Remote sensing
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Remote sensing involves obtaining information about objects through analysis of sensor data without physical contact. It has its origins in aerial photography from tethered balloons in the 1840s. Modern remote sensing uses platforms like satellites carrying active sensors that emit energy or passive sensors that record natural energy like sunlight. Sensors collect data on environmental factors that is processed and can be applied to fields like agriculture, geology, oceanography and more.
Remote sensing
- 1. REMOTE SENSING Pavithra senthilkumar, Msc.,geography,2nt year, Mku university, Madurai.
- 2. REMOTE SENSING • Remote sensing is defined as the technique of obtaining information about objects through the analysis of data collected by special instruments that are not in physical contact with the objects of investigation. • Collection of information about an object without coming into physical contact. • The information needs a physical carrier to travel from the objects/events to the sensors through an intervening medium. • The electromagnetic radiation is normally used as an information carrier in remote sensing. • The output of a remote sensing system is usually an image representing the scene being observed.
- 3. HISTORY • The technology of modern remote sensing began with the invention of the camera more than 150 years ago. • The idea and practice of looking down at the Earth's surface emerged in the 1840s when pictures were taken from cameras secured to tethered balloons for purposes of topographic mapping. • Satellite remote sensing can be traced to the early days of the space age (both Russian and American programs) and actually began as a dual approach to imaging surfaces using several types of sensors from spacecraft. • The term "remote sensing," first used in the United States in the 1950s by Ms. Evelyn Pruitt of the U.S.
- 4. ELEMENTS INVOLVED IN REMOTE SENSING
- 5. ELEMENTS INVOLVED IN REMOTE SENSING 1. Energy Source or Illumination (A) 2. Radiation and the Atmosphere (B) 3. Interaction with the Object (C) 4. Recording of Energy by the Sensor (D) 5. Transmission, Reception and Processing (E) 6. Interpretation and Analysis (F) 7. Application (G)
- 6. REMOTE SENSING SENSORS 1. Active Remote Sensors 2. Passive remote sensors
- 7. ACTIVE REMOTE SENSORS • Active remote sensing uses an artificial source for energy. • For example the satellite itself can send a pulse of energy which can interact with the target. • In active remote sensing, humans can control the nature (wavelength, power, duration) of the source energy. Active remote sensing can be carried out during day and night and in all weather conditions.
- 8. PASSIVE REMOTE SENSORS • Passive remote sensing depends on a natural source to provide energy. • For example sun is the most powerful and commonly used source of energy for passive remote sensing. • The satellite sensor in this case records primarily the radiation that is reflected from the target.
- 9. ACTIVE & PASSIVE REMOTE SENSING
- 10. PLATFORMS •The base on which remote sensors are placed to acquire information about the Earth surface is called platforms. • Ground based • Airborne • Space borne
- 12. PLATFORMS USED FOR REMOTE SENSING • Ground-based platforms: ground, vehicles and/or towers => up to 50 m • Airborne platforms: airplanes, helicopters, high-altitude aircrafts, balloons => up to 50 km • Space borne: rockets, satellites, shuttle => from about 100 km to 36000 km 1. Space shuttle: 250-300 km 2. Space station: 300-400 km 3. Low-level satellites: 700-1500 km 4. High-level satellites: about 36000 km
- 13. ADVANTAGES OF REMOTE SENSING • Provides a regional view (large areas). • Provides repetitive looks at the same area. • Remote sensors "see" over a broader. portion of the spectrum than the human eye. • Provides geo-referenced, digital, data. • Some remote sensors operate in all seasons, at night, and in bad weather
- 14. DISADVANTAGE OF REMOTE SENSING •Expensive to build and operate •Needs ground verification •Not the best tool for small areas • Needs expert system to extract data
- 15. REMOTE SENSING • Meteorology Profiling of atmospheric temp. and water vapor Measuring wind velocity • Oceanography Measurements of sea surface temperature Mapping ocean currents • Glaciology Mapping motion of sea ice and ice sheets Determining the navigability of the sea • Geology Identification of rock types Location of geological faults and anomalies
- 16. APPLICATIONS OF REMOTE SENSING • Agriculture Monitoring the extend and type of vegetation Mapping soil types • Hydrology Assessing water resources Forecasting melt water run-off from snow • Disaster control Warning of sand and dust storms, flooding Monitoring of pollution