Date of Submission

2-28-1991

Date of Award

2-28-1992

Institute Name (Publisher)

Indian Statistical Institute

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Subject Name

Computer Science

Department

Electronics and Communication Sciences Unit (ECSU-Kolkata)

Supervisor

Majumdar, Dwijesh Dutta (ECSU-Kolkata; ISI)

Abstract (Summary of the Work)

The observation of a target by a device plaoed at some distance from it is cal.led remote sensing as ngainst in situ sensing where the sensor is kept in contact with the target. Usually physical emanations such as the electr omagnetic radiation from the target s observed by the sensing device. Sensors mounted on aircraft or satallite platforms measure the amount of energy reflected from or emitted by the earth's surface. Sensors scan the ground below a nd to either side of the satellite platform and as the platform noves forward, an image of the earths surface is formed.A satellite remote sensing system in its simplest form can be conceptualized in Fig. 1.1. The is usually the as sun electromagnetic source and the energy from the sun reaches the target. The radiation by the time it reaches the target is affected by the intervening med.Lum. Some energy gets absorbed; some get reflected and the remain.ng is allowe:d to reach the target. Depending on the type of the target, its surface characteristics, some part of this incident cadiation is absorbed; some transmitted and the remaining energy is reflected back into the medium. This radiation together with the radiation em itted by the target itself and that emitted by the target neighbourhood reaches the satellite sensor after passing through the medium. As before, the medium absorbs a part of the radiation. This process of absorption, transmission and reflection at the target is dependent also on the wavelength or the incident radiation. In principle, all targets at temperatures above 0 deg K radiate electromagnetie energy but the anount of energy radiated and the predominant wavelength bands very according to nature of the target (Barrett and Curtis, 1982, Curran, 1985).Although sensing devices could be designed to observe the entire range of electromagnetic wavelengths, attenuation by atmospheric constituents preclude the utility of certain wavelengths. The actual wavelength band to which a sensor is made sensitive depends upon the application to which the data will be put to use and the interaction mechanism between the electromagnetic radiation and targets being observed.1.2 PROPERTIES OF REMOTE SENSING DATAIt is not possible to directly detect the surface features from satellite images they have to be inferred from the radiance measurements. Recognition of features from a remote sensing image is based on the principle that: every feature has a unique spectral signature. Fig 1.2 shows the idealized spectral reflectance curves for vegetation, soil and water. It is an idealized curve because it has beer obtained under the best conditions, with no atmospheric hind rances and with a spatial resolution approximating a point. Thus vegetation has low reflection in the visible part of the a electromagnetic spectrum and a relatively high reflectance in the near IR part. Non-vegetated surfaces, for e.g., bare soil, water and concrete commonly have similar reflectances at visible and near IR wavelengths, viater has a higher reflectance at shorter wavelengths and virtually reflectance at wavelengths greater than 0.7 pm.

Comments

ProQuest Collection ID: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqm&rft_dat=xri:pqdiss:28842917

Control Number

ISILib-TH297

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

DOI

http://dspace.isical.ac.in:8080/jspui/handle/10263/2146

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