Remote Sensing and GIS.pdf it is not possible to get the same energy
- 1. Dr.S.Poongothai Professor of Civil Engineering Annamalai University, Annamalainagar-608 002 Tamilnadu, India spoong86@yahoo.com REMOTE SENSING AND GIS by
- 2. DEFINITION OF REMOTE SENSING ❖Remote Sensing is an application of photogrammetry in which imagery is acquired with a sensor, other than (or in addition to), a conventional camera through which a scene is recorded, such as by electronic scanning, using radiations outside the normal visual range of the film and camera – microwave, thermal infrared, ultraviolet as well as multispectral. Special techniques are applied to process and interpret remote sensing imagery for the purpose of producing conventional maps, thematic maps, resource surveys and so on, in the fields of agriculture, archaeology, forestry, geography, geology and others.
- 3. REMOTE SENSING IS AN APPLICATION OF PHOTOGRAMMETRY ❖In which imagery is acquired with a sensor, other than (or in addition to), a conventional camera through which a scene is recorded, such as by electronic scanning, using radiations outside the normal visual range of the film and camera – microwave, thermal infrared, ultra violet as well as multi spectral. ❖Special techniques are applied to process and interpret Remote Sensing imagery for his purpose of producing conventional maps, thematic maps, and resource surveys, and so on in the fields of agriculture, archeology, forestry, geography, geology and others.
- 4. ❖Photogrammetry The art and science of technology of taking relative measurements on photographs about physical objects and environment. These measurements are obtained by Interpretation of photographic images. ❖In 1839, Aerial photography-Topographic surveying – (1840) North America by Captain Deville, the surveyor general of Canada. In 1902, Invention of aeroplane by Wright-Brothers led to advanced aerial photography. ❖Photo-Interpretation “The art of examing the photographic images of objects for the purpose of identifying those objects and deducing their significance”.
- 5. ❖Remote sensing is the science and art of obtaining information about an object, area or phenomenon through the analysis of data acquired by a device that is not in contact with the object, area or phenomenon under investigation. (e.g.) Human sight, smell and Hearing. Recognization of words – Remote sensing. ❖Remote sensing of earth resources encompasses all information above or below the Earth, collected from a distance, such as aerial photographs, satellite images etc.. ❖Remote sensing Images, obtained from the orbiting satellites are capable of providing quantitative as well as qualitative information about objects. ❖1950 – Started. But in 1960, Launching of – First US Meteorological satellite TIROS – 1.
- 6. TYPE OF REMOTE SENSING DATA Aerial satellite RS applications Aerial Satellite * Platform used: Aircraft Satellite *Data products: Black & White &Coloured Black& White, FCC,CCT,CDs Applications Agriculture Forestry mapping Forestry, Snowfall Hydrology Environmental studies Res.Sedimentation Disaster management River morphology Oceanography Watershed conservation Terrain Investigation Flood estimation LU/LC Geology Investigation Soil Soil mapping SW &GW LU/LC mapping Geology & Geomorphology Corp yield forecast
- 7. ADVANTAGES 1. Satellite images – permanent record, provide useful + in various wave bands 2. Large area coverage – regional surveys – of large features 3. Repetitive coverage allows monitoring of dynamic themes like water, agriculture, etc. 4. Easy data acquisition over inaccessible area. 5. Data acquisition @ different scales of resolutions 6. Single RS image – Different purposes of applications 7. Compatible to Computer – for processing 8. Lab analysis – Reducing the field work. (Cost effective) 9. Map revision @ moderate to small scales is economical and faster 10.Colour composites can be produced from 3 individual band images, which provide better details of the area than a single band image or aerial photograph. 11.Stereo – satellite data may be used for 3D- studies.
