Remote Sensing
twenty-two perceptible shades of gray in the visible
Most remote sensing systems utilize the sun’s energy, which is a     ...
depth of inundation is calculated for each and every location on
the map. The output from the model is used by emergency
[5]                           [8]
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Remote Sensing Vivek


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A brief presentation on remote sensing

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Remote Sensing Vivek

  1. 1. Remote Sensing Vivek.A ECE, Methodist College of Engineering Address Vivek Abstract— Remote Sensing is the science and art of acquiring To georeference something means to define its existence in information (spectral, spatial, and temporal) about material physical space. That is, establishing its location in terms of map objects, area, or phenomenon, without coming into physical projections or coordinate systems. contact with the objects, or area, or phenomenon under Another factor is that of the platen against which the film is investigation. Without direct contact, some means of pressed can cause severe errors when photographs are used to transferring information through space must be utilized. In measure ground distances. remote sensing, information transfer is accomplished by use of electromagnetic radiation (EMR). EMR is a form of energy that reveals its presence by the observable effects it produces when it strikes the matter. EMR is considered to span the spectrum of C.Classifications of RS wavelengths from 10-10 mm to cosmic rays up to 1010 mm, the broadcast wavelengths, which extend from 0.30-15 mm. There are two kinds of sensors in remote sensing: Passive and Active This paper emphasis on interpretation of the received data by the Passive sensors detect natural radiation that is emitted or sensors which gives the details of the required object which reflected by the object or surrounding area being observed. conserves our resources including time and it concentrates more Examples of passive remote sensors include film photography, on types of sensors and the method of analysis done by them Infrared, charge-coupled devices, and radiometers. Keywords— active and passive sources, EMR, Sea, Lake, and Overland Surge from Hurricanes (SLOSH), resolution, repitivity. A. Introduction In the broadest sense, remote sensing is the measurement of information of some property of an object or phenomenon, using a device that is not in physical or intimate contact with the object or phenomenon under study (from aircraft, spacecraft, or Active collection emits energy in order to scan objects and areas ship). The technique employs such devices as the camera, lasers, whereupon a sensor then detects and measures the radiation that and radio frequency receivers, radar systems, etc. This is done is reflected or backscattered from the target. RADAR is an by the analysis of electromagnetic radiation reflected absorbed example of active remote sensing and scattered by the atmosphere, for the purpose of understanding the Earth's resources and environment B. Conventional Remote Sensing In the early stages of remote sensing, photography was used. This method suffers from one major drawback viz. distances are accurate in the center of the image, with the distortion of measurements increasing the farther you get from the center. This problem is overcome by Georeferencing.
  2. 2. twenty-two perceptible shades of gray in the visible Most remote sensing systems utilize the sun’s energy, which is a spectrum. predominant source of energy. These radiations travel through the atmosphere and are selectively scattered and/or absorbed II. Color Infrared Film (CIR): Detects longer wavelengths depending upon the composition of the atmosphere and the somewhat beyond the red end of the light spectrum. Can be wavelengths involved. These radiations upon reaching the used for temperature mapping. earth’s surface interact with the target objects and are collected by the sensors which gives the idea of the required object. III. Thermal Infrared Multispectral Scanner (TIMS): Superior to CIR and uses a six channel scanner that measures the Generally speaking, remote sensing works on the principle of thermal radiation given off by the ground, with accuracy to the inverse problem. While the object or phenomenon of interest 0.1 degree centigrade. The pixel (picture element) is the (the state) may not be directly measured, there exists some other square area being sensed, and the size of the pixel is variable that can be detected and measured (the observation), directly proportional to sensor height. which may be related to the object of interest through the use of a data-derived computer model. The common analogy given to describe this is trying to determine the type of animal from its footprints. For example, while it is impossible to directly IV.Airborne Oceanographic Lidar (ADI): The laser beam measure temperatures in the upper atmosphere, it is possible to pulses