Remote Sensing 1 1.pptx Remote Sensing11
- 2. DEFINATION AND SCOPE • Remote Sensing is a technology that is used to collect information and examine an object, place, or phenomenon without making any physical contact with it. • Remote sensing allows scientists and researchers to observe and collect data on various phenomena on the Earth's surface and atmosphere. • This technology is used in a wide range of fields, including meteorology, oceanography, geography, geology, ecology, glaciology, hydrology and environmental science.
- 3. History and Development of RS technology • The history of remote sensing begins with photography. • Initial photographs were just simple photographs, but the intention of taking the Earth’s images for its graphic mapping arose during the year 1840 and due to this concept scientists started to fix cameras on balloons just to take a wide range of images. • During the era of World War I, cameras were placed on airplanes just to get an aerial view image of landslides. • The origin of other types of remote sensing can be traced to World War II, with the development of radar, sonar, and thermal infrared detection systems. • Since the 1960s, sensors have been designed to operate in virtually all of the electromagnetic spectrum.
- 4. Electromagnetic Radiation • Electromagnetic radiation, in classical physics, the flow of energy at the universal speed of light through free space or through a material medium in the form of the electric and magnetic fields that make up electromagnetic waves such as radio waves, visible light, and gamma rays. • In such a wave, time-varying electric and magnetic fields are mutually linked with each other at right angles and perpendicular to the direction of motion. • An electromagnetic wave is characterized by its intensity and the frequency of the time variation of the electric and magnetic fields.
- 5. Electromagnetic Radiation • Electromagnetic radiation is a form of energy that propagates as both electrical and magnetic waves traveling in packets of energy called photons. • There is a spectrum of electromagnetic radiation with variable wavelengths and frequency, which in turn imparts different characteristics.
- 6. RS • The Sun emits radiation consistently, the electromagnetic radiation passes through and interacts with the Earth’s atmosphere, as well as objects on the ground surface. • After, this reflected radiation was recorded by the sensors loaded on the satellites to produce the remotely sensed image.
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- 9. Electromagnetic Spectrum • The complete frequency or wavelength distribution of electromagnetic radiation is called the electromagnetic (em) spectrum. • The electromagnetic spectrum encompasses all electromagnetic radiation and is divided into various subranges, known as parts, such as visible light or ultraviolet radiation. • Electromagnetic Spectrum is the classification of these waves according to their frequency.
- 10. Electromagnetic Spectrum From the smallest to the largest frequency (highest to shortest wavelength), the electromagnetic spectrum comprises all radio signals, long wave radiation, visible light, UV irradiation, and X-rays, including gamma rays.
- 11. Waves in the Electromagnetic Spectrum 1) Radio Waves- Radio waves are usually in the frequency range from 500 kHz to 1000 MHz. • Generation of Radio Waves: The accelerated motion of charges in conducting wires generates Radio waves. 2) Generation of Microwaves • Special vacuum tubes called klystrons, magnetrons and Gunn diodes generate microwaves. 3) Generation of Infrared Rays • Hot bodies and molecules generate Infrared rays. Also, the band lies next to the low-frequency or long-wavelength end of the electromagnetic spectrum.
- 12. Waves in the Electromagnetic Spectrum 4) Visible Rays • Most importantly, it is that part of the electromagnetic spectrum that is detected by the human eye. 5) Generation of Ultraviolet Rays • Special lamps and very hot bodies generate Ultraviolet rays. Also, the sun is an important source of ultraviolet rays. 6) Generation of X-rays • X-rays are commonly generated by bombarding a metal target with high energy electrons. 7) Generation of Gamma Rays • Gamma rays are produced in nuclear reactions. Some radioactive nuclei also emit gamma rays.
- 13. EMR INTERACTION WITH ATMOSPHERE AND EARTH SURFACE
- 14. EMR INTERACTION WITH ATMOSPHERE AND EARTH SURFACE The interaction between electromagnetic radiation and the Earth’s atmosphere can be considered to have three components: Refraction that changes the direction of propagation of the radiation field due to density differences between outer space and the atmosphere. Scattering that changes the direction of propagation of individual photons as they are absorbed and re-emitted by gasses or aerosols or other atmospheric constituents without changing wavelength. Absorption that convert photons into vibrations in a molecule, energy which is (later) re-emitted as one or more photons with longer wavelength(s).
- 15. EMR INTERACTION WITH ATMOSPHERE AND EARTH SURFACE
- 16. Atmospheric Window • The places where energy passes through are called "atmospheric windows". • We use these "windows" in remote sensing to peer into the atmosphere, which allows us to obtain much information concerning the weather. • An atmospheric window is a region of the electromagnetic spectrum that can pass through the atmosphere of Earth.