- 8. DISADVANTAGES 1. Expensive for small areas, particularly for one-time analysis. 2. Specialized training for analysis of images. 3. Interpretation equipments, for digital Interpretation, is costly. With the advent of different type of sensor systems, the range of data products that are now available for mapping purposes, besides conventional photographs, has increased. These products are listed bellow: 1. Space photographs: These include metric & non metric, black & white, colour & infrared (dia positives & negatives) mosaics and ortho – photographs. 2. Satellite images: These include LANDSAT MSS &TM,SPOT HRV,IRS LISS I, LISS II & LISS III, etc. dia positives & negatives, FCCs, stereo pair, computer compatible tapes, floppies and CDs
- 9. Basic physical principles of Remote sensing / Wave theory In physical terms , RS is concerned with the Measurement and estimation of the variations in electromagnetic (EM) energy which occur when energy of this type interacts both with the earth’s atmosphere & with the earth’s surface. The terms EM energy refers to all energy which travels in a periodic harmonic manner at the velocity of light using the well-known relationship. λ = c/f Where λ is the wave length f is the frequency c is the velocity of EM energy
- 10. THE EM SPECTRUM 0.4 0.5 0.6 0.7(µm) B G R reflected infrared 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 101 102 103 104 105 106 107 108 109 Visible Infrared Micro wave
- 11. EM spectrum – Region of Interest of Spectral range for Remote Sensing i) Visible - 0.36-0.79 µm @ 0.5 µm Reflected IR ii) Infrared between visible and microwave region Thermal IR iii) Microwave – 1mm (10 3 µm) – 1m (106 µm)
- 12. REFLECTED AND EMITTED EM ENERGY Distinction between Reflected & emitted energy: During daylight, the radiant energy from a scheme consists of 2 components i) At wavelength upto about 3 µm, the energy is predominantly– reflected sunlight *Human eyes & photographic film are sensitive to reflected energy with in this wavelength rays ii) In contrast at longer wavelength (i.e) greater than about 3 µm the dominant type of radiation energy is that which is emitted by a body rather than that which is reflected. (e.g.) Infrared region of the EMS With in this region it is apparent that as the wavelength increase the emitted infrared component becomes progressively more sight perfected infrared – can not be sensed by photographic emulsion
- 13. STEFAN – BOLTZMANN LAW It is possible to quantify the amount of energy a body is emitted by means of …………… Law which states that W = CεT4 Where W- is the Radiant emittance, watts m-2 ε - is the emissitivity of the object C - is the S – B constant equal to 5.7x10-8 watts m-2 k-4 T - is the absolute temperature of the object (k) Three significant conclusions may be drawn from this law:
- 14. I)The energy emitted from a body increases very rapidly with an increase in temperature. II) Emissivity (ε) of an object is defined as a factor which describes how efficiently an object radiates energy in comparison to a “black body” which has an emissivity value of one. Emissivity is defined as Radiant emittance from an object @ a temperature E (λ) = Radiant emittance from a black body @ the same temp. Where E (λ) represents the emissivity @ a particular Wave length value Range of emissivity between 0 and 1
- 15. Table 1 Emissivity of a selection of materials (Within the 8-14 µm W.L band) Material Ave. emissivity Clay soil - 0.98 Water - 0.97 Sandy soil - 0.88 Gravel - 0.88 Buffled stainless steel - 0.16 III It should be possible to infer indirectly the temperature of the body knowing the emissivity of the object. This represents the basis of the technique of thermal infrared RS (Range: 3-14 µm)
- 16. WIEN’S DISPLACEMENT LAW λmax = 2897 T This law states that Where λ max = Wave length of max spectral emittance & T = temperature (ok) # To quantity the wave length at which the maximum spectral emittance will occur #This law explains the Wave length shift or displacement, which occurs in the values associated with the energy emitted from the sun (0.5 µm) and from the earth surface (9.7 µm)
- 17. PRINCIPLE OF CONSERVATION ENERGY When EM energy is incident on the Earth’s features , three fundamental energy interactions with the features are possible EI (λ) Incident energy ER (λ) Reflected energy EA (λ) Absorbed energy EA (λ) Absorbed energy Fig-Basic Interaction between EM energy & Earth surface features Applying the Principle of conservation of energy EI(λ) = ER(λ)+EA(λ)+ET(λ) ET (λ) Transmitted energy
- 18. The proportions of ER(λ), EA(λ) &ET (λ) will vary for different earth features depending on their physical & chemical characteristics conditions. RS may be defined as a method, hereby information about the physical & chemical characteristics of objects can be obtained with the help of a sensor which records reflected EM energy from these objects. An ideal Remote Sensing system may have the following components 1.Source of EM energy 2.Medium (eg) which interact with this energy(atmosphere) 3.Ground object 4.Sensor to detect & record the changes in EM energy.
- 19. ATMOSPHERIC WINDOWS There are certain region of the EMS which can penetrate through without any significant loss of radiation. Such regions are called the Atmospheric Windows as shown in Fig. Fig. explains this concept in relative to the visible and infrared parts of the spectrum. In several regions, for example the visible the atmosphere is highly transmittance and consequently is almost totally free from the effects of absorption. Regions with a high atmosphere transmittance are generally referred to as atmospheric windows. It is important that RS Systems should operate within those portions of the EM spectrum which coincide with these atmospheric windows. e.g.. Thermal Infra Red region: Wavelength region 3-14 µm, two Atmospheric windows exit. 1st is from 3-5.5 µm; II is from 8-14 µm
- 21. RADIATION & THE ATMOSPHERE Atmospheric influence EM radiations in two respect Scattering Absorption This is caused primarily by the presence of molecules of gas + dust + smoke particles in the atmosphere Absorption of EM radiation occurs primarily the attenuating nature of molecules of ozone, Co2 and water vapour in atmosphere. Because these gases absorb EM radiation in specific wave length bands, they govern which regions of spectrum can be sensed .
- 22. TYPES OF SCATTERING Rayleigh scattering occurs in upper atmosphere, caused predominantly by the interaction of gas molecules which have diameters much less than the radiation λ. This is the main reason for the presents of haze on RS imaginary Mie scattering (lower atmosphere) mainly a product of the interaction of dust and smoke particles with the EM signal Non selective scattering when the particles of diameter greater than that of radiation wavelength. eg. Scattering by water droplets ( dia ≈ 50 µm) as they interact with radiation within the visible spectrum λ ≈ 0.5 µm
- 23. Spectral signature: •This ability to spectrally define a feature or surface is often referred to as defining the “Spectral signature” of the feature. •This term implies that features are uniquely and absolutely defined by measuring this parameter. • Quantitative measurement of the properties of an object at one or several wavelengths • Black body Radiation A black body is hypothetical ideal radiation that absorbs and reemits all energy incident on it. A black body transforms heat energy into radiant energy at the maximum possible rate is termed as black body radiation. Eg. If the sun is a perfect emitter it would be an ideal black body.
