Remote sensing by abhishek mahajan
- 1. SHREEJEE INSTITUTE OF TECHNOLOGY AND MANAGEMENT Remote Sensing • Guided by:- Mr. Prakash Singh Panwar • By:- Ravi Rathor • EC BRANCH 1ST YEAR
- 2. A physical quantity (light) emanates from that screen, which is a source of radiation. The radiated light passes over a distance, and thus is "remote" to some extent, until it encounters and is captured by a sensor (your eyes). Each eye sends a signal to a processor (your brain) which records the data and interprets this into information. Several of the human senses gather their awareness of the external world almost entirely by perceiving a variety of signals, either emitted or reflected, actively or passively, from objects that transmit this information in waves or pulses..
- 3. • Two simplified definitions are in order: • Remote sensing involves gathering data and information about the physical world by detecting and measuring radiation, particles, and fields associated with objects located beyond the immediate vicinity of the sensor device(s). • Remote sensing is a technology for sampling electromagnetic radiation to acqire and interpret non- immediate geospatial data from which to extract information about features, objects and classes on the land surface, oceans and atmosphere (and where applicable on the exteriors of other bodies in solar system or in the broadest framework, celestial bodies such as stars and galaxies) .
- 5. The photographic camera has served as prime remote sensor for more than 150 years. It captures an image of targets exterior to it by concentrating electromagnetic (EM) radiation (normally, visible light) through a lens onto a recording medium.
- 6. • The first non-photo sensors were television cameras mounted on unmanned spacecraft and were devoted mainly to looking at clouds. The first U.S. meteorological satellite, TIROS-1, launched by an Atlas rocket into orbit on April 1, 1960, looked similar to this later TIROS vehicle. TIROS, for Television Infrared Observation Satellite, used vidicon cameras to scan wide area at a time.
- 7. • The first multispectral photography from space happened during the famous 1968 Apollo 9 mission. • Multispectral false color picture of southern California round San Diego
- 9. • A more sophistical multispectral imaging sensor, named the Thematic Mapper (TM) has been added to Landsats 4 (1982), 5 (1984), 6 (this last failed to attain orbit during launch and thus has never returned data) and 7 (1999). These TMs flew on redesigned, more advanced platforms, the first of which, Landsat-4 (D before launch) is pictured
- 10. • Radar (an active microwave system) has been flown on both military and civilian spacecraft because of its ability (for certain wavelengths) to penetrate clouds • Another class of satellite remote sensors now in space are radar systems .Radar commonly provides a very different view of the same landscape compared with a visible image
- 11. • Most remote sensing instruments (sensors) are designed to measure photons. The fundamental principle underlying sensor operation centers on what happens in a critical component - the detector. This is the concept of the photoelectric effect This, simply stated, says that there will be an emission of negative particles (electrons) when a negatively charged plate of some appropriate light- sensitive material is subjected to a beam of photons. The electrons can then be made to flow from the plate, collected, and counted as a signal. A key point: The magnitude of the electric current produced (number of photoelectrons per unit time) is directly proportional to the light intensity. Thus, changes in the electric current can be used to measure changes in the photons (numbers; intensity) that strike the plate (detector) during a given time interval.
- 12. • Making spectral measurements depends on the interactions between the incident radiation and the atomic and molecular structures of the material. These interactions lead to a reflected signal, which changes some as it returns through the atmosphere. Finally, the measurement depends on the nature of the detector system's response in the sensor. After testing the response of many materials, remote sensing experts can use spectral measurements to describe an object by its composition. • New kinds of images can be produced by making special data sets using computer processing programs • All these processing and classifying activities are done to lead to some sorts of end results or "bottom lines". The purpose is to gain new information, derive applications, and make action decisions. For example, a Geographic Information System program will utilize a variety of data that may be gathered and processed simply to answer a question like: "Where is the best place in a region of interest to locate (site) a new electric power plant?"
- 13. • India has launched four satellites, the IRS series, each with multispectral sensors. • India successfully operates several Earth- resources satellites that gather data in the Visible and Near IR bands, beginning with IRS-1A in March of 1988. The latest in the series, IRS- 1D, launched on September 29, 1997. Its LISS sensor captures radiation in the blue-green, green, red, and near IR bands at 23 m spatial resolution.
- 15. Depending almost exclusively on imaging capabilities, "spy satellites" have activities. Visible, Near-Infrared; Thermal Infrared, and Radar sensors are applied to gathering been orbited by the hundreds (by several countries) to gather military intelligence or information about terrorist information about ground targets and activities of national security significance .
- 16. • The use of various instruments/machines as diagnostic • tools in medical examinations falls within the broad definition of remote sensing, although the target or surface being analyzed is close to the sensor, which may be exterior to the body or can be inserted inside the body to examine internal organs. Electromagnetic radiation is the sensing medium in most analyses. Both active and passive sensors are used. The usual end product is an image. Most medical remote sensing is designed to "see into" the body without having to be invasive (cutting it open). Some techniques produce only static images; others can actually display the features being examined in dynamic, real time images which show the functional movements of the organ (s) within the body.
- 17. • By use of instruments that move into different directions from which to examine the body, which may also move systematically, the resulting images will form a sequence of slices that can (using the computer to integrate the image set into an assemblage of successive views) produce a three-dimensional reconstruction of the segment of the body being diagnosed. This 3-D capability is a principal output of the process called tomography. Individual slices (cross-sections) are an alternate product. X-ray based tomographic imagery is the outcome of a CAT Scan which today is a widely used means of imaging primarily the body's soft parts. Nuclear Magnetic Resonance Imaging uses a different approach that combines magnetic fields and radio waves to excite hydrogen nuclei in parts of the body to generate images of organs, and vascular and neurological systems through variations in intensity and location of induced emitted radio signals.
- 18. • AVIRIS images, used for mineral exploration near Cuprite, Nevada and other mining districts are displayed following an extended narrative on principles of spectroscopy and further consideration of the hyperspectral approach. A preview of the remarkable results of this technology is given by this trio of images of the Cuprite district.