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Remote sensing

  1. 1. 1
  2. 2. Syllabus 1. Introduction of Remote Sensing. 1.1 Definition 1.2 Principle 1.3 History 1.4 Indian Remote Sensing 2. Types Of Remote Sensing Sensor Systems. 2.1 Active Systems. 2.2 Passive Systems. 3. Remote Sensing Platforms. 4. Remote Sensing Systems. 4.1 Ideal 4.2 Real 4.3 Optimal 4.4 Thermal 4.5 Microwave. 5. Electromagnetic energy. 6. Electromagnetic Spectrum. 7. Electromagnetic radiation. 7.1 Effects of Atmosphere 7.1.2 Scattering. 7.1.2 Absorption. 8. Energy Interaction. 9. Image Resolution In Remote Sensing. 9.1 Intro 9.2 Types Of image Resolution. 10. Applications of Remote Sensing. 11. Advantages & Disadvantages of Remote Sensing 2
  3. 3. INTRODUCTION TO REMOTE SENSING Definition of Remote Sensing • 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 (Lillesand & Kiefer, 2000). • Remote sensing is the science of obtaining and interpreting information from a distance using sensors that are not in physical contact with the object being observed (Randall B. Smith, 2001). 3
  4. 4. What is the principle??? Components of a Remote Sensing System Target Energy source Transmission path Sensor 4
  5. 5. • Target– the object or material that is being studied. The components in the system work together to measure and record information about the target without actually coming into physical contact with it. • Energy source - Illuminates or provides electromagnetic energy to the target. The energy interacts with the target, depending on the properties of the target and the radiation, and will act as a medium for transmitting information from the target to the sensor. 5
  6. 6. • Sensor - a remote device that will collect and record the electromagnetic radiation. Sensors can be used to measure energy that is given off (or emitted) by the target, reflected off of the target, or transmitted through the target. • The resulting set of data is transmitted to a receiving station where the data are processed into a usable format, which is most often as an image. The image is then interpreted in order to extract information about the target. • This interpretation can be done visually or electronically with the aid of computers and image processing software. 6
  7. 7. 7
  8. 8. Familiar forms of remote sensing • medical imaging technologies − Magnetic Resonance Imaging (MRI) − sonograms − X-Ray imaging. • technologies use forms of energy to produce images of the inside of the human body. 8
  9. 9. • Remote sensing is not limited to investigations within our own planet. • Most forms of astronomy are examples of remote sensing, since the targets under investigation are such vast distances from Earth • Astronomers collect and analyze the energy given off by these objects in space by using telescopes and other sensing devices. • This information is recorded and used to draw conclusions about space and our universe 9
  10. 10. Other Examples :- • ocean and atmospheric observing • Magnetic resonance Imaging (MRI) • Positron Emission Tomography (PET) • Space probes 10
  11. 11. HISTORY OF REMOTE SENSING :  Remote sensing starts with the invention of camera more than 150 years ago(1840s)  The idea and practice looking down the earth surface emerged in 1840s cameras secured to tethered balloon 11
  12. 12. HISTORY OF REMOTE SENSING :  Famed pigeons are used for remote sensing 12
  13. 13. HISTORY OF REMOTE SENSING :  In the first world war cameras mounted on airplanes are used to provide images of large surface areas 13
  14. 14. HISTORY OF REMOTE SENSING :  In 1960s and 1970s primary platform changed to satellites 14
  15. 15. HISTORY OF REMOTE SENSING :  Sensors become available to record the earth surface in several bands what human’s eye couldn’t see 15
  16. 16. Starts in 1960s First Indian satellites • Aryabhata (19-April-1975 ) launched in LEO by USSR rocket • Bhaskara I & II carrying two TV cameras • Rohini siries (experimental) INDIAN REMOTE SENSING 16
  17. 17. First Indian Remote Sensing Satellites  IRS-1A (17-March-1988), 904 km  IRS-1B (29-August-1991) Both carrying LISS-1A (Resolution 72.5 m) LISS-2A,LISS-2B (Resolution 36.25 m)  IRS-1C (1995), 817 km  IRS-1D (1997) INDIAN REMOTE SENSING 17
  18. 18. Ground Control Stations  Located at Bangalore( tracking and monitoring)  National Remote Sensing Centre located at Hyderabad (Balanagar &Shadnagar) to process data INDIAN REMOTE SENSING 18
  19. 19. Various Forms Of Collected Data  Acoustic Wave Distribution (Ion based)  Force Distribution (Force based)  Electromagnetic Energy (Wavelength based) and REMOTE SENSING DEALS WITH DATA COLLECTED BY ELECTROMAGNETIC ENERGY PHYSICS OF REMOTE SENSING 19