- 24. Planck’s Law/ Partical theory: It explains the photo-electric effect. Planck’s Law defines the spectral existance of a black body (Henderson, 1970)
- 25. Spectral reflectance patterns /characteristic reflectance of earth objects with EM spectrum This can be quantified by measuring the proportion of energy reflected by the feature ◼ Certain surfaces (Grass) have considerably different reflectance characteristics in the visible & I/R regions of the spectrum. In contrast (Asphalt) has a relatively stable, low reflectance in both regions. ◼ Most appropriate regions of the spectrum for differentiating between the surfaces is the infrared. A clean hierarchy of reflectance exists from grass with a high reflectance through concrete sandy loam soil to asphalt & water which have a relatively low reflectance. In contrast in the blue/green region of the visible spectrum (λ ~ 0.5µm) the discrimination between asphalt & sandy loam soil surfaces is very poor
- 26. ◼ This may indicate for (eg) that difficulty may arise in the interpretation of these surfaces from conventional aerial photography ◼ The graph again illustrates the very low reflectance of water surfaces in the I/R of the spectrum.
- 27. EM Radiation & the earth surface ◼ Specular & diffuse reflection & its relations to surface roughness. ◼ Some features may appear very different . when it is examined by sensors which are able to record reflectance or emittance outside the visible spectrum. ◼ For example, water surfaces appear black when imaged on to a photographic emulsion sensitive to reflected I/R radiation. Reason: Total absorption of I/R radiation by water. In contrast , viewing the same water surface with a photographic emulsion sensitive to the visible region of the spectrum may provide details about submerged features which may not have been sensed. ◼ Reflective properties of the terrain is the function of surface roughness.
- 28. Specular and Diffused Reflection of earth’s objects ◼ The reflective properties of the terrain can be classified as being either Specular or Diffused. ◼ Reflective properties is a function of the surface roughness. ◼ When the surface is relatively smooth, specular reflection occurs. ◼ When the surface is rough, the reflection is more diffused as shown in figure.
- 32. Figure 1. The Geographical Grid of the world Figure 2. Geographic grid and coordinate systems of the globe Figure 3. Cylindrical projection Figure 4. Azimuthal Projection
- 33. Figure 5. Conic Projection Figure 6. Effect of Map scale on earth features Figure 7. A Portable GPS Receiver
- 34. Figure 8. Conceptual models and representation of spatial phenomena Figure 9. The overlay concept of the real world Figure 10. Various sub-systems of a GIS Figure 11. Major hardware components of a GIS
- 35. Figure 12. Major software components of a GIS Figure 13. Sources of Input data Figure 14. Output and presentation of data Figure 15. Fundamental geographical primitives of points, lines and polygons
- 36. Figure 16. Representation of point, line and aerial data in raster and rector form Figure 17.Network data structures for simple polygons Figure 18. Flat bed optical scanner Figure 19. Simple polygon structure with topological errors
- 37. (a) (b) Figure 20. Quadtree structure of the simple region Figure 21. Digital elevation models 4C 1A3f9 4C1A3f5 4C1A3f10 4C1A3f7 4C 1A3f11 4C1A3f15 4C1A3f3 4C1A3f8 4C1A3f2 4C 1A3f1 4C 1A3f14 4C 1A3f19 4C 1A3f4 4C1A3f12 4C 1A3f6 4C 1A3f13 4C 1A3f17 4C 1A3f16 R u n off P o te n ta il.s h p Lo w M od e r ate M od e r ate ly Figure 22. Mini watershed wise runoff potential map
- 38. Figure 23. Mini watershed wise groundwater potential map N 4C1A3f9 4C1A3f5 4C1A3f10 4C1A3f7 4C1A3f11 4C1A3f4 4C1A3f15 4C1A3f8 4C1A3f2 4C1A3f1 4C1A3f14 4C1A3f19 4C1A3f12 4C1A3f6 4C1A3f13 4C1A3f3 4C1A3f17 4C1A3f16 4C1A3f18 Mini Watershed Boundary Soil Irrigability B C Hill Soil Reserve Forest Figure 24. Land capability classification map Mini Watershed Boundary Land Capability Hill Soil II s III s IV es Reserve Forest N 4C1A3f9 4C1A3f5 4C1A3f10 4C1A3f7 4C1A3f11 4C1A3f4 4C1A3f15 4C1A3f8 4C1A3f2 4C1A3f1 4C1A3f14 4C1A3f19 4C1A3f12 4C1A3f6 4C1A3f13 4C1A3f3 4C1A3f17 4C1A3f16 4C1A3f18 Figure 25. Soil irrigability classification map
- 39. Figure 26. Typical Thematic Maps Figure 27. Typical derived Maps