Solution:

Types of remote sensing (Active and Passive) :

• The system of remote sensing is classified into two types.

• 1) Active remote sensing.

• 2) Passive remote sensing.

• (1) Active remote sensing:

• It is the process of sensing the distant target in which the sensors direct their own generated radiations towards the target and then it detect the amount of energy reflected by the target.

• Examples: Radar, Radar Altimeter, Wind scatterometer, Synthetic Aperture Radar (SAR) and Camera with flash.

• (2) Passive remote sensing:

• It is the process of sensing the distant object in which the sensors detect only the amount of energy radiated by the object.

• Examples: Aerial photography, Camera without flash and Microwave radiometer.

Components of remote sensing:

• The electromagnetic remote sensing process is divided into two components namely,

• (1) Date acquisition.

• (2) Date analysis.

• Date acquisition :

• The schematic diagram of data acquisition is shown in the figure. In this process, five distinct elements are involved. They are,

• Energy Sources.

• Propagation of energy through the atmosphere.

• Energy interaction on earth surface.

• Space borne sensors record the reflected energy.

• Conversion of sensors data in the form of pictures or digital information.

• The electromagnetic radiations emitted by the energy source are propagated through the atmosphere and incident on the surface of the earth.

• Then the radiations are reflected back towards the space borne remote sensors. The sensors generate the receiving data into picture or digital forms.

• Data analysis:

• The schematic diagram of data analysis is shown in the figure. The data analysis is divided into two separate processes. They are,

• 1) visual interpretation technique.

• 2) Digital analysis.

• In visual interpretation techniques, various viewing instruments are used for examining and analysing the pictorial data.

• In digital analysis the computers are used to analyse the digital data. All analyzing data are viewed in the information products by users. The data analysis can be carried only with the help of reference data.

• The process that involves examination and analysis of pictorial data is called visual image interpretation techniques.

• This process involves the use of fundamental picture elements like tone, texture, pattern, shape and size in order to identify the various objects. Stereoscopic instruments are used for this purpose.

• Use of computers to analyse digital data is known as digital image processing techniques. If the data is available in digital form, it can be analysed on interactive computer systems for getting statistical data.

• This statistical data is analysed using computers by comparing with the actual “signatures” of the objects collected through field visits. This system of classification of objects is quite accurate.