- 17. Atmospheric Window • The Earth’s atmosphere selectively transmits energy of certain wavelengths and those wavelengths that are easily transmitted through the atmosphere can be referred as atmospheric windows
- 19. Atmospheric Window • This means only radiation in these wavelengths can be transmitted through the atmosphere and the others are blocked. • Thus, these wavelengths are detected by remote sensing satellites and form the basis of remotely sensed images.
- 20. Atmospheric Window • Atmospheric windows are mainly due to the effect of absorption within the atmosphere. • They are of significant importance for remote sensing, because energy within the windows convey information about the radiometric properties of the objects and thus helps produce satellite images. • Thus, interactions with the atmosphere are of great importance to remote sensing, as it will influence the quality of the remotely sensed images
- 21. Remote Sensing PLATFORMS • There are three broad categories of remote sensing platforms: Ground based, Airborne, and Space borne. • Platform is a stage where sensor or camera is mounted to acquire information about a target under investigation • Ground based Platform: Sensors installed over ground based platforms records detailed information about the feature or surface area such as a crop field or road intersection of limited extent (200 to 400 sq.m). Ground observation platforms include- handheld platform, cherry picker, towers, portable masts and vehicles etc.
- 22. Remote Sensing PLATFORMS • To study properties of a single plant or a small patch of grass, ground based platform is used ( hand helds / tripod). • For the field investigations, some of the most popular platforms have been used are ‘ Cherry Picker Platform’, portable masts or towers. • Cherry Picker Platform can be extended to approx 15m. • This platform is used by various laboratories to carry spectral reflectance meters and photographic systems.
- 23. Portable Masts or Towers portable masts are also available in various forms and can be used to support cameras and sensors for testing.
- 24. Towers and Cranes • Towers and Cranes are used for monitoring atmospheric phenomenon and long term monitoring of terrestrial features. • Towers can be built on site and can be tall enough to project through a forest canopy so that a range of measurement can be taken from the forest floor through the canopy and from above the canopy.
- 25. Air Based Platform • Airborne RS is carried out using specially designed aircrafts or hot air balloons depending on the operational requirements and the availibility of budget. • At present, airplanes are the most common airborne platform. • Airborne platforms are employed owing to their mobilization, flexibility and capability of recording data covering large spatial areas as campared to the ground based sensors. • Other platforms like balloons, drones, high altitute sounding rockets, helicopters are occasionally used.
- 26. Space Borne Platform • Space borne RS is carried out from the outer space or at an altitute higher than the earth’s atmosphere and utilizes space shuttle or more commonly satellites as platforms. Advantages: • Large area coverage • Repetitive coverage • Semi-automated computerized processing and analysis. • Relatively lower cost per area unit area of coverage.
- 27. Elements of RS for visual interpretation (a) Shape (b) size (c) tone (d) site (e) texture (f) shadow (g) association (h) pattern
- 28. Elements of RS for visual interpretation • A systematic study and visual interpretation of satellite images usually involves consideration of two basic elements, namely image elements and terrain elements. • Out of the eight elements listed above, the first seven elements comprise image elements and the 8th element; pattern is the terrain element such as drainage, landform, erosion, soil, vegetation and land-use patterns.
- 29. These elements are shown in the order of their complexity (a) Plot showing the primary ordering of image elements that are fundamental to the image analysis process and (b) diagrammatic representation of elements of visual image interpretation
- 30. TONE • Tone refers to the colour or relative brightness of an object in colour image and the relative and quantitative shades of gray in black and white image. • As studied earlier, the tonal variation is due to the reflection, transmission or absorption characteristic of an object. • This may vary from one object to another and from one band to another. Tone is one of the most basic elements because it is difficult to discern other elements without tonal differences.
- 31. TONE Tone in aerial photographs is influenced by the following factors: • light reflectivity of the object • angle of reflected light • type of photography and film sensitivity • light transmission of filters and • photographic processing.
- 32. SIZE • Objects can be misinterpreted if their sizes are not evaluated properly. • Size of objects in an image is a function of scale hence, the size of objects must be considered in the context of the scale of a photograph/image. • Although, the third dimension, which comprises of height of the objects is not readily measurable on satellite images but valuable information can be derived from the shadows of the objects.