  20. 20. Types of Remote Sensing Sensor Systems. Based on Source of energy Active Passive 20
  21. 21. Passive System • The sun provides a very convenient source of energy for remote sensing. • The sun's energy is either reflected, or absorbed and then reemitted. • Remote sensing systems which measure energy that is naturally available are called passive sensors. • Passive sensors can only be used to detect energy when the naturally occurring energy is available. 21
  22. 22. • Passive sensors can only be used to detect energy when the naturally occurring energy is available. • For all reflected energy, this can only take place during the time when the sun is illuminating the Earth. • There is no reflected energy available from the sun at night. • Energy that is naturally emitted (such as thermal infrared) can be detected day or night. 22
  23. 23. Active System • The sensor emits radiation which is directed toward the target to be investigated. • The radiation reflected from that target is detected and measured by the sensor. • Advantages :- the ability to obtain measurements anytime, regardless of the time of day or season. • require the generation of a fairly large amount of energy to adequately illuminate targets. • E.g. a laser fluorosensor and a synthetic aperture radar (SAR) 23
  24. 24. Remote Sensing Platforms Remote sensing platforms can be classified as follows, based on the elevation from the Earth’s surface at which these platforms are placed. Ground level remote sensing o Ground level remote sensors are very close to the ground o They are basically used to develop and calibrate sensors for different features on the Earth’s surface. Aerial remote sensing o Low altitude aerial remote sensing o High altitude aerial remote sensing Space borne remote sensing o Space shuttles o Polar orbiting satellites o Geo-stationary satellites From each of these platforms, remote sensing can be done either in passive or active mode.24
  25. 25. RemoteSensingPlatforms 25
  26. 26. IDEAL Remote Sensing System The basic components of an ideal remote sensing system include: i. A Uniform Energy Source which provides energy over all wavelengths, at a constant, known, high level of output ii. A Non-interfering Atmosphere which will not modify either the energy transmitted from the source or emitted (or reflected) from the object in any manner. iii. A Series of Unique Energy/Matter Interactions at the Earth's Surface which generate reflected and/or emitted signals that are selective with respect to wavelength and also unique to each object or earth surface feature type. 26
  27. 27. Components of an ideal remote sensing system 27
  28. 28. iv. A Super Sensor which is highly sensitive to all wavelengths. A super sensor would be simple, reliable, accurate, economical, and requires no power or space. This sensor yields data on the absolute brightness (or radiance) from a scene as a function of wavelength. v. A Real-Time Data Handling System which generates the instance radiance versus wavelength response and processes into an interpretable format in real time. The data derived is unique to a particular terrain and hence provide insight into its physical-chemical-biological state. vi. Multiple Data Users having knowledge in their respective disciplines and also in remote sensing data acquisition and analysis techniques. The information collected will be available to them faster and at less expense. This information will aid the users in various decision making processes and also further in implementing these decisions. 28
  29. 29. Real Remote Sensing System Real remote sensing systems employed in general operation and utility have many shortcomings when compared with an ideal system explained above. i. Energy Source: The energy sources for real systems are usually non-uniform over various wavelengths and also vary with time and space. This has major effect on the passive remote sensing systems. The spectral distribution of reflected sunlight varies both temporally and spatially. Earth surface materials also emit energy to varying degrees of efficiency. A real remote sensing system needs calibration for source characteristics. ii. The Atmosphere: The atmosphere modifies the spectral distribution and strength of the energy received or emitted (Fig. 8). The effect of atmospheric interaction varies with the wavelength associated, sensor used and the sensing application. Calibration is required to eliminate or compensate these atmospheric effects. 29
