VERSION 2 CE IIT KHARAGPUR PDF

Different types of remotely sensed images 3. Application of Remote Sensing in water resources engineering 4. Application of GIS in water resources engineering 6. The technique of remote sensing has picked up in the past half a decade, largely due to the availability of digital computers, improved communication systems, digital imaging techniques and space technology. Remotely sensed data can be said to have its origin in photography, where the information about a target area is interpreted from photographs.

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Different types of remotely sensed images 3. Application of Remote Sensing in water resources engineering 4. Application of GIS in water resources engineering 6.

The technique of remote sensing has picked up in the past half a decade, largely due to the availability of digital computers, improved communication systems, digital imaging techniques and space technology. Remotely sensed data can be said to have its origin in photography, where the information about a target area is interpreted from photographs.

Later this technique was extended to aeroplane - borne cameras giving rise to the science of aerial photography. This technique is still used, but largely the signal cameras have been replaced by Laser operated ones where the reflectance of a Laser beam projected from the bottom of the aircraft is sensed by electronic sensors. In this chapter we shall discuss remote sensing using satellite as India has strived ahead in this field and made good use of satellite images.

The satellite launching program of our country is one of the most ambitious in the world, and is still continuing to be so in the future as well. Amongst other fields, the Water Resources Engineers have benefited greatly by using satellite imaging techniques, some applications of which have been highlighted in this chapter. The other topic that is discussed in this lesson is the Geographic Information System GIS that has wide applications in planning any spatially distributed projects.

Fundamentally, a GIS is a map in an electronic form, representing any type of spatial features. Additionally, properties or attributes may be attached to the spatial features. Apart from its spatial data analysis capabilities, it provides an interface to remotely sensed images and field surveyed data. This technique has specifically benefited the Water Resources Engineers, which has been discussed in some detail.

Photogrammetry, that is, taking pictures of the land surface from a low flying aircraft and comparing subsequent pictures to obtain the terrain relief has been extensively used in the last century and many books have been written on the subject.

In satellite remote sensing, too, cameras are fitted to the orbiting satellite and are focussed towards the earth. However, the cameras are special in the sense that they are sensitive to other wavelengths of the electromagnetic spectrum as well. As may be observed from Figure1, the electromagnetic spectrum identifies the wavelength of the electromagnetic energy, of which the visible portion or light occupies only a small portion.

Actually, electromagnetic energy refers to light, heat and radio waves. Ordinary camera or the human eye are sensitive only to the visible light. But the satellites are equipped with Electromagnetic Sensors that can sense other forms of electromagnetic radiations as well. This includes not only the Blue 0.

The common remote sensing systems operate in one or more of the visible, reflected-infrared, thermal-infrared and microwave portions of the spectrum. However, as illustrated in Figure 2, not all of this energy reaches the surface of the earth, since part of the energy gets either scattered, absorbed or reflected by the atmosphere or cloud cover, if any. Specifically, it may be said that although the electromagnetic radiation reaching the top of the atmosphere contains all wavelengths emitted by the sun, only specific wave bands of energy can pass through the atmosphere.

This is because the gaseous components of the atmosphere act as selective absorbers. Molecules of different gases present in the atmosphere absorb different wavelengths due to the specific arrangement of atoms within the molecule and their energy levels. The main gaseous component of the atmosphere is nitrogen, but it has no prominent absorption features.

Oxygen, Ozone, Carbon Dioxide and Water Vapour, the other major components absorb electromagnetic wavelengths at certain specific wavelengths. The wavelengths at which electromagnetic radiation are partially or wholly transmitted through the atmosphere to reach the surface of the earth are known as atmospheric windows, as shown in Figure 3. Since these radiations reach the surface of the earth, they are useful for remote sensing as they would be reflected or absorbed by the features of the earth giving the typical signatures for the sensors in the satellite or any other space borne device to record.

This is shown graphically in Figure 4. The remote sensing system sensors are designed in such a way that can capture information for those wavelengths of electromagnetic radiation that occur within the atmospheric windows.

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Version 2 CE IIT, Kharagpur Notes | EduRev

Different types of remotely sensed images 3. Application of Remote Sensing in water resources engineering 4. Application of GIS in water resources engineering 6. The technique of remote sensing has picked up in the past half a decade, largely due to the availability of digital computers, improved communication systems, digital imaging techniques and space technology. Remotely sensed data can be said to have its origin in photography, where the information about a target area is interpreted from photographs.

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Module 3 - NPTel

Irrigation Engineering. The total depth of water required to raise a crop over a unit area of land is usually. How much water is required for the proper growth of important crops How to estimate the water demand of crops What are the different seasons of crop growth What are the usual cropping patterns On what variables does the crop water requirement vary? Primarily, the plot or field is expected to receive water from rain falling on the land surface.

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