagnetic spectrum. The collections of data are carried out by sensors. Camera multi-spectral scanner radar etc. is used as sensors. Aircraft and satellites are common platforms used for remote sensing.
Principle Of Remote Sensing
Remote sensing uses electromagnetic energy and to a great extent relies upon the interaction of electromagnetic energy on the object. It refers to the sensing of electromagnetic radiation which is reflected scattered or emitted from the object.
Classification Of Remote Sensing
Passive remote sensing: In passive remote sensing sun is used as a source of electromagnetic energy and records the energy that is naturally radiated or reflected from the object.
Active remote sensing: Active remote sensing uses own source of electromagnetic energy which is directed towards an object and returns energy is measured by EDM.
Idealized Remote Sensing System
Energy source: The passive remote sensing relies on the sun whereas active remote sensing uses its own source of energy to provide uniform energy over all wavelengths.
Propagation of energy from the atmosphere: The EM energy passes through the atmosphere and the reflected energy from the earth’s surface is caught by sensors.
Interaction of energy with earth surface: The electromagnetic energy propagates through the atmosphere. While propagating some energy is absorbed some energy scattered and only little energy reaches the earth’s surface. These processes are not mutually exclusive. Which process actually occurs depends upon the wavelength of radiation angle of incidence roughness of surface and composition of surface materials.
Airborne/ spaceborne sensors: Sensors are mounted on satellites airplanes or hot air balloons. They are highly sensitive to receive and record re-transmitted radiations.
Transmission of data to earth station and data product generation: Data from sensing system is transmitted to ground stations. The data products may be pictorial or digital.
Multiple data users: Multiple data users are those who have knowledge of remote sensing data and analysis techniques. The same set of data becomes various forms of information for different users as per their skill and understanding.
Uses of Remote sensing in surveying
- It is used in estimating the average and yield of important crops.
- Used to survey the forest coverage.
- To forecast drought conditions.
- To develop irrigation command area Forecast flood areas and decrease the risk.
- For mapping wasteland and classify.
- Groundwater exploration.
- Exploration of minerals and mines Wildlife habitat assessment
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