  30. 30. iii. The Energy/Matter Interactions at the Earth's Surface: Remote sensing is based on the principle that each and every material reflects or emits energy in a unique, known way. However, spectral signatures may be similar for different material types. This makes differentiation difficult. Also, the knowledge of most of the energy/matter interactions for earth surface features is either at elementary level or even completely unknown. iv. The Sensor: Real sensors have fixed limits of spectral sensitivity i.e., they are not sensitive to all wavelengths. Also, they have limited spatial resolution (efficiency in recording spatial details). Selection of a sensor requires a trade-off between spatial resolution and spectral sensitivity. For example, while photographic systems have very good spatial resolution and poor spectral sensitivity, non-photographic systems have poor spatial resolution. v. The Data Handling System: Human intervention is necessary for processing sensor data; even though machines are also included in data handling. This makes the idea of real time data handling almost impossible. The amount of data generated by the sensors far exceeds the data handling capacity. vi. The Multiple Data Users: The success of any remote sensing mission lies on the user who ultimately transforms the data into information. This is possible only if the user understands the problem thoroughly and has a wide knowledge in the data generation. The user should know how to interpret the data generated and should know how best to use them. 30
  31. 31. Electromagnetic Spectrum Remote Sensing • Based on Range of Electromagnetic Spectrum − Optical Remote Sensing − Thermal Remote Sensing − Microwave Remote Sensing 31
  32. 32. Optical Remote Sensing • wavelength range: 300 nm to 3000 nm. • The optical remote sensing devices operate in the visible, near infrared, middle infrared and short wave infrared portion of the electromagnetic spectrum. • Most of the remote sensors record the EMR in this range 32
  33. 33. Thermal Remote Sensing • the wavelength range : 3000 nm to 5000 nm 8000 nm to 14000 nm • Record the energy emitted from the earth • The previous range is related to high temperature phenomenon like forest fire, and later with the general earth features having lower temperatures. 33
  34. 34. Microwave Remote Sensing • wavelength range : 1 mm to 1 m • Most of the microwave sensors are active sensors, having there own sources of energy, e. g, RADARSAT. • Longer wavelength microwave radiation can penetrate through cloud cover, haze, dust • as the longer wavelengths are not susceptible to atmospheric scattering which affects shorter optical wavelengths. • This property allows detection of microwave energy under almost all weather and environmental conditions so that data can be collected at any time. 34
  35. 35.  Combination of Electric and Magnetic fields both are mutually perpendicular to each other passes perpendicular to the light  Travels with a speed of light (3 x 10ᶺ8 m/sec) ELECTROMAGNETIC ENERGY 35
  36. 36. ELECTROMAGNETIC RADIATION  EMR is originated from billions of vibrating electrons, atoms , and molecules which emits EMR in unique combination of wave lengths  All the objects above -273˚C (0˚K) Reflects, Emits and Absorbs EMR  Amount of EMR radiation depends on the Temperature of the Object 36
  37. 37. Data Acquisition:  Source of EM energy  Propagation of EM energy through atmosphere  Interaction of EM energy with earth surface features  Re-transmission of the EM energy through atmosphere  Recording of the reflected EM energy by the sensing systems  Generation of the sensor data in pictorial or digital form GENERAL PROCESS OF REMOTE SENSNG 37
  38. 38. 38
  39. 39. Data Analysis:  Interpretation and analysis of the generated data  Generation of information products  Users GENERAL PROCESS OF REMOTE SENSNG 39
  40. 40. BASIC WAVE THEORY  EM Energy travels in a harmonic sinusoidal fashion (3 x 10ᴧ8 m/sec)  EM wave consists of two fluctuating fields 40
  41. 41.  WAVE LENGTH :- is defined as the distance between two successive wave peaks (λ)usually expressed in micrometers(µm) or manometers (nm).  Frequency:- It is defined as the no of cycles of passing a fixed point in space is called frequency Waves obey the equation c = νλ ----(1.0) ν = frequency λ = wave length c= (3*10^8 m/s) BASIC WAVE THEORY 41
  42. 42. It tells about how the EM Energy interacts with matter The smallest possible unit is photon Each possesses a certain quantity of energy. The Energy of a quanta/photon is given as under:- Q= h.f ------- (1.1) Where Q= energy of quanta(J). h = Planck’s constant 6.626x10ᶺ-34 J-sec f= frequency. From Equation 1.0 &1.1 Q = hc/λ h = Planck’s constant 6.626x10ᶺ-34 J-sec c = velocity of wave = 3*10^8 (m/s) λ = wave length PARTICLE THEORY 42