to the ground 400 times per second, striking the measure the spectral emissions from a known chemical species surface every three and a half inches, and bounces back to (such as carbon dioxide) in that region. The frequency of the its source. In most cases, the beam bounces off the top of emission may then be related to the temperature in that region the vegetation cover and off the ground surface; the via various thermodynamic relations. difference between the two give information on forest height, or even the height of grass in pastures The quality of remote sensing data and the inference we draw depends on spatial, spectral, radiometric and temporal resolutions. Remote sensing not only gives the geographic locations of stationary targets, but with the advancement in the technology like Synthetic Aperture Radars and Sequential Spatial resolution Image Capturing it has been able to provide details of the The size of a pixel that is recorded in a raster image - targets in motion which enables the prediction of weather typically pixels may correspond to square areas ranging accurately- movement of Hurricanes were predicted very in side length from 1 to 1,000 metres (3.3 to 3,280 ft). accurately. Spectral resolution The number of different frequency bands recorded - usually, this is equivalent to the number of sensors carried by the platform(s). Radiometric resolution E. A typical example highlighting the benefits of Remote Sensing. The number of different intensities of radiation the sensor is able to distinguish. Typically, this ranges from 8 to 14 bits, corresponding to 256 levels of the The Sea, Lake, and Overland Surge from Hurricanes (SLOSH) gray scale and up to 16,384 intensities or "shades" of model was developed by the National Oceanic and Atmospheric colour, in each band. Administration (NOAA) National Weather Service (NWS). The Temporal resolution model identifies the potential surge zones associated with the The frequency of flyovers by the satellite or plane, and various storm categories on the Saffir-Simpson hurricane scale is only relevant in time-series studies or those requiring through the Remote Sensing Data. an averaged or mosaic image as in deforesting The hurricane's track, size, and intensity obtained from the monitoring. remote Sensing data must be specified before the model is run. When these parameters are put into the model, a model wind field is produced, which in turn gives the surface stresses. The stresses act as the driving forces to move the water. Friction, the surface wind stress, and the pressure gradient cause the water to D.Detection in Remote Sensing pile up along the coast. The model repeatedly sends the I. Black and White photography: Black and white theoretical hurricanes into shore at various angles of approach. The end result is a near accurate prediction of the oncoming photography is commonly used but it only records about hurricane in the geographic region under study. A maximum
  3. 3. depth of inundation is calculated for each and every location on the map. The output from the model is used by emergency preparedness professionals to decide who may be at risk from an approaching hurricane. G. Industrial Usage and Other application: • Coastal Applications F. Graphical Analysis Remote sensing data can be used to monitor and evaluate shoreline changes both pre- and post- The field of view of the optics is 43 degrees providing a swath beach renourishment used to study shoreline and of 1420 km from 720-km altitude. bluff erosion. The super cyclone that hit Orissa on Oct, 27th, 1999, has brought drastic changes widely through out the coastal districts • Oceanic Applications and in order to monitor the changes that occurred before and Large scale events such as ocean circulation, after the event. current systems, upwelling and eddy formation can be better understood by using satellite imagery • Hazard Assessment A hazard event could include large storms, earthquakes, Remote sensing can be used both to aid in identifying resources prior to an event and also to asses the damage following an event. H. Conclusions: Remote sensing has been able to provide an all round development in various fields like Synoptic View - facilitates the study of various earths’ surface features in their spatial relation to each other and helps to delineate the required features and phenomena. Repitivity – provide repetitive coverage of the earth and this temporal information is very useful for studying landscape dynamics. Accessibility- it possible to gather information about the area when it is not possible to do ground survey like in mountainous areas and foreign areas. Time Conservation - information about a large area can be gathered quickly, the techniques save time and efforts of human. Cost Effective.- It is a cost-effective technique as again and again fieldwork is not required and also a large number of users can share and use the same data. 1. References: [1] moteintro.html [2] [3] [4]
  4. 4. [5] [8] [6] [9] default.asp [10] [7] [11]