- 33. SIZE Variation in size and shapes in the images provides clue for different objects. (a) Automobiles, (b) railway track, (c) baseball court, (d) trailer, (e) swimming pool and (f) a meandering river
- 34. SHAPE • Shape relates to the general form, configuration or outline of an individual object. • Shape is one of the most important single factors for recognising objects from images. • Regular geometric shapes are usually indicators of human presence and use. • Similarly, irregular shapes are usually indicators of natural objects as shown in (f). • Some objects can be identified almost solely on the basis of their shapes. • For example, a railway line is usually readily distinguished from a highway or an unmetalled road because its shape consists of long straight tangents and gentle curves as opposed to the shape of highway (b).
- 35. Texture • Texture is an expression of roughness or smoothness as exhibited by the images. It is the rate of change of tonal values (frequency of tonal changes). • Texture signifies the frequency of change and arrangement of tones in an image and is produced by an aggregate of unit features too small to be clearly recognised individually on an image. • Texture can be expressed qualitatively as coarse, moderate, fine, very fine, smooth, rough, rippled and mottled. It is rather easier to distinguish various textural classes visually than in the digital oriented techniques.
- 36. Texture • Texture is, thus, dependent upon tone, shape, size, pattern, and scale of the imagery, and, is produced by a mixture of features that are too small to be seen individually. • For example, grass and water generally appear ‘smooth’ while trees or a forest canopy may appear ‘rough’ as shown (e).
- 37. Association • Association is occurrence of features in relation to its surroundings. • Sometimes a single feature by itself may not be distinctive enough to permit its identification. • It specifies the occurrence of certain objects or features in association of a particular object or feature. • Many features can be easily identified by examining the associated features. • For example, a primary school and a high school may be similar flat roofed building structures but it may be possible to identify the high school by its association with an adjacent football field.
- 38. Shadow • Shadow is an especially important clue in the interpretation of objects in the following two ways: • The outline or shape of a shadow provides a profile view of objects, which aids in image interpretation and objects within shadow reflect little light and are difficult to discern on image, which hinders interpretation.
- 39. Shadow • Taller features cast larger shadows than shorter features as shown in Fig. • Military image interpreters are often primarily interested in identification of individual items of equipment. • Shadow is significant in distinguishing subtle differences that might not be otherwise visible. Taller objects such as the Qutub Minar cast larger shadow than smaller objects such as buildings and trees
- 40. Pattern • The terrain elements include drainage, topography/landform, soil, vegetation and land use planning patterns. • Pattern develops in an image due to spatial arrangement of objects. Hence, pattern can be defined as the spatial arrangement of objects in an image. • A particular pattern may have its genetic relation with several factors of its origin. • For example, urban and rural settlement areas can be easily identified based on the patterns created by the rows of houses or buildings.
- 41. Pattern • Similarly, drainage pattern have orderly association with the underlying lithology, structure, soil texture and hydrological characteristics of the ground and hence provide clues about them Satellite image showing Doon valley and surroundings. The drainage patterns and lithological differences can be clearly observed
- 42. RS APPLICATIONS IN CIVIL ENGINEERING AND TOWN PLANNING • Remote sensing can be used for mapping and surveying, monitoring infrastructure, environmental monitoring, geotechnical analysis, transportation planning, construction management, water resource management, hazard assessment, urban planning, archaeological analysis, disaster management, structural health monitoring, forestry management, agricultural analysis, and mining exploration.
- 43. RS APPLICATIONS IN CIVIL ENGINEERING AND TOWN PLANNING • Agriculture: Farmers can use RS and GIS to monitor crop health and estimate yields. RS data can provide information about soil moisture, nutrient levels, and crop health, while GIS can help farmers identify areas of their fields that need attention. • Urban Planning: Urban planners can use RS and GIS to assess land use, transportation patterns, and population distribution. This information can help them identify areas where new infrastructure is needed, or where zoning changes may be necessary.
- 44. RS APPLICATIONS IN CIVIL ENGINEERING AND TOWN PLANNING • Forestry: Foresters can use RS and GIS to monitor forest health and estimate timber volumes. RS data can provide information about tree species, canopy cover, and forest health, while GIS can help foresters identify areas that need management. • Environmental Monitoring: Environmental managers can use RS and GIS to monitor air and water quality, and track changes in land use and vegetation cover. This information can be used to assess the impacts of development projects, monitor the spread of invasive species, and identify areas that require restoration.
- 45. RS APPLICATIONS IN CIVIL ENGINEERING AND TOWN PLANNING • Disaster Response: Emergency responders can use RS and GIS to assess the extent of damage after a disaster, such as a hurricane or wildfire. RS data can provide high-resolution images of affected areas, while GIS can help responders identify areas where resources are needed most.