  43. 43. ELECTROMAGNETIC SPECTRUM Distribution of the continuum of radiant energy can be plotted as a function of wavelength (or frequency) and is known as the electromagnetic radiation (EMR) spectrum 43
  46. 46. ENERGY SOURCES AND RADIATION PRINCIPLES • Primary source of energy that illuminates different features on the earth surface is the Sun. • Although the Sun produces electromagnetic radiation in a wide range of wavelengths, the amount of energy it produces is not uniform across all wavelengths. • Other than the solar radiation, the Earth and the terrestrial objects also are the sources of electromagnetic radiation. All matter at temperature above absolute zero (0oK or -273˚C) emits electromagnetic radiations continuously. 46
  47. 47. Stephan Boltzmann’s law M = σΤᶺ4 M = Total radiant existence of material, Watts/mᶺ2 σ = Stephan boltzmann’s constant 5.6697x10ᶺ-8 W/mᶺ2/˚K T = Temperature in ˚K ENERGY SOURCES AND RADIATION PRINCIPLES 47
  48. 48. Black body Radiation: A blackbody is a hypothetical, ideal radiator. It absorbs and reemits the entire energy incident upon it. • No body in space is perfectly blackbody • As the temperature increases, the peak shifts towards the left. This is explained by the Wien’s displacement law. It states that the dominant wavelength at which a black body radiates “ λm ” is inversely proportional to the absolute temperature of the black body ENERGY SOURCES AND RADIATION PRINCIPLES 48
  50. 50. E= Black body spectral radiance measued in w/mᶺ2/m h= Planck’s constant K= Boltzmann’s constant c= speed of light e= base of the logarithm λ= wave length in ‘m’ T= temperature in ˚K ENERGY SOURCES AND RADIATION PRINCIPLES 50
  51. 51. Wien’s displacement law λmax = b/T λmax = wave length of maximum emitted energy measured in, μm b = Wien's displacement constant T = Temperature in ˚K ENERGY SOURCES AND RADIATION PRINCIPLES 51
  52. 52. EARTH’S ATMOSPHERE Composition Of The Atmosphere Atmosphere is the gaseous envelop that surrounds the Earth’s surface. Much of the gases are concentrated within the lower 100km of the atmosphere. Only 3x10-5 percent of the gases are found above 100 km (Gibbson, 2000). 52
  53. 53. Gaseous Composition of The Earth’s Atmosphere EARTH’S ATMOSPHERE 53
  54. 54. The radiation from the energy source passes through some distance of atmosphere before being detected by the remote sensor EFFECTS OF ATMOSPHERE ON ELECTROMAGNETIC RADIATION 54
  55. 55. SCATTERING : Atmospheric scattering is the process by which small particles in the atmosphere diffuse a portion of the incident radiation in all directions TYPES OF SCATTERING:- a). Selective Scattering. b). Non-selective Scattering. EFFECTS OF ATMOSPHERE ON ELECTROMAGNETIC RADIATION 55
  57. 57. Rayleigh scattering : This occurs when the particles causing the scattering are much smaller in diameter (less than one tenth) than the wavelengths of radiation interacting with them. EFFECTS OF ATMOSPHERE ON ELECTROMAGNETIC RADIATION 57
  58. 58. Mie Scattering : • which occurs when the wavelengths of the energy is almost equal to the diameter of the atmospheric particles • longer wavelengths also get scattered compared to Rayleigh scatter EFFECTS OF ATMOSPHERE ON ELECTROMAGNETIC RADIATION 58
  59. 59. Non-selective scattering : • which occurs when the diameters of the atmospheric particles are much larger (approximately 10 times) than the wavelengths being sensed • This scattering is non-selective with respect to wavelength since all visible and IR wavelengths get scattered equally EFFECTS OF ATMOSPHERE ON ELECTROMAGNETIC RADIATION 59
  60. 60. Absorption • Absorption : Process in which the incident energy is retained by particles in the atmosphere • Energy is transformed into other forms • Unlike scattering, atmospheric absorption causes an effective loss of energy • Absorption depends on – Wavelength of the energy – Atmospheric composition – Arrangement of the gaseous molecules and their energy level • The absorbing medium will not only absorb a portion of the total energy, but will also reflect, refract or scatter the energy. The absorbed energy may also be transmitted back to the atmosphere. 60
  61. 61. Absorption…. • The most efficient absorbers of solar radiation are  Water vapour, carbon dioxide, and ozone • Gaseous components are selective absorbers of the electromagnetic radiation  Absorb electromagnetic energy in specific wavelength bands  Depends on the arrangement of the gaseous molecules and their energy levels Atmospheric window • The ranges of wavelength that are partially or wholly transmitted through the atmosphere • Remote sensing data acquisition is limited through these atmospheric windows 61
  62. 62. Atmospheric Window • Wavelengths shorted than 0.1 μm – Absorbed by Nitrogen and other gaseous components • Wavelengths shorter than 0.3μm (X-rays, Gamma rays and part of ultraviolet rays) – Mostly absorbed by the ozone (O3) • Visible part of the spectrum – Little absorption occurs • Oxygen in the atmosphere causes absorption centered at 6.3μm. • Infrared (IR) radiation – Mainly absorbed by water vapour and carbon dioxide molecules • Far infrared region – Mostly absorbed by the atmosphere • Microwave region – Absorption is almost nil 62
  63. 63. Absorption…… • The most common sources of energy are  Incident solar energy – Maximum energy in the visible region  Radiation from the Earth • Maximum energy in the thermal IR region • Two atmospheric windows – at 3 to 5μm and at 8 to 14μm • Radar & Passive microwave systems operate through a window in the region 1 mm-1 m Major atmospheric windows used in remote sensing and their characteristics Atmospheric window Wavelength band (μm) Characteristics Upper ultraviolet, Visible and photographic IR 0.3-1 apprx. 95% transmission Reflected infrared 1.3, 1.6, 2.2 Three narrow bands Thermal infrared 3.0-5.0 8.0-14.0 Two broad bands Microwave >5000 Atmosphere is mostly transparent 63
  64. 64. Sensor Selection For Remote Sensing • The spectral sensitivity of the available sensors • The available atmospheric windows in the spectral range(s) considered. The spectral range of the sensor is selected by considering the energy interactions with the features under investigation. • The source, magnitude, and spectral composition of the energy available in the particular range. • Multi Spectral Sensors sense simultaneously through multiple, narrow wavelength ranges that can be located at various points in visible through the thermal spectral regions ENERGY INTERACTIONS IN THE EARTH’S ATMOSPHERE 64
  65. 65. Energy Interactions • Electromagnetic energy interactions with the surface features Reflection Absorption Transmission Incident radiation Earth Absorption Reflection Transmission 65
  66. 66. REFLECTION : • Reflection is the process in which the incident energy is redirected in such a way that the angle of incidence is equal to the angle of reflection • Electromagnetic energy is incident on the surface, it may get reflected or scattered depending upon the roughness of the surface relative to the wavelength of the incident energy ENERGY INTERACTIONS WITH EARTH’S SURFACE FEATURES 66
  67. 67. Reflection Interaction with the earth surface 67
  68. 68. Types Of Reflections: Diffuse Reflection • It occurs when the surface is smooth and flat • A mirror-like or smooth reflection is obtained where complete or nearly complete incident energy is reflected in one direction Specular Reflection • It occurs when the surface is rough. • The energy is reflected uniformly in all directions ENERGY INTERACTIONS WITH EARTH’S SURFACE FEATURES 68
  70. 70. Spectral Reflectance : Spectral signature : ENERGY INTERACTIONS WITH EARTH’S SURFACE FEATURES 70
  71. 71.  Absorption  Radiation is absorbed by the target  A portion absorbed by the Earth’s surface is available for emission as thermal radiation ENERGY INTERACTIONS WITH EARTH’S SURFACE FEATURES 71
  72. 72. ENERGY INTERACTIONS WITH EARTH’S SURFACE FEATURES • Transmission Radiation is allowed to pass through the target Changes the velocity and wavelength of the radiation Transmitted energy may be further scattered or absorbed in the medium 72
  73. 73. Transmission and Refraction 73
  74. 74. ENERGY INTERACTIONS WITH EARTH’S SURFACE FEATURES • Reflection, Absorption or Transmission ?  Energy incident on a surface may be partially reflected, absorbed or transmitted  Which process takes place on a surface depends on the following factors: • Wavelength of the radiation • Angle at which the radiation intersects the surface • Composition and physical properties of the surface • Relationship between reflection, absorption and transmission  Principle of conservation of energy as a function of wavelength EI (λ) = ER (λ) + EA(λ) + ET (λ) OR ER (λ) = EI (λ) - EA(λ) - ET (λ) EI = Incident energy ER = Reflected energy EA = Absorbed energy ET = Transmitted energy 74
  75. 75. REFLECTION VS SCATTERING Reflection • Incident energy is redirected • Angle of incidence = Angle of reflection  The reflected radiation leaves the surface at the same angle as it approached Scattering  A special type of reflection  Incident energy is diffused in many directions  Often called Diffuse Reflection 75
  76. 76. REFLECTION VS SCATTERING……. Reflection or Scattering? • Depends on the roughness of the surface with respect to the incident wavelength Roughness of the surface < Incident wavelength  Smooth surface  Reflection Roughness of the surface > Incident wavelength  Rough surface  Scattering • Roughness of the surface controls how the energy is reflected • Mainly two types  Specular reflection  Diffuse (Lambertian) reflection 76
  77. 77. Image Resolution • Image resolution refers to the number of pixels in an unit area of a digital photo or image. • The term resolution used in both traditional and digital photography to describe the quality of the image. 77
  78. 78. Image Resolution (Cont...) • Types of Resolution 1. Spatial Resolution 2. Temporal Resolution 3. Spectral Resolution 4. Radiometric Resolution 78
  79. 79. Spatial Resolution (cont.) The spatial resolution specifies the pixel size of satellite images covering the earth surface. High spatial resolution: 0.41 - 4 m Low spatial resolution: 30 - > 1000 m 1 pixel in image = 30mx30m in land 1 pixel in image = 1mx1m in land 79
  80. 80. Spatial Resolution (cont.) Below is an illustration of how the same image might appear at different pixel resolutions (practical aspect) 80
  81. 81. 40 x 40 Spatial Resolution (cont.) 320 x 320 80 x 80 81
  82. 82. Temporal Resolution • The temporal resolution specifies the revisiting frequency of a satellite sensor for a specific location. • High temporal resolution: < 24 hours - 3 days Medium temporal resolution: 4 - 16 days Low temporal resolution: > 16 days 82
  83. 83. Temporal Resolution Time July 1 July 12 July 23 August 3 11 days 16 days July 2 July 18 August 3 83
  84. 84. Spectral Resolution • The ability of a sensor to detect small differences in wavelength • It specifies the number of spectral bands in which the sensor can collect reflected radiance. • High spectral resolution: 220 bands Medium spectral resolution: 3 - 15 bands Low spectral resolution: 3 bands 84
  85. 85. • Example: Black and white image - Single sensing device - Intensity is sum of intensity of all visible wavelengths Can you tell the color of the platform top? How about her sash? Spectral Resolution (Cont.) 0.4 mm 0.7 mm Black & White Images Blue + Green + Red 85
  86. 86. Spectral Resolution (Cont.) • Example: Color image - Color images need least three sensing devices, e.g., red, green, and blue; RGB Using increased spectral resolution (three sensing wavelengths) adds information In this case by “sensing” RGB can combine to get full color rendition 0.4 mm 0.7 mm Color Images Blue Green Red 86
  87. 87. Radiometric Resolution • It measures of a sensor's ability to discriminate small differences in the magnitude of radiation within the ground area that corresponds to a single raster cell. • The greater the bit depth (number of data bits per pixel) of the images that a sensor records, the higher its radiometric resolution. • The AVHRR sensor, for example, stores 210 (1024) bits per pixel, as opposed to the 28 bits per pixel that the Landsat sensors record. Computer store everything in 0 or 1 87
  88. 88. Radiometric Resolution (Cont.) 2 88
  89. 89. Comparison of Satellites based on Resolution 89
  90. 90. Remote sensing application • a software application that processes remote sensing data • enable generating geographic information from satellite and airborne sensor data • read specialized file formats that contain sensor image data, georeferencing information, and sensor metadata. • Some of the more popular remote sensing file formats include: GeoTIFF, NITF, HDF, and NetCDF. 90
  91. 91. APPLICATION OF REMOTE SENSING  Flood estimation 91
  92. 92. APPLICATION OF REMOTE SENSING  Earthquake Estimation 92
  93. 93. APPLICATION OF REMOTE SENSING  Weather Maps 93
  94. 94.  Crop Yielding  Tsunamis  Forest Fires  Regional Planning  Surveying in Inaccessible Areas  Flood and Drought Warnings APPLICATION OF REMOTE SENSING 94
  95. 95. Advantages and Disadvantages of Remote Sensing Advantages of remote sensing are: a) Provides data of large areas b) Provides data of very remote and inaccessible regions c) Able to obtain imagery of any area over a continuous period of time through which the any anthropogenic or natural changes in the landscape can be analyzed d) Relatively inexpensive when compared to employing a team of surveyors e) Easy and rapid collection of data f) Rapid production of maps for interpretation Disadvantages of remote sensing are: a) The interpretation of imagery requires a certain skill level b) Needs cross verification with ground (field) survey data c) Data from multiple sources may create confusion d) Objects can be misclassified or confused e) Distortions may occur in an image due to the relative motion of sensor and source95
  96. 96. 96